Identifying the biological basis of GWAS hits for endometriosis

Endometriosis is a common estrogen-dependent gynecological disease influenced by multiple genetic and environmental factors. Genome-wide association studies (GWAS) have identified eight genomic regions with strong evidence for association with endometriosis risk and excellent replication in multiple studies. The results represent a significant breakthrough toward understanding endometriosis. However, the significance can be realized only when the associated DNA sequence variation is linked to the altered regulation and/or function of specific genes and pathways modifying endometriosis risk. This review sets out the multiple steps required to interpret the genetic association results, identify the specific genes likely to be responsible for the altered risk within each region, and obtain the necessary genomic evidence connecting the genetic results to the target genes. Strategies include fine mapping, functional annotation, genomics, and target gene identification through gene expression, epigenetics, and cell-based studies to define direct interactions between causal single nucleotide polymorphisms (SNPs) and target genes. To help decode GWAS "hits" affecting endometriosis from multiple regions, there is an urgent need for well-powered genome-wide studies of the regulation of gene expression and epigenetic mechanisms in the endometrium and other reproductive tissues. The system genetics and genomic studies needed to follow-up GWAS signals will also provide insights into gene regulation influencing other reproductive functions. These studies require multidisciplinary research combining genetics, genomics, functional biology, and clinical research to determine the biological pathways responsible and translate the new knowledge into better outcomes for patients.