Epigenetic control of ataxin‐1 in multiple sclerosis

Objective: ATXN1 encodes the polyglutamine protein ataxin-1, which we have demonstrated exerting an immunomodulatory function in the context of central nervous system (CNS) autoimmunity, in addition to its classical role in the neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1). In this study, we dissected the contribution of DNA methylation to the regulation of ATXN1 in multiple sclerosis (MS). Methods: We interrogated a DNA methylation dataset previously generated via bisulfate DNA sequencing (BS-seq) in sorted peripheral immune cytotypes (CD4(+) and CD8(+) T cells, CD19(+) B cells, and CD14(+) monocytes) isolated from untreated MS patients at symptoms onset. Results: Here, we report that ATXN1 undergoes hypo-methylation at four distinct regions upon MS, exclusively in B cells. We also highlight how these differentially methylated sites overlap with other regulatory epigenetic marks and MS risk variants. Lastly, we employ luciferase assays to assess the functionality of these regions, showing that the loss of methylation leads to an increase in ATXN1 expression. Interpretation: Altogether, these findings provide biological insights into ataxin-1 regulation in the immune system as well as into the molecular mechanisms underlying MS risk.