FCGR2A promoter variant reveals shared genetic susceptibility between IBD and stroke.

While the epidemiological association between inflammatory bowel disease (IBD) and stroke is well-established, the shared genetic architecture underlying these diseases remains unclear. This study utilized genome-wide association studies (GWAS) summary statistics to explore genetic overlaps between IBD and stroke subtypes. Mendelian randomization (MR) was applied to assess potential causal relationships. Cross-trait meta-analysis identified shared loci, followed by colocalization testing to pinpoint causal variants. Furthermore, functional prediction analysis of variants and verification through in vitro experiments. Finally, use mediation MR to explore potential mechanisms in multiple dimensions. We identified eight pairs with potential genetic correlations, with common genetic variants contributing more on ulcerative colitis (UC) and multiple stroke subtypes than Crohn's disease (CD). Among them, there is a potential causal relationship between IBD/UC and large arterial atherosclerotic stroke (LAS), which is consistent with previous epidemiological statistics. In addition, one locus (rs7522794) was initially identified through cross-trait analysis, and colocalization pointed out that the variant rs7522794 on the FCGR2A promoter was the culprit of the comorbid phenotype. The rs7522794-T allele predicted to be more prone to bind SPI1, thereby increasing FCGR2A expression and susceptibility to stroke in IBD patients. Finally, evidence suggests that gut microbes, blood metabolites, and immune cells may play a crucial regulatory role in the shared pathophysiology of IBD/UC and LAS. The study highlights the shared genetics architecture that exists between IBD and stroke, and demonstrates two different (FCGR2A-mediated immune pathways and other indirect regulation) but complementary verification mechanisms, providing new insights into IBD-stroke comorbidities.