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EZH2-mediated H3K27 trimethylation mediates neurodegeneration in ataxia-telangiectasia

ABSTRACT: The symptoms of ataxia-telangiectasia (A-T) include a progressive neurodegeneration caused by ATM protein deficiency. We previously found that nuclear accumulation of histone deacetylase-4, HDAC4, contributes to this degeneration; we now report that increased histone H3K27 trimethylation (H3K27me3) mediated by polycomb repressive complex 2 (PRC2) also plays an important role in the A-T phenotype. Enhancer of zeste homolog 2 (EZH2), a core catalytic component of PRC2, is identified as a new ATM kinase target, and its S734 phosphorylation reduces protein stability. Thus, PRC2 formation is elevated along with H3K27me3in ATM deficiency. ChIP-sequencing shows a significant increase in H3K27me3 ‘marks’ and a dramatic shift in their location. The change of H3K27me3 chromatin-binding pattern is directly related to cell cycle re-entry and cell death of ATM-deficient neurons. Lentiviral knockdown of EZH2 rescues Purkinje cell degeneration and behavioral abnormalities in Atm / mice, demonstrating that EZH2-mediated H3K27me3 is another key factor in A-T neurodegeneration.

ORGANISM(S): Mus musculus

PROVIDER: GSE50951 | GEO | 2013/10/25

SECONDARY ACCESSION(S): PRJNA219417

REPOSITORIES: GEO

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EZH2-mediated H3K27 trimethylation mediates neurodegeneration in ataxia-telangiectasia

Project description:The symptoms of ataxia-telangiectasia (A-T) include a progressive neurodegeneration caused by ATM protein deficiency. We previously found that nuclear accumulation of histone deacetylase-4, HDAC4, contributes to this degeneration; we now report that increased histone H3K27 trimethylation (H3K27me3) mediated by polycomb repressive complex 2 (PRC2) also plays an important role in the A-T phenotype. Enhancer of zeste homolog 2 (EZH2), a core catalytic component of PRC2, is identified as a new ATM kinase target, and its S734 phosphorylation reduces protein stability. Thus, PRC2 formation is elevated along with H3K27me3in ATM deficiency. ChIP-sequencing shows a significant increase in H3K27me3 ‘marks’ and a dramatic shift in their location. The change of H3K27me3 chromatin-binding pattern is directly related to cell cycle re-entry and cell death of ATM-deficient neurons. Lentiviral knockdown of EZH2 rescues Purkinje cell degeneration and behavioral abnormalities in Atm / mice, demonstrating that EZH2-mediated H3K27me3 is another key factor in A-T neurodegeneration. Two samples each were run of brain total RNA from Atm+/+ and Atm-/- mice.

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Project description:Genomic DNA was prepared, fragmented, and immunoprecipitated with antibodies specific for 5mC or 5hmC prior to standard sequencing. The neurodegenerative disease known as ataxia-telangiectasia (A-T) is caused by the absence of the ATM (A-T mutated) protein. A long-standing mystery surrounding A-T is why cerebellar Purkinje cells (PCs) appear uniquely vulnerable to ATM-deficiency. Here, we present that 5-hydroxymethylcytosine (5hmC), a newly recognized epigenetic marker found at high levels in neurons, is substantially reduced in human A-T and Atm-/- mouse cerebellar PCs. TET1, an enzyme that converts 5mC to 5hmC, responds to DNA damage. Manipulation of TET1 activity directly affects neuronal cell cycle reentry and cell death after the induction of DNA damage. Quantitative, genome-wide analysis of 5hmC of samples from human cerebellum showed that in ATM-deficiency there is a remarkable genome-wide reduction of 5hmC enrichment at both proximal and distal regulatory elements. These results reveal a role of TET1-mediated 5hmC in DNA damage response, and provide insights into the basis of a PC-specific DNA demethylation alteration in ATM-deficiency. There are two groups, A-T and Control. For each group, cerebellar DNA samples were immunoprecipitated with anti-5mC (n=1) or anti-5hmC (n=3). There were also two replicates of input control for each group.

2015-10-30 | E-GEOD-61133 | biostudies-arrayexpress

MeDIP analysis of 5mC and 5hmC marks in human ataxia-telangiectasia cerebellum

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