Non-coding autoimmune risk variant defines role for ICOS in T peripheral helper cell development

ABSTRACT: Our fine-mapping of 76 non-MHC loci associated with risk for rheumatoid arthritis (RA, 11,475 cases, 15,870 controls) has recently identified rs117701653, a non-coding single nucleotide polymorphism (SNP) in the CTLA4/CD28/ICOS locus, as the variant most likely to modulate RA risk within this region, with the minor allele (C) showing disease protection compared to the major allele (A). Notably, this SNP exhibits allele-specific protein binding, further supporting its regulatory nature, including greater binding of proteins from Jurkat T cell nuclear extract to the protective allele (C) than to the risk allele (A) by electrophoretic mobility shift assay (EMSA). To identify this protein or protein complex, we applied an efficient DNA pulldown technique, flanking restriction enhanced pulldown (FREP), using nuclear extract from Jurkat T cells, bait DNA corresponding to the (C) allele of rs117701653, competitor DNA fragment, and irrelevant DNA sequence as a negative control. Mass spectrometry analysis of peptides released from FREP identified 43 proteins. Our strongest candidate was structural maintenance of chromosomes flexible hinge domain-containing protein 1 (SMCHD1), which exhibited specific binding to the (C) allele of rs117701653. We confirmed the allelic affinity of SMCHD1 using multiple orthogonal approaches, including FREP and western blotting, EMSA with anti-SMCHD1 antibodies, and CHIP-qPCR with CRISPR-modified Jurkat clones bearing different genotype at rs117701653. In this study, we identified SMCHD1, a chromatin regulator that binds allelically to the rs117701653 allele (C) associated with protection against RA risk.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): T Cell, Jurkat Cell

DISEASE(S): Disease Free

SUBMITTER: Taehyeung Kim  

LAB HEAD: Peter A Nigrovic

PROVIDER: PXD048977 | Pride | 2024-05-23

REPOSITORIES: Pride