79: Genetic variants at AGTR2 locus increase risk of preterm birth

Abstract

Preterm birth (PTB) complicates approximately 10% of pregnancies in the U.S. While genetic factors contribute to PTB, there has been limited replication of specific genetic risk loci associated with PTB. Recently, we conducted the first large-scale, maternal genome-wide association study (GWAS), utilizing 43,568 women from 23andMe, that identified a locus of variants near the angiotensin II receptor type 2 receptor (AGTR2) gene associated with both PTB and gestational length. We hypothesized that a causative variant in this locus influences expression of AGTR2. We assessed genetic variants previously identified in our GWAS located near AGTR2 (combined analysis p-value of 7.2x10-16 in association with gestational length) to identify genotype-dependent regulation of AGTR2 expression. We computationally prioritized disease variants using available functional genomics data. Implicated variants were then evaluated for possible effects on transcription factor (TF) binding using protein-binding microarray data. Selected variants predicted to alter TF binding were analyzed using electrophoretic mobility shift assays (EMSAs). Luciferase reporter assays were performed to identify rs7889204 genotype-dependent regulation of the AGTR2 promoter. Our computational analyses identified rs7889204 as the top functional candidate variant. EMSA analysis confirmed predicted allele-dependent binding for the transcription factors CEBPB and HOXA10. Luciferase reporter assays revealed allele-dependent reporter activity for rs7889204, with decreased expression for the non-reference “C” allele. We identified candidate mechanisms in which rs7889204 at the AGTR2 locus differentially binds CEBPB and HOXA10. Reporter assays demonstrate decreased enhancer activity for the non-reference allele at rs7889204. These results are consistent with a previously established eQTL for AGTR2 in the uterus, suggesting decreased binding of CEBPB and HOXA10 to the preterm birth rs7889204 risk allele results in decreased AGTR2 expression and possible downstream decidual implantation abnormalities leading to PTB.View Large Image Figure ViewerDownload Hi-res image Download (PPT)