Project description:Astrocytes, the most abundant cells in the central nervous system, promote synapse formation and help refine neural connectivity. Although they are allocated to spatially distinct regional domains during development, it is unknown whether region-restricted astrocytes are functionally heterogeneous. Here we show that postnatal spinal cord astrocytes express several region-specific genes, and that ventral astrocyte-encoded Semaphorin3a (Sema3a) is required for proper motor neuron and sensory neuron circuit organization. Loss of astrocyte-encoded Sema3a led to dysregulated α−motor neuron axon initial segment orientation, markedly abnormal synaptic inputs, and selective death of α−but not of adjacent γ−motor neurons. Additionally, a subset of TrkA+ sensory afferents projected to ectopic ventral positions. These findings demonstrate that stable maintenance of a positional cue by developing astrocytes influences multiple aspects of sensorimotor circuit formation. More generally, they suggest that regional astrocyte heterogeneity may help to coordinate postnatal neural circuit refinement. 12 total samples consisting of three biological replicates each of flow sorted postnatal day 7 dorsal spinal cord astrocytes, ventral spinal cord astrocytes, dorsal SC non astrocytes, and ventral SC non astrocytes
Project description:Astrocytes, the most abundant cells in the central nervous system, promote synapse formation and help refine neural connectivity. Although they are allocated to spatially distinct regional domains during development, it is unknown whether region-restricted astrocytes are functionally heterogeneous. Here we show that postnatal spinal cord astrocytes express several region-specific genes, and that ventral astrocyte-encoded Semaphorin3a (Sema3a) is required for proper motor neuron and sensory neuron circuit organization. Loss of astrocyte-encoded Sema3a led to dysregulated α−motor neuron axon initial segment orientation, markedly abnormal synaptic inputs, and selective death of α−but not of adjacent γ−motor neurons. Additionally, a subset of TrkA+ sensory afferents projected to ectopic ventral positions. These findings demonstrate that stable maintenance of a positional cue by developing astrocytes influences multiple aspects of sensorimotor circuit formation. More generally, they suggest that regional astrocyte heterogeneity may help to coordinate postnatal neural circuit refinement.
Project description:Chromosomes and genes are non-randomly arranged within the mammalian cell nucleus. Clustering of genes is of great significance in transcriptional regulation. However, the relevance of gene clustering in their expression during differentiation of neural precursor cells (NPCs) into astrocytes remains unclear. We performed a genome-wide enhanced circular chromosomal conformation capture (e4C) to screen genes associated with an astrocyte-specific gene, glial fibrillary acidic protein (Gfap), during astrocyte differentiation. We identified 13 genes that were specifically associated with Gfap and expressed in NPC-derived astrocytes. These results provide evidence for functional significance of gene clustering in transcriptional regulation during NPCs differentiation. comparison of NPCs vs LIF+ vs LIF- cells.
Project description:We have developed a nonheuristic genome topography scan (GTS) algorithm to characterize the patterns of genomic alterations in human glioblastoma (GBM), identifying frequent p18INK4C and p16INK4A codeletion. Functional reconstitution of p18INK4C in GBM cells null for both p16INK4A and p18INK4C resulted in impaired cell-cycle progression and tumorigenic potential. Conversely, RNAi-mediated depletion of p18INK4C in p16INK4A-deficient primary astrocytes or established GBM cells enhanced tumorigenicity in vitro and in vivo. Furthermore, acute suppression of p16INK4A in primary astrocytes induced a concomitant increase in p18INK4C. Together, these findings uncover a feedback regulatory circuit in the astrocytic lineage and demonstrate a bona fide tumor suppressor role for p18INK4C in human GBM wherein it functions cooperatively with other INK4 family members to constrain inappropriate proliferation. Keywords: comparative genomic hybridization DNA copy number abberation of human glioblastoma tumors were obtained by comparative genomic hybridization of GBM tumor vs. normal human DNA. 11 human GBM samples were analyzed on Agilent human 244A human cgh array (G4411B). Normal Human DNA was used as reference. Some samples were hybridized with dye-swap replica.
Project description:The epigenetic mechanisms that enable specialized astrocytes to retain neurogenic competence throughout adult life are still poorly understood. Here we show that astrocytes that serve as neural stem cells (NSCs) in the adult mouse subventricular zone (SVZ) express the histone methyltransferase EZH2. This Polycomb repressive factor is required for neurogenesis independent of its role in SVZ NSC proliferation, as Ink4a/Arf-deficiency in Ezh2-deleted SVZ NSCs rescues cell proliferation, but neurogenesis remains defective. Olig2 is a direct target of EZH2, and repression of this bHLH transcription factor is critical for neuronal differentiation. Furthermore, Ezh2 prevents the inappropriate activation of genes that specify non-SVZ neuronal subtypes. In the human brain, SVZ cells including local astroglia also express EZH2, correlating with postnatal neurogenesis. Thus, EZH2 is an epigenetic regulator that distinguishes neurogenic SVZ astrocytes, orchestrating distinct and separable aspects of adult stem cell biology, which has important implications for regenerative medicine and oncogenesis. Examination of histone modifications (H3K27me3 and H3K4me3) in subventricular zone neural stem cells
Project description:Astrocytes perform a wide array of physiological functions. Despite the well-known functional and morphological diversity of astrocytes, molecular markers that label sub populations of astrocytes are limited. BMP and LIF are known to generated astrocytes with different morphology and physiological properties. The goal of this study to identify genes that are differentially expressed in BMP and LIF generated astrocytes.
Project description:Experience-dependent plasticity of synapses modulates information processing in neural circuits and is essential for cognitive functions. Genomic enhancers are thought to modulate specific sets of synapses by regulating experience-induced transcription to thereby promote neural circuit plasticity. However, this idea remains untested. Thus, here we analyze the cellular and circuit functions of the genomic mechanisms that control the experience-induced transcription of Igf1 (Insulin-like growth factor 1) in disinhibitory VIP interneurons in the adult visual cortex. We find that two sensory-induced enhancers selectively and cooperatively drive sensory-induced Igf1 transcription and that these enhancers homeostatically control the ratio between excitation and inhibition (E/I-ratio) and neural activity in VIP interneurons to thereby restrict visual acuity. Thus, single experience-regulated enhancers are essential for maintaining sensory processing. Since cortical plasticity scales with neural activity in VIP interneurons, this also suggests that experience-induced transcription restricts plasticity in adult neural circuits to preserve the brain’s functional integrity.
Project description:We have developed a nonheuristic genome topography scan (GTS) algorithm to characterize the patterns of genomic alterations in human glioblastoma (GBM), identifying frequent p18INK4C and p16INK4A codeletion. Functional reconstitution of p18INK4C in GBM cells null for both p16INK4A and p18INK4C resulted in impaired cell-cycle progression and tumorigenic potential. Conversely, RNAi-mediated depletion of p18INK4C in p16INK4A-deficient primary astrocytes or established GBM cells enhanced tumorigenicity in vitro and in vivo. Furthermore, acute suppression of p16INK4A in primary astrocytes induced a concomitant increase in p18INK4C. Together, these findings uncover a feedback regulatory circuit in the astrocytic lineage and demonstrate a bona fide tumor suppressor role for p18INK4C in human GBM wherein it functions cooperatively with other INK4 family members to constrain inappropriate proliferation. Keywords: comparative genomic hybridization
Project description:Neural stem cells, located in discrete niches in the adult brain, generate new neurons throughout life. These stem cells are specialized astrocytes, but astrocytes in other brain regions (parenchymal astrocytes) do not generate neurons under physiological conditions. After stroke, however, astrocytes in the mouse striatum undergo neurogenesis, triggered by decreased Notch signaling. Notch signaling can be experimentally depleted in mice by deleting the Notch-mediating transcription factor Rbpj. This dataset consists of single-cell RNA sequencing data of astrocytes isolated from the striatum (where astrocytes undergo neurogenesis in response to Rbpj deletion) or somatosensory cortex (where astrocytes don't complete neurogenesis in response to Rbpj deletion) of 4 mice. Cells were isolated from Cx30-CreER; R26-tdTomato; Rbpj(fl/fl) mice at three time points after tamoxifen-induced Rbpj deletion (2, 4, 8 weeks), and from Cx30-CreER; R26-tdTomato mice with intact Rbpj 3 days after tamoxifen. These time points span the transition from astrocyte through transit-amplifying cells to neuroblasts. The dataset contains 1) astrocytes from the striatum that initiate a neurogenic transcriptional program in response to Rbpj deletion and generate transit-amplifying cells and neuroblasts, and 2) astrocytes from the somatosensory cortex that initiate a neurogenic program in response to Rbpj deletion but fail to generate transit-amplifying cells or neuroblasts.