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Multi-omic analysis of cell-of-origin and epigenomic state in pediatric H3K27M gliomas

ABSTRACT: It is not known whether midline pediatric gliomas driven by Histone 3 K27M mutations (oncohistones) or EZHIP expression (oncohistone-mimics) share a common cell-of-origin, or arise from distinct cell types with unique vulnerabilities to PRC2 inhibition and partner alterations. Here, we define the etiological and oncogenic relationship between pediatric midline gliomas characterized by inhibition of K27M and K27M-like oncohistones. We assemble an extensive reference for gliogenesis from the developing mouse and human fetal brain. With bulk and single-cell transcriptomics and epigenomics, we profiled a large cohort of primary tumors comprising H3.1K27M and H3.3K27M pontine gliomas, H3.3K27M thalamic gliomas, and EZHIP+ posterior fossa ependymomas. We focus on differences across axes of location (thalamus vs. pons vs. posterior fossa), tumor type (diffuse midline gliomas vs. ependymomas), and oncohistone (H3.1/2K27M vs. H3.3K27M vs. EZHIP). We use tumor molecular features to delineate transcriptional states and cell-of-origin in each entity. Finally, we use culture models in isogenic contexts to interrogate the effect of each oncohistone or mimic.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE188625 | GEO | 2022/06/27

REPOSITORIES: GEO

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Multi-omic analysis of cell-of-origin and epigenomic state in pediatric H3K27M gliomas

Project description:It is not known whether midline pediatric gliomas driven by Histone 3 K27M mutations (oncohistones) or EZHIP expression (oncohistone-mimics) share a common cell-of-origin, or arise from distinct cell types with unique vulnerabilities to PRC2 inhibition and partner alterations. Here, we define the etiological and oncogenic relationship between pediatric midline gliomas characterized by inhibition of K27M and K27M-like oncohistones. We assemble an extensive reference for gliogenesis from the developing mouse and human fetal brain. With bulk and single-cell transcriptomics and epigenomics, we profiled a large cohort of primary tumors comprising H3.1K27M and H3.3K27M pontine gliomas, H3.3K27M thalamic gliomas, and EZHIP+ posterior fossa ependymomas. We focus on differences across axes of location (thalamus vs. pons vs. posterior fossa), tumor type (diffuse midline gliomas vs. ependymomas), and oncohistone (H3.1/2K27M vs. H3.3K27M vs. EZHIP). We use tumor molecular features to delineate transcriptional states and cell-of-origin in each entity. Finally, we use culture models in isogenic contexts to interrogate the effect of each oncohistone or mimic.

| EGAS00001005773 | EGA

Histone H3 wild-type DIPG/DMG overexpressing EZHIP extend the spectrum diffuse midline gliomas with PRC2 inhibition beyond H3-K27M mutation

Project description:Characterisation of a new subgroup of DMG lacking H3-K27M mutation that is defined by H3K27me3 loss and EZHIP overexpression that can be detected by IHC. These tumors are distinct from EZHIP-positive posterior fossa ependymomas and are associated with a dismal prognosis. We propose that these EZHIP/H3-WT tumors need to be considered similar to canonical DIPG/DMG, thus extending the spectrum of DMG with PRC2 inhibition beyond H3-K27M mutation

2020-03-20 | E-MTAB-8888 | biostudies-arrayexpress

EZHIP / CXorf67 mimics oncohistones to inhibit PRC2 in PFA ependymoma

Project description:Expression of CXorf67 is an oncogenic mechanism that drives H3K27 hypomethylation in PFA ependymomas by mimicking K27M mutated oncohistones. Background: Posterior fossa A (PFA) ependymomas comprise one out of nine molecular groups of ependymoma. PFA tumors are mainly diagnosed in infants and young children, show a poor prognosis and are characterized by a lack of the repressive histone H3 lysine 27 trimethylation (H3K27me3) mark. Recently, we reported CXorf67 overexpression as hallmark of PFA ependymoma and showed that CXorf67 can interact with EZH2 thereby inhibiting polycomb repressive complex 2 (PRC2), but the mechanism of action remained unclear. Methods: We performed mass spectrometry (MS) and peptide modelling analyses to identify the functional domain of CXorf67 responsible for binding and inhibition of EZH2. Our findings were validated by immunocytochemistry, western blot and methyltransferase assays. Results: We find that the inhibitory mechanism of CXorf67 is similar as in diffuse midline gliomas harboring H3K27M mutations. A small, highly conserved peptide sequence located in the C-terminal region of CXorf67 mimics the sequence of K27M mutated histones and binds to the SET domain of EZH2. This interaction blocks EZH2 methyltransferase activity and inhibits PRC2 function causing de-repression of PRC2 target genes including genes involved in neurodevelopment. Conclusions: Expression of CXorf67 is an oncogenic mechanism that drives H3K27 hypomethylation in PFA tumors by mimicking K27M mutated histones. Disrupting the interaction between CXorf67 and EZH2 may serve as a novel targeted therapy for PFA tumors but also for other tumors that overexpress CXorf67. Based on its function, we have renamed CXorf67 into EZH Inhibitory Protein (EZHIP).

2022-03-06 | GSE127941 | GEO

Cxorf67-FLAG co-immunoprecipitation analysis from 293T cells

Project description:The regulation of gene expression is controlled in part by post-translational modifications to histone proteins. Methylation at histone H3, lysine 27 (H3K27), which is catalyzed by Polycomb repressive complex 2 (PRC2), is associated with silenced chromatin. Previous studies have identified dysregulation of H3K27 methylation in pediatric diffuse intrinsic pontine gliomas (DIPGs), the majority of which feature mutation of lysine 27 to methionine. This “oncohistone” potently inhibits PRC2 activity and leads to a global reduction in H3K27 methylation. Similar to DIPG, posterior fossa type A (PFA) ependymomas also show low levels of H3K27 methylation. Although PFAs do not possess the H3K27M oncohistone mutation, they do show increased expression of Cxorf67. Interestingly, Cxorf67 contains a C-terminal sequence that resembles the sequence surrounding H3K27, and we find that this portion of Cxorf67 inhibits PRC2 activity to an even greater extent than the H3K27M oncohistone. Thus, we suggest re-naming Cxorf67 as EZHIP (Enhancer of Zeste Homologs Inhibitory Protein). Furthermore, when expressed in 293T cells, Cxorf67 interacts with several members of PRC2 and induces changes in H3K27 methylation patterns that mirror the changes in H3K27 methylation induced by expression of H3K27M. We propose that PFAs have dysregulated H3K27 methylation by a mechanism that involves inhibition of PRC2 by Cxorf67, which could drive tumorigenesis.

2019-04-09 | PXD013390 | Pride

EZHIP / CXorf67 mimics K27M mutated oncohistones and functions as an intrinsic inhibitor of PRC2 function in aggressive posterior fossa ependymoma

Project description:Posterior fossa A (PFA) ependymomas comprise one out of nine molecular groups of ependymoma. PFA tumors are mainly diagnosed in infants and young children, show a poor prognosis and are characterized by a lack of the repressive histone H3 lysine 27 trimethylation (H3K27me3) mark. Recently, we reported CXorf67 overexpression as hallmark of PFA ependymoma and showed that CXorf67 can interact with EZH2 thereby inhibiting polycomb repressive complex 2 (PRC2). Here, we report that the inhibitory mechanism of this interaction is similar as in diffuse midline gliomas harboring H3K27M mutations. A small, highly conserved peptide sequence located in the C-terminal region of CXorf67 mimics the H3K27M peptide and binds to the SET domain of EZH2. This interaction blocks EZH2 methyltransferase activity and causes H3K27 hypomethylation, an oncogenic mechanism that may be exploited for targeted therapy in PFA ependymoma. Based on its function, we have renamed CXorf67 into EZH2 Inhibitory Protein (EZHIP).

2019-07-08 | PXD012318 | Pride

Ependymoma associated protein EZHIP inhibits PRC2 through a H3 K27M like mechanism (ChIP-Seq Ring1b)

Project description:to understand the genome wide alterations in PRC2-mediated K27me3 and PRC1 distribution caused by oncohistone K27M mutation or novel PRC2 inhibitor – EZHIP

2019-04-08 | GSE124741 | GEO

Ependymoma associated protein EZHIP inhibits PRC2 through a H3 K27M like mechanism (ChIP-Seq H2K27me3)

Project description:to understand the genome wide alterations in PRC2-mediated K27me3 and PRC1 distribution caused by oncohistone K27M mutation or novel PRC2 inhibitor – EZHIP

2019-04-08 | GSE124740 | GEO

Ependymoma associated protein EZHIP inhibits PRC2 through a H3 K27M like mechanism (ChIP-Seq CBX2)

Project description:to understand the genome wide alterations in PRC2-mediated K27me3 and PRC1 distribution caused by oncohistone K27M mutation or novel PRC2 inhibitor – EZHIP

2019-04-08 | GSE124739 | GEO

Ataxia-telangiectasia mutated (Atm) disruption sensitizes spatially-directed H3.3K27M/TP53 diffuse midline gliomas to radiation therapy

Project description:Diffuse midline gliomas (DMGs) are lethal brain tumors characterized by inactivating p53 mutations and oncohistone H3.3K27M mutations that rewire the cellular response to genotoxic stress, presenting therapeutic opportunities. We used RCAS/tv-a retroviruses and Cre recombinase to inactivate p53 and induce K27M in the native H3f3a allele in a lineage- and spatially-directed manner, yielding primary mouse DMGs. Disruption of the DNA damage response kinase Ataxia-telangiectasia mutated (Atm) enhanced the efficacy of focal brain irradiation, extending mouse survival. This finding suggests that targeting ATM will enhance the efficacy of radiation therapy for p53-mutant DMG but not p53-wildtype DMG. We used spatial in situ transcriptomics and an allelic series of primary murine DMG models to identify transactivation-independent p53 activity as the key mediator of such radiosensitivity.

2023-11-04 | GSE246584 | GEO

A Novel Mouse Model of Diffuse Midline Glioma Initiated in Neonatal Oligodendrocyte Progenitor Cells Highlights Cell- of-origin Dependent Effects of H3K27M III

Project description:Diffuse midline glioma (DMG) is a type of lethal brain tumor that develops mainly in children. The majority of DMG harbor the K27M mutation in histone H3. Oligodendrocyte progenitor cells (OPCs) in the brainstem are candidate cells-of-origin for DMG, yet there is no genetically engineered mouse model of DMG initiated in OPCs. Here, we used the RCAS/Tv-a avian retroviral system to generate DMG in Olig2-expressing progenitors and Nestin-expressing progenitors in the neonatal mouse brainstem. PDGF-B overexpression, along with p53 deletion, resulted in gliomas. Exogenous overexpression of H3.3K27M had a significant effect on tumor latency and tumor cell proliferation when compared with H3.3WT in Nestin+ cells but not in Olig2+ cells. Further, the fraction of H3.3K27M-positive cells was significantly lower in DMGs initiated in Olig2+ cells relative to Nestin+ cells, suggesting that the requirement for H3.3K27M is reduced when tumorigenesis is initiated in Olig2+ cells. Interestingly, H3K27 trimethylation was decreased with H3.3K27M induction even in Olig2+ cells. Therefore, we need to find if there is transcriptional changes for the tumorigenesis with H3.3K27M in Olig2+ cells.

2021-10-05 | GSE184936 | GEO

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