Project description:Recent single-cell transcriptomic studies report that IDH-mutant gliomas share a common hierarchy of cellular phenotypes, independent of genetic subtype. However, the genetic differences between IDH-mutant glioma subtypes are prognostic, predictive of response to chemotherapy, and correlate with distinct tumor microenvironments. To reconcile these findings, we profiled 22 human IDH-mutant gliomas via single-cell assay for transposase-accessible chromatin (scATAC-seq). We determined the cell-type specific differences in transcription-factor expression and associated regulatory grammars between IDH-mutant glioma subtypes. We find that while IDH-mutant gliomas do share a common distribution of cell types, there are significant differences in the expression and targeting of transcription factors that regulate glial identity and cytokine elaboration. We knocked out the chromatin-remodeler ATRX, which suffers loss-of-function alterations in most IDH-mutant astrocytomas, in an IDH-mutant immunocompetent intracranial murine model. We find that both human ATRX-mutant gliomas and murine ATRX-knockout gliomas are more heavily infiltrated by immunosuppressive monocytic-lineage cells derived from circulation than ATRX-intact gliomas, in an IDH-mutant background. ATRX knockout in murine glioma recapitulates gene expression and open-chromatin signatures that are specific to human ATRX-mutant astrocytomas, including drivers of astrocytic lineage and immune-cell chemotaxis. ATRX knockout in murine glioma recapitulates gene expression and open chromatin signatures that are specific to human ATRX-mutant astrocytomas, including drivers of astrocytic lineage and immune-cell chemotaxis. Through single-cell cleavage under targets and tagmentation assays and meta-analysis of public data, we show that ATRX loss leads to a global depletion in CCCTC-binding factor association with DNA, gene dysregulation along associated chromatin loops, and protection from therapy-induced senescence.
Project description:RNA-sequencing for myeloid inflammation-related genes was conducted on primary tumor samples from patients with IDH-wildtype glioblastoma (GBM) and grade 4 IDH-mutant astrocytoma (G4IMA). In addition, the IDH-wildtype murine glioma cell line GL261 and a strain of IDH-mutant GL261 were also sequenced using the murine counterpart of the RNA-sequencing myeloid innate immunity panel.
Project description:Recent single-cell RNA-sequencing studies have identified a hierarchy of cell types that is common to all isocitrate dehydrogenase (IDH) -mutant gliomas. This finding is somewhat paradoxical since the genetic differences between IDH-mutant astrocytomas and IDH-mutant oligodendrogliomas are prognostic, predictive of therapeutic response, and correlated with differences in immune infiltrates. To integrate these disparate findings, we constructed a single-cell atlas of 28 human IDH-mutant primary untreated grade-II/III gliomas.
Project description:To analyze the gene expression proflies of oligodendrocyte lineage in IDH-mutant glioma cells, we profiled more than 70000 cells from 16 IDH-mutant glioma samples by single cell RNA-seq.
Project description:Gain-of-function IDH mutations define major clinical and prognostic classes of gliomas. Mutant IDH protein produces a novel onco-metabolite, 2-hydroxyglutarate (2-HG), that interferes with iron-dependent hydroxylase enzymes, including the TET family of 5'-methylcytosine hydroxylases. TET enzymes are critical for the dynamic regulation of DNA methylation. IDH mutant gliomas thus manifest a CpG island methylator phenotype (G-CIMP), though the functional significance of this altered epigenetic state remains unclear. Here we show that IDH1 mutant gliomas exhibit hyper-methylation at CTCF binding sites, leading to reduced binding of this methylation-sensitive insulator protein. Loss of CTCF binding is associated with a loss of insulation between topological domains and aberrant gene activation. We specifically demonstrate that loss of CTCF at a domain boundary permits a constitutive enhancer to aberrantly interact with the receptor tyrosine kinase gene PDGFRA, a prominent glioma oncogene. Treatment of IDH mutant gliomaspheres with demethylating agent partially restores insulator function and reduces PDGFRA expression. Conversely, CRISPR-mediated disruption of the CTCF binding sequence in IDH wildtype gliomaspheres induces PDGFRA expression and increases proliferation. Our study suggests that IDH mutations promote gliomagenesis by disrupting chromosomal topology and allowing aberrant regulatory interactions that induce oncogene expression. CTCF occupancy characterization and histone H3K27 acetylation profiling in IDH1 mutant and wild-type glioma patient specimens and culture models. ChIP-seq raw data is to be made available through dbGaP (controlled access) due to patient privacy concerns.
Project description:IDH mutant cells are deficient in retinoic acid production, which impacts downstream gene expression and pathways. We looked at the effect of supplementing IDH mutant glioma cells with ATRA on gene expression and downstream pathways. We compared gene expression changes with IDH WT cells that were also treated with ATRA
Project description:A subset of patients with IDH-mutant glioma respond to inhibitors of mutant IDH (IDHi), yet the molecular underpinnings of such responses are not understood. Here, we profiled by single-cell or single-nucleus RNA-sequencing three IDH-mutant oligodendrogliomas from patients who derived clinical benefit from IDHi. Importantly, the tissues were sampled on-drug, four weeks from treatment initiation. We further integrate our findings with analysis of single-cell and bulk transcriptomes from independent cohorts and experimental models. We find that IDHi treatment induces a robust differentiation towards the astrocytic lineage, accompanied by a depletion of stem-like cells and a reduction of cell proliferation. Furthermore, mutations in NOTCH1 are associated with decreased astrocytic differentiation and may limit the response to IDHi. Our study highlights the differentiating potential of IDHi on the cellular hierarchies that drive oligodendrogliomas and suggests a genetic modifier that may improve patient stratification.