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Goat anti-Chicken IgY (H+L) Secondary Antibody, Alexa Fluor 488

RRID:AB_2534096

Antibody ID

AB_2534096

Target Antigen

Chicken IgY (H+L) chicken

Proper Citation

(Thermo Fisher Scientific Cat# A-11039, RRID:AB_2534096)

Clonality

polyclonal antibody

Comments

Applications: IF (1-10 µg/mL), Flow (1-10 µg/mL), IHC (1-10 µg/mL), ICC (1-10 µg/mL)

Host Organism

goat

Vendor

Thermo Fisher Scientific Go To Vendor

Cat Num

A-11039

Publications that use this research resource

MTSS1 Regulation of Actin-Nucleating Formin DAAM1 in Dendritic Filopodia Determines Final Dendritic Configuration of Purkinje Cells.

  • Kawabata Galbraith K
  • Cell Rep
  • 2018 Jul 3

Literature context:


Abstract:

Dendritic filopodia of developing neurons function as environmental sensors, regulating the spatial organization of dendrites and proper targeting to presynaptic partners. Dendritic filopodia morphology is determined by the balance of F-actin assembled via two major nucleating pathways, the ARP2/3 complex and formins. The inverse-BAR protein MTSS1 is highly expressed in Purkinje cells (PCs) and has been shown to upregulate ARP2/3 activity. PCs in MTSS1 conditional knockout mice showed dendrite hypoplasia due to excessive contact-induced retraction during development. This phenotype was concomitant with elongated dendritic filopodia and was phenocopied by overactivation of the actin nucleator formin DAAM1 localized in the tips of PC dendritic protrusions. Cell biology assays including single-molecule speckle microscopy demonstrated that MTSS1's C terminus binds to DAAM1 and paused DAAM1-mediated F-actin polymerization. Thus, MTSS1 plays a dual role as a formin inhibitor and ARP2/3 activator in dendritic filopodia, determining final neuronal morphology.

Funding information:
  • Breast Cancer Now - 2012NOVSP024(United Kingdom)

MicroRNAs Overcome Cell Fate Barrier by Reducing EZH2-Controlled REST Stability during Neuronal Conversion of Human Adult Fibroblasts.

  • Lee SW
  • Dev. Cell
  • 2018 Jul 2

Literature context:


Abstract:

The ability to convert human somatic cells efficiently to neurons facilitates the utility of patient-derived neurons for studying neurological disorders. As such, ectopic expression of neuronal microRNAs (miRNAs), miR-9/9∗ and miR-124 (miR-9/9∗-124) in adult human fibroblasts has been found to evoke extensive reconfigurations of the chromatin and direct the fate conversion to neurons. However, how miR-9/9∗-124 break the cell fate barrier to activate the neuronal program remains to be defined. Here, we identified an anti-neurogenic function of EZH2 in fibroblasts that acts outside its role as a subunit of Polycomb Repressive Complex 2 to directly methylate and stabilize REST, a transcriptional repressor of neuronal genes. During neuronal conversion, miR-9/9∗-124 induced the repression of the EZH2-REST axis by downregulating USP14, accounting for the opening of chromatin regions harboring REST binding sites. Our findings underscore the interplay between miRNAs and protein stability cascade underlying the activation of neuronal program.

Funding information:
  • NHLBI NIH HHS - P50 HL077107(United States)

Reversible De-differentiation of Mature White Adipocytes into Preadipocyte-like Precursors during Lactation.

  • Wang QA
  • Cell Metab.
  • 2018 Jun 8

Literature context:


Abstract:

Adipose tissue in the mammary gland undergoes dramatic remodeling during reproduction. Adipocytes are replaced by mammary alveolar structures during pregnancy and lactation, then reappear upon weaning. The fate of the original adipocytes during lactation and the developmental origin of the re-appearing adipocyte post involution are unclear. Here, we reveal that adipocytes in the mammary gland de-differentiate into Pdgfrα+ preadipocyte- and fibroblast-like cells during pregnancy and remain de-differentiated during lactation. Upon weaning, de-differentiated fibroblasts proliferate and re-differentiate into adipocytes. This cycle occurs over multiple pregnancies. These observations reveal the potential of terminally differentiated adipocytes to undergo repeated cycles of de-differentiation and re-differentiation in a physiological setting.

Funding information:
  • NIDDK NIH HHS - P30DK079333(United States)

Ischemic Brain Injury Leads to Brain Edema via Hyperthermia-Induced TRPV4 Activation.

  • Hoshi Y
  • J. Neurosci.
  • 2018 Jun 20

Literature context:


Abstract:

Brain edema is characterized by an increase in net brain water content, which results in an increase in brain volume. Although brain edema is associated with a high fatality rate, the cellular and molecular processes of edema remain largely unclear. Here, we developed an in vitro model of ischemic stroke-induced edema in which male mouse brain slices were treated with oxygen-glucose deprivation (OGD) to mimic ischemia. We continuously measured the cross-sectional area of the brain slice for 150 min under macroscopic microscopy, finding that OGD induces swelling of brain slices. OGD-induced swelling was prevented by pharmacologically blocking or genetically knocking out the transient receptor potential vanilloid 4 (TRPV4), a member of the thermosensitive TRP channel family. Because TRPV4 is activated at around body temperature and its activation is enhanced by heating, we next elevated the temperature of the perfusate in the recording chamber, finding that hyperthermia induces swelling via TRPV4 activation. Furthermore, using the temperature-dependent fluorescence lifetime of a fluorescent-thermosensitive probe, we confirmed that OGD treatment increases the temperature of brain slices through the activation of glutamate receptors. Finally, we found that brain edema following traumatic brain injury was suppressed in TRPV4-deficient male mice in vivo Thus, our study proposes a novel mechanism: hyperthermia activates TRPV4 and induces brain edema after ischemia.SIGNIFICANCE STATEMENT Brain edema is characterized by an increase in net brain water content, which results in an increase in brain volume. Although brain edema is associated with a high fatality rate, the cellular and molecular processes of edema remain unclear. Here, we developed an in vitro model of ischemic stroke-induced edema in which mouse brain slices were treated with oxygen-glucose deprivation. Using this system, we showed that the increase in brain temperature and the following activation of the thermosensitive cation channel TRPV4 (transient receptor potential vanilloid 4) are involved in the pathology of edema. Finally, we confirmed that TRPV4 is involved in brain edema in vivo using TRPV4-deficient mice, concluding that hyperthermia activates TRPV4 and induces brain edema after ischemia.

Funding information:
  • NIGMS NIH HHS - GM58272(United States)

Gain-of-Function Mutation of Card14 Leads to Spontaneous Psoriasis-like Skin Inflammation through Enhanced Keratinocyte Response to IL-17A.

  • Wang M
  • Immunity
  • 2018 Jun 28

Literature context:


Abstract:

Genetic mutations of CARD14 (encoding CARMA2) are observed in psoriasis patients. Here we showed that Card14E138A/+ and Card14ΔQ136/+ mice developed spontaneous psoriasis-like skin inflammation, which resulted from constitutively activated CARMA2 via self-aggregation leading to the enhanced activation of the IL-23-IL-17A cytokine axis. Card14-/- mice displayed attenuated skin inflammation in the imiquimod-induced psoriasis model due to impaired IL-17A signaling in keratinocytes. CARMA2, mainly expressed in keratinocytes, associates with the ACT1-TRAF6 signaling complex and mediates IL-17A-induced NF-κB and MAPK signaling pathway activation, which leads to expression of pro-inflammatory factors. Thus, CARMA2 serves as a key mediator of IL-17A signaling and its constitutive activation in keratinocytes leads to the onset of psoriasis, which indicates an important role of NF-κB activation in keratinocytes in psoriatic initiation.

Funding information:
  • NIGMS NIH HHS - R01 GM28896(United States)

Dopamine D2 Receptors in the Paraventricular Thalamus Attenuate Cocaine Locomotor Sensitization.

  • Clark AM
  • eNeuro
  • 2018 Jun 11

Literature context:


Abstract:

Alterations in thalamic dopamine (DA) or DA D2 receptors (D2Rs) have been measured in drug addiction and schizophrenia, but the relevance of thalamic D2Rs for behavior is largely unknown. Using in situ hybridization and mice expressing green fluorescent protein (GFP) under the Drd2 promoter, we found that D2R expression within the thalamus is enriched in the paraventricular nucleus (PVT) as well as in more ventral midline thalamic nuclei. Within the PVT, D2Rs are inhibitory as their activation inhibits neuronal action potentials in brain slices. Using Cre-dependent anterograde and retrograde viral tracers, we further determined that PVT neurons are reciprocally interconnected with multiple areas of the limbic system including the amygdala and the nucleus accumbens (NAc). Based on these anatomical findings, we analyzed the role of D2Rs in the PVT in behaviors that are supported by these areas and that also have relevance for schizophrenia and drug addiction. Male and female mice with selective overexpression of D2Rs in the PVT showed attenuated cocaine locomotor sensitization, whereas anxiety levels, fear conditioning, sensorimotor gating, and food-motivated behaviors were not affected. These findings suggest the importance of PVT inhibition by D2Rs in modulating the sensitivity to cocaine, a finding that may have novel implications for human drug use.

A Modular Organization of LRR Protein-Mediated Synaptic Adhesion Defines Synapse Identity.

  • Schroeder A
  • Neuron
  • 2018 Jun 27

Literature context:


Abstract:

Pyramidal neurons express rich repertoires of leucine-rich repeat (LRR)-containing adhesion molecules with similar synaptogenic activity in culture. The in vivo relevance of this molecular diversity is unclear. We show that hippocampal CA1 pyramidal neurons express multiple synaptogenic LRR proteins that differentially distribute to the major excitatory inputs on their apical dendrites. At Schaffer collateral (SC) inputs, FLRT2, LRRTM1, and Slitrk1 are postsynaptically localized and differentially regulate synaptic structure and function. FLRT2 controls spine density, whereas LRRTM1 and Slitrk1 exert opposing effects on synaptic vesicle distribution at the active zone. All LRR proteins differentially affect synaptic transmission, and their combinatorial loss results in a cumulative phenotype. At temporoammonic (TA) inputs, LRRTM1 is absent; FLRT2 similarly controls functional synapse number, whereas Slitrk1 function diverges to regulate postsynaptic AMPA receptor density. Thus, LRR proteins differentially control synaptic architecture and function and act in input-specific combinations and a context-dependent manner to specify synaptic properties.

Funding information:
  • NIDDK NIH HHS - DK72473(United States)

The Epigenetic State of PRDM16-Regulated Enhancers in Radial Glia Controls Cortical Neuron Position.

  • Baizabal JM
  • Neuron
  • 2018 Jun 6

Literature context:


Abstract:

The epigenetic landscape is dynamically remodeled during neurogenesis. However, it is not understood how chromatin modifications in neural stem cells instruct the formation of complex structures in the brain. We report that the histone methyltransferase PRDM16 is required in radial glia to regulate lineage-autonomous and stage-specific gene expression programs that control number and position of upper layer cortical projection neurons. PRDM16 regulates the epigenetic state of transcriptional enhancers to activate genes involved in intermediate progenitor cell production and repress genes involved in cell migration. The histone methyltransferase domain of PRDM16 is necessary in radial glia to promote cortical neuron migration through transcriptional silencing. We show that repression of the gene encoding the E3 ubiquitin ligase PDZRN3 by PRDM16 determines the position of upper layer neurons. These findings provide insights into how epigenetic control of transcriptional enhancers in radial glial determines the organization of the mammalian cerebral cortex.

Funding information:
  • NCI NIH HHS - R01 CA109038-04(United States)

Inactivation of hepatic ATRX in Atrx Foxg1cre mice prevents reversal of aging-like phenotypes by thyroxine.

  • Rowland ME
  • Aging (Albany NY)
  • 2018 Jun 7

Literature context:


Abstract:

ATRX is an ATP-dependent chromatin remodeler required for the maintenance of genomic integrity. We previously reported that conditional Atrx ablation in the mouse embryonic forebrain and anterior pituitary using the Foxg1cre driver causes reduced health and lifespan. In these mice, premature aging-like phenotypes were accompanied by low circulating levels of insulin-like growth factor 1 (IGF-1) and thyroxine (T4), hormones that maintain stem cell pools and normal metabolic profiles, respectively. Based on emerging evidence that T4 stimulates expression of IGF-1 in pre-pubertal mice, we tested whether T4 supplementation in Atrx Foxg1cre mice could restore IGF-1 levels and ameliorate premature aging-like phenotypes. Despite restoration of normal serum T4 levels, we did not observe improvements in circulating IGF-1. In the liver, thyroid hormone target genes were differentially affected upon T4 treatment, with Igf1 and several other thyroid hormone responsive genes failing to recover normal expression levels. These findings hinted at Cre-mediated Atrx inactivation in the liver of Atrx Foxg1cre mice, which we confirmed. We conclude that the phenotypes observed in the Atrx Foxg1cre mice can be explained in part by a role of ATRX in the liver to promote T4-mediated Igf1 expression, thus explaining the inefficacy of T4 therapy observed in this study.

Funding information:
  • NIMH NIH HHS - R01MH090910(United States)

Cell-Specific Imd-NF-κB Responses Enable Simultaneous Antibacterial Immunity and Intestinal Epithelial Cell Shedding upon Bacterial Infection.

  • Zhai Z
  • Immunity
  • 2018 May 15

Literature context:


Abstract:

Intestinal infection triggers potent immune responses to combat pathogens and concomitantly drives epithelial renewal to maintain barrier integrity. Current models propose that epithelial renewal is primarily driven by damage caused by reactive oxygen species (ROS). Here we found that in Drosophila, the Imd-NF-κB pathway controlled enterocyte (EC) shedding upon infection, via a mechanism independent of ROS-associated apoptosis. Mechanistically, the Imd pathway synergized with JNK signaling to induce epithelial cell shedding specifically in the context of bacterial infection, requiring also the reduced expression of the transcription factor GATAe. Furthermore, cell-specific NF-κB responses enabled simultaneous production of antimicrobial peptides (AMPs) and epithelial shedding in different EC populations. Thus, the Imd-NF-κB pathway is central to the intestinal antibacterial response by mediating both AMP production and the maintenance of barrier integrity. Considering the similarities between Drosophila Imd signaling and mammalian TNFR pathway, our findings suggest the existence of an evolutionarily conserved genetic program in immunity-induced epithelial shedding.

Funding information:
  • NIA NIH HHS - R01 AG31675(United States)

Neuroanatomical details of the lateral neurons of Drosophila melanogaster support their functional role in the circadian system.

  • Schubert FK
  • J. Comp. Neurol.
  • 2018 May 1

Literature context:


Abstract:

Drosophila melanogaster is a long-standing model organism in the circadian clock research. A major advantage is the relative small number of about 150 neurons, which built the circadian clock in Drosophila. In our recent work, we focused on the neuroanatomical properties of the lateral neurons of the clock network. By applying the multicolor-labeling technique Flybow we were able to identify the anatomical similarity of the previously described E2 subunit of the evening oscillator of the clock, which is built by the 5th small ventrolateral neuron (5th s-LNv ) and one ITP positive dorsolateral neuron (LNd ). These two clock neurons share the same spatial and functional properties. We found both neurons innervating the same brain areas with similar pre- and postsynaptic sites in the brain. Here the anatomical findings support their shared function as a main evening oscillator in the clock network like also found in previous studies. A second quite surprising finding addresses the large lateral ventral PDF-neurons (l-LNv s). We could show that the four hardly distinguishable l-LNv s consist of two subgroups with different innervation patterns. While three of the neurons reflect the well-known branching pattern reproduced by PDF immunohistochemistry, one neuron per brain hemisphere has a distinguished innervation profile and is restricted only to the proximal part of the medulla-surface. We named this neuron "extra" l-LNv (l-LNv x). We suggest the anatomical findings reflect different functional properties of the two l-LNv subgroups.

Funding information:
  • NCI NIH HHS - R01 CA031363(United States)

A Hierarchical, Data-Driven Approach to Modeling Single-Cell Populations Predicts Latent Causes of Cell-To-Cell Variability.

  • Loos C
  • Cell Syst
  • 2018 May 23

Literature context:


Abstract:

All biological systems exhibit cell-to-cell variability. Frameworks exist for understanding how stochastic fluctuations and transient differences in cell state contribute to experimentally observable variations in cellular responses. However, current methods do not allow identification of the sources of variability between and within stable subpopulations of cells. We present a data-driven modeling framework for the analysis of populations comprising heterogeneous subpopulations. Our approach combines mixture modeling with frameworks for distribution approximation, facilitating the integration of multiple single-cell datasets and the detection of causal differences between and within subpopulations. The computational efficiency of our framework allows hundreds of competing hypotheses to be compared. We initially validate our method using simulated data with an understood ground truth, then we analyze data collected using quantitative single-cell microscopy of cultured sensory neurons involved in pain initiation. This approach allows us to quantify the relative contribution of neuronal subpopulations, culture conditions, and expression levels of signaling proteins to the observed cell-to-cell variability in NGF/TrkA-initiated Erk1/2 signaling.

Funding information:
  • NIAID NIH HHS - R01 AI024157(United States)

Drosophila TNF Modulates Tissue Tension in the Embryo to Facilitate Macrophage Invasive Migration.

  • Ratheesh A
  • Dev. Cell
  • 2018 May 7

Literature context:


Abstract:

Migrating cells penetrate tissue barriers during development, inflammatory responses, and tumor metastasis. We study if migration in vivo in such three-dimensionally confined environments requires changes in the mechanical properties of the surrounding cells using embryonic Drosophila melanogaster hemocytes, also called macrophages, as a model. We find that macrophage invasion into the germband through transient separation of the apposing ectoderm and mesoderm requires cell deformations and reductions in apical tension in the ectoderm. Interestingly, the genetic pathway governing these mechanical shifts acts downstream of the only known tumor necrosis factor superfamily member in Drosophila, Eiger, and its receptor, Grindelwald. Eiger-Grindelwald signaling reduces levels of active Myosin in the germband ectodermal cortex through the localization of a Crumbs complex component, Patj (Pals-1-associated tight junction protein). We therefore elucidate a distinct molecular pathway that controls tissue tension and demonstrate the importance of such regulation for invasive migration in vivo.

Funding information:
  • NCI NIH HHS - P50 CA130805(United States)

Re-evaluating microglia expression profiles using RiboTag and cell isolation strategies.

  • Haimon Z
  • Nat. Immunol.
  • 2018 May 20

Literature context:


Abstract:

Transcriptome profiling is widely used to infer functional states of specific cell types, as well as their responses to stimuli, to define contributions to physiology and pathophysiology. Focusing on microglia, the brain's macrophages, we report here a side-by-side comparison of classical cell-sorting-based transcriptome sequencing and the 'RiboTag' method, which avoids cell retrieval from tissue context and yields translatome sequencing information. Conventional whole-cell microglial transcriptomes were found to be significantly tainted by artifacts introduced by tissue dissociation, cargo contamination and transcripts sequestered from ribosomes. Conversely, our data highlight the added value of RiboTag profiling for assessing the lineage accuracy of Cre recombinase expression in transgenic mice. Collectively, this study indicates method-based biases, reveals observer effects and establishes RiboTag-based translatome profiling as a valuable complement to standard sorting-based profiling strategies.

Funding information:
  • NIBIB NIH HHS - EB003537(United States)

RNP-Granule Assembly via Ataxin-2 Disordered Domains Is Required for Long-Term Memory and Neurodegeneration.

  • Bakthavachalu B
  • Neuron
  • 2018 May 16

Literature context:


Abstract:

Human Ataxin-2 is implicated in the cause and progression of amyotrophic lateral sclerosis (ALS) and type 2 spinocerebellar ataxia (SCA-2). In Drosophila, a conserved atx2 gene is essential for animal survival as well as for normal RNP-granule assembly, translational control, and long-term habituation. Like its human homolog, Drosophila Ataxin-2 (Atx2) contains polyQ repeats and additional intrinsically disordered regions (IDRs). We demonstrate that Atx2 IDRs, which are capable of mediating liquid-liquid phase transitions in vitro, are essential for efficient formation of neuronal mRNP assemblies in vivo. Remarkably, ΔIDR mutants that lack neuronal RNP granules show normal animal development, survival, and fertility. However, they show defects in long-term memory formation/consolidation as well as in C9ORF72 dipeptide repeat or FUS-induced neurodegeneration. Together, our findings demonstrate (1) that higher-order mRNP assemblies contribute to long-term neuronal plasticity and memory, and (2) that a targeted reduction in RNP-granule formation efficiency can alleviate specific forms of neurodegeneration.

Funding information:
  • NCI NIH HHS - 5K12 CA 076931(United States)

Identification of a critical sulfation in chondroitin that inhibits axonal regeneration.

  • Pearson CS
  • Elife
  • 2018 May 15

Literature context:


Abstract:

The failure of mammalian CNS neurons to regenerate their axons derives from a combination of intrinsic deficits and extrinsic factors. Following injury, chondroitin sulfate proteoglycans (CSPGs) within the glial scar inhibit axonal regeneration, an action mediated by the sulfated glycosaminoglycan (GAG) chains of CSPGs, especially those with 4-sulfated (4S) sugars. Arylsulfatase B (ARSB) selectively cleaves 4S groups from the non-reducing ends of GAG chains without disrupting other, growth-permissive motifs. We demonstrate that ARSB is effective in reducing the inhibitory actions of CSPGs both in in vitro models of the glial scar and after optic nerve crush (ONC) in adult mice. ARSB is clinically approved for replacement therapy in patients with mucopolysaccharidosis VI and therefore represents an attractive candidate for translation to the human CNS.

Funding information:
  • National Institutes of Health - 1ZIAHL006135()
  • NIEHS NIH HHS - 2T32ES007329-10(United States)

Phasic Stimulation of Midbrain Dopamine Neuron Activity Reduces Salt Consumption.

  • Sandhu EC
  • eNeuro
  • 2018 May 17

Literature context:


Abstract:

Salt intake is an essential dietary requirement, but excessive consumption is implicated in hypertension and associated conditions. Little is known about the neural circuit mechanisms that control motivation to consume salt, although the midbrain dopamine system, which plays a key role in other reward-related behaviors, has been implicated. We, therefore, examined the effects on salt consumption of either optogenetic excitation or chemogenetic inhibition of ventral tegmental area (VTA) dopamine neurons in male mice. Strikingly, optogenetic excitation of dopamine neurons decreased salt intake in a rapid and reversible manner, despite a strong salt appetite. Importantly, optogenetic excitation was not aversive, did not induce hyperactivity, and did not alter salt concentration preferences in a need-free state. In addition, we found that chemogenetic inhibition of dopamine neurons had no effect on salt intake. Lastly, optogenetic excitation of dopamine neurons reduced consumption of sucrose following an overnight fast, suggesting a more general role of VTA dopamine neuron excitation in organizing motivated behaviors.

Funding information:
  • NHLBI NIH HHS - T32 HL007501(United States)

Nav1.1-Overexpressing Interneuron Transplants Restore Brain Rhythms and Cognition in a Mouse Model of Alzheimer's Disease.

  • Martinez-Losa M
  • Neuron
  • 2018 Apr 4

Literature context:


Abstract:

Inhibitory interneurons regulate the oscillatory rhythms and network synchrony that are required for cognitive functions and disrupted in Alzheimer's disease (AD). Network dysrhythmias in AD and multiple neuropsychiatric disorders are associated with hypofunction of Nav1.1, a voltage-gated sodium channel subunit predominantly expressed in interneurons. We show that Nav1.1-overexpressing, but not wild-type, interneuron transplants derived from the embryonic medial ganglionic eminence (MGE) enhance behavior-dependent gamma oscillatory activity, reduce network hypersynchrony, and improve cognitive functions in human amyloid precursor protein (hAPP)-transgenic mice, which simulate key aspects of AD. Increased Nav1.1 levels accelerated action potential kinetics of transplanted fast-spiking and non-fast-spiking interneurons. Nav1.1-deficient interneuron transplants were sufficient to cause behavioral abnormalities in wild-type mice. We conclude that the efficacy of interneuron transplantation and the function of transplanted cells in an AD-relevant context depend on their Nav1.1 levels. Disease-specific molecular optimization of cell transplants may be required to ensure therapeutic benefits in different conditions.

Funding information:
  • NCRR NIH HHS - C06 RR018928()
  • NIA NIH HHS - F32 AG043301()
  • NIA NIH HHS - R01 AG030207()
  • NIA NIH HHS - R01 AG036884()
  • NIA NIH HHS - R01 AG047313()
  • NIA NIH HHS - R01 AG051390()
  • NIA NIH HHS - R01 AG054214()
  • NIAID NIH HHS - R01 AI059738-05(United States)
  • NINDS NIH HHS - P30 NS065780()
  • NINDS NIH HHS - R01 NS041787()
  • NINDS NIH HHS - U54 NS100717()

An Attractive Reelin Gradient Establishes Synaptic Lamination in the Vertebrate Visual System.

  • Di Donato V
  • Neuron
  • 2018 Mar 7

Literature context:


Abstract:

A conserved organizational and functional principle of neural networks is the segregation of axon-dendritic synaptic connections into laminae. Here we report that targeting of synaptic laminae by retinal ganglion cell (RGC) arbors in the vertebrate visual system is regulated by a signaling system relying on target-derived Reelin and VLDLR/Dab1a on the projecting neurons. Furthermore, we find that Reelin is distributed as a gradient on the target tissue and stabilized by heparan sulfate proteoglycans (HSPGs) in the extracellular matrix (ECM). Through genetic manipulations, we show that this Reelin gradient is important for laminar targeting and that it is attractive for RGC axons. Finally, we suggest a comprehensive model of synaptic lamina formation in which attractive Reelin counter-balances repulsive Slit1, thereby guiding RGC axons toward single synaptic laminae. We establish a mechanism that may represent a general principle for neural network assembly in vertebrate species and across different brain areas.

Funding information:
  • NIAID NIH HHS - AI091977(United States)

Rescue of Learning and Memory Deficits in the Human Nonsyndromic Intellectual Disability Cereblon Knock-Out Mouse Model by Targeting the AMP-Activated Protein Kinase-mTORC1 Translational Pathway.

  • Bavley CC
  • J. Neurosci.
  • 2018 Mar 14

Literature context:


Abstract:

A homozygous nonsense mutation in the cereblon (CRBN) gene results in autosomal recessive, nonsyndromic intellectual disability that is devoid of other phenotypic features, suggesting a critical role of CRBN in mediating learning and memory. In this study, we demonstrate that adult male Crbn knock-out (CrbnKO) mice exhibit deficits in hippocampal-dependent learning and memory tasks that are recapitulated by focal knock-out of Crbn in the adult dorsal hippocampus, with no changes in social or repetitive behavior. Cellular studies identify deficits in long-term potentiation at Schaffer collateral CA1 synapses. We further show that Crbn is robustly expressed in the mouse hippocampus and CrbnKO mice exhibit hyperphosphorylated levels of AMPKα (Thr172). Examination of processes downstream of AMP-activated protein kinase (AMPK) finds that CrbnKO mice have a selective impairment in mediators of the mTORC1 translation initiation pathway in parallel with lower protein levels of postsynaptic density glutamatergic proteins and higher levels of excitatory presynaptic markers in the hippocampus with no change in markers of the unfolded protein response or autophagy pathways. Acute pharmacological inhibition of AMPK activity in adult CrbnKO mice rescues learning and memory deficits and normalizes hippocampal mTORC1 activity and postsynaptic glutamatergic proteins without altering excitatory presynaptic markers. Thus, this study identifies that loss of Crbn results in learning, memory, and synaptic defects as a consequence of exaggerated AMPK activity, inhibition of mTORC1 signaling, and decreased glutamatergic synaptic proteins. Thus, CrbnKO mice serve as an ideal model of intellectual disability to further explore molecular mechanisms of learning and memory.SIGNIFICANCE STATEMENT Intellectual disability (ID) is one of the most common neurodevelopmental disorders. The cereblon (CRBN) gene has been linked to autosomal recessive, nonsyndromic ID, characterized by an intelligence quotient between 50 and 70 but devoid of other phenotypic features, making cereblon an ideal protein for the study of the fundamental aspects of learning and memory. Here, using the cereblon knock-out mouse model, we show that cereblon deficiency disrupts learning, memory, and synaptic function via AMP-activated protein kinase hyperactivity, downregulation of mTORC1, and dysregulation of excitatory synapses, with no changes in social or repetitive behaviors, consistent with findings in the human population. This establishes the cereblon knock-out mouse as a model of pure ID without the confounding behavioral phenotypes associated with other current models of ID.

Funding information:
  • Medical Research Council - MC_U137761446(United Kingdom)
  • NIDA NIH HHS - R01 DA029122()

Insm1 Induces Neural Progenitor Delamination in Developing Neocortex via Downregulation of the Adherens Junction Belt-Specific Protein Plekha7.

  • Tavano S
  • Neuron
  • 2018 Mar 21

Literature context:


Abstract:

Delamination of neural progenitor cells (NPCs) from the ventricular surface is a crucial prerequisite to form the subventricular zone, the germinal layer linked to the expansion of the mammalian neocortex in development and evolution. Here, we dissect the molecular mechanism by which the transcription factor Insm1 promotes the generation of basal progenitors (BPs). Insm1 protein is most highly expressed in newborn BPs in mouse and human developing neocortex. Forced Insm1 expression in embryonic mouse neocortex causes NPC delamination, converting apical to basal radial glia. Insm1 represses the expression of the apical adherens junction belt-specific protein Plekha7. CRISPR/Cas9-mediated disruption of Plekha7 expression suffices to cause NPC delamination. Plekha7 overexpression impedes the intrinsic and counteracts the Insm1-induced, NPC delamination. Our findings uncover a novel molecular mechanism underlying NPC delamination in which a BP-genic transcription factor specifically targets the integrity of the apical adherens junction belt, rather than adherens junction components as such.

Funding information:
  • Intramural NIH HHS - ZIA BC010763-05(United States)

Spatial-Temporal Lineage Restrictions of Embryonic p63+ Progenitors Establish Distinct Stem Cell Pools in Adult Airways.

  • Yang Y
  • Dev. Cell
  • 2018 Mar 26

Literature context:


Abstract:

Basal cells (BCs) are p63-expressing multipotent progenitors of skin, tracheoesophageal and urinary tracts. p63 is abundant in developing airways; however, it remains largely unclear how embryonic p63+ cells contribute to the developing and postnatal respiratory tract epithelium, and ultimately how they relate to adult BCs. Using lineage-tracing and functional approaches in vivo, we show that p63+ cells arising from the lung primordium are initially multipotent progenitors of airway and alveolar lineages but later become restricted proximally to generate the tracheal adult stem cell pool. In intrapulmonary airways, these cells are maintained immature to adulthood in bronchi, establishing a rare p63+Krt5- progenitor cell population that responds to H1N1 virus-induced severe injury. Intriguingly, this pool includes a CC10 lineage-labeled p63+Krt5- cell subpopulation required for a full H1N1-response. These data elucidate key aspects in the establishment of regionally distinct adult stem cell pools in the respiratory system, potentially with relevance to other organs.

Funding information:
  • Intramural NIH HHS - ZIA HL006151-02(United States)
  • NCI NIH HHS - R01 CA112403()
  • NCI NIH HHS - R01 CA193455()
  • NHLBI NIH HHS - R35 HL135834()
  • NIAID NIH HHS - HHSN272201400008C()

Synapse maintenance and restoration in the retina by NGL2.

  • Soto F
  • Elife
  • 2018 Mar 19

Literature context:


Abstract:

Synaptic cell adhesion molecules (CAMs) promote synapse formation in the developing nervous system. To what extent they maintain and can restore connections in the mature nervous system is unknown. Furthermore, how synaptic CAMs affect the growth of synapse-bearing neurites is unclear. Here, we use adeno-associated viruses (AAVs) to delete, re-, and overexpress the synaptic CAM NGL2 in individual retinal horizontal cells. When we removed NGL2 from horizontal cells, their axons overgrew and formed fewer synapses, irrespective of whether Ngl2 was deleted during development or in mature circuits. When we re-expressed NGL2 in knockout mice, horizontal cell axon territories and synapse numbers were restored, even if AAVs were injected after phenotypes had developed. Finally, overexpression of NGL2 in wild-type horizontal cells elevated synapse numbers above normal levels. Thus, NGL2 promotes the formation, maintenance, and restoration of synapses in the developing and mature retina, and restricts axon growth throughout life.

Funding information:
  • National Eye Institute - R01EY023341()
  • National Eye Institute - R01EY026978()
  • National Eye Institute - R01EY027411()
  • NCI NIH HHS - CA 110793(United States)

The signaling lipid sphingosine 1-phosphate regulates mechanical pain.

  • Hill RZ
  • Elife
  • 2018 Mar 21

Literature context:


Abstract:

Somatosensory neurons mediate responses to diverse mechanical stimuli, from innocuous touch to noxious pain. While recent studies have identified distinct populations of A mechanonociceptors (AMs) that are required for mechanical pain, the molecular underpinnings of mechanonociception remain unknown. Here, we show that the bioactive lipid sphingosine 1-phosphate (S1P) and S1P Receptor 3 (S1PR3) are critical regulators of acute mechanonociception. Genetic or pharmacological ablation of S1PR3, or blockade of S1P production, significantly impaired the behavioral response to noxious mechanical stimuli, with no effect on responses to innocuous touch or thermal stimuli. These effects are mediated by fast-conducting A mechanonociceptors, which displayed a significant decrease in mechanosensitivity in S1PR3 mutant mice. We show that S1PR3 signaling tunes mechanonociceptor excitability via modulation of KCNQ2/3 channels. Our findings define a new role for S1PR3 in regulating neuronal excitability and establish the importance of S1P/S1PR3 signaling in the setting of mechanical pain thresholds.

Funding information:
  • Howard Hughes Medical Institute - Faculty Scholar Award()
  • Medical Research Council - G0800297(United Kingdom)
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases - AR051219()
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases - AR059385()
  • National Institute of General Medical Sciences - GM007367()
  • National Institute of Neurological Disorders and Stroke - NS077224()
  • National Institute of Neurological Disorders and Stroke - NS098097()
  • National Institute of Neurological Disorders and Stroke - NS105449()

Inhibition of Methyltransferase Setd7 Allows the In Vitro Expansion of Myogenic Stem Cells with Improved Therapeutic Potential.

  • Judson RN
  • Cell Stem Cell
  • 2018 Feb 1

Literature context:


Abstract:

The development of cell therapy for repairing damaged or diseased skeletal muscle has been hindered by the inability to significantly expand immature, transplantable myogenic stem cells (MuSCs) in culture. To overcome this limitation, a deeper understanding of the mechanisms regulating the transition between activated, proliferating MuSCs and differentiation-primed, poorly engrafting progenitors is needed. Here, we show that methyltransferase Setd7 facilitates such transition by regulating the nuclear accumulation of β-catenin in proliferating MuSCs. Genetic or pharmacological inhibition of Setd7 promotes in vitro expansion of MuSCs and increases the yield of primary myogenic cell cultures. Upon transplantation, both mouse and human MuSCs expanded with a Setd7 small-molecule inhibitor are better able to repopulate the satellite cell niche, and treated mouse MuSCs show enhanced therapeutic potential in preclinical models of muscular dystrophy. Thus, Setd7 inhibition may help bypass a key obstacle in the translation of cell therapy for muscle disease.

Funding information:
  • BLRD VA - I01 BX002324()
  • NCI NIH HHS - R01 CA073808(United States)
  • NIA NIH HHS - P01 AG036695()
  • NIAMS NIH HHS - R21 AR071039()
  • RRD VA - I01 RX001222()

Small Networks Encode Decision-Making in Primary Auditory Cortex.

  • Francis NA
  • Neuron
  • 2018 Feb 21

Literature context:


Abstract:

Sensory detection tasks enhance representations of behaviorally meaningful stimuli in primary auditory cortex (A1). However, it remains unclear how A1 encodes decision-making. Neurons in A1 layer 2/3 (L2/3) show heterogeneous stimulus selectivity and complex anatomical connectivity, and receive input from prefrontal cortex. Thus, task-related modulation of activity in A1 L2/3 might differ across subpopulations. To study the neural coding of decision-making, we used two-photon imaging in A1 L2/3 of mice performing a tone-detection task. Neural responses to targets showed attentional gain and encoded behavioral choice. To characterize network representation of behavioral choice, we analyzed functional connectivity using Granger causality, pairwise noise correlations, and neural decoding. During task performance, small groups of four to five neurons became sparsely linked, locally clustered, and rostro-caudally oriented, while noise correlations both increased and decreased. Our results suggest that sensory-based decision-making involves small neural networks driven by the sum of sensory input, attentional gain, and behavioral choice.

Funding information:
  • NCI NIH HHS - U54 CA143874(United States)

Role of Purinergic Receptor P2Y1 in Spatiotemporal Ca2+ Dynamics in Astrocytes.

  • Shigetomi E
  • J. Neurosci.
  • 2018 Feb 7

Literature context:


Abstract:

Fine processes of astrocytes enwrap synapses and are well positioned to sense neuronal information via synaptic transmission. In rodents, astrocyte processes sense synaptic transmission via Gq-protein coupled receptors (GqPCR), including the P2Y1 receptor (P2Y1R), to generate Ca2+ signals. Astrocytes display numerous spontaneous microdomain Ca2+ signals; however, it is not clear whether such signals are due to local synaptic transmission and/or in what timeframe astrocytes sense local synaptic transmission. To ask whether GqPCRs mediate microdomain Ca2+ signals, we engineered mice (both sexes) to specifically overexpress P2Y1Rs in astrocytes, and we visualized Ca2+ signals via a genetically encoded Ca2+ indicator, GCaMP6f, in astrocytes from adult mice. Astrocytes overexpressing P2Y1Rs showed significantly larger Ca2+ signals in response to exogenously applied ligand and to repetitive electrical stimulation of axons compared with controls. However, we found no evidence of increased microdomain Ca2+ signals. Instead, Ca2+ waves appeared and propagated to occupy areas that were up to 80-fold larger than microdomain Ca2+ signals. These Ca2+ waves accounted for only 2% of total Ca2+ events, but they were 1.9-fold larger and 2.9-fold longer in duration than microdomain Ca2+ signals at processes. Ca2+ waves did not require action potentials for their generation and occurred in a probenecid-sensitive manner, indicating that the endogenous ligand for P2Y1R is elevated independently of synaptic transmission. Our data suggest that spontaneous microdomain Ca2+ signals occur independently of P2Y1R activation and that astrocytes may not encode neuronal information in response to synaptic transmission at a point source of neurotransmitter release.SIGNIFICANCE STATEMENT Astrocytes are thought to enwrap synapses with their processes to receive neuronal information via Gq-protein coupled receptors (GqPCRs). Astrocyte processes display numerous microdomain Ca2+ signals that occur spontaneously. To determine whether GqPCRs play a role in microdomain Ca2+ signals and the timeframe in which astrocytes sense neuronal information, we engineered mice whose astrocytes specifically overexpress the P2Y1 receptor, a major GqPCR in astrocytes. We found that overexpression of P2Y1 receptors in astrocytes did not increase microdomain Ca2+ signals in astrocyte processes but caused Ca2+ wavelike signals. Our data indicate that spontaneous microdomain Ca2+ signals do not require activation of P2Y1 receptors.

Funding information:
  • Intramural NIH HHS - Z99 AR999999(United States)

Myocardial Polyploidization Creates a Barrier to Heart Regeneration in Zebrafish.

  • González-Rosa JM
  • Dev. Cell
  • 2018 Feb 26

Literature context:


Abstract:

Correlative evidence suggests that polyploidization of heart muscle, which occurs naturally in post-natal mammals, creates a barrier to heart regeneration. Here, we move beyond a correlation by demonstrating that experimental polyploidization of zebrafish cardiomyocytes is sufficient to suppress their proliferative potential during regeneration. Initially, we determined that zebrafish myocardium becomes susceptible to polyploidization upon transient cytokinesis inhibition mediated by dominant-negative Ect2. Using a transgenic strategy, we generated adult animals containing mosaic hearts composed of differentially labeled diploid and polyploid-enriched cardiomyocyte populations. Diploid cardiomyocytes outcompeted their polyploid neighbors in producing regenerated heart muscle. Moreover, hearts composed of equivalent proportions of diploid and polyploid cardiomyocytes failed to regenerate altogether, demonstrating that a critical percentage of diploid cardiomyocytes is required to achieve heart regeneration. Our data identify cardiomyocyte polyploidization as a barrier to heart regeneration and suggest that mobilizing rare diploid cardiomyocytes in the human heart will improve its regenerative capacity.

Funding information:
  • Canadian Institutes of Health Research - (Canada)
  • NHLBI NIH HHS - R01 HL127067()

Immune or Genetic-Mediated Disruption of CASPR2 Causes Pain Hypersensitivity Due to Enhanced Primary Afferent Excitability.

  • Dawes JM
  • Neuron
  • 2018 Feb 21

Literature context:


Abstract:

Human autoantibodies to contactin-associated protein-like 2 (CASPR2) are often associated with neuropathic pain, and CASPR2 mutations have been linked to autism spectrum disorders, in which sensory dysfunction is increasingly recognized. Human CASPR2 autoantibodies, when injected into mice, were peripherally restricted and resulted in mechanical pain-related hypersensitivity in the absence of neural injury. We therefore investigated the mechanism by which CASPR2 modulates nociceptive function. Mice lacking CASPR2 (Cntnap2-/-) demonstrated enhanced pain-related hypersensitivity to noxious mechanical stimuli, heat, and algogens. Both primary afferent excitability and subsequent nociceptive transmission within the dorsal horn were increased in Cntnap2-/- mice. Either immune or genetic-mediated ablation of CASPR2 enhanced the excitability of DRG neurons in a cell-autonomous fashion through regulation of Kv1 channel expression at the soma membrane. This is the first example of passive transfer of an autoimmune peripheral neuropathic pain disorder and demonstrates that CASPR2 has a key role in regulating cell-intrinsic dorsal root ganglion (DRG) neuron excitability.

Funding information:
  • NINDS NIH HHS - NS18400(United States)

Recurrent Circuitry for Balancing Sleep Need and Sleep.

  • Donlea JM
  • Neuron
  • 2018 Jan 17

Literature context:


Abstract:

Sleep-promoting neurons in the dorsal fan-shaped body (dFB) of Drosophila are integral to sleep homeostasis, but how these cells impose sleep on the organism is unknown. We report that dFB neurons communicate via inhibitory transmitters, including allatostatin-A (AstA), with interneurons connecting the superior arch with the ellipsoid body of the central complex. These "helicon cells" express the galanin receptor homolog AstA-R1, respond to visual input, gate locomotion, and are inhibited by AstA, suggesting that dFB neurons promote rest by suppressing visually guided movement. Sleep changes caused by enhanced or diminished allatostatinergic transmission from dFB neurons and by inhibition or optogenetic stimulation of helicon cells support this notion. Helicon cells provide excitation to R2 neurons of the ellipsoid body, whose activity-dependent plasticity signals rising sleep pressure to the dFB. By virtue of this autoregulatory loop, dFB-mediated inhibition interrupts processes that incur a sleep debt, allowing restorative sleep to rebalance the books. VIDEO ABSTRACT.

Funding information:
  • Intramural NIH HHS - ZIA BC010301-16(United States)
  • NIDA NIH HHS - R01 NS096290()
  • Wellcome Trust - 090309()
  • Wellcome Trust - R01 DA030601()

Abolishment of Spontaneous Flight Turns in Visually Responsive Drosophila.

  • Ferris BD
  • Curr. Biol.
  • 2018 Jan 22

Literature context:


Abstract:

Animals react rapidly to external stimuli, such as an approaching predator, but in other circumstances, they seem to act spontaneously, without any obvious external trigger. How do the neural processes mediating the execution of reflexive and spontaneous actions differ? We studied this question in tethered, flying Drosophila. We found that silencing a large but genetically defined set of non-motor neurons virtually eliminates spontaneous flight turns while preserving the tethered flies' ability to perform two types of visually evoked turns, demonstrating that, at least in flies, these two modes of action are almost completely dissociable.

Funding information:
  • Wellcome Trust - BB/G006156/1(United Kingdom)

Molecular basis of fatty acid taste in Drosophila.

  • Ahn JE
  • Elife
  • 2017 Dec 12

Literature context:


Abstract:

Behavioral studies have established that Drosophila appetitive taste responses towards fatty acids are mediated by sweet sensing Gustatory Receptor Neurons (GRNs). Here we show that sweet GRN activation requires the function of the Ionotropic Receptor genes IR25a, IR76b and IR56d. The former two IR genes are expressed in several neurons per sensillum, while IR56d expression is restricted to sweet GRNs. Importantly, loss of appetitive behavioral responses to fatty acids in IR25a and IR76b mutant flies can be completely rescued by expression of respective transgenes in sweet GRNs. Interestingly, appetitive behavioral responses of wild type flies to hexanoic acid reach a plateau at ~1%, but decrease with higher concentration, a property mediated through IR25a/IR76b independent activation of bitter GRNs. With our previous report on sour taste, our studies suggest that IR-based receptors mediate different taste qualities through cell-type specific IR subunits.

Funding information:
  • NIAAA NIH HHS - T32 AA007463(United States)
  • NIDCD NIH HHS - R01 DC013967()

Nigrotectal Stimulation Stops Interval Timing in Mice.

  • Toda K
  • Curr. Biol.
  • 2017 Dec 18

Literature context:


Abstract:

Considerable evidence implicates the basal ganglia in interval timing, yet the underlying mechanisms remain poorly understood. Using a novel behavioral task, we demonstrate that head-fixed mice can be trained to show the key features of timing behavior within a few sessions. Single-trial analysis of licking behavior reveals stepping dynamics with variable onset times, which is responsible for the canonical Gaussian distribution of timing behavior. Moreover, the duration of licking bouts decreased as mice became sated, showing a strong motivational modulation of licking bout initiation and termination. Using optogenetics, we examined the role of the basal ganglia output in interval timing. We stimulated a pathway important for licking behavior, the GABAergic output projections from the substantia nigra pars reticulata to the deep layers of the superior colliculus. We found that stimulation of this pathway not only cancelled licking but also delayed the initiation of anticipatory licking for the next interval in a frequency-dependent manner. By combining quantitative behavioral analysis with optogenetics in the head-fixed setup, we established a new approach for studying the neural basis of interval timing.

Funding information:
  • Intramural NIH HHS - Z01 ES70065,(United States)

Zebrafish Regulatory T Cells Mediate Organ-Specific Regenerative Programs.

  • Hui SP
  • Dev. Cell
  • 2017 Dec 18

Literature context:


Abstract:

The attenuation of ancestral pro-regenerative pathways may explain why humans do not efficiently regenerate damaged organs. Vertebrate lineages that exhibit robust regeneration, including the teleost zebrafish, provide insights into the maintenance of adult regenerative capacity. Using established models of spinal cord, heart, and retina regeneration, we discovered that zebrafish Treg-like (zTreg) cells rapidly homed to damaged organs. Conditional ablation of zTreg cells blocked organ regeneration by impairing precursor cell proliferation. In addition to modulating inflammation, infiltrating zTreg cells stimulated regeneration through interleukin-10-independent secretion of organ-specific regenerative factors (Ntf3: spinal cord; Nrg1: heart; Igf1: retina). Recombinant regeneration factors rescued the regeneration defects associated with zTreg cell depletion, whereas Foxp3a-deficient zTreg cells infiltrated damaged organs but failed to express regenerative factors. Our data delineate organ-specific roles for Treg cells in maintaining pro-regenerative capacity that could potentially be harnessed for diverse regenerative therapies.

Funding information:
  • NIEHS NIH HHS - ES016005(United States)

Melanocyte Stem Cell Activation and Translocation Initiate Cutaneous Melanoma in Response to UV Exposure.

  • Moon H
  • Cell Stem Cell
  • 2017 Nov 2

Literature context:


Abstract:

Melanoma is one of the deadliest cancers, yet the cells of origin and mechanisms of tumor initiation remain unclear. The majority of melanomas emerge from clear skin without a precursor lesion, but it is unknown whether these melanomas can arise from melanocyte stem cells (MCSCs). Here we employ mouse models to define the role of MCSCs as melanoma cells of origin, demonstrate that MCSC quiescence acts as a tumor suppressor, and identify the extrinsic environmental and molecular factors required for the critical early steps of melanoma initiation. Specifically, melanomas originate from melanoma-competent MCSCs upon stimulation by UVB, which induces MCSC activation and translocation via an inflammation-dependent process. Moreover, the chromatin-remodeling factor Hmga2 in the skin plays a critical role in UVB-mediated melanomagenesis. These findings delineate melanoma formation from melanoma-competent MCSCs following extrinsic stimuli, and they suggest that abrogation of Hmga2 function in the microenvironment can suppress MCSC-originating cutaneous melanomas.

Parallel, but Dissociable, Processing in Discrete Corticostriatal Inputs Encodes Skill Learning.

  • Kupferschmidt DA
  • Neuron
  • 2017 Oct 11

Literature context:


Abstract:

Changes in cortical and striatal function underlie the transition from novel actions to refined motor skills. How discrete, anatomically defined corticostriatal projections function in vivo to encode skill learning remains unclear. Using novel fiber photometry approaches to assess real-time activity of associative inputs from medial prefrontal cortex to dorsomedial striatum and sensorimotor inputs from motor cortex to dorsolateral striatum, we show that associative and sensorimotor inputs co-engage early in action learning and disengage in a dissociable manner as actions are refined. Disengagement of associative, but not sensorimotor, inputs predicts individual differences in subsequent skill learning. Divergent somatic and presynaptic engagement in both projections during early action learning suggests potential learning-related in vivo modulation of presynaptic corticostriatal function. These findings reveal parallel processing within associative and sensorimotor circuits that challenges and refines existing views of corticostriatal function and expose neuronal projection- and compartment-specific activity dynamics that encode and predict action learning.

Regulation of Hippocampal 5-HT Release by P2X7 Receptors in Response to Optogenetic Stimulation of Median Raphe Terminals of Mice.

  • Gölöncsér F
  • Front Mol Neurosci
  • 2017 Oct 28

Literature context:


Abstract:

Serotonergic and glutamatergic neurons of median raphe region (MRR) play a pivotal role in the modulation of affective and cognitive functions. These neurons synapse both onto themselves and remote cortical areas. P2X7 receptors (P2rx7) are ligand gated ion channels expressed by central presynaptic excitatory nerve terminals and involved in the regulation of neurotransmitter release. P2rx7s are implicated in various neuropsychiatric conditions such as schizophrenia and depression. Here we investigated whether 5-HT release released from the hippocampal terminals of MRR is subject to modulation by P2rx7s. To achieve this goal, an optogenetic approach was used to selectively activate subpopulation of serotonergic terminals derived from the MRR locally, and one of its target area, the hippocampus. Optogenetic activation of neurons in the MRR with 20 Hz was correlated with freezing and enhanced locomotor activity of freely moving mice and elevated extracellular levels of 5-HT, glutamate but not GABA in vivo. Similar optical stimulation (OS) significantly increased [3H]5-HT and [3H]glutamate release in acute MRR and hippocampal slices. We examined spatial and temporal patterns of [3H]5-HT release and the interaction between the serotonin and glutamate systems. Whilst [3H]5-HT release from MRR neurons was [Ca2+]o-dependent and sensitive to TTX, CNQX and DL-AP-5, release from hippocampal terminals was not affected by the latter drugs. Hippocampal [3H]5-HT released by electrical but not OS was subject to modulation by 5- HT1B/D receptors agonist sumatriptan (1 μM), whereas the selective 5-HT1A agonist buspirone (0.1 μM) was without effect. [3H]5-HT released by electrical and optical stimulation was decreased in mice genetically deficient in P2rx7s, and after perfusion with selective P2rx7 antagonists, JNJ-47965567 (0.1 μM), and AZ-10606120 (0.1 μM). Optical and electrical stimulation elevated the extracellular level of ATP. Our results demonstrate for the first time the modulation of 5-HT release from hippocampal MRR terminals by the endogenous activation of P2rx7s. P2rx7 mediated modulation of 5-HT release could contribute to various physiological and pathophysiological phenomena, related to hippocampal serotonergic transmission.

Funding information:
  • European Research Council - 294313()

Sleep homeostasis regulated by 5HT2b receptor in a small subset of neurons in the dorsal fan-shaped body of drosophila.

  • Qian Y
  • Elife
  • 2017 Oct 6

Literature context:


Abstract:

Our understanding of the molecular mechanisms underlying sleep homeostasis is limited. We have taken a systematic approach to study neural signaling by the transmitter 5-hydroxytryptamine (5-HT) in drosophila. We have generated knockout and knockin lines for Trh, the 5-HT synthesizing enzyme and all five 5-HT receptors, making it possible for us to determine their expression patterns and to investigate their functional roles. Loss of the Trh, 5HT1a or 5HT2b gene decreased sleep time whereas loss of the Trh or 5HT2b gene diminished sleep rebound after sleep deprivation. 5HT2b expression in a small subset of, probably a single pair of, neurons in the dorsal fan-shaped body (dFB) is functionally essential: elimination of the 5HT2b gene from these neurons led to loss of sleep homeostasis. Genetic ablation of 5HT2b neurons in the dFB decreased sleep and impaired sleep homeostasis. Our results have shown that serotonergic signaling in specific neurons is required for the regulation of sleep homeostasis.

Homeostatic plasticity shapes the visual system's first synapse.

  • Johnson RE
  • Nat Commun
  • 2017 Oct 31

Literature context:


Abstract:

Vision in dim light depends on synapses between rods and rod bipolar cells (RBCs). Here, we find that these synapses exist in multiple configurations, in which single release sites of rods are apposed by one to three postsynaptic densities (PSDs). Single RBCs often form multiple PSDs with one rod; and neighboring RBCs share ~13% of their inputs. Rod-RBC synapses develop while ~7% of RBCs undergo programmed cell death (PCD). Although PCD is common throughout the nervous system, its influences on circuit development and function are not well understood. We generate mice in which ~53 and ~93% of RBCs, respectively, are removed during development. In these mice, dendrites of the remaining RBCs expand in graded fashion independent of light-evoked input. As RBC dendrites expand, they form fewer multi-PSD contacts with rods. Electrophysiological recordings indicate that this homeostatic co-regulation of neurite and synapse development preserves retinal function in dim light.

Funding information:
  • NEI NIH HHS - R01 EY023341()
  • NEI NIH HHS - R01 EY026978()
  • NEI NIH HHS - R01 EY027411()

Role of the Astroglial Glutamate Exchanger xCT in Ventral Hippocampus in Resilience to Stress.

  • Nasca C
  • Neuron
  • 2017 Oct 11

Literature context:


Abstract:

We demonstrate that stress differentially regulates glutamate homeostasis in the dorsal and ventral hippocampus and identify a role for the astroglial xCT in ventral dentate gyrus (vDG) in stress and antidepressant responses. We provide an RNA-seq roadmap for the stress-sensitive vDG. The transcription factor REST binds to xCT promoter in co-occupancy with the epigenetic marker H3K27ac to regulate expression of xCT, which is also reduced in a genetic mouse model of inherent susceptibility to depressive-like behavior. Pharmacologically, modulating histone acetylation with acetyl-L-carnitine (LAC) or acetyl-N-cysteine (NAC) rapidly increases xCT and activates a network with mGlu2 receptors to prime an enhanced glutamate homeostasis that promotes both pro-resilient and antidepressant-like responses. Pharmacological xCT blockage counteracts NAC prophylactic effects. GFAP+-Cre-dependent overexpression of xCT in vDG mimics pharmacological actions in promoting resilience. This work establishes a mechanism by which vDG protection leads to stress resilience and antidepressant responses via epigenetic programming of an xCT-mGlu2 network.

Functional Convergence at the Retinogeniculate Synapse.

  • Litvina EY
  • Neuron
  • 2017 Oct 11

Literature context:


Abstract:

Precise connectivity between retinal ganglion cells (RGCs) and thalamocortical (TC) relay neurons is thought to be essential for the transmission of visual information. Consistent with this view, electrophysiological measurements have previously estimated that 1-3 RGCs converge onto a mouse geniculate TC neuron. Recent advances in connectomics and rabies tracing have yielded much higher estimates of retinogeniculate convergence, although not all identified contacts may be functional. Here we use optogenetics and a computational simulation to determine the number of functionally relevant retinogeniculate inputs onto TC neurons in mice. We find an average of ten RGCs converging onto a mature TC neuron, in contrast to >30 inputs before developmental refinement. However, only 30% of retinogeniculate inputs exceed the threshold for dominating postsynaptic activity. These results signify a greater role for the thalamus in visual processing and provide a functional perspective of anatomical connectivity data.

Ionotropic Receptors Mediate Drosophila Oviposition Preference through Sour Gustatory Receptor Neurons.

  • Chen Y
  • Curr. Biol.
  • 2017 Sep 25

Literature context:


Abstract:

Carboxylic acids are present in many foods, being especially abundant in fruits. Yet, relatively little is known about how acids are detected by gustatory systems and whether they have a potential role in nutrition or provide other health benefits. Here we identify sour gustatory receptor neurons (GRNs) in tarsal taste sensilla of Drosophila melanogaster. We find that most tarsal sensilla harbor a sour GRN that is specifically activated by carboxylic and mineral acids but does not respond to sweet- and bitter-tasting chemicals or salt. One pair of taste sensilla features two GRNs that respond only to a subset of carboxylic acids and high concentrations of salt. All sour GRNs prominently express two Ionotropic Receptor (IR) genes, IR76b and IR25a, and we show that both these genes are necessary for the detection of acids. Furthermore, we establish that IR25a and IR76b are essential in sour GRNs of females for oviposition preference on acid-containing food. Our investigations reveal that acids activate a unique set of taste cells largely dedicated to sour taste, and they indicate that both pH/proton concentration and the structure of carboxylic acids contribute to sour GRN activation. Together, our studies provide new insights into the cellular and molecular basis of sour taste.

Funding information:
  • NIDCD NIH HHS - R01 DC005606()
  • NIDCD NIH HHS - R01 DC013967()

Aldosterone-Sensing Neurons in the NTS Exhibit State-Dependent Pacemaker Activity and Drive Sodium Appetite via Synergy with Angiotensin II Signaling.

  • Resch JM
  • Neuron
  • 2017 Sep 27

Literature context:


Abstract:

Sodium deficiency increases angiotensin II (ATII) and aldosterone, which synergistically stimulate sodium retention and consumption. Recently, ATII-responsive neurons in the subfornical organ (SFO) and aldosterone-sensitive neurons in the nucleus of the solitary tract (NTSHSD2 neurons) were shown to drive sodium appetite. Here we investigate the basis for NTSHSD2 neuron activation, identify the circuit by which NTSHSD2 neurons drive appetite, and uncover an interaction between the NTSHSD2 circuit and ATII signaling. NTSHSD2 neurons respond to sodium deficiency with spontaneous pacemaker-like activity-the consequence of "cardiac" HCN and Nav1.5 channels. Remarkably, NTSHSD2 neurons are necessary for sodium appetite, and with concurrent ATII signaling their activity is sufficient to produce rapid consumption. Importantly, NTSHSD2 neurons stimulate appetite via projections to the vlBNST, which is also the effector site for ATII-responsive SFO neurons. The interaction between angiotensin signaling and NTSHSD2 neurons provides a neuronal context for the long-standing "synergy hypothesis" of sodium appetite regulation.

Funding information:
  • NIDDK NIH HHS - F32 DK103387()
  • NIDDK NIH HHS - P30 DK046200()
  • NIDDK NIH HHS - P30 DK057521()
  • NIDDK NIH HHS - R01 DK075632()
  • NIDDK NIH HHS - R01 DK089044()
  • NIDDK NIH HHS - R01 DK096010()
  • NIDDK NIH HHS - R01 DK111401()
  • NINDS NIH HHS - K08 NS099425()

Memory Erasure Experiments Indicate a Critical Role of CaMKII in Memory Storage.

  • Rossetti T
  • Neuron
  • 2017 Sep 27

Literature context:


Abstract:

The abundant synaptic protein CaMKII is necessary for long-term potentiation (LTP) and memory. However, whether CaMKII is required only during initial processes or whether it also mediates memory storage remains unclear. The most direct test of a storage role is the erasure test. In this test, a putative memory molecule is inhibited after learning. The key prediction is that this should produce persistent memory erasure even after the inhibitory agent is removed. We conducted this test using transient viral (HSV) expression of dominant-negative CaMKII-alpha (K42M) in the hippocampus. This produced persistent erasure of conditioned place avoidance. As an additional test, we found that expression of activated CaMKII (T286D/T305A/T306A) impaired place avoidance, a result not expected if a process other than CaMKII stores memory. Our behavioral results, taken together with prior experiments on LTP, strongly support a critical role of CaMKII in LTP maintenance and memory storage.

Funding information:
  • NIDA NIH HHS - R01 DA043195()
  • NINDS NIH HHS - R01 NS103168()
  • NINDS NIH HHS - R56 NS096710()
  • NINDS NIH HHS - U01 NS090583()

Input-Timing-Dependent Plasticity in the Hippocampal CA2 Region and Its Potential Role in Social Memory.

  • Leroy F
  • Neuron
  • 2017 Aug 30

Literature context:


Abstract:

Input-timing-dependent plasticity (ITDP) is a circuit-based synaptic learning rule by which paired activation of entorhinal cortical (EC) and Schaffer collateral (SC) inputs to hippocampal CA1 pyramidal neurons (PNs) produces a long-term enhancement of SC excitation. We now find that paired stimulation of EC and SC inputs also induces ITDP of SC excitation of CA2 PNs. However, whereas CA1 ITDP results from long-term depression of feedforward inhibition (iLTD) as a result of activation of CB1 endocannabinoid receptors on cholecystokinin-expressing interneurons, CA2 ITDP results from iLTD through activation of δ-opioid receptors on parvalbumin-expressing interneurons. Furthermore, whereas CA1 ITDP has been previously linked to enhanced specificity of contextual memory, we find that CA2 ITDP is associated with enhanced social memory. Thus, ITDP may provide a general synaptic learning rule for distinct forms of hippocampal-dependent memory mediated by distinct hippocampal regions.

Early Integration of Temperature and Humidity Stimuli in the Drosophila Brain.

  • Frank DD
  • Curr. Biol.
  • 2017 Aug 7

Literature context:


Abstract:

The Drosophila antenna contains receptor neurons for mechanical, olfactory, thermal, and humidity stimuli. Neurons expressing the ionotropic receptor IR40a have been implicated in the selection of an appropriate humidity range [1, 2], but although previous work indicates that insect hygroreceptors may be made up by a "triad" of neurons (with a dry-, a cold-, and a humid-air-responding cell [3]), IR40a expression included only cold- and dry-air cells. Here, we report the identification of the humid-responding neuron that completes the hygrosensory triad in the Drosophila antenna. This cell type expresses the Ir68a gene, and Ir68a mutation perturbs humidity preference. Next, we follow the projections of Ir68a neurons to the brain and show that they form a distinct glomerulus in the posterior antennal lobe (PAL). In the PAL, a simple sensory map represents related features of the external environment with adjacent "hot," "cold," "dry," and "humid" glomeruli-an organization that allows for both unique and combinatorial sampling by central relay neurons. Indeed, flies avoided dry heat more robustly than humid heat, and this modulation was abolished by silencing of dry-air receptors. Consistently, at least one projection neuron type received direct synaptic input from both temperature and dry-air glomeruli. Our results further our understanding of humidity sensing in the Drosophila antenna, uncover a neuronal substrate for early sensory integration of temperature and humidity in the brain, and illustrate the logic of how ethologically relevant combinations of sensory cues can be processed together to produce adaptive behavioral responses.

Distinct Neural Circuits for the Formation and Retrieval of Episodic Memories.

  • Roy DS
  • Cell
  • 2017 Aug 24

Literature context:


Abstract:

The formation and retrieval of a memory is thought to be accomplished by activation and reactivation, respectively, of the memory-holding cells (engram cells) by a common set of neural circuits, but this hypothesis has not been established. The medial temporal-lobe system is essential for the formation and retrieval of episodic memory for which individual hippocampal subfields and entorhinal cortex layers contribute by carrying out specific functions. One subfield whose function is poorly known is the subiculum. Here, we show that dorsal subiculum and the circuit, CA1 to dorsal subiculum to medial entorhinal cortex layer 5, play a crucial role selectively in the retrieval of episodic memories. Conversely, the direct CA1 to medial entorhinal cortex layer 5 circuit is essential specifically for memory formation. Our data suggest that the subiculum-containing detour loop is dedicated to meet the requirements associated with recall such as rapid memory updating and retrieval-driven instinctive fear responses.

Primary Cilia Signaling Shapes the Development of Interneuronal Connectivity.

  • Guo J
  • Dev. Cell
  • 2017 Aug 7

Literature context:


Abstract:

Appropriate growth and synaptic integration of GABAergic inhibitory interneurons are essential for functional neural circuits in the brain. Here, we demonstrate that disruption of primary cilia function following the selective loss of ciliary GTPase Arl13b in interneurons impairs interneuronal morphology and synaptic connectivity, leading to altered excitatory/inhibitory activity balance. The altered morphology and connectivity of cilia mutant interneurons and the functional deficits are rescued by either chemogenetic activation of ciliary G-protein-coupled receptor (GPCR) signaling or the selective induction of Sstr3, a ciliary GPCR, in Arl13b-deficient cilia. Our results thus define a specific requirement for primary cilia-mediated GPCR signaling in interneuronal connectivity and inhibitory circuit formation.

Funding information:
  • NIDDK NIH HHS - P30 DK074038()
  • NIMH NIH HHS - R01 MH060929()
  • NINDS NIH HHS - P30 NS045892()
  • NINDS NIH HHS - R01 NS090029()
  • NINDS NIH HHS - R56 NS090029()

Loss of Tuberous Sclerosis Complex1 in Adult Oligodendrocyte Progenitor Cells Enhances Axon Remyelination and Increases Myelin Thickness after a Focal Demyelination.

  • McLane LE
  • J. Neurosci.
  • 2017 Aug 2

Literature context:


Abstract:

Although the mammalian target of rapamycin (mTOR) is an essential regulator of developmental oligodendrocyte differentiation and myelination, oligodendrocyte-specific deletion of tuberous sclerosis complex (TSC), a major upstream inhibitor of mTOR, surprisingly also leads to hypomyelination during CNS development. However, the function of TSC has not been studied in the context of remyelination. Here, we used the inducible Cre-lox system to study the function of TSC in the remyelination of a focal, lysolecithin-demyelinated lesion in adult male mice. Using two different mouse models in which Tsc1 is deleted by Cre expression in oligodendrocyte progenitor cells (OPCs) or in premyelinating oligodendrocytes, we reveal that deletion of Tsc1 affects oligodendroglia differently depending on the stage of the oligodendrocyte lineage. Tsc1 deletion from NG2+ OPCs accelerated remyelination. Conversely, Tsc1 deletion from proteolipid protein (PLP)-positive oligodendrocytes slowed remyelination. Contrary to developmental myelination, there were no changes in OPC or oligodendrocyte numbers in either model. Our findings reveal a complex role for TSC in oligodendrocytes during remyelination in which the timing of Tsc1 deletion is a critical determinant of its effect on remyelination. Moreover, our findings suggest that TSC has different functions in developmental myelination and remyelination.SIGNIFICANCE STATEMENT Myelin loss in demyelinating disorders such as multiple sclerosis results in disability due to loss of axon conductance and axon damage. Encouragingly, the nervous system is capable of spontaneous remyelination, but this regenerative process often fails. Many chronically demyelinated lesions have oligodendrocyte progenitor cells (OPCs) within their borders. It is thus of great interest to elucidate mechanisms by which we might enhance endogenous remyelination. Here, we provide evidence that deletion of Tsc1 from OPCs, but not differentiating oligodendrocytes, is beneficial to remyelination. This finding contrasts with the loss of oligodendroglia and hypomyelination seen with Tsc1 or Tsc2 deletion in the oligodendrocyte lineage during CNS development and points to important differences in the regulation of developmental myelination and remyelination.

Funding information:
  • NINDS NIH HHS - R01 NS082203()

Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT.

  • Aguilar JI
  • Neuron
  • 2017 Aug 30

Literature context:


Abstract:

The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content.

An FAK-YAP-mTOR Signaling Axis Regulates Stem Cell-Based Tissue Renewal in Mice.

  • Hu JK
  • Cell Stem Cell
  • 2017 Jul 6

Literature context:


Abstract:

Tissue homeostasis requires the production of newly differentiated cells from resident adult stem cells. Central to this process is the expansion of undifferentiated intermediates known as transit-amplifying (TA) cells, but how stem cells are triggered to enter this proliferative TA state remains an important open question. Using the continuously growing mouse incisor as a model of stem cell-based tissue renewal, we found that the transcriptional cofactors YAP and TAZ are required both to maintain TA cell proliferation and to inhibit differentiation. Specifically, we identified a pathway involving activation of integrin α3 in TA cells that signals through an LATS-independent FAK/CDC42/PP1A cascade to control YAP-S397 phosphorylation and nuclear localization. This leads to Rheb expression and potentiates mTOR signaling to drive the proliferation of TA cells. These findings thus reveal a YAP/TAZ signaling mechanism that coordinates stem cell expansion and differentiation during organ renewal.

Funding information:
  • NIDCR NIH HHS - F32 DE023705()
  • NIDCR NIH HHS - K99 DE025874()
  • NIDCR NIH HHS - R01 DE024988()
  • NIDCR NIH HHS - R35 DE026602()

Physiological and pathophysiological control of synaptic GluN2B-NMDA receptors by the C-terminal domain of amyloid precursor protein.

  • Pousinha PA
  • Elife
  • 2017 Jul 6

Literature context:


Abstract:

The amyloid precursor protein (APP) harbors physiological roles at synapses and is central to Alzheimer's disease (AD) pathogenesis. Evidence suggests that APP intracellular domain (AICD) could regulate synapse function, but the underlying molecular mechanisms remain unknown. We addressed AICD actions at synapses, per se, combining in vivo AICD expression, ex vivo AICD delivery or APP knock-down by in utero electroporation of shRNAs with whole-cell electrophysiology. We report a critical physiological role of AICD in controlling GluN2B-containing NMDA receptors (NMDARs) at immature excitatory synapses, via a transcription-dependent mechanism. We further show that AICD increase in mature neurons, as reported in AD, alters synaptic NMDAR composition to an immature-like GluN2B-rich profile. This disrupts synaptic signal integration, via over-activation of SK channels, and synapse plasticity, phenotypes rescued by GluN2B antagonism. We provide a new physiological role for AICD, which becomes pathological upon AICD increase in mature neurons. Thus, AICD could contribute to AD synaptic failure.

Analysis of SUMO1-conjugation at synapses.

  • Daniel JA
  • Elife
  • 2017 Jun 9

Literature context:


Abstract:

SUMO1-conjugation of proteins at neuronal synapses is considered to be a major post-translational regulatory process in nerve cell and synapse function, but the published evidence for SUMO1-conjugation at synapses is contradictory. We employed multiple genetic mouse models for stringently controlled biochemical and immunostaining analyses of synaptic SUMO1-conjugation. By using a knock-in reporter mouse line expressing tagged SUMO1, we could not detect SUMO1-conjugation of seven previously proposed synaptic SUMO1-targets in the brain. Further, immunostaining of cultured neurons from wild-type and SUMO1 knock-out mice showed that anti-SUMO1 immunolabelling at synapses is non-specific. Our findings indicate that SUMO1-conjugation of synaptic proteins does not occur or is extremely rare and hence not detectable using current methodology. Based on our data, we discuss a set of experimental strategies and minimal consensus criteria for the validation of SUMOylation that can be applied to any SUMOylation substrate and SUMO isoform.

Feature Integration Drives Probabilistic Behavior in the Drosophila Escape Response.

  • von Reyn CR
  • Neuron
  • 2017 Jun 21

Literature context:


Abstract:

Animals rely on dedicated sensory circuits to extract and encode environmental features. How individual neurons integrate and translate these features into behavioral responses remains a major question. Here, we identify a visual projection neuron type that conveys predator approach information to the Drosophila giant fiber (GF) escape circuit. Genetic removal of this input during looming stimuli reveals that it encodes angular expansion velocity, whereas other input cell type(s) encode angular size. Motor program selection and timing emerge from linear integration of these two features within the GF. Linear integration improves size detection invariance over prior models and appropriately biases motor selection to rapid, GF-mediated escapes during fast looms. Our findings suggest feature integration, and motor control may occur as simultaneous operations within the same neuron and establish the Drosophila escape circuit as a model system in which these computations may be further dissected at the circuit level. VIDEO ABSTRACT.

Amitosis of Polyploid Cells Regenerates Functional Stem Cells in the Drosophila Intestine.

  • Lucchetta EM
  • Cell Stem Cell
  • 2017 May 4

Literature context:


Abstract:

Organ fitness depends on appropriate maintenance of stem cell populations, and aberrations in functional stem cell numbers are associated with malignancies and aging. Symmetrical division is the best characterized mechanism of stem cell replacement, but other mechanisms could also be deployed, particularly in situations of high stress. Here, we show that after severe depletion, intestinal stem cells (ISCs) in the Drosophila midgut are replaced by spindle-independent ploidy reduction of cells in the enterocyte lineage through a process known as amitosis. Amitosis is also induced by the functional loss of ISCs coupled with tissue demand and in aging flies, underscoring the generality of this mechanism. However, we also found that random homologous chromosome segregation during ploidy reduction can expose deleterious mutations through loss of heterozygosity. Together, our results highlight amitosis as an unappreciated mechanism for restoring stem cell homeostasis, but one with some associated risk in animals carrying mutations.

Funding information:
  • NICHD NIH HHS - T32 HD055165()
  • NIDDK NIH HHS - R01 DK107702()

Macrophages Facilitate Electrical Conduction in the Heart.

  • Hulsmans M
  • Cell
  • 2017 Apr 20

Literature context:


Abstract:

Organ-specific functions of tissue-resident macrophages in the steady-state heart are unknown. Here, we show that cardiac macrophages facilitate electrical conduction through the distal atrioventricular node, where conducting cells densely intersperse with elongated macrophages expressing connexin 43. When coupled to spontaneously beating cardiomyocytes via connexin-43-containing gap junctions, cardiac macrophages have a negative resting membrane potential and depolarize in synchrony with cardiomyocytes. Conversely, macrophages render the resting membrane potential of cardiomyocytes more positive and, according to computational modeling, accelerate their repolarization. Photostimulation of channelrhodopsin-2-expressing macrophages improves atrioventricular conduction, whereas conditional deletion of connexin 43 in macrophages and congenital lack of macrophages delay atrioventricular conduction. In the Cd11bDTR mouse, macrophage ablation induces progressive atrioventricular block. These observations implicate macrophages in normal and aberrant cardiac conduction.

Funding information:
  • NHLBI NIH HHS - K24 HL105780()
  • NHLBI NIH HHS - R01 HL092577()
  • NHLBI NIH HHS - R01 HL096576()
  • NHLBI NIH HHS - R01 HL114477()
  • NHLBI NIH HHS - R01 HL117829()
  • NHLBI NIH HHS - R01 HL125428()
  • NHLBI NIH HHS - R01 HL128264()
  • NHLBI NIH HHS - R01 HL131495()
  • NICHD NIH HHS - R01 HD069623()
  • NIDDK NIH HHS - P30 DK043351()
  • NIDDK NIH HHS - P30 DK057521()
  • NINDS NIH HHS - R01 NS084863()

Perturbation of Serotonin Homeostasis during Adulthood Affects Serotonergic Neuronal Circuitry.

  • Pratelli M
  • eNeuro
  • 2017 Apr 24

Literature context:


Abstract:

Growing evidence shows that the neurotransmitter serotonin (5-HT) modulates the fine-tuning of neuron development and the establishment of wiring patterns in the brain. However, whether serotonin is involved in the maintenance of neuronal circuitry in the adult brain remains elusive. Here, we use a Tph2fl°x conditional knockout (cKO) mouse line to assess the impact of serotonin depletion during adulthood on serotonergic system organization. Data show that the density of serotonergic fibers is increased in the hippocampus and decreased in the thalamic paraventricular nucleus (PVN) as a consequence of brain serotonin depletion. Strikingly, these defects are rescued following reestablishment of brain 5-HT signaling via administration of the serotonin precursor 5-hydroxytryptophan (5-HTP). Finally, 3D reconstruction of serotonergic fibers reveals that changes in serotonin homeostasis affect axonal branching complexity. These data demonstrate that maintaining proper serotonin homeostasis in the adult brain is crucial to preserve the correct serotonergic axonal wiring.

Synaptotagmin2 (Syt2) Drives Fast Release Redundantly with Syt1 at the Output Synapses of Parvalbumin-Expressing Inhibitory Neurons.

  • Bouhours B
  • J. Neurosci.
  • 2017 Apr 26

Literature context:


Abstract:

Parvalbumin-expressing inhibitory neurons in the mammalian CNS are specialized for fast transmitter release at their output synapses. However, the Ca2+ sensor(s) used by identified inhibitory synapses, including the output synapses of parvalbumin-expressing inhibitory neurons, have only recently started to be addressed. Here, we investigated the roles of Syt1 and Syt2 at two types of fast-releasing inhibitory connections in the mammalian CNS: the medial nucleus of the trapezoid body to lateral superior olive glycinergic synapse, and the basket/stellate cell-Purkinje GABAergic synapse in the cerebellum. We used conditional and conventional knock-out (KO) mouse lines, with viral expression of Cre-recombinase and a light-activated ion channel for optical stimulation of the transduced fibers, to produce Syt1-Syt2 double KO synapses in vivo Surprisingly, we found that KO of Syt2 alone had only minor effects on evoked transmitter release, despite the clear presence of the protein in inhibitory nerve terminals revealed by immunohistochemistry. We show that Syt1 is weakly coexpressed at these inhibitory synapses and must be genetically inactivated together with Syt2 to achieve a significant reduction and desynchronization of fast release. Thus, our work identifies the functionally relevant Ca2+ sensor(s) at fast-releasing inhibitory synapses and shows that two major Syt isoforms can cooperate to mediate release at a given synaptic connection.SIGNIFICANCE STATEMENT During synaptic transmission, the influx of Ca2+ into the presynaptic nerve terminal activates a Ca2+ sensor for vesicle fusion, a crucial step in the activity-dependent release of neurotransmitter. Synaptotagmin (Syt) proteins, and especially Syt1 and Syt2, have been identified as the Ca2+ sensor at excitatory synapses, but the Ca2+ sensor(s) at inhibitory synapses in native brain tissue are not well known. We found that both Syt1 and Syt2 need to be genetically inactivated to cause a significant reduction of activity-evoked release at two types of fast inhibitory synapses in mouse brain. Thus, we identify Syt2 as a functionally important Ca2+ sensor at fast-releasing inhibitory synapses, and show that Syt1 and Syt2 can redundantly control transmitter release at specific brain synapses.

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()

Hallmarks of Alzheimer's Disease in Stem-Cell-Derived Human Neurons Transplanted into Mouse Brain.

  • Espuny-Camacho I
  • Neuron
  • 2017 Mar 8

Literature context:


Abstract:

Human pluripotent stem cells (PSCs) provide a unique entry to study species-specific aspects of human disorders such as Alzheimer's disease (AD). However, in vitro culture of neurons deprives them of their natural environment. Here we transplanted human PSC-derived cortical neuronal precursors into the brain of a murine AD model. Human neurons differentiate and integrate into the brain, express 3R/4R Tau splice forms, show abnormal phosphorylation and conformational Tau changes, and undergo neurodegeneration. Remarkably, cell death was dissociated from tangle formation in this natural 3D model of AD. Using genome-wide expression analysis, we observed upregulation of genes involved in myelination and downregulation of genes related to memory and cognition, synaptic transmission, and neuron projection. This novel chimeric model for AD displays human-specific pathological features and allows the analysis of different genetic backgrounds and mutations during the course of the disease.

Tridimensional Visualization and Analysis of Early Human Development.

  • Belle M
  • Cell
  • 2017 Mar 23

Literature context:


Abstract:

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.

MicroRNAs Establish Uniform Traits during the Architecture of Vertebrate Embryos.

  • Kasper DM
  • Dev. Cell
  • 2017 Mar 27

Literature context:


Abstract:

Proper functioning of an organism requires cells and tissues to behave in uniform, well-organized ways. How this optimum of phenotypes is achieved during the development of vertebrates is unclear. Here, we carried out a multi-faceted and single-cell resolution screen of zebrafish embryonic blood vessels upon mutagenesis of single and multi-gene microRNA (miRNA) families. We found that embryos lacking particular miRNA-dependent signaling pathways develop a vascular trait similar to wild-type, but with a profound increase in phenotypic heterogeneity. Aberrant trait variance in miRNA mutant embryos uniquely sensitizes their vascular system to environmental perturbations. We discovered a previously unrecognized role for specific vertebrate miRNAs to protect tissue development against phenotypic variability. This discovery marks an important advance in our comprehension of how miRNAs function in the development of higher organisms.

Funding information:
  • NHLBI NIH HHS - F32 HL132475()
  • NHLBI NIH HHS - R01 HL130246()
  • NHLBI NIH HHS - R56 HL123998()

Bassoon Controls Presynaptic Autophagy through Atg5.

  • Okerlund ND
  • Neuron
  • 2017 Feb 22

Literature context:


Abstract:

Mechanisms regulating the surveillance and clearance of synaptic proteins are not well understood. Intriguingly, the loss of the presynaptic active zone proteins Piccolo and Bassoon triggers the loss of synaptic vesicles (SVs) and compromises synaptic integrity. Here we report that the destruction of SVs in boutons lacking Piccolo and Bassoon was associated with the induction of presynaptic autophagy, a process that depended on poly-ubiquitination, but not the E3 ubiquitin ligase Siah1. Surprisingly, gain or loss of function (LOF) of Bassoon alone suppressed or enhanced presynaptic autophagy, respectively, implying a fundamental role for Bassoon in the local regulation of presynaptic autophagy. Mechanistically, Bassoon was found to interact with Atg5, an E3-like ligase essential for autophagy, and to inhibit the induction of autophagy in heterologous cells. Importantly, Atg5 LOF as well as targeting an Atg5-binding peptide derived from Bassoon inhibited presynaptic autophagy in boutons lacking Piccolo and Bassoon, providing insights into the molecular mechanisms regulating presynaptic autophagy.

Funding information:
  • BLRD VA - I21 BX003357()

Quantitative Predictions Orchestrate Visual Signaling in Drosophila.

  • Kim AJ
  • Cell
  • 2017 Jan 12

Literature context:


Abstract:

Vision influences behavior, but ongoing behavior also modulates vision in animals ranging from insects to primates. The function and biophysical mechanisms of most such modulations remain unresolved. Here, we combine behavioral genetics, electrophysiology, and high-speed videography to advance a function for behavioral modulations of visual processing in Drosophila. We argue that a set of motion-sensitive visual neurons regulate gaze-stabilizing head movements. We describe how, during flight turns, Drosophila perform a set of head movements that require silencing their gaze-stability reflexes along the primary rotation axis of the turn. Consistent with this behavioral requirement, we find pervasive motor-related inputs to the visual neurons, which quantitatively silence their predicted visual responses to rotations around the relevant axis while preserving sensitivity around other axes. This work proposes a function for a behavioral modulation of visual processing and illustrates how the brain can remove one sensory signal from a circuit carrying multiple related signals.

Funding information:
  • NIDA NIH HHS - DP2 DA035148()

Loss of Frataxin activates the iron/sphingolipid/PDK1/Mef2 pathway in mammals.

  • Chen K
  • Elife
  • 2016 Nov 30

Literature context:


Abstract:

Friedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disease caused by mutations in Frataxin (FXN). Loss of FXN causes impaired mitochondrial function and iron homeostasis. An elevated production of reactive oxygen species (ROS) was previously proposed to contribute to the pathogenesis of FRDA. We recently showed that loss of frataxin homolog (fh), a Drosophila homolog of FXN, causes a ROS independent neurodegeneration in flies (Chen et al., 2016). In fh mutants, iron accumulation in the nervous system enhances the synthesis of sphingolipids, which in turn activates 3-phosphoinositide dependent protein kinase-1 (Pdk1) and myocyte enhancer factor-2 (Mef2) to trigger neurodegeneration of adult photoreceptors. Here, we show that loss of Fxn in the nervous system in mice also activates an iron/sphingolipid/PDK1/Mef2 pathway, indicating that the mechanism is evolutionarily conserved. Furthermore, sphingolipid levels and PDK1 activity are also increased in hearts of FRDA patients, suggesting that a similar pathway is affected in FRDA.

Funding information:
  • NIDDK NIH HHS - U24 DK059637(United States)

Frazzled promotes growth cone attachment at the source of a Netrin gradient in the Drosophila visual system.

  • Akin O
  • Elife
  • 2016 Oct 15

Literature context:


Abstract:

Axon guidance is proposed to act through a combination of long- and short-range attractive and repulsive cues. The ligand-receptor pair, Netrin (Net) and Frazzled (Fra) (DCC, Deleted in Colorectal Cancer, in vertebrates), is recognized as the prototypical effector of chemoattraction, with roles in both long- and short-range guidance. In the Drosophila visual system, R8 photoreceptor growth cones were shown to require Net-Fra to reach their target, the peak of a Net gradient. Using live imaging, we show, however, that R8 growth cones reach and recognize their target without Net, Fra, or Trim9, a conserved binding partner of Fra, but do not remain attached to it. Thus, despite the graded ligand distribution along the guidance path, Net-Fra is not used for chemoattraction. Based on findings in other systems, we propose that adhesion to substrate-bound Net underlies both long- and short-range Net-Fra-dependent guidance in vivo, thereby eroding the distinction between them.

Funding information:
  • NIH HHS - R24-OD-011199(United States)

Dopamine Neuron-Specific Optogenetic Stimulation in Rhesus Macaques.

  • Stauffer WR
  • Cell
  • 2016 Sep 8

Literature context:


Abstract:

Optogenetic studies in mice have revealed new relationships between well-defined neurons and brain functions. However, there are currently no means to achieve the same cell-type specificity in monkeys, which possess an expanded behavioral repertoire and closer anatomical homology to humans. Here, we present a resource for cell-type-specific channelrhodopsin expression in Rhesus monkeys and apply this technique to modulate dopamine activity and monkey choice behavior. These data show that two viral vectors label dopamine neurons with greater than 95% specificity. Infected neurons were activated by light pulses, indicating functional expression. The addition of optical stimulation to reward outcomes promoted the learning of reward-predicting stimuli at the neuronal and behavioral level. Together, these results demonstrate the feasibility of effective and selective stimulation of dopamine neurons in non-human primates and a resource that could be applied to other cell types in the monkey brain.

Age-Related Hearing Loss and Degeneration of Cochlear Hair Cells in Mice Lacking Thyroid Hormone Receptor β1.

  • Ng L
  • Endocrinology
  • 2015 Oct 19

Literature context:


Abstract:

A key function of the thyroid hormone receptor β (Thrb) gene is in the development of auditory function. However, the roles of the 2 receptor isoforms, TRβ1 and TRβ2, expressed by the Thrb gene are unclear, and it is unknown whether these isoforms promote the maintenance as well as development of hearing. We investigated the function of TRβ1 in mice with a Thrb(b1) reporter allele that expresses β-galactosidase instead of TRβ1. In the immature cochlea, β-galactosidase was detected in the greater epithelial ridge, sensory hair cells, spiral ligament, and spiral ganglion and in adulthood, at low levels in the hair cells, support cells and root cells of the outer sulcus. Although deletion of all TRβ isoforms causes severe, early-onset deafness, deletion of TRβ1 or TRβ2 individually caused no obvious hearing loss in juvenile mice. However, over subsequent months, TRβ1 deficiency resulted in progressive loss of hearing and loss of hair cells. TRβ1-deficient mice had minimal changes in serum thyroid hormone and thyrotropin levels, indicating that hormonal imbalances were unlikely to cause hearing loss. The results suggest mutually shared roles for TRβ1 and TRβ2 in cochlear development and an unexpected requirement for TRβ1 in the maintenance of hearing in adulthood.

Funding information:
  • NIMH NIH HHS - R01 MH100217(United States)

Adrenal Development in Mice Requires GATA4 and GATA6 Transcription Factors.

  • Tevosian SG
  • Endocrinology
  • 2015 Jul 20

Literature context:


Abstract:

The adrenal glands consist of an outer cortex and an inner medulla, and their primary purposes include hormone synthesis and secretion. The adrenal cortex produces a complex array of steroid hormones, whereas the medulla is part of the sympathetic nervous system and produces the catecholamines epinephrine and norepinephrine. In the mouse, GATA binding protein (GATA) 4 and GATA6 transcription factors are coexpressed in several embryonic tissues, including the adrenal cortex. To explore the roles of GATA4 and GATA6 in mouse adrenal development, we conditionally deleted these genes in adrenocortical cells using the Sf1Cre strain of animals. We report here that mice with Sf1Cre-mediated double deletion of Gata4 and Gata6 genes lack identifiable adrenal glands, steroidogenic factor 1-positive cortical cells and steroidogenic gene expression in the adrenal location. The inactivation of the Gata6 gene alone (Sf1Cre;Gata6(flox/flox)) drastically reduced the adrenal size and corticosterone production in the adult animals. Adrenocortical aplasia is expected to result in the demise of the animal within 2 weeks after birth unless glucocorticoids are provided. In accordance, Sf1Cre;Gata4(flox/flox)Gata6(flox/flox) females depend on steroid supplementation to survive after weaning. Surprisingly, Sf1Cre;Gata4(flox/flox)Gata6(flox/flox) males appear to live normal lifespans as vital steroidogenic synthesis shifts to their testes. Our results reveal a requirement for GATA factors in adrenal development and provide a novel tool to characterize the transcriptional network controlling adrenocortical cell fates.

Funding information:
  • NINDS NIH HHS - R56 NS042861(United States)

Identifying functional connections of the inner photoreceptors in Drosophila using Tango-Trace.

  • Jagadish S
  • Neuron
  • 2014 Aug 6

Literature context:


Abstract:

In Drosophila, the four inner photoreceptor neurons exhibit overlapping but distinct spectral sensitivities and mediate behaviors that reflect spectral preference. We developed a genetic strategy, Tango-Trace, that has permitted the identification of the connections of the four chromatic photoreceptors. Each of the four stochastically distributed chromatic photoreceptor subtypes make distinct connections in the medulla with four different TmY cells. Moreover, each class of TmY cells forms a retinotopic map in both the medulla and the lobula complex, generating four overlapping topographic maps that could carry different color information. Thus, the four inner photoreceptors transmit spectral information through distinct channels that may converge in both the medulla and lobula complex. These projections could provide an anatomic basis for color vision and may relay information about color to motion sensitive areas. Moreover, the Tango-Trace strategy we used may be applied more generally to identify neural circuits in the fly brain.

Age increase of estrogen receptor-α (ERα) in cortical astrocytes impairs neurotrophic support in male and female rats.

  • Arimoto JM
  • Endocrinology
  • 2013 Jun 20

Literature context:


Abstract:

Rodent models show decreased neuronal responses to estradiol (E2) during aging (E2-desensitization) in association with reduced neuronal estrogen receptor (ER)-α, but little is known about age changes of E2-dependent astrocytic neurotrophic support. Because elevated expression of astrocyte glial fibrillary acidic protein (GFAP) is associated with impaired neurotrophic activity and because the GFAP promoter responds to ERα, we investigated the role of astrocytic ERα and ERβ in impaired astrocyte neurotrophic activity during aging. In vivo and in vitro, ERα was increased greater than 50% with age in astrocytes from the cerebral cortex of male rats (24 vs 3 months), whereas ERβ did not change. In astrocytes from 3-month-old males, experimentally increasing the ERα to ERβ ratio induced the aging phenotype of elevated GFAP and impaired E2-dependent neurite outgrowth. In 24-month-old male astrocytes, lowering ERα reversed the age elevation of GFAP and partially restored E2-dependent neurite outgrowth. Mixed glia (astrocytes to microglia, 3:1) of both sexes also showed these age changes. In a model of perimenopause, mixed glia from 9- to 15-month rats showed E2 desensitization: 9-month regular cyclers retained young-like ERα to ERβ ratios and neurotrophic activity, whereas 9-month noncyclers had elevated ERα and GFAP but low E2-dependent neurotrophic activity. In vivo, ERα levels in cortical astrocytes were also elevated. The persisting effects of ovarian acyclicity in vitro are hypothesized to arise from steroidal perturbations during ovarian senescence. These findings suggest that increased astrocyte ERα expression during aging contributes to the E2 desensitization of the neuronal responses in both sexes.

Funding information:
  • NIDCD NIH HHS - R01 DC014728(United States)