Reproduction Abstracts

Gametogenesis is a complex process with striking sexual dimorphism. Although oogenesis and spermatogenesis share several global features (e.g., the production of haploid cells through meiotic divisions and extended periods of gamete maturation), the timing of events, their order and the propensity for errors during the process differ markedly. Our interest is in the factors – both endogenous (e.g., age) and endogenous (e.g., environmental exposures) – that influence the genetic quality of the resultant gamete. Increasing evidence suggests that both male and female reproduction are susceptible to the effects of endocrine disrupting chemicals (EDCs), and our focus has been understanding potential sex-specific effects of these chemicals on gametogenesis. Data from our studies in mouse, monkey and sheep suggest that exposure to BPA in the female and to either BPA or other exogenous estrogens in the male can induce meiotic effects. Temporal differences in the timing of events, however, result in different developmental windows of vulnerability in the two sexes. Further, our findings suggest that EDCs induce meiotic effects by altering the germline epigenome and, importantly, demonstrate strikingly different consequences in males and females. These findings underscore the necessity of considering sex-specific differences in developmental timing when devising accurate methods of measuring the impact of exposures and evaluating the reproductive risk posed by chemicals with endocrine disrupting potential.