Project description:A subgroup of Posterior fossa ependymomas show reduced H3K27me3, global DNA hypomethylation, are more invasive, exhibit poor prognosis and epigenetically deregulated genes converge on radial glial factors, suggesting developing cerebellar radial glia as candidate cells-of-origin.
Project description:A subgroup of Posterior fossa ependymomas show reduced H3K27me3, global DNA hypomethylation, are more invasive, exhibit poor prognosis and epigenetically deregulated genes converge on radial glial factors, suggesting developing cerebellar radial glia as candidate cells-of-origin.
Project description:A subset of genomically silent childhood posterior fossa ependymomas show reduced H3K27me3, global DNA hypomethylation, are more invasive, exhibit poor prognosis and epigenetically deregulated genes converge on radial glial factors, suggesting developing cerebellar radial glia as candidate cells-of-origin.
Project description:A subgroup of Posterior fossa ependymomas show reduced H3K27me3 are more invasive, exhibit poor prognosis and epigenetically deregulated genes converge on radial glial factors, suggesting developing cerebellar radial glia as candidate cells-of-origin.
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).
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.
