Literature context: 16046; RRID:AB_2107107 rabbit anti-Tbr1 Abcam Cat# ab3
The mechanisms instructing genesis of neuronal subtypes from mammalian neural precursors are not well understood. To address this issue, we have characterized the transcriptional landscape of radial glial precursors (RPs) in the embryonic murine cortex. We show that individual RPs express mRNA, but not protein, for transcriptional specifiers of both deep and superficial layer cortical neurons. Some of these mRNAs, including the superficial versus deep layer neuron transcriptional regulators Brn1 and Tle4, are translationally repressed by their association with the RNA-binding protein Pumilio2 (Pum2) and the 4E-T protein. Disruption of these repressive complexes in RPs mid-neurogenesis by knocking down 4E-T or Pum2 causes aberrant co-expression of deep layer neuron specification proteins in newborn superficial layer neurons. Thus, cortical RPs are transcriptionally primed to generate diverse types of neurons, and a Pum2/4E-T complex represses translation of some of these neuronal identity mRNAs to ensure appropriate temporal specification of daughter neurons.
Literature context: 16046, RRID:AB_2107107 guinea pig anti-En1 Thomas Jess
Walking is the predominant locomotor behavior expressed by land-dwelling vertebrates, but it is unknown when the neural circuits that are essential for limb control first appeared. Certain fish species display walking-like behaviors, raising the possibility that the underlying circuitry originated in primitive marine vertebrates. We show that the neural substrates of bipedalism are present in the little skate Leucoraja erinacea, whose common ancestor with tetrapods existed ∼420 million years ago. Leucoraja exhibits core features of tetrapod locomotor gaits, including left-right alternation and reciprocal extension-flexion of the pelvic fins. Leucoraja also deploys a remarkably conserved Hox transcription factor-dependent program that is essential for selective innervation of fin/limb muscle. This network encodes peripheral connectivity modules that are distinct from those used in axial muscle-based swimming and has apparently been diminished in most modern fish. These findings indicate that the circuits that are essential for walking evolved through adaptation of a genetic regulatory network shared by all vertebrates with paired appendages. VIDEO ABSTRACT.
Literature context: tibody, 1:2,000 (Abcam ab16046, RRID:AB_2107107) in BioSite Histo antibody dilu
The Ntsr1-Cre GN220 mouse expresses Cre-recombinase in corticothalamic (CT) neurons in neocortical layer 6. It is not known if the other major types of pyramidal neurons in this layer also express this enzyme. By electrophysiological recordings in slices and histological analysis of the uptake of retrogradely transported beads we show that Cre-positive neurons are CT and not corticocortical or corticoclaustral types. Furthermore, we show that Ntsr1-Cre-positive cells are immuno-positive for the nuclear transcription factor Forkhead box protein P2 (FoxP2). We conclude that Cre-expression is limited to a specific type of pyramidal neuron: CT. However, it appears as not all CT neurons are Cre-expressing; there are indications that the penetrance of the gene is about 90%. We demonstrate the utility of assigning a specific identity to individual neurons by determining that the CT neurons are potently modulated by acetylcholine acting on both nicotinic and muscarinic acetylcholine receptors. These results corroborate the suggested function of these neurons in regulating the gain of thalamocortical transfer of sensory information depending on attentional demand and state of arousal.
Literature context: am, RRID:AB_2107107), goat anti-Foxp2 (1:1000, Abca
The intercalated cells (ITCs) of the amygdala have been shown to be critical regulatory components of amygdalar circuits, which control appropriate fear responses. Despite this, the molecular processes guiding ITC development remain poorly understood. Here we establish the zinc finger transcription factor Tshz1 as a marker of ITCs during their migration from the dorsal lateral ganglionic eminence through maturity. Using germline and conditional knock-out (cKO) mouse models, we show that Tshz1 is required for the proper migration and differentiation of ITCs. In the absence of Tshz1, migrating ITC precursors fail to settle in their stereotypical locations encapsulating the lateral amygdala and BLA. Furthermore, they display reductions in the ITC marker Foxp2 and ectopic persistence of the dorsal lateral ganglionic eminence marker Sp8. Tshz1 mutant ITCs show increased cell death at postnatal time points, leading to a dramatic reduction by 3 weeks of age. In line with this, Foxp2-null mutants also show a loss of ITCs at postnatal time points, suggesting that Foxp2 may function downstream of Tshz1 in the maintenance of ITCs. Behavioral analysis of male Tshz1 cKOs revealed defects in fear extinction as well as an increase in floating during the forced swim test, indicative of a depression-like phenotype. Moreover, Tshz1 cKOs display significantly impaired social interaction (i.e., increased passivity) regardless of partner genetics. Together, these results suggest that Tshz1 plays a critical role in the development of ITCs and that fear, depression-like and social behavioral deficits arise in their absence.SIGNIFICANCE STATEMENT We show here that the zinc finger transcription factor Tshz1 is expressed during development of the intercalated cells (ITCs) within the mouse amygdala. These neurons have previously been shown to play a crucial role in fear extinction. Tshz1 mouse mutants exhibit severely reduced numbers of ITCs as a result of abnormal migration, differentiation, and survival of these neurons. Furthermore, the loss of ITCs in mouse Tshz1 mutants correlates well with defects in fear extinction as well as the appearance of depression-like and abnormal social interaction behaviors reminiscent of depressive disorders observed in human patients with distal 18q deletions, including the Tshz1 locus.
Literature context: cam Cat# ab16046; RRID:AB_2107107 Mouse monoclonal anti-Sox2 Mill
Human brain evolution is associated with expansion and folding of the neocortex. Increased diversity in neural progenitor (NP) populations (such as basally located radial glia [RG], which reside in an enlarged outer subventricular zone [OSVZ]) likely contributes to this evolutionary expansion, although their characteristics and relative contributions are only partially understood. Through single-cell transcriptional profiling of sorted human NP subpopulations, we identified the primate-specific TMEM14B gene as a marker of basal RG. Expression of TMEM14B in embryonic NPs induces cortical thickening and gyrification in postnatal mice. This is accompanied by SVZ expansion, the appearance of outer RG-like cells, and the proliferation of multiple NP subsets, with proportional increases in all cortical layers and normal lamination. TMEM14B drives NP proliferation by increasing the phosphorylation and nuclear translocation of IQGAP1, which in turn promotes G1/S cell cycle transitions. These data show that a single primate-specific gene can drive neurodevelopmental changes that contribute to brain evolution.
Literature context: cam Cat# ab16046; RRID:AB_2107107 Mouse monoclonal anti-Syt2 ZIRC
The size and shape of dendritic arbors are prime determinants of neuronal connectivity and function. We asked how ON-OFF direction-selective ganglion cells (ooDSGCs) in mouse retina acquire their bistratified dendrites, in which responses to light onset and light offset are segregated to distinct strata. We found that the transcriptional regulator Satb1 is selectively expressed by ooDSGCs. In Satb1 mutant mice, ooDSGC dendrites lack ON arbors, and the cells selectively lose ON responses. Satb1 regulates expression of a homophilic adhesion molecule, Contactin 5 (Cntn5). Both Cntn5 and its co-receptor Caspr4 are expressed not only by ooDSGCs, but also by interneurons that form a scaffold on which ooDSGC ON dendrites fasciculate. Removing Cntn5 from either ooDSGCs or interneurons partially phenocopies Satb1 mutants, demonstrating that Satb1-dependent Cntn5 expression in ooDSGCs leads to branch-specific homophilic interactions with interneurons. Thus, Satb1 directs formation of a morphologically and functionally specialized compartment within a complex dendritic arbor.
Literature context: rabbit anti-Foxp2 (1:500; abcam ab16046,Â Cambridge,Â UK), rabbit anti-OT
The medial subnucleus of the amygdala (MeA) plays a central role in processing sensory cues required for innate behaviors. However, whether there is a link between developmental programs and the emergence of inborn behaviors remains unknown. Our previous studies revealed that the telencephalic preoptic area (POA) embryonic niche is a novel source of MeA destined progenitors. Here, we show that the POA is comprised of distinct progenitor pools complementarily marked by the transcription factors Dbx1 and Foxp2. As determined by molecular and electrophysiological criteria this embryonic parcellation predicts postnatal MeA inhibitory neuronal subtype identity. We further find that Dbx1-derived and Foxp2+ cells in the MeA are differentially activated in response to innate behavioral cues in a sex-specific manner. Thus, developmental transcription factor expression is predictive of MeA neuronal identity and sex-specific neuronal responses, providing a potential developmental logic for how innate behaviors could be processed by different MeA neuronal subtypes.
Literature context: ab16046; RRID:AB_2107107 Rabbit pol
Generating a precise cellular and molecular cartography of the human embryo is essential to our understanding of the mechanisms of organogenesis in normal and pathological conditions. Here, we have combined whole-mount immunostaining, 3DISCO clearing, and light-sheet imaging to start building a 3D cellular map of the human development during the first trimester of gestation. We provide high-resolution 3D images of the developing peripheral nervous, muscular, vascular, cardiopulmonary, and urogenital systems. We found that the adult-like pattern of skin innervation is established before the end of the first trimester, showing important intra- and inter-individual variations in nerve branches. We also present evidence for a differential vascularization of the male and female genital tracts concomitant with sex determination. This work paves the way for a cellular and molecular reference atlas of human cells, which will be of paramount importance to understanding human development in health and disease. PAPERCLIP.
Literature context: TBR1, 1:500 (RRID:AB_2200219); rabbit anti-FOXP2 1:1000 (RRID:AB_2107107); goat anti-TLE4, 1:200 (RRID:AB_
Corticothalamic projection neurons (CThPN) are a diverse set of neurons, critical for function of the neocortex. CThPN development and diversity need to be precisely regulated, but little is known about molecular controls over their differentiation and functional specialization, critically limiting understanding of cortical development and complexity. We report the identification of a set of genes that both define CThPN and likely control their differentiation, diversity, and function. We selected the CThPN-specific transcriptional coregulator Fog2 for functional analysis. We identify that Fog2 controls CThPN molecular differentiation, axonal targeting, and diversity, in part by regulating the expression level of Ctip2 by CThPN, via combinatorial interactions with other molecular controls. Loss of Fog2 specifically disrupts differentiation of subsets of CThPN specialized in motor function, indicating that Fog2 coordinates subtype and functional-area differentiation. These results confirm that we identified key controls over CThPN development and identify Fog2 as a critical control over CThPN diversity.
Literature context: ab16046, RRID:AB_2107107) Campbell
Cortical interneurons are generated predominantly in the medial ganglionic eminence (MGE) and migrate through the ventral and dorsal telencephalon before taking their final positions within the developing cortical plate. Previously we demonstrated that interneurons from Robo1 knockout (Robo1(-/-)) mice contain reduced levels of neuropilin 1 (Nrp1) and PlexinA1 receptors, rendering them less responsive to the chemorepulsive actions of semaphorin ligands expressed in the striatum and affecting their course of migration (Hernandez-Miranda et al.  J. Neurosci. 31:6174-6187). Earlier studies have highlighted the importance of Nrp1 and Nrp2 in interneuron migration, and here we assess the role of PlexinA1 in this process. We observed significantly fewer cells expressing the interneuron markers Gad67 and Lhx6 in the cortex of PlexinA1(-/-) mice compared with wild-type littermates at E14.5 and E18.5. Although the level of apoptosis was similar in the mutant and control forebrain, proliferation was significantly reduced in the former. Furthermore, progenitor cells in the MGE of PlexinA1(-/-) mice appeared to be poorly anchored to the ventricular surface and showed reduced adhesive properties, which may account for the observed reduction in proliferation. Together our data uncover a novel role for PlexinA1 in forebrain development.
Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder with variable expressivity. Heterozygous mutations in either of two genes, TSC1 (hamartin) or TSC2 (tuberin), are responsible for most cases. Hamartin and tuberin form a heterodimer that functions as a major cellular inhibitor of the mammalian target of rapamycin complex 1 (mTORC1) kinase. Genotype-phenotype studies suggest that TSC2 mutations are associated with a more severe neurologic phenotype, although the biologic basis for the difference between TSC1- and TSC2-based disease is unclear. Here we performed a study to compare and contrast the brain phenotypes of Tsc1 and Tsc2 single and double mutants. Using Tsc1 and Tsc2 floxed alleles and a radial glial transgenic Cre driver (FVB-Tg(GFAP-cre)25Mes/J), we deleted Tsc1 and/or Tsc2 in radial glial progenitor cells. Single and double mutants had remarkably similar phenotypes: early postnatal mortality, brain overgrowth, laminar disruption, astrogliosis, a paucity of oligodendroglia, and myelination defects. Double Tsc1/Tsc2 mutants died earlier than single mutants, and single mutants showed differences in the location of heterotopias and the organization of the hippocampal stratum pyramidale. The differences were not due to differential mTORC1 activation or feedback inhibition on Akt. These data provide further genetic evidence for individual hamartin and tuberin functions that may explain some of the genotype-phenotype differences seen in the human disease.
The guidance of axonal projections to ipsilateral and contralateral regions is essential for integration of bilateral sensory information and coordination of movement. In the development of olivocerebellar projections, newborn neurons of inferior olivary (IO) nuclei ventrally migrate from the hindbrain rhombic lip to the floor plate (FP). The cell bodies of IO neurons cannot cross the FP but their axons can, and thus IO neurons project their axons only to the contralateral cerebellar cortex. The molecular mechanisms determining the contralateral axonal projections of IO neurons, however, are obscure. The IO neurons and their axons express EphA4, whereas the FP expresses an EphA4 ligand, EphrinB3, from embryonic day 12.5. Therefore, we tested whether EphA4-deficient mice (EphA4(-/-) ) would show impairment in the development of olivocerebellar projections. We found that, in EphA4(-/-) embryos, some of the IO neurons projected their axons to the ipsilateral cerebellar cortex because the cell bodies of the IO neurons abnormally crossed the FP. Furthermore, even in adults, EphA4(-/-) cerebella were bilaterally innervated by unilateral IO subnuclei. These observations indicate that EphA4 is involved in the contralateral axonal projections of IO neurons by preventing their cell bodies from crossing the midline FP.
Tourette syndrome (TS) is an inherited developmental neuropsychiatric disorder characterized by vocal and motor tics. Multiple lines of neurophysiological evidence implicate dysfunction in the corticostriatal-thalamocortical circuits in the etiology of TS. We recently identified rare sequence variants in the Slit and Trk-like family member 1 (SLITRK1) gene associated with TS. SLITRK1, a single-pass transmembrane protein, displays similarities to the SLIT family of secreted ligands, which have roles in axonal repulsion and dendritic patterning, but its function and developmental expression remain largely unknown. Here we provide evidence that SLITRK1 has a developmentally regulated expression pattern in projection neurons of the corticostriatal-thalamocortical circuits. SLITRK1 is further enriched in the somatodendritic compartment and cytoplasmic vesicles of cortical pyramidal neurons in mouse, monkey, and human brain, observations suggestive of an evolutionarily conserved function in mammals. SLITRK1 is transiently expressed in the striosomal/patch compartment of the mammalian striatum and moreover is associated with the direct output pathway; adult striatal expression is confined to cholinergic interneurons. These analyses demonstrate that the expression of SLITRK1 is dynamic and specifically associated with the circuits most commonly implicated in TS and related disorders, suggesting that SLITRK1 contributes to the development of corticostriatal-thalamocortical circuits.
FOXP2, the first gene causally linked to a human language disorder, is implicated in song acquisition, production, and perception in oscine songbirds, the evolution of speech and language in hominids, and the evolution of echolocation in bats. Despite the evident relevance of Foxp2 to vertebrate acoustic communication, a comprehensive description of neural expression patterns is currently lacking in mammals. Here we use immunocytochemistry to systematically describe the neural distribution of Foxp2 protein in four species of muroid rodents: Scotinomys teguina and S. xerampelinus ("singing mice"), the deer mouse, Peromyscus maniculatus, and the lab mouse, Mus musculus. While expression patterns were generally highly conserved across brain regions, we identified subtle but consistent interspecific differences in Foxp2 distribution, most notably in the medial amygdala and nucleus accumbens, and in layer V cortex throughout the brain. Throughout the brain, Foxp2 was highly enriched in areas involved in modulation of fine motor output (striatum, mesolimbic dopamine circuit, olivocerebellar system) and in multimodal sensory processing and sensorimotor integration (thalamus, cortex). We propose a generalized model for Foxp2-modulated pathways in the adult brain including, but not limited to, fine motor production and auditory perception.