The epigenetic identity of oligodendrocytes is modulated by post-translational modifications of histones. Acetylation of histone H3 results from the balance between the activity of histone-acetyltransferases (HATs) and histone deacetylases (HDACs) and modulates transcriptional activation. We have previously shown that in rodents histone deacetylation favors oligodendrocyte differentiation, while acetylation is associated with increased levels of transcriptional inhibitors of oligodendrocyte differentiation. Here we report in humans brains, a shift towards histone acetylation in the white matter of the frontal lobes of aged subjects and in patients with chronic multiple sclerosis (MS). Increased immunoreactivity for acetylated histone H3 was observed in the nuclei of NogoA+ oligodendrocytes in a subset of MS samples. These changes were associated with high levels of transcriptional inhibitors of oligodendrocyte differentiation (i.e. TCF7L2, ID2 and SOX2) and higher HAT transcript levels (i.e. CBP, P300) in female MS patients compared to non-neurological controls and correlated with disease duration. Chromatin immunoprecipitation from samples of MS patients revealed enrichment of acetyl-histone H3 at the promoter of the increased target genes (i.e. TCF7L2). The data in chronic lesions contrasted with findings in early MS lesions, where a marked oligodendroglial histone deacetylation was observed. Together these data suggest that histone deacetylation is a process that occurs at the early stages of the disease and whose efficiency decreases with disease duration.
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