Genome-wide association studies (GWAS) have identified a large number of genetic risk loci for autoimmune diseases. However, the functional variants underlying these disease associations remain largely unknown. There is evidence that microRNA-mediated regulation may play an important role in this context. Therefore, we assessed whether autoimmune disease loci unfold their effects via altering microRNA expression in relevant immune cells. To this end, we performed comprehensive data integration of many large and publicly available datasets to combine information on autoimmune disease risk loci with RNA-Seq-based microRNA expression data. Specifically, we carried out microRNA expression quantitative trait loci (eQTL) analyses across 115 GWAS regions associated with 12 autoimmune diseases using next-generation sequencing data of 345 lymphoblastoid cell lines. Statistical analyses included the application and extension of a recently proposed framework (joint likelihood mapping) to microRNA expression data and microRNA target gene enrichment analyses of relevant GWAS data. Overall, only a minority of autoimmune disease risk loci may exert their pathophysiologic effects by altering microRNA expression based on JLIM. However, detailed functional fine-mapping revealed two independent GWAS regions harboring autoimmune disease risk SNPs with significant effects on microRNA expression. These relate to SNPs associated with Crohn's disease (CD; rs102275) and rheumatoid arthritis (RA; rs968567), which affect the expression of miR-1908-5p (prs102275 = 1.44e-20, prs968567 = 2.54e-14). In addition, an independent CD risk SNP, rs3853824, was found to alter the expression of miR-3614-5p (p = 5.70e-7). To support these findings, we demonstrate that GWAS signals for RA and CD were enriched in genes predicted to be targeted by both microRNAs (all with p < 0.05). In summary, our study points towards a potential pathophysiological role of miR-1908-5p and miR-3614-5p in autoimmunity.
Keywords: Gene expression; Genetic association; Immune system; Immunobase; Immunology; miRNA.
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