Meeting Abstract
Vertebrates with temperature-dependent sex determination (TSD), a mechanism that relies on incubation temperature to irreversibly determine the sex of developing embryos, are threatened by ongoing changes in climate and local environmental conditions. Previous studies have suggested that behavioral and molecular plasticity in this system may provide opportunities for species with TSD to adapt to these changes. Although decades of research have uncovered key aspects, a complete molecular mechanism of TSD remains elusive. DNA methylation is a well-known epigenetic mark characterized by its dynamic ability to silence genes, and evidence is accumulating for its role in determining sex in TSD systems. Using the painted turtle, Chrysemys picta, as a model for TSD, we examined epigenetic profiles, variation, and their implications for sex determination in the TSD system. We leveraged a long-term study site to assess sex-specific epigenetic profiles across the genome and environmentally-induced epigenetic variation. We found clear sex-specific DNA methylation profiles, with adult males exhibiting higher levels of methylation than adult females. We also saw DNA methylation decrease with age, regardless of sex. Additional epigenetic variation was induced by environmental factors, including incubation temperature and embryonic exposure to endocrine disrupting compounds. We then assessed the biological significance of these findings in the context of inheritance by comparing epigenetic profiles between adult females and their offspring. Inheritance of epigenetic variation has the potential to mediate the effects of environmental change on species with TSD, as the methylation composition of genes in the sex determining pathway may play a role in gonadal sex differentiation and ultimately influence the final sex of the individual.
