Cross-Trait Cross-Genome Cross-Organ Analysis of Gastrointestinal Disorders and Depression

The aim of this study was to explore the shared genetic architecture between inflammatory bowel disease and depression and other upper gastrointestinal dysfunctions and inflammatory diseases, and to identify shared risk loci, potential key tissues, and associated genetic mechanisms to study.

Based on pooled data from a large-scale genome-wide association study (GWAS), we observed a genetic correlation between inflammatory bowel disease and depression and other upper gastrointestinal tract dysfunctions and inflammatory disorders and performed cross-trait pleiotropy analyses to detect shared pleiotropic loci and genes. In addition, we performed a series of functional annotation and tissue-specific analyses to determine the impact of pleiotropic genes. Genetic power enrichment analysis was used to detect key immune cells and tissues. Finally, immunological associations between these diseases were explored using an immunolocalization approach.

Our study highlights the existence of shared genetic mechanisms between depression, IBS, GORD, chronic gastritis, and IBD. A total of 160 promising pleiotropic loci were identified at the genome-wide significance level (P: 5 × 10^-8) and annotation identified 54 dominant risk SNP loci, 30 of which passed causal co-localization tests. Further gene level analyses identified 2 unique pleiotropic genes such as rs142762983 and rs7865719. Pathway analyses identified nikolsky breast cancer 17q11 q21 amplicon, kegg type idiabetes mellitus, and gg intestinal immune network for iga production. The key role of these signaling pathways in these disorders was demonstrated by SNP level and gene level tissue enrichment analyses, which showed that pleiotropic mechanisms were significantly enriched in WholB blood, Spleen, Colon Transverse, and Small Intestine Terminal Ileum. Final analysis of immune cells by phenotypic level immunolocalization results showed 49 pleiotropic loci that support an important role for five unique immune cells in IBD and depression and three other gastrointestinal disorders through shared causal variants.

Our study demonstrates the existence of a genetic association between symptomatic bowel disease and depression and other upper gastrointestinal tract dysfunctions and inflammatory disorders and reveals underlying immunomodulatory mechanisms.