ABSTRACT: Background: Although genome-wide association studies (GWAS) have identified hundreds of variants associated with risk of autoimmune and immune-related disorders (AID), our understanding of the diseases mechanisms is limited. In particular, more than 90% of the risk variants lie in non-coding regions, and almost 10% of these map to long non-coding RNA transcripts (lncRNAs). LncRNAs are known to show more cell-type specificity than protein-coding genes. Methods: In this study, we aimed to characterize lncRNAs and protein-coding genes located in loci associated with nine AID which have been well-defined by Immunochip analysis, by transcriptome analysis across seven peripheral blood leukocyte populations (granulocytes, monocytes, NK cells, B-cells, memory-T cells, naive CD4+ and naive CD8+ T-cells) and four cord blood derived T-helper cell populations (precursor, primary, polarized (Th1, Th2) T-helper cells). Results: We show that lncRNAs mapping to loci shared between AIDs are significantly enriched in immune cell types when compared to lncRNAs from the whole genome (α<0.005). We were not able to prioritize single cell types relevant for specific diseases, but we observed five cell types enriched (α<0.005) in five AID (NK cells for inflammatory bowel disease, juvenile idiopathic arthritis, primary biliary cirrhosis, psoriasis; memory-T and CD8+ T-cells in juvenile idiopathic arthritis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis; Th0 and Th2 cells for inflammatory bowel disease, juvenile idiopathic arthritis, primary biliary cirrhosis, psoriasis, rheumatoid arthritis). Furthermore we show that co-expression analyses of lncRNAs and protein-coding genes can predict the signaling pathways in which these AID-associated lncRNAs are involved. Conclusions: The observed enrichment of lncRNA transcripts in AID loci implies an important role for lncRNAs in AID etiology and suggests that lncRNA genes should be studied in more detail to correctly interpret GWAS findings. The co-expression results strongly support a model in which the lncRNA and protein-coding genes function together in the same pathways.
