Project description:We mapped the binding sites of Chd7 in cerebellar granule cells, and compared with the pattern of H3K27ac. To examine the impact of Chd7 loss to Top2b binding, we mapped the binding sites of Top2b in control and Chd7 mutant cells
Project description:Regulation of chromatin plays fundamental roles in the normal development of the brain. Haploinsufficiency of the chromatin remodeling enzyme CHD7 causes CHARGE syndrome, a genetic disorder that prominently affects the development of the cerebellum. However, how CHD7 controls chromatin states in the cerebellum remains incompletely understood. Using conditional knockout of CHD7 in granule cell precursors in the mouse cerebellum, we find that CHD7 robustly promotes the accessibility and activity of enhancers in granule cell precursors. Remarkably, in vivo profiling of genome architecture reveals that CHD7 operates locally to stimulate enhancer activation, thereby driving the expression of topologically-interacting genes. Genome and gene ontology studies show that CHD7-regulated enhancers are associated prominently with genes that control brain tissue morphogenesis. Accordingly, conditional knockout of CHD7 triggers a striking phenotype of cerebellar polymicrogyria, which we have also found in a case of CHARGE syndrome. Finally, we uncover a CHD7-dependent switch in the preferred orientation of granule cell precursor division in the developing cerebellum, providing a cellular basis for the cerebellar polymicrogyria phenotype upon loss of CHD7. Collectively, our findings define CHD7 function in the regulation of the epigenome in granule cell precursors and identify a surprising link of CHD7 to the control of cerebellar cortical morphogenesis, with potential implications for our understanding of CHARGE syndrome.
Project description:We performed ATAC-seq to profile the open chromatin lanscape in primary Chd7 WT and mutant GNPs. By analyzing the differentiate peaks between WT and mutant, we identified Chd7-dependent maintance of open chromatin at many neuronal genes.
Project description:Mutation of the gene encoding the ATP-dependent chromatin remodeler CHD7 causes CHARGE syndrome. The mechanisms underlying the neurodevelopmental deficits associated with the syndrome, which include cerebellar hypoplasia, developmental delay, coordination problems and autistic features, are not known. CHD7 is expressed in neural stem and progenitor cells, but its role in neurogenesis during brain development remains unknown. Here we show that deletion of Chd7 from cerebellar granule cell precursors (GCps) in the mouse results in reduced GCp proliferation, cerebellar hypoplasia, developmental delay and motor deficits. Genome-wide expression profiling revealed downregulated Reln gene expression in Chd7-deficient GCps. Recessive RELN mutations is associated with severe cerebellar hypoplasia in humans. We provide molecular and genetic evidence that reduced Reln expression contributes substantially to the GCp proliferative defect and cerebellar hypoplasia in GCp-specific Chd7 mouse mutants. Finally, we show that CHD7 is necessary for the maintenance of an open, accessible chromatin state at the Reln locus. Taken together, this study shows that Reln gene expression is regulated by chromatin remodeling, identifies CHD7 as a previously unrecognized upstream regulator of Reln and provides the first evidence that a mammalian CHD protein controls brain development by modulating chromatin accessibility in neuronal progenitors in vivo.
Project description:Origins of the brain tumor, medulloblastoma, from stem cells or restricted pro-genitor cells are unclear. To investigate this, we activated oncogenic Hedgehog signaling in multipotent and lineage-restricted CNS progenitors. We observed that normal unipo-tent cerebellar granule neuron precursors (CGNP) derive from hGFAP+ and Olig2+ rhombic lip progenitors. Hedgehog activation in a spectrum of early and late stage CNS progenitors generated similar medulloblastomas, but not other brain cancers, indicating that acquisition of CGNP identity is essential for tumorigenesis. We show in human and mouse medulloblastoma that cells expressing the glia-associated markers Gfap and Olig2 are neoplastic and that they retain features of embryonic-type granule lineage progenitors. Thus, oncogenic Hedgehog signaling promotes medulloblastoma from lineage-restricted granule cell progenitors. Gene expression profiling of cerebellar tumors generated from various early and late stage CNS progenitor cells. Experiment Overall Design: Group comparisons with biological replicates
Project description:It is generally believed that cerebellar granule neurons originate exclusively from granule neuron precursors (GNPs) in the external germinal layer (EGL). Here we identify a rare population of neuronal progenitors in the developing cerebellum that expresses Nestin. Although Nestin is widely considered a marker for multipotent stem cells, these Nestin-expressing progenitors (NEPs) are committed to the granule neuron lineage. Unlike conventional GNPs, which reside in the outer EGL and proliferate extensively, NEPs reside in the deep part of the EGL and are quiescent. Expression profiling reveals that NEPs are distinct from GNPs, and in particular, express markedly reduced levels of genes associated with DNA repair. Consistent with this, upon aberrant activation of Sonic hedgehog (Shh) signaling, NEPs exhibit more severe genomic instability and give rise to tumors more efficiently than GNPs. These studies identify a novel progenitor for cerebellar granule neurons and a novel cell of origin for medulloblastoma. 4 samples of Nestin expressing progenitors (NEPs), 4 samples of Math1 positive cells (GNPs) and 3 samples of Neural stem cells (CD133+ NSCs) were used for microarray analysis to determine the distinct genetic profile of NEPs. 4 samples of NEP-derived tumor and 4 samples of GNP-derived tumor were used to determine the similarity of those tumors by microarray analysis.