Battle of sex hormones in genitalia anomalies

Maternal Exposure to Disinfection By-Products and Risk of Hypospadias in the National Birth Defects Prevention Study (2000-2005)

The purpose of this study was to estimate the association between 2nd and 3rd degree hypospadias and maternal exposure to disinfection by-products (DBPs) using data from a large case-control study in the United States. Concentration estimates for total trihalomethanes (TTHMs), the sum of the five most prevalent haloacetic acids (HAA5), and individual species of each were integrated with data on maternal behaviors related to water-use from the National Birth Defects Prevention Study (NBDPS) to create three different exposure metrics: (1) household DBP concentrations; (2) estimates of DBP ingestion; (3) predicted uptake (i.e., internal dose) of trihalomethanes (THMs) via ingestion, showering, and bathing. The distribution of DBP exposure was categorized as follows: (Q1/referent) < 50%; (Q2) ≥ 50% to < 75%; and (Q3) ≥ 75%. Logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Generally, null associations were observed with increasing TTHM or HAA5 exposure. An increased risk was observed among women with household bromodichloromethane levels in the second quantile (aOR: 1.8; 95% CI: 1.2, 2.7); however, this association did not persist after the inclusion of individual-level water-use data. Findings from the present study do not support the hypothesis that maternal DBP exposures are related to the occurrence of hypospadias.

Altered mechanisms of genital development identified through integration of DNA methylation and genomic measures in hypospadias

Hypospadias is a common birth defect where the urethral opening forms on the ventral side of the penis. We performed integrative methylomic, genomic, and transcriptomic analyses to characterize sites of DNA methylation that influence genital development. In case–control and case-only epigenome-wide association studies (EWAS) of preputial tissue we identified 25 CpGs associated with hypospadias characteristics and used one-sample two stage least squares Mendelian randomization (2SLS MR) to show a causal relationship for 21 of the CpGs. The largest difference was 15.7% lower beta-value at cg14436889 among hypospadias cases than controls (EWAS P = 5.4e−7) and is likely causal (2SLS MR P = 9.8e−15). Integrative annotation using two-sample Mendelian randomization of these methylation regions highlight potentially causal roles of genes involved in germ layer differentiation (WDHD1, DNM1L, TULP3), beta-catenin signaling (PKP2, UBE2R2, TNKS), androgens (CYP4A11, CYP4A22, CYP4B1, CYP4X1, CYP4Z2P, EPHX1, CD33/SIGLEC3, SIGLEC5, SIGLEC7, KLK5, KLK7, KLK10, KLK13, KLK14), and reproductive traits (ACAA1, PLCD1, EFCAB4B, GMCL1, MKRN2, DNM1L, TEAD4, TSPAN9, KLK family). This study identified CpGs that remained differentially methylated after urogenital development and used the most relevant tissue sample available to study hypospadias. We identified multiple methylation sites and candidate genes that can be further evaluated for their roles in regulating urogenital development.