Methylation differences at the HLA-DRB1 locus in CD4+ T-Cells are associated with multiple sclerosis

Background: Multiple sclerosis (MS) is thought to be caused by T-cell mediated autoimmune dysfunction. Risk ofdeveloping MS is influenced by environmental and genetic factors. Modifiable differences in DNA methylation arerecognized as epigenetic contributors to MS risk and may provide a valuable link between environmental exposure andinherited genetic systems.Objectives and methods: To identify methylation changes associated with MS, we performed a genome-wide DNAmethylation analysis of CD4+ T cells from 30 patients with relapsing-remitting MS and 28 healthy controls using Illumina450K methylation arrays.Results: A striking differential methylation signal was observed at chr. 6p21, with a peak signal at HLA-DRB1. Afterprioritisation, we identified a panel of 74 CpGs associated with MS in this cohort. Most notably we found evidence of amajor effect CpG island in DRB1 in MS cases (pFDR <3 x 10^-3). In addition, we found 55 non-HLA CpGs that exhibiteddifferential methylation, many of which localise to genes previously linked to MS.Conclusions: Our findings provide the first evidence for association of DNA methylation at HLA-DRB1 in relation toMS risk. Further studies are now warranted to validate and understand how these findings are involved in MS pathology.