GWAS of stool frequency reveals genes, pathways, and cell types relevant to human gastrointestinal motility and irritable bowel syndrome

Abstract

ABSTRACT

Objective

Gut dysmotility is associated with constipation, diarrhea, and functional gastrointestinal disorders (FGID) like irritable bowel syndrome (IBS). Its molecular underpinnings, and their anomalies in FGID disorders are poorly characterized, hence we sought to gain mechanistic insight through a large-scale genetic investigation.

Design

We used stool frequency (STL-FRQ) as a (surrogate) quantitative trait to study the genetics of gut motility, exploiting questionnaire and genotype data from UK Biobank and four smaller population-based cohorts (LifeLines-Deep, Genes for Good, Flemish Gut Flora Project and PopCol), in a GWAS meta-analysis spanning 8,817,117 high-quality SNP markers and 167,875 individuals of European descent.

Results

We identify 13 genome-wide significant loci (P≤5.0×10 −8 ) harboring prioritized genes that are: i) involved in sensory perception and neurotransmitter/neuropeptide signaling; ii) enriched for their expression in enteric motor neurons associated with the control of peristalsis (P=7.0×10 −8 ) iii) previously linked to other traits and conditions, including GI motility and dysmotility syndromes, and the response to their pharmacological treatment. The genetic architecture of STL-FRQ most strongly correlates with that of IBS (r g =0.42; P=1.1×10 −3 ). In UK Biobank, the risk of IBS with diarrhea was 4x higher in individuals from the top 1% of the distribution of polygenic scores (PGS) computed based on STL-FRQ GWAS summary statistics (ORs=4.14; P=1.2×10 −97 ).

Conclusion

We identify loci harboring genes with a plausible role in GI motility, possibly acting via neurotransmission and similar pathways in specialized enteric neurons. The demonstrated relevance of these findings to IBS warrants further study for the identification of actionable pathomechanisms in the dysmotility syndromes.