X
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.

neurofilament (NF-M) antibody - Jessell, T.M. / Dodd, J.; HHMI/Columbia University

RRID:AB_531793

Antibody ID

AB_531793

Target Antigen

neurofilament (NF-M) human, mouse, rat

Proper Citation

(DSHB Cat# 2H3, RRID:AB_531793)

Clonality

monoclonal antibody

Comments

consolidated with AB_2314897 on 02/2018 by curator.; Application(s): Immunofluorescence,Immunohistochemistry,Western Blot; Date Deposited: 03/15/1989

Host Organism

mouse

Vendor

DSHB Go To Vendor

Eye-specific segregation and differential fasciculation of developing retinal ganglion cell axons in the mouse visual pathway.

  • Sitko AA
  • J. Comp. Neurol.
  • 2018 May 1

Literature context:


Abstract:

Prior to forming and refining synaptic connections, axons of projection neurons navigate long distances to their targets. While much is known about guidance cues for axon navigation through intermediate choice points, whether and how axons are organized within tracts is less clear. Here we analyze the organization of retinal ganglion cell (RGC) axons in the developing mouse retinogeniculate pathway. RGC axons are organized by both eye-specificity and topography in the optic nerve and tract: ipsilateral RGC axons are segregated from contralateral axons and are offset laterally in the tract relative to contralateral axon topographic position. To identify potential cell-autonomous factors contributing to the segregation of ipsilateral and contralateral RGC axons in the visual pathway, we assessed their fasciculation behavior in a retinal explant assay. Ipsilateral RGC neurites self-fasciculate more than contralateral neurites in vitro and maintain this difference in the presence of extrinsic chiasm cues. To further probe the role of axon self-association in circuit formation in vivo, we examined RGC axon organization and fasciculation in an EphB1-/- mutant, in which a subset of ipsilateral RGC axons aberrantly crosses the midline but targets the ipsilateral zone in the dorsal lateral geniculate nucleus on the opposite side. Aberrantly crossing axons retain their association with ipsilateral axons in the contralateral tract, indicating that cohort-specific axon affinity is maintained independently of guidance signals present at the midline. Our results provide a comprehensive assessment of RGC axon organization in the retinogeniculate pathway and suggest that axon self-association contributes to pre-target axon organization.

Funding information:
  • NIGMS NIH HHS - SC3GM08153(United States)

Spatiotemporal distribution of glia in and around the developing mouse optic tract.

  • Lee MA
  • J. Comp. Neurol.
  • 2018 May 9

Literature context:


Abstract:

In the developing mouse optic tract, retinal ganglion cell (RGC) axon position is organized by topography and laterality (i.e., eye-specific or ipsi- and contralateral segregation). Our lab previously showed that ipsilaterally-projecting RGCs are segregated to the lateral aspect of the developing optic tract and found that ipsilateral axons self-fasciculate to a greater extent than contralaterally-projecting RGC axons in vitro. However, the full complement of axon-intrinsic and -extrinsic factors mediating eye-specific segregation in the tract remain poorly understood. Glia, which are known to express several guidance cues in the visual system and regulate the navigation of ipsilateral and contralateral RGC axons at the optic chiasm, are natural candidates for contributing to eye-specific pre-target axon organization. Here, we investigate the spatiotemporal expression patterns of both putative astrocytes (Aldh1l1+ cells) and microglia (Iba1+ cells) in the embryonic and neonatal optic tract. We quantified the localization of ipsilateral RGC axons to the lateral two-thirds of the optic tract, and analyzed glia position and distribution relative to eye-specific axon organization. While our results indicate that glial segregation patterns do not strictly align with eye-specific RGC axon segregation in the tract, we identify distinct spatiotemporal organization of both Aldh1l1+ cells and microglia in and around the developing optic tract. These findings inform future research into molecular mechanisms of glial involvement in RGC axon growth and organization in the developing retinogeniculate pathway. This article is protected by copyright. All rights reserved.

Funding information:
  • NHLBI NIH HHS - R01 HL115238(United States)

Distinct projection targets define subpopulations of mouse brainstem vagal neurons that express the autism-associated MET receptor tyrosine kinase.

  • Kamitakahara A
  • J. Comp. Neurol.
  • 2017 Dec 15

Literature context:


Abstract:

Detailed anatomical tracing and mapping of the viscerotopic organization of the vagal motor nuclei has provided insight into autonomic function in health and disease. To further define specific cellular identities, we paired information based on visceral connectivity with a cell-type specific marker of a subpopulation of neurons in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (nAmb) that express the autism-associated MET receptor tyrosine kinase. As gastrointestinal disturbances are common in children with autism spectrum disorder (ASD), we sought to define the relationship between MET-expressing (MET+) neurons in the DMV and nAmb, and the gastrointestinal tract. Using wholemount tissue staining and clearing, or retrograde tracing in a METEGFP transgenic mouse, we identify three novel subpopulations of EGFP+ vagal brainstem neurons: (a) EGFP+ neurons in the nAmb projecting to the esophagus or laryngeal muscles, (b) EGFP+ neurons in the medial DMV projecting to the stomach, and (b) EGFP+ neurons in the lateral DMV projecting to the cecum and/or proximal colon. Expression of the MET ligand, hepatocyte growth factor (HGF), by tissues innervated by vagal motor neurons during fetal development reveal potential sites of HGF-MET interaction. Furthermore, similar cellular expression patterns of MET in the brainstem of both the mouse and nonhuman primate suggests that MET expression at these sites is evolutionarily conserved. Together, the data suggest that MET+ neurons in the brainstem vagal motor nuclei are anatomically positioned to regulate distinct portions of the gastrointestinal tract, with implications for the pathophysiology of gastrointestinal comorbidities of ASD.

ESRP1 Mutations Cause Hearing Loss due to Defects in Alternative Splicing that Disrupt Cochlear Development.

  • Rohacek AM
  • Dev. Cell
  • 2017 Nov 6

Literature context:


Abstract:

Alternative splicing contributes to gene expression dynamics in many tissues, yet its role in auditory development remains unclear. We performed whole-exome sequencing in individuals with sensorineural hearing loss (SNHL) and identified pathogenic mutations in Epithelial Splicing-Regulatory Protein 1 (ESRP1). Patient-derived induced pluripotent stem cells showed alternative splicing defects that were restored upon repair of an ESRP1 mutant allele. To determine how ESRP1 mutations cause hearing loss, we evaluated Esrp1-/- mouse embryos and uncovered alterations in cochlear morphogenesis, auditory hair cell differentiation, and cell fate specification. Transcriptome analysis revealed impaired expression and splicing of genes with essential roles in cochlea development and auditory function. Aberrant splicing of Fgfr2 blocked stria vascularis formation due to erroneous ligand usage, which was corrected by reducing Fgf9 gene dosage. These findings implicate mutations in ESRP1 as a cause of SNHL and demonstrate the complex interplay between alternative splicing, inner ear development, and auditory function.

Funding information:
  • NHGRI NIH HHS - U01 HG006546()
  • NIA NIH HHS - R01 AG046544()
  • NIDCD NIH HHS - F31 DC014647()
  • NIDCD NIH HHS - R01 DC006254()
  • NIDCR NIH HHS - R01 DE024749()
  • NIGMS NIH HHS - T32 GM008216()

Dystroglycan Maintains Inner Limiting Membrane Integrity to Coordinate Retinal Development.

  • Clements R
  • J. Neurosci.
  • 2017 Aug 30

Literature context:


Abstract:

Proper neural circuit formation requires the precise regulation of neuronal migration, axon guidance, and dendritic arborization. Mutations affecting the function of the transmembrane glycoprotein dystroglycan cause a form of congenital muscular dystrophy that is frequently associated with neurodevelopmental abnormalities. Despite its importance in brain development, the role of dystroglycan in regulating retinal development remains poorly understood. Using a mouse model of dystroglycanopathy (ISPDL79* ) and conditional dystroglycan mutants of both sexes, we show that dystroglycan is critical for the proper migration, axon guidance, and dendritic stratification of neurons in the inner retina. Using genetic approaches, we show that dystroglycan functions in neuroepithelial cells as an extracellular scaffold to maintain the integrity of the retinal inner limiting membrane. Surprisingly, despite the profound disruptions in inner retinal circuit formation, spontaneous retinal activity is preserved. These results highlight the importance of dystroglycan in coordinating multiple aspects of retinal development.SIGNIFICANCE STATEMENT The extracellular environment plays a critical role in coordinating neuronal migration and neurite outgrowth during neural circuit development. The transmembrane glycoprotein dystroglycan functions as a receptor for multiple extracellular matrix proteins and its dysfunction leads to a form of muscular dystrophy frequently associated with neurodevelopmental defects. Our results demonstrate that dystroglycan is required for maintaining the structural integrity of the inner limiting membrane (ILM) in the developing retina. In the absence of functional dystroglycan, ILM degeneration leads to defective migration, axon guidance, and mosaic spacing of neurons and a loss of multiple neuron types during retinal development. These results demonstrate that disorganization of retinal circuit development is a likely contributor to visual dysfunction in patients with dystroglycanopathy.

Funding information:
  • Intramural NIH HHS - ZO1-HL001285(United States)
  • NINDS NIH HHS - P30 NS061800()
  • NINDS NIH HHS - R01 NS091027()
  • NINDS NIH HHS - U54 NS053672()

SoxC Transcription Factors Promote Contralateral Retinal Ganglion Cell Differentiation and Axon Guidance in the Mouse Visual System.

  • Kuwajima T
  • Neuron
  • 2017 Mar 8

Literature context:


Abstract:

Transcription factors control cell identity by regulating diverse developmental steps such as differentiation and axon guidance. The mammalian binocular visual circuit is comprised of projections of retinal ganglion cells (RGCs) to ipsilateral and contralateral targets in the brain. A transcriptional code for ipsilateral RGC identity has been identified, but less is known about the transcriptional regulation of contralateral RGC development. Here we demonstrate that SoxC genes (Sox4, 11, and 12) act on the progenitor-to-postmitotic transition to implement contralateral, but not ipsilateral, RGC differentiation, by binding to Hes5 and thus repressing Notch signaling. When SoxC genes are deleted in postmitotic RGCs, contralateral RGC axons grow poorly on chiasm cells in vitro and project ipsilaterally at the chiasm midline in vivo, and Plexin-A1 and Nr-CAM expression in RGCs is downregulated. These data implicate SoxC transcription factors in the regulation of contralateral RGC differentiation and axon guidance.

Funding information:
  • NEI NIH HHS - R01 EY012736()
  • NEI NIH HHS - R01 EY015290()
  • NIAMS NIH HHS - R01 AR046249()
  • NIAMS NIH HHS - R01 AR060016()

MAP7 Regulates Axon Collateral Branch Development in Dorsal Root Ganglion Neurons.

  • Tymanskyj SR
  • J. Neurosci.
  • 2017 Feb 8

Literature context:


Abstract:

Collateral branches from axons are key components of functional neural circuits that allow neurons to connect with multiple synaptic targets. Like axon growth and guidance, formation of collateral branches depends on the regulation of microtubules, but how such regulation is coordinated to ensure proper circuit development is not known. Based on microarray analysis, we have identified a role for microtubule-associated protein 7 (MAP7) during collateral branch development of dorsal root ganglion (DRG) sensory neurons. We show that MAP7 is expressed at the onset of collateral branch formation. Perturbation of its expression by overexpression or shRNA knockdown alters axon branching in cultured DRG neurons. Localization and time-lapse imaging analysis reveals that MAP7 is enriched at branch points and colocalizes with stable microtubules, but enters the new branch with a delay, suggesting a role in branch maturation. We have also investigated a spontaneous mutant mouse that expresses a truncated MAP7 and found a gain-of-function phenotype both in vitro and in vivo Further domain analysis suggests that the amino half of MAP7 is responsible for branch formation, suggesting a mechanism that is independent of its known interaction with kinesin. Moreover, this mouse exhibits increased pain sensitivity, a phenotype that is consistent with increased collateral branch formation. Therefore, our study not only uncovers the first neuronal function of MAP7, but also demonstrates the importance of proper microtubule regulation in neural circuit development. Furthermore, our data provide new insights into microtubule regulation during axonal morphogenesis and may shed light on MAP7 function in neurological disorders.SIGNIFICANCE STATEMENT Neurons communicate with multiple targets by forming axonal branches. In search of intrinsic factors that control collateral branch development, we identified a role for microtubule-associated protein 7 (MAP7) in dorsal root ganglion sensory neurons. We show that MAP7 expression is developmentally regulated and perturbation of this expression alters branch formation. Cell biological analysis indicates that MAP7 promotes branch maturation. Analysis of a spontaneous mouse mutant suggests a molecular mechanism for branch regulation and the potential influence of collateral branches on pain sensitivity. Our studies thus establish the first neuronal function of MAP7 and demonstrate its role in branch morphogenesis and neural circuit function. These findings may help in our understanding of the contribution of MAP7 to neurological disorders and nerve regeneration.

Funding information:
  • NINDS NIH HHS - R01 NS062047()

Heterochromatin remodeling in embryonic stem cells proceeds through stochastic de-stabilization of regional steady-states.

  • Christogianni A
  • Biochim. Biophys. Acta
  • 2017 Jan 24

Literature context:


Abstract:

Cell differentiation is associated with progressive immobilization of chromatin proteins, expansion of heterochromatin, decrease of global transcriptional activity and induction of lineage-specific genes. However, how these processes relate to one another remains unknown. We show here that the heterochromatic domains of mouse embryonic stem cells (ESCs) are dynamically distinct and possesses a mosaic sub-structure. Although random spatio-temporal fluctuations reshuffle continuously the chromatin landscape, each heterochromatic territory maintains its dynamic profile, exhibiting robustness and resembling a quasi-steady state. Transitions towards less dynamic states are detected sporadically as ESCs downregulate Nanog and exit the self-renewal phase. These transitions increase in frequency after lineage-commitment, but evolve differently depending on cellular context and transcriptional status. We propose that chromatin remodeling is a step-wise process, which involves stochastic de-stabilization of regional steady states and formation of new dynamic ensembles in coordination to changes in the gene expression program.

Suppression of ischemia in arterial occlusive disease by JNK-promoted native collateral artery development.

  • Ramo K
  • Elife
  • 2016 Aug 9

Literature context:


Abstract:

Arterial occlusive diseases are major causes of morbidity and mortality. Blood flow to the affected tissue must be restored quickly if viability and function are to be preserved. We report that disruption of the mixed-lineage protein kinase (MLK) - cJun NH2-terminal kinase (JNK) signaling pathway in endothelial cells causes severe blockade of blood flow and failure to recover in the murine femoral artery ligation model of hindlimb ischemia. We show that the MLK-JNK pathway is required for the formation of native collateral arteries that can restore circulation following arterial occlusion. Disruption of the MLK-JNK pathway causes decreased Dll4/Notch signaling, excessive sprouting angiogenesis, and defects in developmental vascular morphogenesis. Our analysis demonstrates that the MLK-JNK signaling pathway is a key regulatory mechanism that protects against ischemia in arterial occlusive disease.

Funding information:
  • NIMH NIH HHS - K01 MH109747(United States)

Neuromuscular NMDA Receptors Modulate Developmental Synapse Elimination.

  • Personius KE
  • J. Neurosci.
  • 2016 Aug 24

Literature context:


Abstract:

At birth, each mammalian skeletal muscle fiber is innervated by multiple motor neurons, but in a few weeks, all but one of those axons retracts (Redfern, 1970) and differential activity between inputs controls this phenomenon (Personius and Balice-Gordon, 2001; Sanes and Lichtman, 2001; Personius et al., 2007; Favero et al., 2012). Acetylcholine, the primary neuromuscular transmitter, has long been presumed to mediate this activity-dependent process (O'Brien et al., 1978), but glutamatergic transmission also occurs at the neuromuscular junction (Berger et al., 1995; Grozdanovic and Gossrau, 1998; Mays et al., 2009). To test the role of neuromuscular NMDA receptors, we assessed their contribution to muscle calcium fluxes in mice and tested whether they influence removal of excess innervation at the end plate. Developmental synapse pruning was slowed by reduction of NMDA receptor activation or expression and by reduction of glutamate production. Conversely, pruning is accelerated by application of exogenous NMDA. We also found that NMDA induced increased muscle calcium only during the first 2 postnatal weeks. Therefore, neuromuscular NMDA receptors play previously unsuspected roles in neuromuscular activity and synaptic pruning during development. SIGNIFICANCE STATEMENT: In normal adult muscle, each muscle fiber is innervated by a single axon, but at birth, fibers are multiply innervated. Elimination of excess connections requires neural activity; because the neuromuscular junction (NMJ) is a cholinergic synapse, acetylcholine has been assumed to be the critical mediator of activity. However, glutamate receptors are also expressed at the NMJ. We found that axon removal in mice is slowed by pharmacological and molecular manipulations that decrease signaling through neuromuscular NMDA receptors, whereas application of exogenous NMDA at the NMJ accelerates synapse elimination and increases muscle calcium levels during the first 2 postnatal weeks. Therefore, neuromuscular NMDA receptors play previously unsuspected roles in neuromuscular activity and elimination of excess synaptic input during development.

Funding information:
  • NIGMS NIH HHS - R01 GM083254(United States)

The sodium channel isoform transition at developing nodes of Ranvier in the peripheral nervous system: dependence on a Genetic program and myelination-induced cluster formation.

  • Luo S
  • J. Comp. Neurol.
  • 2014 Dec 15

Literature context:


Abstract:

Among sodium channel isoforms, Nav 1.6 is selectively expressed at nodes of Ranvier in both the CNS and the PNS. However, non-Nav 1.6 isoforms such as Nav 1.2 are also present at the CNS nodes in early development but gradually diminish later. It has been proposed that myelination is part of a glia-neuron signaling mechanism that produces this change in nodal isoform expression. The present study used isoform-specific antibodies to demonstrate that, in the PNS, four other neuronal sodium channel isoforms were also clustered at nodes in early development but eventually disappeared during maturation. To study possible roles of myelination in such transitions, we investigated the nodal expression of selected isoforms in the sciatic nerve of the transgenic mouse Oct6(ΔSCE/βgeo) , whose PNS myelination is delayed in the first postnatal week but eventually resumes. We found that delayed myelination retarded the formation of nodal channel clusters and altered the expression-elimination patterns of sodium channel isoforms, resulting in significantly reduced expression levels of non-Nav 1.6 isoforms in such delayed nodes. However, delayed myelination did not significantly affect the gene expression, protein synthesis, or axonal trafficking of any isoform studied. Rather, we found evidence for a developmentally programmed increase in neuronal Nav 1.6 expression with constant or decreasing neuronal expression of other isoforms that were unaffected by delayed myelination. Thus our results suggest that, in the developmental isoform switch of the PNS, myelination does not play a signaling role as that proposed for the CNS but rather serves only to form nodal clusters from existing isoform pools.

Postnatal expression of neurotrophic factors accessible to spiral ganglion neurons in the auditory system of adult hearing and deafened rats.

  • Bailey EM
  • J. Neurosci.
  • 2014 Sep 24

Literature context:


Abstract:

Spiral ganglion neurons (SGNs) receive input from cochlear hair cells and project from the cochlea to the cochlear nucleus. After destruction of hair cells with aminoglycoside antibiotics or noise, SGNs gradually die. It has been assumed that SGN death is attributable to loss of neurotrophic factors (NTFs) derived from hair cells or supporting cells in the organ of Corti (OC). We used quantitative PCR (qPCR) to assay NTF expression-neurotrophin-3 (NT-3), BDNF, GDNF, neurturin, artemin, and CNTF-in the OC and cochlear nucleus at various ages from postnatal day 0 (P0) to P90 in control hearing and neonatally deafened rats. NT-3, neurturin, and CNTF were most abundant in the postnatal hearing OC; CNTF and neurturin most abundant in the cochlear nucleus. In the OC, NT-3 and CNTF showed a postnatal increase in expression approximately concomitant with hearing onset. In rats deafened by daily kanamycin injections (from P8 to P16), surviving inner hair cells were evident at P16 but absent by P19, with most postsynaptic boutons lost before P16. NT-3 and CNTF, which normally increase postnatally, had significantly reduced expression in the OC of deafened rats, although CNTF was expressed throughout the time that SGNs were dying. In contrast, neurturin expression was constant, unaffected by deafening or by age. CNTF and neurturin expression in the cochlear nucleus was unaffected by deafening or age. Thus, NTFs other than NT-3 are available to SGNs even as they are dying after deafening, apparently conflicting with the hypothesis that SGN death is attributable to lack of NTFs.

Funding information:
  • NEI NIH HHS - R01-EY016155(United States)

Transneuronal propagation of mutant huntingtin contributes to non-cell autonomous pathology in neurons.

  • Pecho-Vrieseling E
  • Nat. Neurosci.
  • 2014 Aug 28

Literature context:


Abstract:

In Huntington's disease (HD), whether transneuronal spreading of mutant huntingtin (mHTT) occurs and its contribution to non-cell autonomous damage in brain networks is largely unknown. We found mHTT spreading in three different neural network models: human neurons integrated in the neural network of organotypic brain slices of HD mouse model, an ex vivo corticostriatal slice model and the corticostriatal pathway in vivo. Transneuronal propagation of mHTT was blocked by two different botulinum neurotoxins, each known for specifically inactivating a single critical component of the synaptic vesicle fusion machinery. Moreover, healthy human neurons in HD mouse model brain slices displayed non-cell autonomous changes in morphological integrity that were more pronounced when these neurons bore mHTT aggregates. Altogether, our findings suggest that transneuronal propagation of mHTT might be an important and underestimated contributor to the pathophysiology of HD.

Funding information:
  • NIGMS NIH HHS - R01 GM082949(United States)

The intracellular redox protein MICAL-1 regulates the development of hippocampal mossy fibre connections.

  • Van Battum EY
  • Nat Commun
  • 2014 Jul 10

Literature context:


Abstract:

Mical is a reduction-oxidation (redox) enzyme that functions as an unusual F-actin disassembly factor during Drosophila development. Although three Molecule interacting with CasL (MICAL) proteins exist in vertebrate species, their mechanism of action remains poorly defined and their role in vivo unknown. Here, we report that vertebrate MICAL-1 regulates the targeting of secretory vesicles containing immunoglobulin superfamily cell adhesion molecules (IgCAMs) to the neuronal growth cone membrane through its ability to control the actin cytoskeleton using redox chemistry, thereby maintaining appropriate IgCAM cell surface levels. This precise regulation of IgCAMs by MICAL-1 is essential for the lamina-specific targeting of mossy fibre axons onto CA3 pyramidal neurons in the developing mouse hippocampus in vivo. These findings reveal the first in vivo role for a vertebrate MICAL protein, expand the repertoire of cellular functions controlled through MICAL-mediated effects on the cytoskeleton, and provide insights into the poorly characterized mechanisms underlying neuronal protein cell surface expression and lamina-specific axonal targeting.

Funding information:
  • NIDCR NIH HHS - R21DE025352(United States)

Subdomain-mediated axon-axon signaling and chemoattraction cooperate to regulate afferent innervation of the lateral habenula.

  • Schmidt ERE
  • Neuron
  • 2014 Jul 16

Literature context:


Abstract:

A dominant feature of neural circuitry is the organization of neuronal projections and synapses into specific brain nuclei or laminae. Lamina-specific connectivity is controlled by the selective expression of extracellular guidance and adhesion molecules in the target field. However, how (sub)nucleus-specific connections are established and whether axon-derived cues contribute to subdomain targeting are largely unknown. Here, we demonstrate that the lateral subnucleus of the habenula (lHb) determines its own afferent innervation by sending out efferent projections that express the cell adhesion molecule LAMP to reciprocally collect and guide dopaminergic afferents to the lHb-a phenomenon we term subdomain-mediated axon-axon signaling. This process of reciprocal axon-axon interactions cooperates with lHb-specific chemoattraction mediated by Netrin-1, which controls axon target entry, to ensure specific innervation of the lHb. We propose that cooperation between pretarget reciprocal axon-axon signaling and subdomain-restricted instructive cues provides a highly precise and general mechanism to establish subdomain-specific neural circuitry.

Funding information:
  • NIGMS NIH HHS - R01-GM084947(United States)
  • NIGMS NIH HHS - T32 GM008471(United States)

Geissoschizine methyl ether, an alkaloid from the Uncaria hook, improves remyelination after cuprizone-induced demyelination in medial prefrontal cortex of adult mice.

  • Morita S
  • Neurochem. Res.
  • 2014 Jan 3

Literature context:


Abstract:

Accumulating evidence indicates that the medial prefrontal cortex (mPFC) is a site of myelin and oligodendrocyte abnormalities that contribute to psychotic symptoms of schizophrenia. The development of therapeutic approaches to enhance remyelination, a regenerative process in which new myelin sheaths are formed on demyelinated axons, may be an attractive remedial strategy. Geissoschizine methyl ether (GM) in the Uncaria hook, a galenical constituent of the traditional Japanese medicine yokukansan (Yi-gan san), is one of the active components responsible for the psychotropic effects of yokukansan, though little is known about the mechanisms underlying the effects of either that medicine or GM itself. In the present study, we employed a cuprizone (CPZ)-induced demyelination model and examined the cellular changes in response to GM administration during the remyelination phase in the mPFC of adult mice. Using the mitotic marker 5-bromo-2'-deoxyuridine (BrdU), we demonstrated that CPZ treatment significantly increased the number of BrdU-positive NG2 cells, as well as microglia and mature oligodendrocytes in the mPFC. Newly formed oligodendrocytes were increased by GM administration after CPZ exposure. In addition, GM attenuated a decrease in myelin basic protein immunoreactivity caused by CPZ administration. Taken together, our findings suggest that GM administration ameliorated the myelin deficit by mature oligodendrocyte formation and remyelination in the mPFC of CPZ-fed mice. The present findings provide experimental evidence supporting the role for GM and its possible use as a remedy for schizophrenia symptoms by promoting the differentiation of progenitor cells to and myelination by oligodendrocytes.

CLAC-P/collagen type XXV is required for the intramuscular innervation of motoneurons during neuromuscular development.

  • Tanaka T
  • J. Neurosci.
  • 2014 Jan 22

Literature context:


Abstract:

Formation of proper neuromuscular connections is a process coordinated by both motoneuron-intrinsic and target-dependent programs. Under these programs, motoneurons innervate target muscles, escape programmed cell death during fetal development, and form neuromuscular junctions (NMJ). Although a number of studies have revealed molecules involved in axon guidance to target muscles and NMJ formation, little is known about the molecular mechanisms linking intramuscular innervation and target-derived trophic factor-dependent prevention of motoneuron apoptosis. Here we studied the physiological function of CLAC-P/collagen XXV, a transmembrane-type collagen originally identified as a component of senile plaque amyloid of Alzheimer's disease brains, by means of generating Col25a1-deficient (KO) mice. Col25a1 KO mice died immediately after birth of respiratory failure. In Col25a1 KO mice, motor axons projected properly toward the target muscles but failed to elongate and branch within the muscle, followed by degeneration of axons. Failure of muscular innervation in Col25a1 KO mice led to excessive apoptosis during development, resulting in almost complete and exclusive loss of spinal motoneurons and immaturity in skeletal muscle development. Bax deletion in Col25a1 KO mice rescued motoneurons from apoptosis, although motor axons remained halted around the muscle entry site. Furthermore, these motoneurons were positive for phosphorylated c-Jun, an indicator of insufficient supply of target-derived survival signals. Together, these observations indicate that CLAC-P/collagen XXV is a novel essential factor that regulates the initial phase of intramuscular motor innervation, which is required for subsequent target-dependent motoneuron survival and NMJ formation during development.

Funding information:
  • Austrian Science Fund FWF - W 1101(Austria)

Frizzled3 controls axonal development in distinct populations of cranial and spinal motor neurons.

  • Hua ZL
  • Elife
  • 2013 Dec 17

Literature context:


Abstract:

Disruption of the Frizzled3 (Fz3) gene leads to defects in axonal growth in the VII(th) and XII(th) cranial motor nerves, the phrenic nerve, and the dorsal motor nerve in fore- and hindlimbs. In Fz3(-/-) limbs, dorsal axons stall at a precise location in the nerve plexus, and, in contrast to the phenotypes of several other axon path-finding mutants, Fz3(-/-) dorsal axons do not reroute to other trajectories. Affected motor neurons undergo cell death 2 days prior to the normal wave of developmental cell death that coincides with innervation of muscle targets, providing in vivo evidence for the idea that developing neurons with long-range axons are programmed to die unless their axons arrive at intermediate targets on schedule. These experiments implicate planar cell polarity (PCP) signaling in motor axon growth and they highlight the question of how PCP proteins, which form cell-cell complexes in epithelia, function in the dynamic context of axonal growth. DOI: http://dx.doi.org/10.7554/eLife.01482.001.

Funding information:
  • Wellcome Trust - 098051(United Kingdom)

Productive vs non-productive infection by cell-free varicella zoster virus of human neurons derived from embryonic stem cells is dependent upon infectious viral dose.

  • Sloutskin A
  • Virology
  • 2013 Sep 1

Literature context:


Abstract:

Varicella Zoster virus (VZV) productively infects humans causing varicella upon primary infection and herpes zoster upon reactivation from latency in neurons. In vitro studies using cell-associated VZV infection have demonstrated productive VZV-infection, while a few recent studies of human neurons derived from stem cells incubated with cell-free, vaccine-derived VZV did not result in generation of infectious virus. In the present study, 90%-pure human embryonic stem cell-derived neurons were incubated with recombinant cell-free pOka-derived virus made with an improved method or VZV vaccine. We found that cell-free pOka and vOka at higher multiplicities of infection elicited productive infection in neurons followed by spread of infection, cytopathic effect and release of infectious virus into the medium. These results further validate the use of this unlimited source of human neurons for studying unexplored aspects of VZV interaction with neurons such as entry, latency and reactivation.

Axonal neuregulin 1 is a rate limiting but not essential factor for nerve remyelination.

  • Fricker FR
  • Brain
  • 2013 Jul 26

Literature context:


Abstract:

Neuregulin 1 acts as an axonal signal that regulates multiple aspects of Schwann cell development including the survival and migration of Schwann cell precursors, the ensheathment of axons and subsequent elaboration of the myelin sheath. To examine the role of this factor in remyelination and repair following nerve injury, we ablated neuregulin 1 in the adult nervous system using a tamoxifen inducible Cre recombinase transgenic mouse system. The loss of neuregulin 1 impaired remyelination after nerve crush, but did not affect Schwann cell proliferation associated with Wallerian degeneration or axon regeneration or the clearance of myelin debris by macrophages. Myelination changes were most marked at 10 days after injury but still apparent at 2 months post-crush. Transcriptional analysis demonstrated reduced expression of myelin-related genes during nerve repair in animals lacking neuregulin 1. We also studied repair over a prolonged time course in a more severe injury model, sciatic nerve transection and reanastamosis. In the neuregulin 1 mutant mice, remyelination was again impaired 2 months after nerve transection and reanastamosis. However, by 3 months post-injury axons lacking neuregulin 1 were effectively remyelinated and virtually indistinguishable from control. Neuregulin 1 signalling is therefore an important factor in nerve repair regulating the rate of remyelination and functional recovery at early phases following injury. In contrast to development, however, the determination of myelination fate following nerve injury is not dependent on axonal neuregulin 1 expression. In the early phase following injury, axonal neuregulin 1 therefore promotes nerve repair, but at late stages other signalling pathways appear to compensate.

Funding information:
  • NCI NIH HHS - 1U54CA121852(United States)

Axonal pruning is actively regulated by the microtubule-destabilizing protein kinesin superfamily protein 2A.

  • Maor-Nof M
  • Cell Rep
  • 2013 Apr 25

Literature context:


Abstract:

Extensive axonal pruning and neuronal cell death are critical events for the development of the nervous system. Like neuronal cell death, axonal elimination occurs in discrete steps; however, the regulators of these processes remain mostly elusive. Here, we identify the kinesin superfamily protein 2A (KIF2A) as a key executor of microtubule disassembly and axonal breakdown during axonal pruning. Knockdown of Kif2a, but not other microtubule depolymerization or severing proteins, protects axonal microtubules from disassembly upon trophic deprivation. We further confirmed and extended this result to demonstrate that the entire degeneration process is delayed in neurons from the Kif2a knockout mice. Finally, we show that the Kif2a-null mice exhibit normal sensory axon patterning early during development, but abnormal target hyperinnervation later on, as they compete for limited skin-derived trophic support. Overall, these findings reveal a central regulatory mechanism of axonal pruning during development.

Funding information:
  • NIGMS NIH HHS - GM62414(United States)

Gbx2 regulates thalamocortical axon guidance by modifying the LIM and Robo codes.

  • Chatterjee M
  • Development
  • 2012 Dec 22

Literature context:


Abstract:

Combinatorial expression of transcription factors forms transcriptional codes to confer neuronal identities and connectivity. However, how these intrinsic factors orchestrate the spatiotemporal expression of guidance molecules to dictate the responsiveness of axons to guidance cues is less understood. Thalamocortical axons (TCAs) represent the major input to the neocortex and modulate cognitive functions, consciousness and alertness. TCAs travel a long distance and make multiple target choices en route to the cortex. The homeodomain transcription factor Gbx2 is essential for TCA development, as loss of Gbx2 abolishes TCAs in mice. Using a novel TCA-specific reporter, we have discovered that thalamic axons are mostly misrouted to the ventral midbrain and dorsal midline of the diencephalon in Gbx2-deficient mice. Furthermore, conditionally deleting Gbx2 at different embryonic stages has revealed a sustained role of Gbx2 in regulating TCA navigation and targeting. Using explant culture and mosaic analyses, we demonstrate that Gbx2 controls the intrinsic responsiveness of TCAs to guidance cues. The guidance defects of Gbx2-deficient TCAs are associated with abnormal expression of guidance receptors Robo1 and Robo2. Finally, we demonstrate that Gbx2 controls Robo expression by regulating LIM-domain transcription factors through three different mechanisms: Gbx2 and Lhx2 compete for binding to the Lmo3 promoter and exert opposing effects on its transcription; repressing Lmo3 by Gbx2 is essential for Lhx2 activity to induce Robo2; and Gbx2 represses Lhx9 transcription, which in turn induces Robo1. Our findings illustrate the transcriptional control of differential expression of Robo1 and Robo2, which may play an important role in establishing the topography of TCAs.

Funding information:
  • NIMH NIH HHS - P20 MH57180(United States)

Onecut transcription factors act upstream of Isl1 to regulate spinal motoneuron diversification.

  • Roy A
  • Development
  • 2012 Sep 8

Literature context:


Abstract:

During development, spinal motoneurons (MNs) diversify into a variety of subtypes that are specifically dedicated to the motor control of particular sets of skeletal muscles or visceral organs. MN diversification depends on the coordinated action of several transcriptional regulators including the LIM-HD factor Isl1, which is crucial for MN survival and fate determination. However, how these regulators cooperate to establish each MN subtype remains poorly understood. Here, using phenotypic analyses of single or compound mutant mouse embryos combined with gain-of-function experiments in chick embryonic spinal cord, we demonstrate that the transcriptional activators of the Onecut family critically regulate MN subtype diversification during spinal cord development. We provide evidence that Onecut factors directly stimulate Isl1 expression in specific MN subtypes and are therefore required to maintain Isl1 production at the time of MN diversification. In the absence of Onecut factors, we observed major alterations in MN fate decision characterized by the conversion of somatic to visceral MNs at the thoracic levels of the spinal cord and of medial to lateral MNs in the motor columns that innervate the limbs. Furthermore, we identify Sip1 (Zeb2) as a novel developmental regulator of visceral MN differentiation. Taken together, these data elucidate a comprehensive model wherein Onecut factors control multiple aspects of MN subtype diversification. They also shed light on the late roles of Isl1 in MN fate decision.

Funding information:
  • NHGRI NIH HHS - HG 2 P50 HG002790-06(United States)

EYA1 and SIX1 drive the neuronal developmental program in cooperation with the SWI/SNF chromatin-remodeling complex and SOX2 in the mammalian inner ear.

  • Ahmed M
  • Development
  • 2012 Jun 9

Literature context:


Abstract:

Inner ear neurogenesis depends upon the function of the proneural basic helix-loop-helix (bHLH) transcription factors NEUROG1 and NEUROD1. However, the transcriptional regulation of these factors is unknown. Here, using loss- and gain-of-function models, we show that EYA1 and SIX1 are crucial otic neuronal determination factors upstream of NEUROG1 and NEUROD1. Overexpression of both Eya1 and Six1 is sufficient to convert non-neuronal epithelial cells within the otocyst and cochlea as well as the 3T3 fibroblast cells into neurons. Strikingly, all the ectopic neurons express not only Neurog1 and Neurod1 but also mature neuronal markers such as neurofilament, indicating that Eya1 and Six1 function upstream of, and in the same pathway as, Neurog1 and Neurod1 to not only induce neuronal fate but also regulate their differentiation. We demonstrate that EYA1 and SIX1 interact directly with the SWI/SNF chromatin-remodeling subunits BRG1 and BAF170 to drive neurogenesis cooperatively in 3T3 cells and cochlear nonsensory epithelial cells, and that SOX2 cooperates with these factors to mediate neuronal differentiation. Importantly, we show that the ATPase BRG1 activity is required for not only EYA1- and SIX1-induced ectopic neurogenesis but also normal neurogenesis in the otocyst. These findings indicate that EYA1 and SIX1 are key transcription factors in initiating the neuronal developmental program, probably by recruiting and interacting with the SWI/SNF chromatin-remodeling complex to specifically mediate Neurog1 and Neurod1 transcription.

Funding information:
  • NINDS NIH HHS - NS37853(United States)

Exogenous leukemia inhibitory factor stimulates oligodendrocyte progenitor cell proliferation and enhances hippocampal remyelination.

  • Deverman BE
  • J. Neurosci.
  • 2012 Feb 8

Literature context:


Abstract:

New CNS neurons and glia are generated throughout adulthood from endogenous neural stem and progenitor cells. These progenitors can respond to injury, but their ability to proliferate, migrate, differentiate, and survive is usually insufficient to replace lost cells and restore normal function. Potentiating the progenitor response with exogenous factors is an attractive strategy for the treatment of nervous system injuries and neurodegenerative and demyelinating disorders. Previously, we reported that delivery of leukemia inhibitory factor (LIF) to the CNS stimulates the self-renewal of neural stem cells and the proliferation of parenchymal glial progenitors. Here we identify these parenchymal glia as oligodendrocyte (OL) progenitor cells (OPCs) and show that LIF delivery stimulates their proliferation through the activation of gp130 receptor signaling within these cells. Importantly, this effect of LIF on OPC proliferation can be harnessed to enhance the generation of OLs that express myelin proteins and reform nodes of Ranvier in the context of chronic demyelination in the adult mouse hippocampus. Our findings, considered together with the known beneficial effects of LIF on OL and neuron survival, suggest that LIF has both reparative and protective activities that make it a promising potential therapy for CNS demyelinating disorders and injuries.

Funding information:
  • HHMI - R01 ES021667(United States)

ZNRF1 promotes Wallerian degeneration by degrading AKT to induce GSK3B-dependent CRMP2 phosphorylation.

  • Wakatsuki S
  • Nat. Cell Biol.
  • 2011 Nov 6

Literature context:


Abstract:

Wallerian degeneration is observed in many neurological disorders, and it is therefore important to elucidate the axonal degeneration mechanism to prevent, and further develop treatment for, such diseases. The ubiquitin-proteasome system (UPS) has been implicated in Wallerian degeneration, but the underlying molecular mechanism remains unclear. Here we show that ZNRF1, an E3 ligase, promotes Wallerian degeneration by targeting AKT to degrade through the UPS. AKT phosphorylates glycogen synthase kinase-3β (GSK3B), and thereby inactivates it in axons. AKT overexpression significantly delays axonal degeneration. Overexpression of the active (non-phosphorylated) form of GSK3B induces CRMP2 phosphorylation, which is required for the microtubule reorganization observed in the degenerating axon. The inhibition of GSK3B and the overexpression of non-phosphorylated CRMP2 both protected axons from Wallerian degeneration. These findings indicate that the ZNRF1-AKT-GSK3B-CRMP2 pathway plays an important role in controlling Wallerian degeneration.

Funding information:
  • European Research Council - 281699(International)

Generation and characterization of a novel neural crest marker allele, Inka1-LacZ, reveals a role for Inka1 in mouse neural tube closure.

  • Reid BS
  • Dev. Dyn.
  • 2010 Apr 29

Literature context:


Abstract:

Previous studies identified Inka1 as a gene regulated by AP-2alpha in the neural crest required for craniofacial morphogenesis in fish and frog. Here, we extend the analysis of Inka1 function and regulation to the mouse by generating a LacZ knock-in allele. Inka1-LacZ allele expression occurs in the cephalic mesenchyme, heart, and paraxial mesoderm prior to E8.5. Subsequently, expression is observed in the migratory neural crest cells and their derivatives. Consistent with expression of Inka1 in tissues of the developing head during neurulation, a low percentage of Inka1(-/-) mice show exencephaly while the remainder are viable and fertile. Further studies indicate that AP-2alpha is not required for Inka1 expression in the mouse, and suggest that there is no significant genetic interaction between these two factors during embryogenesis. Together, these data demonstrate that while the expression domain of Inka1 is conserved among vertebrates, its function and regulation are not.

Disorganized olfactory bulb lamination in mice deficient for transcription factor AP-2epsilon.

  • Feng W
  • Mol. Cell. Neurosci.
  • 2009 Nov 1

Literature context:


Abstract:

Within the olfactory bulb, neurons and their axonal connections are organized into distinct layers corresponding to different functionalities. Here we demonstrate that transcription factor AP-2epsilon is required for olfactory bulb development, specifically the establishment of appropriate neuronal lamination. During normal mouse embryogenesis, AP-2epsilon transcripts are one of the earliest markers of olfactory bulb formation, and expression eventually becomes refined to the projection neurons, the mitral and tufted cells. To assess the function of AP-2epsilon in olfaction, we generated a null allele (the "AK" allele) by inserting a Cre recombinase transgene into the endogenous AP-2epsilon genomic locus. AP-2epsilon-null mice exhibited defective olfactory bulb architecture. The mitral cell layer was disorganized, typified by misoriented and aberrantly positioned projection neurons, and the adjacent internal plexiform layer was absent. Despite the significant disruption of olfactory bulb organization, AP-2epsilon null mice were viable and could discriminate a variety of odors. AP-2epsilon-null mice thus provide compelling evidence for the robust nature of the mouse olfactory system, and serve as a model system to probe both the regulation of neuronal lamination and the functional circuitry of the olfactory bulb. We also show that Cre recombinase expression directed by the AP-2epsilon locus can specifically target floxed genes within the olfactory bulb, extending the utility of this AK allele.

Axial and appendicular skeletal transformations, ligament alterations, and motor neuron loss in Hoxc10 mutants.

  • Hostikka SL
  • Int. J. Biol. Sci.
  • 2009 Jun 3

Literature context:


Abstract:

Vertebrate Hox genes regulate many aspects of embryonic body plan development and patterning. In particular, Hox genes have been shown to regulate regional patterning of the axial and appendicular skeleton and of the central nervous system. We have identified patterning defects resulting from the targeted mutation of Hoxc10, a member of the Hox10 paralogous family. Hoxc10 mutant mice have skeletal transformations in thoracic, lumbar, and sacral vertebrae and in the pelvis, along with alterations in the bones and ligaments of the hindlimbs. These results suggest that Hoxc10, along with other members of the Hox10 paralogous gene family, regulates vertebral identity at the transition from thoracic to lumbar and lumbar to sacral regions. Our results also suggest a general role for Hoxc10 in regulating chondrogenesis and osteogenesis in the hindlimb, along with a specific role in shaping femoral architecture. In addition, mutant mice have a reduction in lumbar motor neurons and a change in locomotor behavior. These results suggest a role for Hoxc10 in generating or maintaining the normal complement of lumbar motor neurons.

Funding information:
  • Medical Research Council - G0501173(United Kingdom)

Nicotinamide mononucleotide adenylyltransferase expression in mitochondrial matrix delays Wallerian degeneration.

  • Yahata N
  • J. Neurosci.
  • 2009 May 13

Literature context:


Abstract:

Studies of naturally occurring mutant mice, wld(s), showing delayed Wallerian degeneration phenotype, suggest that axonal degeneration is an active process. We previously showed that increased nicotinamide adenine dinucleotide (NAD)-synthesizing activity by overexpression of nicotinamide mononucleotide adenylyltransferase (NMNAT) is the essential component of the Wld(s) protein, the expression of which is responsible for the delayed Wallerian degeneration phenotype in wld(s) mice. Indeed, NMNAT overexpression in cultured neurons provides robust protection to neurites, as well. To examine the effect of NMNAT overexpression in vivo and to analyze the mechanism that causes axonal protection, we generated transgenic mice (Tg) overexpressing NMNAT1 (nuclear isoform), NMNAT3 (mitochondrial isoform), or the Wld(s) protein bearing a W258A mutation, which disrupts NAD-synthesizing activity of the Wld(s) protein. Wallerian degeneration delay in NMNAT3-Tg was similar to that in wld(s) mice, whereas axonal protection in NMNAT1-Tg or Wld(s)(W258A)-Tg was not detectable. Detailed analysis of subcellular localization of the overexpressed proteins revealed that the axonal protection phenotype was correlated with localization of NMNAT enzymatic activity to mitochondrial matrix. Furthermore, we found that isolated mitochondria from mice showing axonal protection expressed unchanged levels of respiratory chain components, but were capable of increased ATP production. These results suggest that axonal protection by NMNAT expression in neurons is provided by modifying mitochondrial function. Alteration of mitochondrial function may constitute a novel tool for axonal protection, as well as a possible treatment of diseases involving axonopathy.

Funding information:
  • NIMH NIH HHS - R36 MH078694-01(United States)

Loss of the Prader-Willi syndrome protein necdin causes defective migration, axonal outgrowth, and survival of embryonic sympathetic neurons.

  • Tennese AA
  • Dev. Dyn.
  • 2008 Jul 30

Literature context:


Abstract:

Prader-Willi syndrome is a neurodevelopmental disorder marked by abnormalities in feeding, drinking, thermoregulation, intestinal motility, and reproduction, suggesting disruption of the autonomic nervous system. Necdin, one of several proteins genetically inactivated in individuals with Prader-Willi syndrome, is important for the differentiation of central and sensory neurons. We now show that formation, migration, and survival of sympathetic superior cervical ganglion neurons are impaired in Ndn-null embryos. We observed reduced innervation of superior cervical ganglion target organs, including the submandibular gland, parotid gland, and nasal mucosa. While the formation of other sympathetic chain ganglia is unaffected, axonal extension is impaired throughout the sympathetic nervous system. These results demonstrate a novel role for necdin in cellular migration, in addition to its roles in survival and axon outgrowth. Furthermore, reduced sympathetic function provides a plausible explanation for deficiencies of salivary gland function in individuals with congenital necdin deficiency consequent to Prader-Willi syndrome.

Funding information:
  • NHLBI NIH HHS - HL-090554(United States)

The receptor guanylyl cyclase Npr2 is essential for sensory axon bifurcation within the spinal cord.

  • Schmidt H
  • J. Cell Biol.
  • 2007 Oct 22

Literature context:


Abstract:

Sensory axonal projections into the spinal cord display a highly stereotyped pattern of T- or Y-shaped axon bifurcation at the dorsal root entry zone (DREZ). Here, we provide evidence that embryonic mice with an inactive receptor guanylyl cyclase Npr2 or deficient for cyclic guanosine monophosphate-dependent protein kinase I (cGKI) lack the bifurcation of sensory axons at the DREZ, i.e., the ingrowing axon either turns rostrally or caudally. This bifurcation error is maintained to mature stages. In contrast, interstitial branching of collaterals from primary stem axons remains unaffected, indicating that bifurcation and interstitial branching are processes regulated by a distinct molecular mechanism. At a functional level, the distorted axonal branching at the DREZ is accompanied by reduced synaptic input, as revealed by patch clamp recordings of neurons in the superficial layers of the spinal cord. Hence, our data demonstrate that Npr2 and cGKI are essential constituents of the signaling pathway underlying axonal bifurcation at the DREZ and neuronal connectivity in the dorsal spinal cord.

Funding information:
  • NINDS NIH HHS - NS30816(United States)
  • NINDS NIH HHS - R01 NS084396(United States)

Temporal and spatial regulation of alpha6 integrin expression during the development of the cochlear-vestibular ganglion.

  • Davies D
  • J. Comp. Neurol.
  • 2007 Jun 10

Literature context:


Abstract:

The neurons of the cochlear-vestibular ganglion (CVG) that innervate the sensory hair cells of the inner ear are derived from the otic epithelium early in development. Neuroblasts detach from neighboring cells, migrate into the mesenchyme where they coalesce to form the ganglion complex, then send processes back into the epithelium. Cell migration and neuronal process formation involve changes in cellular interactions with other cells and proteins in the extracellular matrix that are orchestrated by cell surface-expressed adhesion molecules, including the integrins. I studied the expression pattern of the alpha6 integrin subunit during the early development of the CVG using immunohistochemistry and reverse-transcriptase polymerase chain reaction (RT-PCR) in murine tissue sections, otocyst, and ganglion explants. At embryonic day (E)10.5 alpha6 integrin was expressed in the otic epithelium but not in migrating neuroblasts. Importantly, the loss of alpha6 was associated with exit from the epithelium, not neuronal determination, revealing differentiation cues acutely associated with the cellular environment. Markers of glial and neuronal phenotype showed that alpha6-expressing cells present in the CVG at this stage were glia of neural crest origin. By E12.5 alpha6 expression in the ganglion increased alongside the elaboration of neuronal processes. Immunohistochemistry applied to otocyst cultures in the absence of glia revealed that neuronal processes remained alpha6-negative at this developmental stage and confirmed that alpha6 was expressed by closely apposed glia. The spatiotemporal modulation of alpha6 expression suggests changing roles for this integrin during the early development of inner ear innervation.

Funding information:
  • NICHD NIH HHS - Z01-HD008776(United States)

Effects of body temperature on neural activity in the hippocampus: regulation of resting membrane potentials by transient receptor potential vanilloid 4.

  • Shibasaki K
  • J. Neurosci.
  • 2007 Feb 14

Literature context:


Abstract:

Physiological body temperature is an important determinant for neural functions, and it is well established that changes in temperature have dynamic influences on hippocampal neural activities. However, the detailed molecular mechanisms have never been clarified. Here, we show that hippocampal neurons express functional transient receptor potential vanilloid 4 (TRPV4), one of the thermosensitive TRP (transient receptor potential) channels, and that TRPV4 is constitutively active at physiological temperature. Activation of TRPV4 at 37 degrees C depolarized the resting membrane potential in hippocampal neurons by allowing cation influx, which was observed in wild-type (WT) neurons, but not in TRPV4-deficient (TRPV4KO) cells, although dendritic morphology, synaptic marker clustering, and synaptic currents were indistinguishable between the two genotypes. Furthermore, current injection studies revealed that TRPV4KO neurons required larger depolarization to evoke firing, equivalent to WT neurons, indicating that TRPV4 is a key regulator for hippocampal neural excitabilities. We conclude that TRPV4 is activated by physiological temperature in hippocampal neurons and thereby controls their excitability.

Funding information:
  • NIMH NIH HHS - T32 MH019983(United States)

Alpha N-catenin deficiency causes defects in axon migration and nuclear organization in restricted regions of the mouse brain.

  • Uemura M
  • Dev. Dyn.
  • 2006 Sep 30

Literature context:


Abstract:

Alpha N-catenin is a cadherin-binding protein, widely expressed in the nervous system; and it plays a crucial role in cadherin-mediated cell-cell adhesion. Here we report the effects of alpha N-catenin gene deficiency on brain morphogenesis. In addition to the previously reported phenotypes, we found that some of the axon tracts did not normally develop, in particular, axons of the anterior commissure failed to cross the midline, migrating, rather, to ectopic places. In restricted nuclei, a population of neurons was missing or their laminar arrangement was distorted. The ventricular structures were also deformed. These results indicate that alpha N-catenin has diverse roles in the organization of the central nervous system, but only in limited portions of the brain.

Funding information:
  • NCI NIH HHS - U54CA119338(United States)
  • NIMH NIH HHS - MH48866(United States)

Endogenous bone morphogenetic protein antagonists regulate mammalian neural crest generation and survival.

  • Anderson RM
  • Dev. Dyn.
  • 2006 Sep 30

Literature context:


Abstract:

We demonstrate here that Chordin and Noggin function as bone morphogenetic protein (BMP) antagonists in vivo to promote mammalian neural crest development. Using Chrd and Nog single and compound mutants, we find that Noggin has a major role in promoting neural crest formation, in which Chordin is partially redundant. BMP signaling is increased in dorsal tissues lacking Noggin and is further increased when Chordin is also absent. The early neural crest domain is expanded with decreased BMP antagonism in vivo. Noggin and Chordin also regulate subsequent neural crest cell emigration from the neural tube. However, reduced levels of these BMP antagonists ultimately result in perturbation of neural crest cell derived peripheral nervous system and craniofacial skeletal elements. Such defects reflect, at least in part, a function to limit apoptosis in neural crest cells. Noggin and Chordin, therefore, function together to regulate both the generation and survival of neural crest cells in mammalian development.

Funding information:
  • Canadian Institutes of Health Research - GMX-211012(Canada)

Distribution of EphB receptors and ephrin-B1 in the developing vertebrate spinal cord.

  • Jevince AR
  • J. Comp. Neurol.
  • 2006 Aug 10

Literature context:


Abstract:

Contact-dependent interactions between EphB receptors and ephrin-B ligands mediate a variety of cell-cell communication events in the developing and mature central nervous system (CNS). These predominantly repulsive interactions occur at the interface between what are considered to be mutually exclusive EphB and ephrin-B expression domains. We previously used receptor and ligand affinity probes to show that ephrin-B ligands are expressed in the floor plate and within a dorsal region of the embryonic mouse spinal cord, while EphB receptors are present on decussated segments of commissural axons that navigate between these ephrin-B domains. Here we present the generation and characterization of two new monoclonal antibodies, mAb EfB1-3, which recognizes EphB1, EphB2, and EphB3, and mAb efrnB1, which is specific for ephrin-B1. We use these reagents and polyclonal antibodies specific for EphB1, EphB2, EphB3, or ephrin-B1 to describe the spatiotemporal expression patterns of EphB receptors and ephrin-B1 in the vertebrate spinal cord. Consistent with affinity probe binding, we show that EphB1, EphB2, and EphB3 are each preferentially expressed on decussated segments of commissural axons in vivo and in vitro, and that ephrin-B1 is expressed in a dorsal domain of the spinal cord that includes the roof plate. In contrast to affinity probe binding profiles, we show here that EphB1, EphB2, and EphB3 are present on the ventral commissure, and that EphB1 and EphB3 are expressed on axons that compose the dorsal funiculus. In addition, we unexpectedly find that mesenchymal cells, which surround the spinal cord and dorsal root ganglion, express ephrin-B1.

Funding information:
  • PHS HHS - HHSN272200900018C(United States)

Smad1 and Smad8 function similarly in mammalian central nervous system development.

  • Hester M
  • Mol. Cell. Biol.
  • 2005 Jun 18

Literature context:


Abstract:

Smads 1, 5, and 8 are the intracellular mediators for the bone morphogenetic proteins (BMPs), which play crucial roles during mammalian development. Previous research has shown that Smad1 is important in the formation of the allantois, while Smad5 has been shown to be critical in the process of angiogenesis. To further analyze the BMP-responsive Smads, we disrupted the murine Smad8 gene utilizing the Cre/loxP system. A Smad8 hypomorphic allele (Smad8(Deltaexon3)) was constructed that contains an in-frame deletion of exon 3, removing one-third of the MH2 domain and a small portion of the linker region. Xenopus injection assays indicated that this Smad8 deletion allele is still functional but has reduced ventralizing capability compared to the wild type. Although Smad8(Deltaexon3/Deltaexon3) embryos are phenotypically normal, homozygotes of another hypomorphic allele of Smad8 (Smad8(3loxP)) containing a neomycin cassette within intron 3, phenocopy an embryonic brain defect observed in roughly 22% of Smad1(+/)(-) embryos analyzed at embryonic day 11.5. These observations suggest that BMP-responsive Smads have critical functions in the development of the mammalian central nervous system.

Funding information:
  • NIGMS NIH HHS - R01 GM 61671(United States)
  • NIMH NIH HHS - R01 MH604687(United States)

Effects of Schwann cell secreted factors on PC12 cell neuritogenesis and survival.

  • Bampton ET
  • J. Neurobiol.
  • 2005 Apr 1

Literature context:


Abstract:

We have used PC12 cells to examine the effects of factors secreted by Schwann cells that promote cell survival and neurite outgrowth, and hence are likely candidates for promoting neuronal regeneration. RT-PCR showed that primary Schwann cells produced a range of neurotrophins, excluding NT3, but this profile was different from either of two cell lines SCTM41 or PVGSCSV40T, or forskolin-expanded Schwann cells. The effects of Schwann cell conditioned media on neurite outgrowth was tested against a range of factors, and showed clear neuritogenic effects. Of the factors tested, only NGF had a significant response on neuritogenesis. Western blotting for neurofilaments showed that primary Schwann cells induced a strong response close to that of NGF. The Trk tyrosine kinase inhibitor K252a did not block the neuritogenic effects of primary Schwann cells. In contrast, K252a blocked both NGF and the SCTM41 cell effects. Schwann cell conditioned media also enhanced PC12 cell survival. Again, in contrast with NGF or SCTM41 cells, the primary Schwann cell effect was Trk tyrosine kinase independent. The Schwann cell conditioned medium contains a protein factor (greater than 12 kDa and broken down by trypsin treatment) with remarkable thermal stability (unaffected at 95 degrees C for 15 min) and the ability to bind heparin. Our results provide clear evidence that Schwann cells produce factors other than those already known to stimulate a neural phenotype in PC12 cells, and which thus have potential regeneration enhancing effects.

Funding information:
  • NHGRI NIH HHS - R01 HG5690(United States)

Differential requirement for Plexin-A3 and -A4 in mediating responses of sensory and sympathetic neurons to distinct class 3 Semaphorins.

  • Yaron A
  • Neuron
  • 2005 Feb 17

Literature context:


Abstract:

The class 3 Semaphorins Sema3A and Sema3F are potent axonal repellents that cause repulsion by binding Neuropilin-1 and Neuropilin-2, respectively. Plexins are implicated as signaling coreceptors for the Neuropilins, but the identity of the Plexins that transduce Sema3A and Sema3F responses in vivo is uncertain. Here, we show that Plexin-A3 and -A4 are key determinants of these responses, through analysis of a Plexin-A3/Plexin-A4 double mutant mouse. Sensory and sympathetic neurons from the double mutant are insensitive to Sema3A and Sema3F in vitro, and defects in axonal projections in vivo correspond to those seen in Neuropilin-1 and -2 mutants. Interestingly, we found a differential requirement for these two Plexins: signaling via Neuropilin-1 is mediated principally by Plexin-A4, whereas signaling via Neuropilin-2 is mediated principally by Plexin-A3. Thus, Plexin-A3 and -A4 contribute to the specificity of axonal responses to class 3 Semaphorins.

Funding information:
  • NIGMS NIH HHS - R01 GM058634(United States)

Twist is required for patterning the cranial nerves and maintaining the viability of mesodermal cells.

  • Ota MS
  • Dev. Dyn.
  • 2004 Jun 26

Literature context:


Abstract:

Twist encodes a basic helix-loop-helix transcription factor that is required for normal craniofacial morphogenesis in the mouse. Loss of Twist activity in the cranial mesenchyme leads to aberrant migratory behaviour of the neural crest cells, whereas Twist-deficient neural crest cells are located in an inappropriate location in the first branchial arch and display defective osteogenic and odontogenic differentiation (Soo et al. [2002] Dev. Biol. 247:251-270). Results of the present study further show that loss of Twist impacts on the patterning of the cranial ganglia and nerves but not that of the peripheral ganglia and nerves in the trunk region of the body axis. Analyses of the expression of molecular markers of early differentiation of the paraxial mesoderm and the histogenetic potency of somites of Twist(-/-) embryos reveal that Twist-deficient somites can differentiate into muscles, cartilage, and bones, albeit less prolifically. Twist function, therefore, is not essential for mesoderm differentiation. The poor growth of the Twist-deficient somites after transplantation to the ectopic site may be attributed to reduced proliferative capacity and extensive apoptosis of the paraxial mesoderm, suggesting that Twist is required for maintaining cell proliferation and viability in the mesodermal progenitors.

Funding information:
  • NIAAA NIH HHS - AA13341(United States)
  • NIGMS NIH HHS - R01 GM101352(United States)

Suppression of neural fate and control of inner ear morphogenesis by Tbx1.

  • Raft S
  • Development
  • 2004 Apr 15

Literature context:


Abstract:

Inner ear sensory organs and VIIIth cranial ganglion neurons of the auditory/vestibular pathway derive from an ectodermal placode that invaginates to form an otocyst. We show that in the mouse otocyst epithelium, Tbx1 suppresses neurogenin 1-mediated neural fate determination and is required for induction or proper patterning of gene expression related to sensory organ morphogenesis (Otx1 and Bmp4, respectively). Tbx1 loss-of-function causes dysregulation of neural competence in otocyst regions linked to the formation of either mechanosensory or structural sensory organ epithelia. Subsequently, VIIIth ganglion rudiment form is duplicated posteriorly, while the inner ear is hypoplastic and shows neither a vestibular apparatus nor a coiled cochlear duct. We propose that Tbx1 acts in the manner of a selector gene to control neural and sensory organ fate specification in the otocyst.

Funding information:
  • NEI NIH HHS - R01 EY018005(United States)

Ephrin-B1 forward and reverse signaling are required during mouse development.

  • Davy A
  • Genes Dev.
  • 2004 Mar 1

Literature context:


Abstract:

Eph receptors and ephrin ligands are key players in many developmental processes including embryo patterning, angiogenesis, and axon guidance. Eph/ephrin interactions lead to the generation of a bidirectional signal, in which both the Eph receptors and the ephrins activate downstream signaling cascades simultaneously. To understand the role of ephrin-B1 and the importance of ephrin-B1-induced reverse signaling during embryonic development, we have generated mouse lines carrying mutations in the efnb1 gene. Complete ablation of ephrin-B1 resulted in perinatal lethality associated with a range of phenotypes, including defects in neural crest cell (NCC)-derived tissues, incomplete body wall closure, and abnormal skeletal patterning. Conditional deletion of ephrin-B1 demonstrated that ephrin-B1 acts autonomously in NCCs, and controls their migration. Last, a mutation in the PDZ binding domain indicated that ephrin-B1-induced reverse signaling is required in NCCs. Our results demonstrate that ephrin-B1 acts both as a ligand and as a receptor in a tissue-specific manner during embryogenesis.

Funding information:
  • NEI NIH HHS - K12 EY022299(United States)

Ephrin-B2 and EphB1 mediate retinal axon divergence at the optic chiasm.

  • Williams SE
  • Neuron
  • 2003 Sep 11

Literature context:


Abstract:

In animals with binocular vision, retinal ganglion cell (RGC) axons either cross or avoid the midline at the optic chiasm. Here, we show that ephrin-Bs in the chiasm region direct the divergence of retinal axons through the selective repulsion of a subset of RGCs that express EphB1. Ephrin-B2 is expressed at the mouse chiasm midline as the ipsilateral projection is generated and is selectively inhibitory to axons from ventrotemporal (VT) retina, where ipsilaterally projecting RGCs reside. Moreover, blocking ephrin-B2 function in vitro rescues the inhibitory effect of chiasm cells and eliminates the ipsilateral projection in the semiintact mouse visual system. A receptor for ephrin-B2, EphB1, is found exclusively in regions of retina that give rise to the ipsilateral projection. EphB1 null mice exhibit a dramatically reduced ipsilateral projection, suggesting that this receptor contributes to the formation of the ipsilateral retinal projection, most likely through its repulsive interaction with ephrin-B2.

Funding information:
  • Medical Research Council - G1002033(United Kingdom)

Neurogenin2 specifies the connectivity of thalamic neurons by controlling axon responsiveness to intermediate target cues.

  • Seibt J
  • Neuron
  • 2003 Jul 31

Literature context:


Abstract:

Many lines of evidence indicate that important traits of neuronal phenotype, such as cell body position and neurotransmitter expression, are specified through complex interactions between extrinsic and intrinsic genetic determinants. However, the molecular mechanisms specifying neuronal connectivity are less well understood at the transcriptional level. Here we demonstrate that the bHLH transcription factor Neurogenin2 cell autonomously specifies the projection of thalamic neurons to frontal cortical areas. Unexpectedly, Ngn2 determines the projection of thalamic neurons to specific cortical domains by specifying the responsiveness of their axons to cues encountered in an intermediate target, the ventral telencephalon. Our results thus demonstrate that in parallel to their well-documented proneural function, bHLH transcription factors also contribute to the specification of neuronal connectivity in the mammalian brain.

Funding information:
  • NIDCD NIH HHS - R01 DC00189(United States)

c-jun regulation and function in the developing hindbrain.

  • Mechta-Grigoriou F
  • Dev. Biol.
  • 2003 Jun 15

Literature context:


Abstract:

Hindbrain development is a well-characterised segmentation process in vertebrates. The bZip transcription factor MafB/kreisler is specifically expressed in rhombomeres (r) 5 and 6 of the developing vertebrate hindbrain and is required for proper caudal hindbrain segmentation. Here, we provide evidence that the mouse protooncogene c-jun, which encodes a member of the bZip family, is coexpressed with MafB in prospective r5 and r6. Analysis of mouse mutants suggests that c-jun expression in these territories is dependent on MafB but independent of the zinc-finger transcription factor Krox20, another essential determinant of r5 development. Loss- and gain-of-function studies, performed in mouse and chick embryos, respectively, demonstrate that c-Jun participates, together with MafB and Krox20, in the transcriptional activation of the Hoxb3 gene in r5. The action of c-Jun is likely to be direct, since c-Jun homodimers and c-Jun/MafB heterodimers can bind to essential regulatory elements within the transcriptional enhancer responsible for Hoxb3 expression in r5. These data indicate that c-Jun acts both as a downstream effector and a cofactor of MafB and belongs to the complex network of factors governing hindbrain patterning.

Funding information:
  • NCRR NIH HHS - 5P20RR018788(United States)
  • NINDS NIH HHS - NS39084(United States)

The isthmic organizer signal FGF8 is required for cell survival in the prospective midbrain and cerebellum.

  • Chi CL
  • Development
  • 2003 Jun 8

Literature context:


Abstract:

Numerous studies have demonstrated that the midbrain and cerebellum develop from a region of the early neural tube comprising two distinct territories known as the mesencephalon (mes) and rostral metencephalon (met; rhombomere 1), respectively. Development of the mes and met is thought to be regulated by molecules produced by a signaling center, termed the isthmic organizer (IsO), which is localized at the boundary between them. FGF8 and WNT1 have been implicated as key components of IsO signaling activity, and previous studies have shown that in Wnt1(-/-) embryos, the mes/met is deleted by the 30 somite stage ( approximately E10) (McMahon, A. P. and Bradley, A. (1990) Cell 62, 1073-1085). We have studied the function of FGF8 in mouse mes/met development using a conditional gene inactivation approach. In our mutant embryos, Fgf8 expression was transiently detected, but then was eliminated in the mes/met by the 10 somite stage ( approximately E8.75). This resulted in a failure to maintain expression of Wnt1 as well as Fgf17, Fgf18, and Gbx2 in the mes/met at early somite stages, and in the absence of the midbrain and cerebellum at E17.5. We show that a major cause of the deletion of these structures is ectopic cell death in the mes/met between the 7 and 30 somite stages. Interestingly, we found that the prospective midbrain was deleted at an earlier stage than the prospective cerebellum. We observed a remarkably similar pattern of cell death in Wnt1 null homozygotes, and also detected ectopic mes/met cell death in En1 null homozygotes. Our data show that Fgf8 is part of a complex gene regulatory network that is essential for cell survival in the mes/met.

Funding information:
  • NIAID NIH HHS - R01 AI118985(United States)

Distribution of keratin 8-containing cell clusters in mouse embryonic tongue: evidence for a prepattern for taste bud development.

  • Mbiene JP
  • J. Comp. Neurol.
  • 2003 Mar 3

Literature context:


Abstract:

The initiation of the morphogenesis of gustatory papillae is independent of innervation. To address the question of whether taste bud formation is associated with gustatory papilla morphogenesis, we examined developing tongues in mouse embryos from embryonic day 11 to birth. Despite the smooth morphological appearance of the lingual dorsal surface at 13 days of gestation, we observed embryonic taste bud primordia as discrete collections of cytokeratin 8-positive and elongated cells in epithelial placodes in the anterior tongue. In subsequent stages until birth, cytokeratin 8 continues to be expressed in embryonic taste buds distributed in punctuate patterns at regular intervals along rows that are symmetrically located on both sides of the median sulcus in the dorsal anterior developing tongue. Embryonic taste buds were observed in the developing circumvallate papillae from 15.5 days of gestation until birth. The dorsal epithelium of the anterior tongue is not innervated when embryonic taste buds first occur. The increased numbers of embryonic taste buds in developing fungiform papillae until birth are not correlated with the neural invasion of the epithelium. Thus, taste buds occur prenatally more likely independently of the innervation.

Funding information:
  • NIMH NIH HHS - R01 MH110404(United States)

Integration and differentiation of human embryonic stem cells transplanted to the chick embryo.

  • Goldstein RS
  • Dev. Dyn.
  • 2002 Sep 30

Literature context:


Abstract:

Human embryonic stem (ES) cells are pluripotent cells that can differentiate into a large array of cell types and, thus, hold promise for advancing our understanding of human embryology and for contributing to transplantation medicine. In this study, differentiation of human ES cells was examined in vivo by in ovo transplantation to organogenesis-stage embryos. Colonies of human ES cells were grafted into or in place of epithelial-stage somites of chick embryos of 1.5 to 2 days of development. The grafted human ES cells survived in the chick host and were identified by vital staining with carboxyfluorescein diacetate or use of a green fluorescent protein-expressing cells. Histologic analysis showed that human ES cells are easily distinguished from host cells by their larger, more intensely staining nuclei. Some grafted cells differentiated en masse into epithelia, whereas others migrated and mingled with host tissues, including the dorsal root ganglion. Colonies grafted directly adjacent to the host neural tube produced primarily structures with the morphology and molecular characteristics of neural rosettes. These structures contain differentiated neurons as shown by beta-3-tubulin and neurofilament expression in axons and cell bodies. Axons derived from the grafted cells penetrate the host nervous system, and host axons enter the structures derived from the graft. Our results show that human ES cells transplanted in ovo survive, divide, differentiate, and integrate with host tissues and that the host embryonic environment may modulate their differentiation. The chick embryo, therefore, may serve as an accessible and unique experimental system for the study of in vivo development of human ES cells.

Funding information:
  • NIDCD NIH HHS - R56 DC010183(United States)

The Dlx5 homeobox gene is essential for vestibular morphogenesis in the mouse embryo through a BMP4-mediated pathway.

  • Merlo GR
  • Dev. Biol.
  • 2002 Aug 1

Literature context:


Abstract:

In the mouse embryo, Dlx5 is expressed in the otic placode and vesicle, and later in the semicircular canals of the inner ear. In mice homozygous for a null Dlx5/LacZ allele, a severe dysmorphogenesis of the vestibular region is observed, characterized by the absence of semicircular canals and the shortening of the endolymphatic duct. Minor defects are observed in the cochlea, although Dlx5 is not expressed in this region. Cristae formation is severely impaired; however, sensory epithelial cells, recognized by calretinin immunostaining, are present in the vestibular epithelium of Dlx5(-/-) mice. The maculae of utricle and saccule are present but cells appear sparse and misplaced. The abnormal morphogenesis of the semicircular canals is accompanied by an altered distribution of proliferating and apoptotic cells. In the Dlx5(-/-) embryos, no changes in expression of Nkx5.1(Hmx3), Pax2, and Lfng have been seen, while expression of bone morphogenetic protein-4 (Bmp4) was drastically reduced. Notably, BMP4 has been shown to play a fundamental role in vestibular morphogenesis of the chick embryo. We propose that development of the semicircular canals and the vestibular inner ear requires the independent control of several homeobox genes, which appear to exert their function via tight regulation of BPM4 expression and the regional organization of cell differentiation, proliferation, and apoptosis.

Funding information:
  • NIDDK NIH HHS - R01DK078749(United States)

The basic helix-loop-helix factor olig2 is essential for the development of motoneuron and oligodendrocyte lineages.

  • Takebayashi H
  • Curr. Biol.
  • 2002 Jul 9

Literature context:


Abstract:

Sonic hedgehog (Shh), an organizing signal from ventral midline structures, is essential for the induction and maintenance of many ventral cell types in the embryonic neural tube. Olig1 and Olig2 are related basic helix-loop-helix factors induced by Shh in the ventral neural tube. Although expression analyses and gain-of-function experiments suggested that these factors were involved in motoneuron and oligodendrocyte development, they do not clearly define the functional differences between Olig1 and Olig2. We generated mice with a homozygous inactivation of Olig2. These mice did not feed and died on the day of birth. In the spinal cord of the mutant mice, motoneurons are largely eliminated and oligodendrocytes are not produced. Olig2(-/-) neuroepithelial cells in the ventral spinal cord failed to differentiate into motoneurons or oligodendrocytes and expressed an astrocyte marker, S100beta, at the time of oligodendrogenesis. Olig1 or Olig3, other family members, were expressed in the descendent cells that should have expressed Olig2. We concluded that Olig2 is an essential transcriptional regulator in motoneuron and oligodendrocyte development. Our data provide the first evidence that a single gene mutation leads to the loss of two cell types, motoneuron and oligodendrocyte.

Funding information:
  • NIGMS NIH HHS - R01 GM095867(United States)

Differential expression of alpha 3 and alpha 6 integrins in the developing mouse inner ear.

  • Davies D
  • J. Comp. Neurol.
  • 2002 Apr 1

Literature context:


Abstract:

The development of the mammalian inner ear involves a complex series of cell-cell and cell-extracellular matrix interactions. These interactions are likely to be mediated by families of adhesion molecules, including the integrins. We have studied the expression of three integrin subunits known to be expressed on epithelia in a number of tissues (namely, alpha3, alpha6, and beta4) during the development of the murine inner ear. At E10.5, both alpha3 and alpha6 were expressed in the epithelial layers of the otocyst. The expression of alpha6 was concentrated in an anterioventral region of the epithelium and in a proportion of the cells forming the cochlear-vestibular and facial ganglia. By E12.5, alpha6 showed a more restricted expression, confined mainly to the pro-sensory epithelia and the neural processes from the cochlear-vestibular ganglion. In contrast, alpha3 was expressed in epithelia adjacent to the pro-sensory areas. This reciprocal expression pattern was maintained until birth. Between birth and P6, a switch in expression occurred such that alpha3 was upregulated and alpha6 was downregulated in the sensory epithelia of both the auditory and vestibular systems. At this stage, alpha3 was expressed in all the epithelia lining the scala media, thus defining the endolymph compartment. The expression of beta4 was restricted to epithelial/mesenchymal borders throughout the developmental stages studied, suggesting that alpha6 expression observed within the epithelium and neuronal tissue was alpha6beta1. The early expression and changing pattern of alpha3 and alpha6 integrins during development of the mammalian inner ear suggests that they may be involved in the molecular processes that define epithelial boundaries and guide sensory innervation.

Funding information:
  • NIMH NIH HHS - MH101188(United States)

Axial skeletal defects caused by mutation in the spondylocostal dysplasia/pudgy gene Dll3 are associated with disruption of the segmentation clock within the presomitic mesoderm.

  • Dunwoodie SL
  • Development
  • 2002 Apr 29

Literature context:


Abstract:

A loss-of-function mutation in the mouse delta-like3 (Dll3) gene has been generated following gene targeting, and results in severe axial skeletal defects. These defects, which consist of highly disorganised vertebrae and costal defects, are similar to those associated with the Dll3-dependent pudgy mutant in mouse and with spondylocostal dysplasia (MIM 277300) in humans. This study demonstrates that Dll3(neo) and Dll3(pu) are functionally equivalent alleles with respect to the skeletal dysplasia, and we suggest that the three human DLL3 mutations associated with spondylocostal dysplasia are also functionally equivalent to the Dll3(neo) null allele. Our phenotypic analysis of Dll3(neo)/Dll3(neo) mutants shows that the developmental origins of the skeletal defects lie in delayed and irregular somite formation, which results in the perturbation of anteroposterior somite polarity. As the expression of Lfng, Hes1, Hes5 and Hey1 is disrupted in the presomitic mesoderm, we suggest that the somitic aberrations are founded in the disruption of the segmentation clock that intrinsically oscillates within presomitic mesoderm.

Funding information:
  • NEI NIH HHS - 5-T32EY013360-13(United States)
  • NINDS NIH HHS - NS33553(United States)

Apoptosis, axonal growth defects, and degeneration of peripheral neurons in mice lacking CREB.

  • Lonze BE
  • Neuron
  • 2002 Apr 25

Literature context:


Abstract:

CRE-binding protein (CREB) belongs to a family of transcription factors that mediates stimulus-dependent gene expression in neuronal and non-neuronal cells. Here we show that CREB is phosphorylated on its transcriptional regulatory site, Ser-133, in vivo in a neurotrophin-dependent manner. In mice harboring a null mutation in the Creb gene, sensory neurons exhibit excess apoptosis and degeneration, and display impaired axonal growth and projections. Interestingly, excess apoptosis is not observed in the central nervous system. CREB is required within sensory and sympathetic neurons for survival and axon extension since both of these neurotrophin-dependent processes are compromised in cultured neurons from CREB null mice. Thus, during their period of neurotrophin dependency, peripheral neurons require CREB-mediated gene expression for both survival and growth in vivo.

Funding information:
  • NCRR NIH HHS - P41 RR001081(United States)

Requirement of neuropilin 1-mediated Sema3A signals in patterning of the sympathetic nervous system.

  • Kawasaki T
  • Development
  • 2002 Feb 6

Literature context:


Abstract:

Neuropilin 1 is the specific receptor for Sema3A and plays a role in nerve fiber guidance. We report that neuropilin 1 and Sema3A mutant mouse embryos, generated by targeted gene disruption, showed displacement of sympathetic neurons and their precursors and abnormal morphogenesis in the sympathetic trunk. We also show that Sema3A suppressed the cell migration activity of sympathetic neurons from wild-type but not neuropilin 1 mutant embryos in vitro and instead promoted their accumulation into compact cell masses and fasciculation of their neurites. These findings suggest that the neuropilin 1-mediated Sema3A signals regulate arrest and aggregation of sympathetic neuron precursors and sympathetic neurons themselves at defined target sites and axon fasciculation to produce the stereotyped sympathetic nerve pattern.

Funding information:
  • Wellcome Trust - (United Kingdom)

Hoxa3 regulates integration of glossopharyngeal nerve precursor cells.

  • Watari N
  • Dev. Biol.
  • 2001 Dec 1

Literature context:


Abstract:

In vertebrates, certain Hox genes are known to control cellular identities along the anterior-posterior (A-P) axis in the developing hindbrain. In mouse Hoxa3 mutants, truncation of the glossopharyngeal (IXth) nerve or the fusion of the IXth and vagus (Xth) nerves was reported, although its underlying mechanism is largely unknown. To elucidate the mechanism of the IXth nerve defects, we reexamined the phenotype of Hoxa3 mutant embryos. In Hoxa3 mutants, we observed an abnormal caudal stream of the migrating Hoxa3-expressing neural crest cells at the prospective IXth nerve-forming area. Dorsomedial migration of the placode-derived neuronal precursor cells of the IXth nerve was also affected. Motor neurons at rhombomere 6 (r6), where those of the IXth nerve were positioned, often projected axons to the Xth nerve. In summary, the Hoxa3 gene has crucial roles in ensuring the correct axon projection pattern of all three components of the IXth nerve, i.e., motor neurons and sensory neurons of the proximal and distal ganglia.

Funding information:
  • NINDS NIH HHS - R01 NS087632(United States)

Identification and characterization of a cell surface marker for embryonic rat spinal accessory motor neurons.

  • Schubert W
  • J. Comp. Neurol.
  • 2001 Oct 22

Literature context:


Abstract:

The developing mammalian spinal cord contains distinct populations of motor neurons that can be distinguished by their cell body positions, by the expression of specific combinations of regulatory genes, and by the paths that their axons take to exit the central nervous system (CNS). Subclasses of spinal motor neurons are also thought to express specific cell surface proteins that function as receptors which control the guidance of their axons. We identified monoclonal antibody (mAb) SAC1 in a screen aimed at generating markers for specific subsets of neurons/axons in the developing rat spinal cord. During early embryogenesis, mAb SAC1 selectively labels a small subset of Isl1-positive motor neurons located exclusively within cervical segments of the spinal cord. Strikingly, these neurons extend mAb SAC1-positive axons along a dorsally directed trajectory toward the lateral exit points. Consistent with the finding that mAb SAC1 also labels spinal accessory nerves, these observations identify mAb SAC1 as a specific marker of spinal accessory motor neurons/axons. During later stages of embryogenesis, mAb SAC1 is transiently expressed on both dorsally and ventrally projecting spinal motor neurons/axons. Interestingly, mAb SAC1 also labels the notochord and floor plate during most stages of spinal cord development. The mAb SAC1 antigen is a 100-kD glycoprotein that is likely to be the rat homolog of SC1/BEN/DM-GRASP, a homophilic adhesion molecule that mediates axon outgrowth and fasciculation.

The paired homeobox gene Uncx4.1 specifies pedicles, transverse processes and proximal ribs of the vertebral column.

  • Leitges M
  • Development
  • 2000 Jun 14

Literature context:


Abstract:

The axial skeleton develops from the sclerotome, a mesenchymal cell mass derived from the ventral halves of the somites, segmentally repeated units located on either side of the neural tube. Cells from the medial part of the sclerotome form the axial perichondral tube, which gives rise to vertebral bodies and intervertebral discs; the lateral regions of the sclerotome will form the vertebral arches and ribs. Mesenchymal sclerotome cells condense and differentiate into chondrocytes to form a cartilaginous pre-skeleton that is later replaced by bone tissue. Uncx4.1 is a paired type homeodomain transcription factor expressed in a dynamic pattern in the somite and sclerotome. Here we show that mice homozygous for a targeted mutation of the Uncx4.1 gene die perinatally and exhibit severe malformations of the axial skeleton. Pedicles, transverse processes and proximal ribs, elements derived from the lateral sclerotome, are lacking along the entire length of the vertebral column. The mesenchymal anlagen for these elements are formed initially, but condensation and chondrogenesis do not occur. Hence, Uncx4.1 is required for the maintenance and differentiation of particular elements of the axial skeleton.

Funding information:
  • NCRR NIH HHS - RR13642(United States)

A large targeted deletion of Hoxb1-Hoxb9 produces a series of single-segment anterior homeotic transformations.

  • Medina-Martínez O
  • Dev. Biol.
  • 2000 Jun 1

Literature context:


Abstract:

Hox genes regulate axial regional specification during animal embryonic development and are grouped into four clusters. The mouse HoxB cluster contains 10 genes, Hoxb1 to Hoxb9 and Hoxb13, which are transcribed in the same direction. We have generated a mouse strain with a targeted 90-kb deletion within the HoxB cluster from Hoxb1 to Hoxb9. Surprisingly, heterozygous mice show no detectable abnormalities. Homozygous mutant embryos survive to term and exhibit an ordered series of one-segment anterior homeotic transformations along the cervical and thoracic vertebral column and defects in sternum morphogenesis. Neurofilament staining indicates abnormalities in the IXth cranial nerve. Notably, simultaneous deletion of Hoxb1 to Hoxb9 resulted in the sum of phenotypes of single HoxB gene mutants. Although a higher penetrance is observed, no synergistic or new phenotypes were observed, except for the loss of ventral curvature at the cervicothoracic boundary of the vertebral column. Although Hoxb13, the most 5' gene, is separated from the rest by 70 kb, it has been suggested to be expressed with temporal and spatial colinearity. Here, we show that the expression pattern of Hoxb13 is not affected by the targeted deletion of the other 9 genes. Thus, Hoxb13 expression seems to be independent of the deleted region, suggesting that its expression pattern could be achieved independent of the colinear pattern of the cluster or by a regulatory element located 5' of Hoxb9.

The branchial arches and HGF are growth-promoting and chemoattractant for cranial motor axons.

  • Caton A
  • Development
  • 2000 Apr 30

Literature context:


Abstract:

During development, cranial motor neurons extend their axons along distinct pathways into the periphery. For example, branchiomotor axons extend dorsally to leave the hindbrain via large dorsal exit points. They then grow in association with sensory ganglia, to their targets, the muscles of the branchial arches. We have investigated the possibility that pathway tissues might secrete diffusible chemorepellents or chemoattractants that guide cranial motor axons, using co-cultures in collagen gels. We found that explants of dorsal neural tube or hindbrain roof plate chemorepelled cranial motor axons, while explants of cranial sensory ganglia were weakly chemoattractive. Explants of branchial arch mesenchyme were strongly growth-promoting and chemoattractive for cranial motor axons. Enhanced and oriented axon outgrowth was also elicited by beads loaded with Hepatocyte Growth Factor (HGF); antibodies to this protein largely blocked the outgrowth and orientation effects of the branchial arch on motor axons. HGF was expressed in the branchial arches, whilst Met, which encodes an HGF receptor, was expressed by subpopulations of cranial motor neurons. Mice with targetted disruptions of HGF or Met showed defects in the navigation of hypoglossal motor axons into the branchial region. Branchial arch tissue may thus act as a target-derived factor that guides motor axons during development. This influence is likely to be mediated partly by Hepatocyte Growth Factor, although a component of branchial arch-mediated growth promotion and chemoattraction was not blocked by anti-HGF antibodies.

Funding information:
  • PHS HHS - HHSN272200900018C(United States)

Winged helix transcription factor Foxb1 is essential for access of mammillothalamic axons to the thalamus.

  • Alvarez-Bolado G
  • Development
  • 2000 Mar 3

Literature context:


Abstract:

Our aim was to study the mechanisms of brain histogenesis. As a model, we have used the role of winged helix transcription factor gene Foxb1 in the emergence of a very specific morphological trait of the diencephalon, the mammillary axonal complex. Foxb1 is expressed in a large hypothalamic neuronal group (the mammillary body), which gives origin to a major axonal bundle with branches to thalamus, tectum and tegmentum. We have generated mice carrying a targeted mutation of Foxb1 plus the tau-lacZ reporter. In these mutants, a subpopulation of dorsal thalamic ventricular cells "thalamic palisade" show abnormal persistence of Foxb1 transcriptional activity; the thalamic branch of the mammillary axonal complex is not able to grow past these cells and enter the thalamus. The other two branches of the mammillary axonal complex (to tectum and tegmentum) are unaffected by the mutation. Most of the neurons that originate the mammillothalamic axons suffer apoptosis after navigational failure. Analysis of chimeric brains with wild-type and Foxb1 mutant cells suggests that correct expression of Foxb1 in the thalamic palisade is sufficient to rescue the normal phenotype. Our results indicate that Foxb1 is essential for diencephalic histogenesis and that it exerts its effects by controlling access to the target by one particular axonal branch.

Funding information:
  • Medical Research Council - G0900740(United Kingdom)

Targeted disruption of Hoxd9 and Hoxd10 alters locomotor behavior, vertebral identity, and peripheral nervous system development.

  • de la Cruz CC
  • Dev. Biol.
  • 1999 Dec 15

Literature context:


Abstract:

The five most 5' HoxD genes, which are related to the Drosophila Abd-B gene, play an important role in patterning axial and appendicular skeletal elements and the nervous system of developing vertebrate embryos. Three of these genes, Hoxd11, Hoxd12, and Hoxd13, act synergistically to pattern the hindlimb autopod. In this study, we examine the combined effects of two additional 5' HoxD genes, Hoxd9 and Hoxd10. Both of these genes are expressed posteriorly in overlapping domains in the developing neural tube and axial mesoderm as well as in developing limbs. Locomotor behavior in animals carrying a double mutation in these two genes was altered; these alterations included changes in gait, mobility, and adduction. Morphological analysis showed alterations in axial and appendicular skeletal structure, hindlimb peripheral nerve organization and projection, and distal hindlimb musculature. These morphological alterations are likely to provide the substrate for the observed alterations in locomotor behavior. The alterations observed in double-mutant mice are distinct from the phenotypes observed in mice carrying single mutations in either gene, but exhibit most of the features of both individual phenotypes. This suggests that the combined activity of two adjacent Hox genes provides more patterning information than activity of each gene alone. These observations support the idea that adjacent Hox genes with overlapping expression patterns may interact functionally to provide patterning information to the same regions of developing mouse embryos.

Shroom, a PDZ domain-containing actin-binding protein, is required for neural tube morphogenesis in mice.

  • Hildebrand JD
  • Cell
  • 1999 Nov 24

Literature context:


Abstract:

Using gene trap mutagenesis, we have identified a mutation in mice that causes exencephaly, acrania, facial clefting, and spina bifida, all of which can be attributed to failed neural tube closure. This mutation is designated shroom (shrm) because the neural folds "mushroom" outward and do not converge at the dorsal midline. shrm encodes a PDZ domain protein that is involved at several levels in regulating aspects of cytoarchitecture. First, endogenous Shrm localizes to adherens junctions and the cytoskeleton. Second, ectopically expressed Shrm alters the subcellular distribution of F-actin. Third, Shrm directly binds F-actin. Finally, cytoskeletal polarity within the neuroepithelium is perturbed in mutant embryos. In concert, these observations suggest that Shrm is a critical determinant of the cellular architecture required for proper neurulation.

Mice mutant for both Hoxa1 and Hoxb1 show extensive remodeling of the hindbrain and defects in craniofacial development.

  • Rossel M
  • Development
  • 1999 Nov 17

Literature context:


Abstract:

The analysis of mice mutant for both Hoxa1 and Hoxb1 suggests that these two genes function together to pattern the hindbrain. Separately, mutations in Hoxa1 and Hoxb1 have profoundly different effects on hindbrain development. Hoxa1 mutations disrupt the rhombomeric organization of the hindbrain, whereas Hoxb1 mutations do not alter the rhombomeric pattern, but instead influence the fate of cells originating in rhombomere 4. We suggest that these differences are not the consequences of different functional roles for these gene products, but rather reflect differences in the kinetics of Hoxa1 and Hoxb1 gene expression. In strong support of the idea that Hoxa1 and Hoxb1 have overlapping functions, Hoxa1/Hoxb1 double mutant homozygotes exhibit a plethora of defects either not seen, or seen only in a very mild form, in mice mutant for only Hoxa1 or Hoxb1. Examples include: the loss of both rhombomeres 4 and 5, the selective loss of the 2(nd) branchial arch, and the loss of most, but not all, 2(nd) branchial arch-derived tissues. We suggest that the early role for both of these genes in hindbrain development is specification of rhombomere identities and that the aberrant development of the hindbrain in Hoxa1/Hoxb1 double mutants proceeds through two phases, the misspecification of rhombomeres within the hindbrain, followed subsequently by size regulation of the misspecified hindbrain through induction of apoptosis.

Funding information:
  • Austrian Science Fund FWF - P 18986(Austria)

Key roles of retinoic acid receptors alpha and beta in the patterning of the caudal hindbrain, pharyngeal arches and otocyst in the mouse.

  • Dupé V
  • Development
  • 1999 Nov 17

Literature context:


Abstract:

Mouse fetuses carrying targeted inactivations of both the RAR(&agr;) and the RARbeta genes display a variety of malformations in structures known to be partially derived from the mesenchymal neural crest originating from post-otic rhombomeres (e.g. thymus and great cephalic arteries) (Ghyselinck, N., Dupé, V., Dierich, A., Messaddeq, N., Garnier, J.M., Rochette-Egly, C., Chambon, P. and Mark M. (1997). Int. J. Dev. Biol. 41, 425-447). In a search for neural crest defects, we have analysed the rhombomeres, cranial nerves and pharyngeal arches of these double null mutants at early embryonic stages. The mutant post-otic cranial nerves are disorganized, indicating that RARs are involved in the patterning of structures derived from neurogenic neural crest, even though the lack of RARalpha and RARbeta has no detectable effect on the number and migration path of neural crest cells. Interestingly, the double null mutation impairs early developmental processes known to be independent of the neural crest e.g., the initial formation of the 3rd and 4th branchial pouches and of the 3rd, 4th and 6th arch arteries. The double mutation also results in an enlargement of rhombomere 5, which is likely to be responsible for the induction of supernumerary otic vesicles, in a disappearance of the rhombomere 5/6 boundary, and in profound alterations of rhombomere identities. In the mutant hindbrain, the expression domain of kreisler is twice its normal size and the caudal stripe of Krox-20 extends into the presumptive rhombomeres 6 and 7 region. In this region, Hoxb-1 is ectopically expressed, Hoxb-3 is ectopically up-regulated and Hoxd-4 expression is abolished. These data, which indicate that retinoic acid signaling through RARalpha and/or RARbeta is essential for the specification of rhombomere identities and for the control of caudal hindbrain segmentation by restricting the expression domains of kreisler and of Krox-20, also strongly suggest that this signaling plays a crucial role in the posteriorization of the hindbrain neurectoderm.

Funding information:
  • NCRR NIH HHS - UL1 RR024996(United States)

Dlx5 regulates regional development of the branchial arches and sensory capsules.

  • Depew MJ
  • Development
  • 1999 Sep 28

Literature context:


Abstract:

We report the generation and analysis of mice homozygous for a targeted deletion of the Dlx5 homeobox gene. Dlx5 mutant mice have multiple defects in craniofacial structures, including their ears, noses, mandibles and calvaria, and die shortly after birth. A subset (28%) exhibit exencephaly. Ectodermal expression of Dlx5 is required for the development of olfactory and otic placode-derived epithelia and surrounding capsules. The nasal capsules are hypoplastic (e.g. lacking turbinates) and, in most cases, the right side is more severely affected than the left. Dorsal otic vesicle derivatives (e. g. semicircular canals and endolymphatic duct) and the surrounding capsule, are more severely affected than ventral (cochlear) structures. Dlx5 is also required in mandibular arch ectomesenchyme, as the proximal mandibular arch skeleton is dysmorphic. Dlx5 may control craniofacial development in part through the regulation of the goosecoid homeobox gene. goosecoid expression is greatly reduced in Dlx5 mutants, and both goosecoid and Dlx5 mutants share a number of similar craniofacial malformations. Dlx5 may perform a general role in skeletal differentiation, as exemplified by hypomineralization within the calvaria. The distinct focal defects within the branchial arches of the Dlx1, Dlx2 and Dlx5 mutants, along with the nested expression of their RNAs, support a model in which these genes have both redundant and unique functions in the regulation of regional patterning of the craniofacial ectomesenchyme.

Funding information:
  • NHLBI NIH HHS - HL66621(United States)

Expression and genetic interaction of transcription factors GATA-2 and GATA-3 during development of the mouse central nervous system.

  • Nardelli J
  • Dev. Biol.
  • 1999 Jun 15

Literature context:


Abstract:

Here we examine the expression of transcription factors GATA-2 and GATA-3 during early stages of embryonic development in the central nervous system (CNS) of the mouse. GATA-2 is expressed as early as 9 dpc in the hindbrain, in ventral rhombomere 4, and transiently in ventral rhombomere 2 (r2). From 9.5 to 11.5 dpc, activation of the gene spreads to many sites of early neuronal differentiation, such as the olfactory bulbs, the pretectum, and the oculomotor nucleus in the midbrain, a thin stripe of cells lining the floor plate from the mesencephalon to the cervical spinal cord and a ventral column of cells spanning the neural tube from rostral hindbrain and including motor neuron as well as ventral interneuron precursors. GATA-3 is expressed in a pattern very similar to that of GATA-2. Distinguishing features are the lack of expression in r2 at 9 dpc and a slight delay in its activation. In addition, GATA-2 is activated in both the ventricular and the subventricular zones of the neural tube, whereas GATA-3 is restricted mainly to the subventricular zone. Expression analyses performed on GATA-2 -/- mouse embryos between E9.5 and 10.5 dpc established that: (i) the expression of GATA-3 in the developing CNS of the mouse embryo is dependent on the presence of GATA-2 and (ii) loss of GATA-2 leads to severe defects in neurogenesis, which strongly suggests that GATA-2 is involved, as in hematopoiesis, in the maintenance of the pool of ventral neuronal progenitors.

Hoxa1 and Krox-20 synergize to control the development of rhombomere 3.

  • Helmbacher F
  • Development
  • 1998 Dec 18

Literature context:


Abstract:

The transcription factor genes Hoxa1 and Krox-20 have been shown to play important roles in vertebrate hindbrain segmentation. In this report, we present evidence for novel functions of these genes which co-operate in specifying cellular identity in rhombomere (r) 3. Although Hoxa1 has not been observed to be expressed rostrally to the prospective r3/r4 boundary, its inactivation results in (i) the appearance of patches of cells presenting an r2-like molecular identity within r3, (ii) early neuronal differentiation in r3, normally characteristic of even-numbered rhombomeres, and (iii) abnormal navigation of r3 motor axons, similar to that observed in even-numbered rhombomeres. These phenotypic manifestations become more severe in the context of the additional inactivation of one allele of the Krox-20 gene, demonstrating that Hoxa1 and Krox-20 synergize in a dosage-dependent manner to specify r3 identity and odd- versus even-numbered rhombomere characters. In addition, these data suggest that the control of the development of r3 may not be autonomous but dependent on interactions with Hoxa1-expressing cells.

Funding information:
  • NIGMS NIH HHS - GM41624(United States)

Hoxa1 and Hoxb1 synergize in patterning the hindbrain, cranial nerves and second pharyngeal arch.

  • Gavalas A
  • Development
  • 1998 Mar 1

Literature context:


Abstract:

The analysis of Hoxa1 and Hoxb1 null mutants suggested that these genes are involved in distinct aspects of hindbrain segmentation and specification. Here we investigate the possible functional synergy of the two genes. The generation of Hoxa1(3'RARE)/Hoxb1(3'RARE) compound mutants resulted in mild facial motor nerve defects reminiscent of those present in the Hoxb1 null mutants. Strong genetic interactions between Hoxa1 and Hoxb1 were uncovered by introducing the Hoxb1(3'RARE) and Hoxb1 null mutations into the Hoxa1 null genetic background. Hoxa1(null)/Hoxb1(3'RARE) and Hoxa1(null)/Hoxb1(null )double homozygous embryos showed additional patterning defects in the r4-r6 region but maintained a molecularly distinct r4-like territory. Neurofilament staining and retrograde labelling of motor neurons indicated that Hoxa1 and Hoxb1 synergise in patterning the VIIth through XIth cranial nerves. The second arch expression of neural crest cell markers was abolished or dramatically reduced, suggesting a defect in this cell population. Strikingly, the second arch of the double mutant embryos involuted by 10.5 dpc and this resulted in loss of all second arch-derived elements and complete disruption of external and middle ear development. Additional defects, most notably the lack of tympanic ring, were found in first arch-derived elements, suggesting that interactions between first and second arch take place during development. Taken together, our results unveil an extensive functional synergy between Hoxa1 and Hoxb1 that was not anticipated from the phenotypes of the simple null mutants.

Funding information:
  • NLM NIH HHS - 4R00LM-010943-02(United States)

Vinculin knockout results in heart and brain defects during embryonic development.

  • Xu W
  • Development
  • 1998 Jan 12

Literature context:


Abstract:

The vinculin gene codes for a cytoskeletal protein, found in focal adhesion plaques and in cell-cell adherens junctions. Vinculin was inactivated by homologous recombination using a targeting vector in embryonic stem (ES) cells. The heterozygous ES cells were introduced into mice by established procedures to produce heterozygous animals that were normal and fertile. No homozygous vinculin-/- embryos were born and analyses during the gestational period showed that the vinculin null embryos were small and abnormal from day E8 but some survived until E10. The most prominent defect was lack of midline fusion of the rostral neural tube, producing a cranial bilobular appearance and attenuation of cranial and spinal nerve development. Heart development was curtailed at E9.5, with severely reduced and akinetic myocardial and endocardial structures. Mutant embryos were 30-40% smaller, somites and limbs were retarded and ectodermal tissues were sparse and fragile. Fibroblasts (MEF) isolated from mutant embryos were shown to have reduced adhesion to fibronectin, vitronectin, laminin and collagen compared to wild-type levels. In addition, migration rates over these substrata were two-fold higher and the level of focal adhesion kinase (FAK) activity was three-fold higher. We conclude that vinculin is necessary for normal embryonic development, probably because of its role in the regulation of cell adhesion and locomotion, cell behaviors essential for normal embryonic morphogenesis, although specific roles in neural and cardiac development cannot be ruled out.

Funding information:
  • NHGRI NIH HHS - P41HG002273-09S1(United States)

Hox group 3 paralogous genes act synergistically in the formation of somitic and neural crest-derived structures.

  • Manley NR
  • Dev. Biol.
  • 1997 Dec 15

Literature context:


Abstract:

Hox genes encode transcription factors that are used to regionalize the mammalian embryo. Analysis of mice carrying targeted mutations in individual and multiple Hox genes is beginning to reveal a complex network of interactions among these closely related genes which is responsible for directing the formation of spatially restricted tissues and structures. In this report we present an analysis of the genetic interactions between all members of the third paralogous group, Hoxa3, Hoxb3, and Hoxd3. Previous analysis has shown that although mice homozygous for loss-of-function mutations in either Hoxa3 or Hoxd3 have no defects in common, mice mutant for both genes demonstrate that these two genes strongly interact in a dosage-dependent manner. To complete the analysis of this paralogous gene family, mice with a targeted disruption of the Hoxb3 gene were generated. Homozygous mutants have minor defects at low penetrance in the formation of both the cervical vertebrae and the IXth cranial nerve. Analysis and comparison of all double-mutant combinations demonstrate that all three members of this paralogous group interact synergistically to affect the development of both neuronal and mesenchymal neural crest-derived structures, as well as somitic mesoderm-derived structures. Surprisingly, with respect to the formation of the cervical vertebrae, mice doubly mutant for Hoxa3 and Hoxd3 or Hoxb3 and Hoxd3 show an indistinguishable defect, loss of the entire atlas. This suggests that the identity of the specific Hox genes that are functional in a given region may not be as critical as the total number of Hox genes operating in that region.

Funding information:
  • NIMH NIH HHS - R13-MH066849(United States)

Targeted disruption of Hoxd-10 affects mouse hindlimb development.

  • Carpenter EM
  • Development
  • 1997 Nov 22

Literature context:


Abstract:

Targeted disruption of the Hoxd-10 gene, a 5' member of the mouse HoxD linkage group, produces mice with hindlimb-specific defects in gait and adduction. To determine the underlying causes of this locomotor defect, mutant mice were examined for skeletal, muscular and neural abnormalities. Mutant mice exhibit alterations in the vertebral column and in the bones of the hindlimb. Sacral vertebrae beginning at the level of S2 exhibit homeotic transformations to adopt the morphology of the next most anterior vertebra. In the hindlimb, there is an anterior shift in the position of the patella, an occasional production of an anterior sesamoid bone, and an outward rotation of the lower part of the leg, all of which contribute to the defects in locomotion. No major alterations in hindlimb musculature were observed, but defects in the nervous system were evident. There was a decrease in the number of spinal segments projecting nerve fibers through the sacral plexus to innervate the musculature of the hindlimb. Deletion of a hindlimb nerve was seen in some animals, and a shift was evident in the position of the lumbar lateral motor column. These observations suggest a role for the Hoxd-10 gene in establishing regional identity within the spinal cord and imply that patterning of the spinal cord may have intrinsic components and is not completely imposed by the surrounding mesoderm.

Funding information:
  • NIGMS NIH HHS - P41 GM103545(United States)

Role of Hoxa-2 in axon pathfinding and rostral hindbrain patterning.

  • Gavalas A
  • Development
  • 1997 Oct 11

Literature context:


Abstract:

Segmentation plays an important role in neuronal diversification and organisation in the developing hindbrain. For instance, cranial nerve branchiomotor nuclei are organised segmentally within the basal plates of successive pairs of rhombomeres. To reach their targets, motor axons follow highly stereotyped pathways exiting the hindbrain only via specific exit points in the even-numbered rhombomeres. Hox genes are good candidates for controlling this pathfinding, since they are segmentally expressed and involved in rhombomeric patterning. Here we report that in Hoxa-2(-/-) embryos, the segmental identities of rhombomere (r) 2 and r3 are molecularly as well as anatomically altered. Cellular analysis by retrograde dye labelling reveals that r2 and r3 trigeminal motor axons turn caudally and exit the hindbrain from the r4 facial nerve exit point and not from their normal exit point in r2. Furthermore, dorsal r2-r3 patterning is affected, with loss of cochlear nuclei and enlargement of the lateral part of the cerebellum. These results point to a novel role for Hoxa-2 in the control of r2-r3 motor axon guidance, and also suggest that its absence may lead to homeotic changes in the alar plates of these rhombomeres.

Funding information:
  • NINDS NIH HHS - 1-R01 NS054814-05(United States)

The Evi1 proto-oncogene is required at midgestation for neural, heart, and paraxial mesenchyme development.

  • Hoyt PR
  • Mech. Dev.
  • 1997 Sep 25

Literature context:


Abstract:

The ecotropic viral integration site-1 (Evi1) locus was initially identified as a common site of retroviral integration in myeloid tumors of the AKXD-23 recombinant inbred mouse strain. The full-length Evi1 transcript encodes a putative transcription factor, containing ten zinc finger motifs found within two domains of the protein. To determine the biological function of the Evi1 proto-oncogene, the full-length, but not an alternately spliced, transcript was disrupted using targeted mutagenesis in embryonic stem cells. Evi1 homozygous mutant embryos die at approximately 10.5 days post coitum. Mutants were distinguished at 10.5 days post coitum by widespread hypocellularity, hemorrhaging, and disruption in the development of paraxial mesenchyme. In addition, defects in the heart, somites, and cranial ganglia were detected and the peripheral nervous system failed to develop. These results correlated with whole-mount in situ hybridization analyses of embryos which showed expression of the Evi1 proto-oncogene in embryonic mesoderm and neural crest-derived cells associated with the peripheral nervous system. These data suggest that Evi1 has important roles in general cell proliferation, vascularization, and cell-specific developmental signaling, at midgestation.

Funding information:
  • NLM NIH HHS - T15 LM009451(United States)

Cadherin-6 expression transiently delineates specific rhombomeres, other neural tube subdivisions, and neural crest subpopulations in mouse embryos.

  • Inoue T
  • Dev. Biol.
  • 1997 Mar 15

Literature context:


Abstract:

Mammalian cadherin-6 (K-cadherin, cad6) was originally identified by means of the polymerase chain reaction, but its biological functions have not yet been determined. We analyzed the expression pattern of the mouse homologue of this cadherin during development and found that it was transiently expressed in restricted rhombomeres and in other subdivisions of the neural plate and tube. In the midbrain and anterior hindbrain of E8.0-8.5 embryos, cad6 was expressed only in neural crest-generating regions. In contrast, in the posterior hindbrain and contiguous spinal cord of these embryos, cad6 occurred throughout the neural plate, forming a sharp anterior limit at the future rhombomere 4 and 5 boundary. Subsequently, this neural plate expression became confined to rhombomere 6, although most of the neural crest-generating areas remained positive throughout the body. Neural crest cells expressing cad6 migrated out of the neural tube, and subsequently accumulated mainly along peripheral nerves. We then studied the effect of Hoxa-1 mutation on the expression of cad6, as their expressions spatiotemporally overlapped with each other in the early posterior hindbrain. In E8.0-8.5 Hoxa-1 mutants, cad6 expression was suppressed in the region of rhombomeres 4 to 6, although that in the other regions was not essentially affected. At later stages, however, cad6-positive crest cells appeared and migrated out of rhombomeres 4 to 6, indicating that the suppression of cad6 expression was transient and restricted to early stages. Importantly, this effect of the Hoxa-1 mutation concurred with the timing of the expression of this gene. We also studied Hoxa-3 mutants, but found no effect of this mutation on the cad6 expression pattern. These findings suggest that cad6 may contribute to the formation of the segmental structure of the early brain through its ability to confer specific adhesiveness on cells and that Hoxa-1 may be required for early cad6 expression in the posterior hindbrain.

Funding information:
  • Canadian Institutes of Health Research - (Canada)

Evidence that absence of Wnt-3a signaling promotes neuralization instead of paraxial mesoderm development in the mouse.

  • Yoshikawa Y
  • Dev. Biol.
  • 1997 Mar 15

Literature context:


Abstract:

Wnt-3a mutant embryos show defects caudal to the forelimb level; somites are absent, the notochord is disrupted, and the central nervous system has a pronounced dysmorphology. Previous studies revealed that the primary defects of the mutant embryos are likely to be in the process of paraxial mesoderm formation. In this study, we analyzed the phenotype of Wnt-3a mutant embryos at early somite stages (8.0 days post coitum), when somite formation is initiated. In Wnt-3a mutants, cells which have ingressed through the primitive streak do not migrate laterally but remain under the streak and form an ectopic tubular structure. Several neural-specific molecular markers, but no paraxial mesoderm markers, are expressed in this structure, suggesting that the ectopic tube is an additional neural tube. In normal embryos, Wnt-3a is expressed in the primitive ectoderm, including the cells which are fated to give rise to the paraxial mesoderm and neurectoderm, but expression is absent in migrating mesoderm cells. These results suggest that Wnt-3a signaling may play a role in regulating paraxial mesodermal fates, at the expense of neurectodermal fates, within the primitive ectoderm of the gastrulating mouse embryo.

Funding information:
  • Howard Hughes Medical Institute - R01 NS054814-06(United States)

In vivo functional analysis of the Hoxa-1 3' retinoic acid response element (3'RARE).

  • Dupé V
  • Development
  • 1997 Jan 13

Literature context:


Abstract:

Retinoids are essential for normal development and both deficiency and excess of retinoic acid (RA) are teratogenic. Retinoic acid response elements (RAREs) have been identified in Hox gene promoters suggesting that endogenous retinoids may be involved in the direct control of Hox gene patterning functions. In order to test this hypothesis, we have mutated the Hoxa-1 3'RARE using the Cre-loxP targeting strategy, and studied its functional role during mouse development. We find that this enhancer plays an important role in the early establishment of the Hoxa-1 anterior expression boundary in the neural plate. This early disturbance in Hoxa-1 activation results in rhombomere and cranial nerve abnormalities reminiscent of those obtained in the Hoxa-1 total knockout, although their severity and penetrance are lower, thus providing strong evidence for direct control of Hox gene function by retinoids during normal development. Interestingly, we also find that the Hoxa-1 expression response to RA treatment is not entirely controlled by the RARE, suggesting the existence of other retinoid-induced factors mediating the Hoxa-1 response to RA and/or the presence of additional RAREs. Interestingly, although the RARE is not required for the spatiotemporal control of colinear expression of the Hoxa genes, it is absolutely required for correct Hoxa-2 expression in rhombomere 5.

Funding information:
  • NIDA NIH HHS - R01 DA014546(United States)
  • NINDS NIH HHS - NS24698(United States)

Targeted disruption of hoxc-4 causes esophageal defects and vertebral transformations.

  • Boulet AM
  • Dev. Biol.
  • 1996 Jul 10

Literature context:


Abstract:

Mice carrying a nonfunctional allele of hoxc-4 have been generated by gene targeting. The phenotype of mice homozygous for this mutation is strikingly different from those reported in mice lacking the paralogous genes hoxa-4, hoxb-4, and hoxd-4. In contrast to the mutants of the paralogous family members, hoxc-4 homozygotes do not manifest abnormalities in the cervical vertebrae, but instead show vertebral defects that extend from the second thoracic vertebra (t2) to t11. Therefore, defects do not correspond to the anterior limit of expression of hoxc-4, but rather begin within the region of strong hoxc-4 expression in the prevertebral anlagen (i.e., pv7-14). While hoxc-4 mutant homozygotes that reach adulthood are fertile and appear outwardly normal, most die before weaning age. The high lethality appears to result from partial or complete blockage of the lumen of the esophagus over a large portion of its length, as well as disorganization of the esophageal musculature. Although the Drosophila homolog of hoxc-4, Deformed, is autoregulated, mutation of the hoxc-4 gene does not affect transcription of its paralogous family members. However, in hoxc-4 mutant embryos, transcription of both the hoxc-5 and hoxc-6 genes is altered. Employment of cissolidustrans analysis showed that the hoxc-4 mutation acts in cis to affect the pattern of hoxc-5 expression. Therefore, this mutation is likely to cause a reduction of hoxc-5 function as well as complete loss of hoxc-4 function.

Funding information:
  • Medical Research Council - G0001354(United Kingdom)

Mice lacking all isoforms of retinoic acid receptor beta develop normally and are susceptible to the teratogenic effects of retinoic acid.

  • Luo J
  • Mech. Dev.
  • 1995 Sep 27

Literature context:


Abstract:

Retinoic acids (RA) are vitamin A derivatives essential for normal embryonic development and viability of vertebrates. The RA signal is mediated by two distinct classes of receptors, RA receptors (RARs) and retinoid X receptors (RXRs). The RAR family is composed of three genes: RAR alpha, beta, and gamma. The expression of RAR beta gene is spatially and temporally restricted in certain structures in the developing embryo, suggesting that RAR beta could play specific roles during morphogenesis. Four isoforms of the RAR beta gene (beta 1-beta 4) are generated by differential usage of promoters and alternative splicing. It has recently been demonstrated that the RAR beta 2 isoform is dispensable for normal development. To ascertain the function of all RAR beta isoforms in vivo, we have generated a mutation that disrupts all isoforms of the RAR beta gene in the mouse by gene targeting in embryonic stem cells. Mice homozygous for the mutation are viable and fertile with no externally apparent abnormalities. During development, 1/11 RAR beta mutant embryos showed fusion of the ninth and tenth cranial ganglia on both sides of the hindbrain. However, no obvious alterations in the spatial pattern of expression of Hoxb-1, Hoxb-4 and Hoxb-5 were observed in day 9.5 p.c. embryos. The RAR beta null mutation did not alter the pattern or extent of the limb and craniofacial malformations induced by RA excess, suggesting that RAR beta may not be mandatory to mediate the observed teratological effects of RA in these structures. These experiments demonstrate that RAR beta isoforms are not absolutely required for embryonic development and provide additional support to the concept of functional redundancy among members of the RAR family.

Funding information:
  • Cancer Research UK - CA095525(United Kingdom)

Involvement of Wnt-1 in the formation of the mes/metencephalic boundary.

  • Bally-Cuif L
  • Mech. Dev.
  • 1995 Sep 27

Literature context:


Abstract:

Wnt-1, a putative signaling molecule, is required before the 7 somite stage (E8.5) for the development of midbrain structures in the mouse. We show here that Wnt-1 is also needed for the formation of a boundary between the mesencephalic and metencephalic domains of the neural tube. In embryos homozygous for the Wnt-1sw allele, mesencephalic and metencephalic markers fail to segregate and the establishment of a straight limit of Otx-2 and Wnt-1 expression at the mid-hindbrain junction is impaired. In addition, as observed previously in heterotopic mes/metencephalic transplantation experiments in avian embryos, Wnt-1 expression is induced at the border of ectopic mes- and metencephalic islands observed in Wnt-1sw/sw mutants, suggesting that, in situ, interactions between mes- and metencephalic cells reinforce Wnt-1 expression at the boundary.

Funding information:
  • NCRR NIH HHS - UL1 RR024996(United States)

Chemorepulsion of developing motor axons by the floor plate.

  • Guthrie S
  • Neuron
  • 1995 Jun 11

Literature context:


Abstract:

In the developing nervous system, motor axons grow away from the ventral midline floor plate, suggesting that the latter might be a source of repulsive axonal guidance cues. In donor to host transplantation experiments, ectopic pieces of floor plate were positioned between chick hindbrain motor neurons and their exit points. Immunohistochemistry and retrograde axonal labeling techniques demonstrated that motor axons diverted from their normal pathways to avoid grafted floor plate, often traversing abnormally long circuitous trajectories to reach exit points. When ventral explants of rat hindbrain and spinal cord were cocultured at a distance from floor plate explants within collagen gel matrices, the outgrowth of motor axons was dramatically reduced from explant borders that faced the floor plate. Thus, the floor plate secretes diffusible repulsive cues in vitro that may exclude motor axons from the midline during development.

Funding information:
  • PHS HHS - NIH-NINDS R37-31146(United States)

Notch1 is required for the coordinate segmentation of somites.

  • Conlon RA
  • Development
  • 1995 May 27

Literature context:


Abstract:

Members of the Notch family of transmembrane receptors mediate a number of developmental decisions in invertebrates. In order to study Notch function in a vertebrate organism, we have mutated the Notch1 gene of the mouse. Notch1 gene function is required for embryonic survival in the second half of gestation. In the first half of gestation, we have found no effect of the mutation on the normal programs of neurogenesis, myogenesis or apoptosis. We conclude that Notch1 function is not essential for these processes, at least in early postimplantation development. However, we have found that somitogenesis is delayed and disorganized in Notch1 mutant embryos. We propose that Notch1 normally coordinates the process of somitogenesis, and we provide a model of how this might occur.

Funding information:
  • Medical Research Council - G0900414(United Kingdom)

Targeted disruptions of the murine Hoxa-4 and Hoxa-6 genes result in homeotic transformations of components of the vertebral column.

  • Kostic D
  • Mech. Dev.
  • 1994 Nov 22

Literature context:


Abstract:

It is becoming clear that Hox genes, which encode transcription factors of the Antennapedia homeodomain family, are key players in establishing the body plan of mammalian embryos. They have already been implicated in the formation of the central nervous system, tissues derived from neural crest, the vertebral column and the limbs. In order to examine the roles of hoxa-4 and hoxa-6 during development, mice with targeted disruptions in these genes were generated. Each shows homeotic transformation of cervical vertebrae, at positions that approximate the anterior borders of expression of these genes in the prevertebrae. Defects were not observed in other tissues that normally express these genes. Hoxa-4-/hoxa-4- mice show, with 100% penetrance, anterior transformations of the dorsal aspects of the third cervical vertebra by acquiring features normally associated with the second cervical vertebra. Mice homozygous for the hoxa-6 mutation show, with incomplete penetrance, even on opposite sides of the same animal, posterior transformations of the seventh cervical vertebra to the first thoracic vertebra. In addition, both hoxa-4-/hoxa-4- and hoxa-6-/hoxa-6- mice show variability in expressivity. These data indicate that alternative genetic pathways can partially, and at times completely, substitute for the function of these two genes. Other members of these two paralogous Hox families are good candidates for providing the substitutions. As paralogous genes lie on different chromosomes, it is possible to examine the degree of redundancy among these genes by intercrossing mice with the appropriate individual disruptions. The analysis of double, triple and even quadruple mutants should determine the ways in which these Hox genes interact in order to specify the multitude of tissues in a restricted region of the developing mouse embryo.

Funding information:
  • NHGRI NIH HHS - P01-35HG000205(United States)
  • NINDS NIH HHS - NS25054(United States)

Ectopic Hoxa-1 induces rhombomere transformation in mouse hindbrain.

  • Zhang M
  • Development
  • 1994 Sep 23

Literature context:


Abstract:

Homeobox genes are expressed with a specific spatial and temporal order, which is essential for pattern formation during the early development of both invertebrates and vertebrates. Here we show that widespread ectopic expression of the Hoxa-1 (Hox 1.6) gene directed by a human beta-actin promoter in transgenic mice is embryolethal and produces abnormal phenotypes in a subset of domains primarily located in anterior regions. Interestingly, this abnormal development in the Hoxa-1 transgenic mice is associated with ectopic expression of the Hoxb-1 (Hox 2.9) gene in select hindbrain regions. At gestation day 9.5, two domains of strong Hoxb-1 expression are found in the anterior region of the hindbrains of Hoxa-1 transgenic embryos. One region represents the normal pattern of Hoxb-1 expression in rhombomere 4 and its associated migrating neural crest cells, while another major domain of Hoxb-1 expression consistently appears in rhombomere 2. Similar ectopic domains of beta-galactosidase activity are detected in dual transgenic embryos containing both beta-actin/Hoxa-1 transgene and a Hoxb-1/lacZ reporter construct. Expression of another lacZ reporter gene that directs beta-galactosidase activity predominantly in rhombomere 2 is suppressed in the Hoxa-1 transgenic embryos. We have also detected weaker and variable ectopic Hoxb-1 expression in rhombomeres 1, 3 and 6. No ectopic Hoxb-1 expression is detected in rhombomere 5 and the expression of Hoxa-3 and Krox-20 in this region is unchanged in the Hoxa-1 transgenic embryos. While no obvious change in the morphology of the trigeminal or facial-acoustic ganglia is evident, phenotypic changes do occur in neurons that emanate from rhombomeres 2 and 3 in the Hoxa-1 transgenic embryos. Additionally, alterations in the pattern of Hoxa-2 and Hoxb-1 expression in a subpopulation of neural crest cells migrating from the rhombomere 2 region are detected in these transgenics. Taken together, these data suggest that ectopic Hoxa-1 expression can reorganize select regions of the developing hindbrain by inducing partial transformations of several rhombomeres into a rhombomere-4-like identity.

Funding information:
  • NCRR NIH HHS - P41 RR008605(United States)

The kreisler mouse: a hindbrain segmentation mutant that lacks two rhombomeres.

  • McKay IJ
  • Development
  • 1994 Aug 31

Literature context:


Abstract:

kreisler is a recessive mutation resulting in gross malformation of the inner ear of homozygous mice. The defects in the inner ear are related to abnormalities in the hindbrain of the embryo, adjacent to the ear rudiments. At E9.5, the neural tube posterior to the boundary between the third and fourth rhombomeres, r3 and r4, appears unsegmented, and the region that would normally correspond to r4 is unusually thick-walled and contains many dying cells. The absence of morphological segmentation in the posterior hindbrain corresponds to an altered pattern of gene expression in that region, with major abnormalities posterior to the r4/5 boundary and minor abnormalities anterior to it. From the expression patterns at E9.5 of Krox-20, Hoxb-1 (Hox 2.9), Hoxb-2 (Hox 2.8), Hoxa-3 (Hox 1.5), Hoxd-4 (Hox 4.2) and cellular retinoic-acid binding protein I (CRABP I), it appears that the fundamental defect is a loss of r5 and r6. Correspondingly, the glossopharyngeal ganglion and nerve, associated with r6 are missing and the abducens nerve, which originates from r5 and r6, is also absent. Examination of Krox-20 expression at stages as early as E8.5 indicates that Krox-20 fails ever to be expressed in its r5 domain in the homozygous kreisler mutant. The abnormal amount of cell death is seen only later. An interpretation is that the cells that would normally become specified at an early stage as r5 and r6 adopt an r4 character instead, producing an excess of r4 cells that is disposed of subsequently by cell death.

Funding information:
  • NINDS NIH HHS - NS 27694(United States)
  • NLM NIH HHS - R01-LM008106(United States)

Multiple developmental defects in Engrailed-1 mutant mice: an early mid-hindbrain deletion and patterning defects in forelimbs and sternum.

  • Wurst W
  • Development
  • 1994 Jul 1

Literature context:


Abstract:

During mouse development, the homeobox-containing gene En-1 is specifically expressed across the mid-hindbrain junction, the ventral ectoderm of the limb buds, and in regions of the hindbrain, spinal cord, somites and somite-derived tissues. To address the function of En-1 during embryogenesis, we have generated mice homozygous for a targeted deletion of the En-1 homeobox. En-1 mutant mice died shortly after birth and exhibited multiple developmental defects. In the brains of newborn mutants, most of the colliculi and cerebellum were missing and the third and fourth cranial nerves were absent. A deletion of midhindbrain tissue was observed as early as 9.5 days of embryonic development and the phenotype resembles that previously reported for Wnt-1 mutant mice. In addition, patterning of the forelimb paws and sternum was disrupted, and the 13th ribs were truncated. The results of these studies suggest a cell autonomous role for En-1 in generation and/or survival of mid-hindbrain precursor cells and also a non-cell autonomous role in signalling normal development of the limbs and possibly sternum.

Funding information:
  • NIDA NIH HHS - R21 DA13754-01(United States)

Mice homozygous for a targeted disruption of the proto-oncogene int-2 have developmental defects in the tail and inner ear.

  • Mansour SL
  • Development
  • 1993 Jan 29

Literature context:


Abstract:

We derived mice that carry a targeted insertion of a neor gene in the int-2 (Fgf-3) proto-oncogene coding sequences. The mutation was found to be recessive and mice that were homozygous for the insertion did not often survive to adulthood. The mutant mice had defects in the development of the tail and inner ear that could be correlated with disruption of int-2 expression in the posterior primitive streak and hindbrain or otic vesicle. While the tail phenotype was 100% penetrant, we found that the inner ear phenotype had reduced penetrance and variable expressivity. The variable expressivity could not be attributed to variability in the genetic background of the mutant allele or to leaky expression from the mutant allele. Thus, we conclude that even in a uniform genetic background, stochastic variation in the expression of a developmental circuit can result in dramatic differences in phenotypic consequences.

Funding information:
  • NHGRI NIH HHS - HG 02273(United States)

Spatial regulation of axonal glycoprotein expression on subsets of embryonic spinal neurons.

  • Dodd J
  • Neuron
  • 1988 Apr 6

Literature context:


Abstract:

The identification of surface proteins restricted to subsets of embryonic axons and growth cones may provide information on the mechanisms underlying axon fasciculation and pathway selection in the vertebrate nervous system. We describe here the characterization of a 135 kd cell surface glycoprotein, TAG-1, that is expressed transiently on subsets of embryonic spinal cord axons and growth cones. TAG-1 is immunochemically distinct from the cell adhesion molecules N-CAM and L1 (NILE) and is expressed on commissural and motor neurons over the period of initial axon extension. Moreover, TAG-1 and L1 appear to be segregated on different segments of the same embryonic spinal axons. These observations provide evidence that axonal guidance and pathway selection in vertebrates may be regulated in part by the transient and selective expression of distinct surface glycoproteins on subsets of developing neurons.

Funding information:
  • NHGRI NIH HHS - P01 HG004120(United States)