Project description:One of the key aspects of neuronal differentiation is the array of neurotransmitters and neurotransmitter receptors that each neuron possesses. One important goal of developmental neuroscience is to understand how these differentiated properties are established during development. In this paper, we use fluorescence activated cell sorting and RNA-seq to determine the transcriptome of the Drosophila CNS midline cells, which consist of a small number of well-characterized neurons and glia. These data revealed that midline cells express 9 neuropeptide precursor genes, 13 neuropeptide receptor genes, and 31 small-molecule neurotransmitter receptor genes. In situ hybridization and high-resolution confocal analyses were carried-out to determine the midline cell identity for these neuropeptides and the neuropeptide receptors. The results revealed a surprising level of diversity. Neuropeptide genes are expressed in a variety of midline cell types, including motoneurons, GABAergic interneurons, and midline glia. These data revealed previously unknown functional differences among the highly-related iVUM neurons. There also exist segmental differences in expression for the same neuronal sub-type. Similar experiments on midline-expressed neuropeptide receptor genes reveal considerable diversity in synaptic inputs. Multiple receptor types were expressed in midline interneurons and motoneurons, and, in one case, link feeding behavior to gut peristalsis and locomotion. There were also segmental differences, variations between the 3 iVUMs, and three hormone receptor genes were broadly expressed in most midline cells. The Drosophila Castor transcription factor is present at high levels in iVUM5, which is both GABAergic and expresses the short neuropeptide F precursor gene. Genetic and misexpression experiments indicated that castor specifically controls expression of the short neuropeptide F precursor gene, but does not affect iVUM cell fate or expression of Gad1. This indicates a novel function for castor in regulating neuropeptide gene expression. To study the development and differentiation of the CNS midline cells of Drosophila melanogaster on a genome-wide scale, these cells were labeled with GFP using the GAL/UAS system and FACS purified at 2 ermbryonic time-points; 6-8 hours and 14-16 hours after egg laying. Poly(A) mRNA was collected from these samples and cDNA libraries were generated. Sequencing was performed on 6 independent samples: Two FACS purified CNS-midline cell samples and one non-midline sample taken from 6-8 hours After Egg Laying (AEL) embryos and from 14-16 hours AEL embryos.

Project description:GABAergic interneurons are lost in conditions including epilepsy and CNS injury, but there are few culture models available to study their function. Towards the goal of obtaining renewable sources of GABAergic neurons, we used the molecular profile of a functionally-incomplete GABAergic precursor clone to screen 17 new clones isolated from GFP+ rat E14.5 cortex and ganglionic eminence (GE) that were generated by viral introduction of v-myc. The clones grow as neurospheres in medium with FGF2, and after withdrawal of FGF2 they exhibit varying patterns of differentiation. Transcriptional profiling and qPCR indicated that one clone (GE6) expresses high levels of mRNAs encoding Dlx1, 2, 5 and 6, glutamate decarboxylases, and presynaptic proteins including neuropeptide Y and somatostatin. Protein expression confirmed that GE6 is a progenitor with restricted differentiation giving rise mostly to neurons with GABAergic markers. In co-cultures with hippocampal neurons, GE6 neurons became electrically excitable and received both inhibitory and excitatory synapses. After withdrawal of FGF2 in cultures of GE6 alone, neurons matured to express BetaIII-tubulin, and staining for synaptophysin and vesicular GABA transporter (VGAT) were robust after 1-2 weeks of differentiation. GE6 neurons also became electrically excitable and displayed synaptic activity, but synaptic currents were carried by chloride and were blocked by bicuculline. The results suggest that the GE6 clone, which is ventrally derived from the GE, resembles GABAergic interneuron progenitors that migrate into the developing forebrain. This is the first report of a relatively stable fetal clone that can be differentiated into GABAergic interneurons with functional synapses. The purpose was to compare differentiation patterns of several different immortalized rat neural progenitor clones to identify early stages in differentiation. The cell clones studies were: GE6 (GABAergic neuronal precursor), GE2 (non-neuronal precursor, CTX8 (multipotential precursor), L2.2 (interneuronal precursor), and L2.3 (multipotential precursor). Five rat neural precursor cell clones were compared at three different time points following FGF2 withdrawal, which triggers differentiation. Three sister culture replicates were performed for each cell clone and time point, yielding 45 samples. One microarray failed so we have 44 microarray results in the dataset.

Project description:Summary: We build a model for the molecular and cellular events underlying phenotypic discordance in glycine receptor defects (beta subunit). Some mice progress and die, while their littermates recover and get better, despite the same mutation on an inbred genetic background. We find evidence for glycine neurotransmitter toxicity and loss of glycinergic interneurons early in the disease, but some mice are able to keep things going until they can over-express homomeric alpha1 channels, whereupon they recover. In the mice progressing towards lethality, neurotransmitter toxicity too quickly extends to GABAergic interneurons and motorneurons, and they lose their window of time to upregulate the alpha1 glycine receptor, and they crash and burn. Importantly, human patients with glycine receptor defects typically show a resolution of their phenotype with age, and we propose that the same remodeling events are occuring in human patients. Hypothesis: Our data suggests that functional recovery of GlyRb mutant mice is likely due to expression of homomeric glycine receptors, rescue from excitotoxicity, and subsequent neuronal remodeling. We propose that human patients with hyperekplexia (mutations of glycine receptors) show remodeling similar to that of the recovering spastic mice, as human patients also show a lessening of symptoms as a function of age. Specific Aim: Murine models for human Startle Disease show clinical variability between littermates. Here, we determined the molecular remodeling of spastic GlyRb mutant spinal cord through the course of the disease, and develop a model for clinical disparity between littermates. At young ages, all animals were spastic, showed loss of glycine receptors, increased expression of vesicular glycine/GABA transporter and NMDA receptors, induction of activated caspase3, and preferential loss of glycinergic interneurons consistent with neurotransmitter toxicity model. Those littermates that recovered from symptoms showed strong over-expression of the GlyRa1 subunit, and increased myelination and synaptic plasticity. Littermates that showed a deteriorating clinical course failed to over-express GlyRa1, and also showed relative loss of gephyrin. These molecular changes were associated with preferential loss of GABAergic interneurons, and extensive motorneuron loss.

Project description:GABAergic interneurons are lost in conditions including epilepsy and CNS injury, but there are few culture models available to study their function. Towards the goal of obtaining renewable sources of GABAergic neurons, we used the molecular profile of a functionally-incomplete GABAergic precursor clone to screen 17 new clones isolated from GFP+ rat E14.5 cortex and ganglionic eminence (GE) that were generated by viral introduction of v-myc. The clones grow as neurospheres in medium with FGF2, and after withdrawal of FGF2 they exhibit varying patterns of differentiation. Transcriptional profiling and qPCR indicated that one clone (GE6) expresses high levels of mRNAs encoding Dlx1, 2, 5 and 6, glutamate decarboxylases, and presynaptic proteins including neuropeptide Y and somatostatin. Protein expression confirmed that GE6 is a progenitor with restricted differentiation giving rise mostly to neurons with GABAergic markers. In co-cultures with hippocampal neurons, GE6 neurons became electrically excitable and received both inhibitory and excitatory synapses. After withdrawal of FGF2 in cultures of GE6 alone, neurons matured to express BetaIII-tubulin, and staining for synaptophysin and vesicular GABA transporter (VGAT) were robust after 1-2 weeks of differentiation. GE6 neurons also became electrically excitable and displayed synaptic activity, but synaptic currents were carried by chloride and were blocked by bicuculline. The results suggest that the GE6 clone, which is ventrally derived from the GE, resembles GABAergic interneuron progenitors that migrate into the developing forebrain. This is the first report of a relatively stable fetal clone that can be differentiated into GABAergic interneurons with functional synapses. The purpose was to compare differentiation patterns of several different immortalized rat neural progenitor clones to identify early stages in differentiation. The cell clones studies were: GE6 (GABAergic neuronal precursor), GE2 (non-neuronal precursor, CTX8 (multipotential precursor), L2.2 (interneuronal precursor), and L2.3 (multipotential precursor).

Project description:Summary: We build a model for the molecular and cellular events underlying phenotypic discordance in glycine receptor defects (beta subunit). Some mice progress and die, while their littermates recover and get better, despite the same mutation on an inbred genetic background. We find evidence for glycine neurotransmitter toxicity and loss of glycinergic interneurons early in the disease, but some mice are able to keep things going until they can over-express homomeric alpha1 channels, whereupon they recover. In the mice progressing towards lethality, neurotransmitter toxicity too quickly extends to GABAergic interneurons and motorneurons, and they lose their window of time to upregulate the alpha1 glycine receptor, and they crash and burn. Importantly, human patients with glycine receptor defects typically show a resolution of their phenotype with age, and we propose that the same remodeling events are occuring in human patients. Hypothesis: Our data suggests that functional recovery of GlyRb mutant mice is likely due to expression of homomeric glycine receptors, rescue from excitotoxicity, and subsequent neuronal remodeling. We propose that human patients with hyperekplexia (mutations of glycine receptors) show remodeling similar to that of the recovering spastic mice, as human patients also show a lessening of symptoms as a function of age. Specific Aim: Murine models for human Startle Disease show clinical variability between littermates. Here, we determined the molecular remodeling of spastic GlyRb mutant spinal cord through the course of the disease, and develop a model for clinical disparity between littermates. At young ages, all animals were spastic, showed loss of glycine receptors, increased expression of vesicular glycine/GABA transporter and NMDA receptors, induction of activated caspase3, and preferential loss of glycinergic interneurons consistent with neurotransmitter toxicity model. Those littermates that recovered from symptoms showed strong over-expression of the GlyRa1 subunit, and increased myelination and synaptic plasticity. Littermates that showed a deteriorating clinical course failed to over-express GlyRa1, and also showed relative loss of gephyrin. These molecular changes were associated with preferential loss of GABAergic interneurons, and extensive motorneuron loss. Keywords: other

Project description:Background: V0v spinal interneurons are highly-conserved, glutamatergic, commissural neurons that function in locomotor circuits. We have previously shown that Evx1 and Evx2 are required to specify the neurotransmitter phenotype of these cells. However, we still know very little about the gene regulatory networks that act downstream of these transcription factors in V0v cells. Methods: To identify candidate members of V0v gene regulatory networks, we FAC-sorted WT and evx1;evx2 double mutant zebrafish V0v spinal interneurons and expression-profiled them using microarrays and scRNA-seq. We also used in situ hybridization to compare expression of a subset of candidate genes in evx1;evx2 mutants and wild-type siblings. Results: Our data reveal two molecularly-distinct subtypes of V0v spinal interneurons at 48 h and suggest that, by this stage of development, evx1;evx2 double mutant cells transfate into either inhibitory spinal interneurons, or motoneurons. Our results also identify 25 transcriptional regulator genes that require Evx1/2 for their expression in V0v interneurons, plus a further 11 transcriptional regulator genes that are repressed in V0v interneurons by Evx1/2. Two of the latter genes are hmx2 and hmx3a. Intriguingly, we show that Hmx2/3a, repress dI2 interneuronal expression of skor1a and nefma, two genes that require Evx1/2 for their expression in V0v interneurons. This suggests that Evx1/2 might regulate skor1a and nefma expression in V0v interneurons by repressing Hmx2/3a expression. Conclusions: This study identifies two molecularly-distinct subsets of V0v spinal interneurons, as well as multiple transcriptional regulators that are strong candidates for acting downstream of Evx1/2 to specify the essential functional characteristics of V0v interneurons. Our data further suggest that in the absence of both Evx1 and Evx2, V0v spinal interneurons initially change their neurotransmitter phenotypes from excitatory to inhibitory and then, later, start to express markers of distinct types of inhibitory spinal interneurons, or motoneurons. Taken together, our findings significantly increase our knowledge of V0v spinal development and move us closer towards the essential goal of identifying the complete gene regulatory networks that specify this crucial cell type.

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Transcriptome analysis of Drosophila CNS midline cells reveals diverse peptidergic properties and a role for castor in neuronal differentiation

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