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ATRX mutant neuroblastoma is sensitive to EZH2 inhibition via modulation of neuronal differentiation

ABSTRACT: We report on the characterization of ATRX in-frame fusion neuroblastoma and identify that ATRX IFF proteins re-locate from H3K9me3 enriched regions to active chromatin, such as the promoter of neural repressor REST. We further identify that REST is upregulated in ATRX IFF NB and that several neurogenesis and REST target genes are transcriptionally downregulated. Through ChIP-seq analysis, we observe that REST is bound to ATRX IFF Down genes, which have higher levels of H3K27me3. We further show that ATRX in-frame fusion neuroblastoma cells are sensitive to EZH2 inhibitors through de-repression of H3K27me3 bound neuronal function genes, includiing a subset of REST targets.

ORGANISM(S): Homo sapiens

PROVIDER: GSE100148 | GEO | 2019/10/15

REPOSITORIES: GEO

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Two opposing gene expression patterns within ATRX aberrant neuroblastoma

Project description:To study the role of distinct ATRX aberrations in neuroblastoma we created isogenic ATRX aberrant models using CRISPR-Cas9 in several neuroblastoma cell lines and one tumoroid. We created ATRX knock-out models, ATRX in-frame exon 2-10 deletions and ATRX in-frame exon 2-13 deletions. Additionally, we included patient-derived models data (i.e. cell line data and one tumoroid).

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ATRX mutant neuroblastoma is sensitive to EZH2 inhibition via modulation of neuronal differentiation.

Project description:Mutations and structural alterations of the SWI/SNF-like chromatin remodeler ATRX have been reported at high frequency in a number of adult and pediatric tumors1. However, the consequences of ATRX (Alpha Thalassemia/Mental Retardation, X-linked) mutations in cancer and their underlying epigenetic sensitivities remain ill defined. Particularly intriguing are the large N-terminal deletions of ATRX in neuroblastoma that generate in-frame fusion (IFF) proteins1Â–3 devoid of key chromatin interaction domains. Here we demonstrate that neuroblastoma cells harbouring ATRX IFFs have distinct gene expression programs compared to neuroblastoma cells that are wild type for ATRX. This is due in part to H3K27me3-mediated silencing of REST (RE1 Silencing Transcription Factor) target genes involved in neuronal differentiation. In turn, we find that ATRX IFF cells display exquisite sensitivity to EZH2 inhibition in both adherent and tumorsphere conditions, due in part to derepression of neurogenesis genes, including REST targets. Examination of the epigenomic landscape of a pediatric neuroblastoma tumor harboring an ATRX IFF revealed that H3K27me3 occupies a subset of REST target genes that are transcriptionally silenced, and are sensitive to EZH2 inhibition in our cell-based assays. Thus, our study greatly advances our understanding of indolent neuroblastoma and identifies EZH2 inhibition as a potential therapy for patients with ATRX mutant disease. Further, these studies may be applicable to other ATRX mutant pediatric malignancies, particularly those carrying similar structural alterations of ATRX.

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Examining the role of ATRX-RNA interactions in ATRX and PRC2 localization and gene expression.

Project description:We disrupted the RNA binding region in endogenous ATRX and tested localization of ATRX, EZH2 and H3K27me3 by CUT&RUN. We show that ATRX-RNA binding is important to regulate ATRX and PRC2 localization to specific genes.

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The chromatin remodeler ATRX binds to atypical chromatin domains at the 3â exons of ZNF genes to preserve H3K9me3 enrichment

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MYCN Amplification and ATRX Mutations are Incompatible in Neuroblastoma

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PCGP ATRX ChIP-Seq1 - samples

Project description:ChIP-Seq files for PCGP ATRX study paper titled "MYCN Amplification and ATRX Mutations are Incompatible in Neuroblastoma"

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ATRX regulates binding of Polycomb repressive complex 2 to Xist RNA and Polycomb targets

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Project description:ATRX is a member of the SWI2/SNF2 family of chromatin remodeling proteins and primarily functions at heterochromatic loci via its recognition of M-bM-^@M-^XrepressiveM-bM-^@M-^Y histone modifications (e.g., H3K9me3). Despite significant roles for ATRX during normal neural development, as well as its relationship to human disease, ATRX function in the central nervous system is not well understood. Here, we describe ATRXM-bM-^@M-^Ys ability to recognize an activity-dependent combinatorial histone modification, H3K9me3S10ph, in post-mitotic neurons. In neurons, this M-bM-^@M-^\methyl/phosM-bM-^@M-^] switch occurs exclusively following periods of stimulation and is highly enriched at heterochromatic repeats associated with centromeres. Using a multifaceted approach, we reveal that H3K9me3S10ph bound Atrx represses non-coding transcription of centromeric minor satellite sequences during instances of heightened activity. Our results indicate an essential interaction between ATRX and a previously uncharacterized histone modification in the central nervous system and suggest a potential role for abnormal repetitive element transcription in pathological states manifested by ATRX dysfunction. For Atrx ChIP-seq, IPs were performed on three control vs. three KCl stimulated (all representing biological, and not technical replicates) primary cultured mouse cortical neurons at DIV 8. All samples were normalized to background input levels. For H3K9me3S10phos ChIP-seq, biological singlecates (control vs. forskolin) were analyzed against respective inputs.

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