Regulatory Effects of Endometriosis-Associated Genetic Variants: A Multi-Tissue eQTL Analysis

Endometriosis is a chronic, estrogen-dependent inflammatory disease characterized by the ectopic presence of endometrial-like tissue. Although genome-wide association studies (GWAS) have identified susceptibility variants, their tissue-specific regulatory impact remains poorly understood.

To functionally characterize endometriosis-associated variants by exploring their regulatory effects as expression quantitative trait loci (eQTLs) across six physiologically relevant tissues: peripheral blood, sigmoid colon, ileum, ovary, uterus, and vagina.

GWAS-identified variants were cross-referenced with tissue-specific eQTL data from the GTEx v8 database. We prioritized genes either frequently regulated by eQTLs or showing the strongest regulatory effects (based on slope values, which indicate the direction and magnitude of the effect on gene expression). Functional interpretation was performed using MSigDB Hallmark gene sets and Cancer Hallmarks gene collections.

A tissue specificity was observed in the regulatory profiles of eQTL-associated genes. In the colon, ileum, and peripheral blood, immune and epithelial signaling genes predominated. In contrast, reproductive tissues showed the enrichment of genes involved in hormonal response, tissue remodeling, and adhesion. Key regulators such as MICB, CLDN23, and GATA4 were consistently linked to hallmark pathways, including immune evasion, angiogenesis, and proliferative signaling. Notably, a substantial subset of regulated genes was not associated with any known pathway, indicating potential novel regulatory mechanisms.

This integrative approach highlights the com-plexity of tissue-specific gene regulation mediated by endometriosis-associated variants. Our findings provide a functional framework to prioritize candidate genes and support new mechanistic hypotheses for the molecular pathophysiology of endometriosis.