Project description:We performed RNA-seq on head tissue collected from Drosophila expressing N-terminal (UAS-HTTNT231Q128) or full-length (UAS-HTTFL200Q) human mHTT in neurons (elav-GAL4) or glia (repo-GAL4).
Project description:Proteins exhibit dynamics in their expression level in response to intracellular and extracellular signals. Regulation of protein turnover allows cells to rapidly and efficiently remodel their proteomes. It is known that proteins can show very different turnover rates in different tissue of the same organism, but little is known about protein turnover rates in different brain cell types. We used a dynamic SILAC approach to determine protein half-lives in primary hippocampal cultures (containing a mixture of neurons and glia cells) as well as in neuron-enriched and glia-enriched cultures. We determined the protein half-lives for over 5100 proteins and found half-lives ranging from <1 to > 20 days with a median half-life of 5.4 days in mixed cultures. Membrane proteins as a group were shorter-lived and mitochondrial proteins, surprisingly, were longer-lived. Proteins in glia possessed significantly shorter half-lives than the same proteins in neurons. The presence of glia sped up or slowed down the half-lives of neuronal proteins. Our results demonstrate that both the cell-type of origin as well as the nature of the extracellular environment have potent influences on protein turnover.
Project description:In Huntington's disease (HD), mutated huntingtin (mhtt) causes striatal neurodegeneration which is paralleled by elevated microglia cell numbers. In vitro corticostriatal slice and primary neuronal culture models, in which neuronal expression of mhtt fragments drives HD-like neurotoxicity, were employed to examine wild type microglia during both the initiation and progression of neuronal pathology. As neuronal pathology progressed, microglia initially localized in the vicinity of neurons expressing mhtt fragments increased in number, demonstrated morphological evidence of activation, and expressed the proliferation marker, Ki67. These microglia were positioned along irregular neurites, but did not localize with mhtt inclusions nor exacerbate mhtt fragment-induced neurotoxicity. Prior to neuronal pathology, microglia upregulated ionized calcium binding adaptor molecule 1 (Iba1), signaling a functional shift. With neurodegeneration, interleukin-6 and complement component 1q were increased. The results suggest a stimulatory, proliferative signal for microglia present at the onset of mhtt fragment-induced neurodegeneration. Thus, microglia effect a localized inflammatory response to neuronal mhtt expression that may serve to direct microglial removal of dysfunctional neurites or aberrant synapses, as is required for reparative actions in vivo.
Project description:We produced bulk RNA sequencing data on Drosophila neurons, glia and hemocytes at embryonic and larval stages to extrapolate the most significant and specific features that identify a cell type as a whole. We also tracked changes in the expression in the two stages. We identified stable features that define a cell type functionally and developmentally as well as plastic features including stage-specific metabolic states, which likely depend on the environment.
Project description:Huntington's disease (HD) is an autosomal dominant inherited neurodegenerative disorder that is caused by a CAG expansion in the Huntingtin (HTT) gene, leading to HTT inclusion formation in the brain. The mutant huntingtin protein (mHTT) is ubiquitously expressed and therefore nuclear inclusions could be present in all brain cells. The effects of nuclear inclusion formation have been mainly studied in neurons, while the effect on glia has been comparatively disregarded. Astrocytes, microglia, and oligodendrocytes are glial cells that are essential for normal brain function and are implicated in several neurological diseases. Here we examined the number of nuclear mHTT inclusions in both neurons and various types of glia in the two brain areas that are the most affected in HD, frontal cortex, and striatum. We compared nuclear mHTT inclusion body formation in three HD mouse models that express either full-length HTT or an N-terminal exon1 fragment of mHTT, and we observed nuclear inclusions in neurons, astrocytes, oligodendrocytes, and microglia. When studying the frequency of cells with nuclear inclusions in mice, we found that half of the population of neurons contained nuclear inclusions at the disease end stage, whereas the proportion of GFAP-positive astrocytes and oligodendrocytes having a nuclear inclusion was much lower, while microglia hardly showed any nuclear inclusions. Nuclear inclusions were also present in neurons and all studied glial cell types in human patient material. This is the first report to compare nuclear mHTT inclusions in glia and neurons in different HD mouse models and HD patient brains. GLIA 2016;65:50-61.
Project description:Huntington’s disease (HD), caused by a CAG repeat expansion in the huntingtin (HTT) gene, is characterized by abnormal protein aggregates and motor and cognitive dysfunction. Htt protein is ubiquitously expressed, but the striatal medium spiny neuron (MSN) is most susceptible to neuronal dysfunction and death. Abnormal gene expression represents a core pathogenic feature of HD, but the relative roles of cell-autonomous and non-cell-autonomous effects on transcription remain unclear. To determine the extent of cell-autonomous dysregulation in the striatum in vivo, we examined genome-wide RNA expression in symptomatic D9-N171-98Q (a.k.a. DE5) transgenic mice in which the forebrain expression of the first 171 amino acids of human Htt with a 98Q repeat expansion is limited to MSNs. Microarray data generated from these mice were compared to those generated on the identical array platform from a pan-neuronal HD mouse model, R6/2, carrying two different CAG repeat lengths, and a relatively high degree of overlap of changes in gene expression was revealed. We further focused on known canonical pathways associated with excitotoxicity, oxidative stress, mitochondrial dysfunction, dopamine signaling and trophic support, among others. While genes related to excitotoxicity, dopamine signaling and trophic support, were altered in both DE5 and R6/2 transgenic mice, which may be either cell-autonomous or non-cell-autonomous,, genes related to mitochondrial dysfunction, oxidative stress and the peroxisome proliferator-activated receptor are primarily affected in DE5 transgenic mice, indicating cell autonomous mechanisms Overall, our results demonstrate that HD-induced dysregulation of the striatal transcriptome can be largely attributed to intrinsic effects of mutant Htt,,such that mutant Htt-induced effects in cortical neurons is not necessary for striatal dysfunction/degeneration. Striatum from DE5 transgenic mice vs. wt littermate controls
Project description:Non-mammalian vertebrates have a robust ability to regenerate injured retinal neurons from Müller glia cells (MG) that activate the proneural factor Achaete-scute homolog 1 (Ascl1/Mash1) and de-differentiate into progenitors cells. In contrast, mammalian MG have a limited regenerative response and fail to upregulate Ascl1 after injury. To test whether Ascl1 could restore a neurogenic potential to mammalian MG, we over-expressed Ascl1 in dissociated mouse MG cultures and intact retinal explants. Ascl1-infected MG upregulate retinal progenitor-specific genes, while downregulating glial genes. Furthermore, Ascl1 remodeled the chromatin at its targets from a repressive to active configuration. MG-derived progenitors differentiated into cells that exhibited neuronal morphologies, expressed retinal subtype-specific neuronal markers, and displayed neuron-like physiological responses. These results indicate that a single transcription factor, Ascl1, can produce a neurogenic state in mature Muller glia. Expresssion profiling was used to determine the genes that were changed after Ascl1 infection of P12 cultured Müller glia compared with those present in P0 progenitors and P7-P21 Müller glia Retinas were dissociated and FAC-sorted from Hes5-GFP mice at P0, P7, P10, P14 or P21 and submitted for profiling. WT Retinas were dissociated at P12, grown for 1 week in culture, and infected with lentiviruses expressing Ascl1 or GFP for four days. Total RNA was extracted and submitted for profiling.
Project description:To identify the gene expression profile of enteric glia and assess the transcriptional similarity between enteric and extraenteric glia, we performed RNA sequencing analysis on PLP1-expressing cells in the mouse intestine. This analysis shows that enteric glia are transcriptionally unique and distinct from other cell types in the nervous system. Enteric glia express many genes characteristic of the myelinating glia, Schwann cells and oli- godendrocytes, although there is no evidence of myelination in the murine ENS. Total RNA expression profiles of PLP1 expressing enteric glial cells (GFP+) and non-glial cells (GFP-negative) were obtained from the ileum and colon of juvenile PLP1-eGFP transgenic mice.
Project description:Zebrafish display widespread and pronounced adult neurogenesis, which is fundamental for their regeneration capability after central nervous system injury. However, the cellular identity and the biological properties of adult newborn neurons are elusive for most brain areas. Here, we used short-term lineage tracing of radial glia progeny to prospectively isolate newborn neurons from the her4.1+ radial glia lineage in the homeostatic adult forebrain. Transcriptome analysis of radial glia, newborn neurons and mature neurons using single cell sequencing identified distinct transcriptional profiles including novel markers for each population. Specifically, we detected 2 separate newborn neuron types, which showed diversity of cell fate commitment and location. Further analyses showed homology of these cell types to neurogenic cells in the mammalian brain, identified neurogenic commitment in proliferating radial glia and indicated that glutamatergic projection neurons fate are generated in the adult zebrafish telecephalon. Thus, we prospectively isolated adult newborn neurons from the adult zebrafish forebrain, identified markers for newborn and mature neurons in the adult brain, revealed intrinsic heterogeneity among adult newborn neurons and their homology to mammalian adult neurogenic cell types.