Meeting Abstract
Ionizing radiation (IR) is a ubiquitous environmental stressor under which all life evolved. Further, radiological accidents at Chernobyl and Fukushima along with occupational and biomedical exposures are sources of IR that humans and wildlife must contend with. Historically, studies on the impacts of radiation have primarily focused on mutagenic effects and responses to acute doses of radiation, thus, adaptive organismal responses to environmentally relevant exposures are not well understood. Epigenetic mechanisms are capable of mediating organismal responses to environmental factors and DNA methylation plays important roles in gene regulation and promoting chromosomal stability. Further, although evidence is limited, studies suggest that variation in the DNA methylome might be heritable across generations. Here, we analyze changes to the DNA methylome due to low dose rate exposures in medaka (Oryzias latipes). We hypothesized that low, chronic doses of IR would result in global shifts in the DNA methylome. To test this, medaka were exposed in a replicated mesocosm array to environmentally relevant dose regimes (2, 20, or 200 mGy/day) and were subsampled at three- and six-months. In addition, following a six-month exposure, a subset of fish were allowed a three-month recovery period and were bred to produce an F1 generation. Global DNA methylation was quantified in hepatic tissues across all doses at all time points. Whereas gonadal regression was observed in fish exposed to the highest dose rates, a significant effect of dose on global DNA methylation was not detected. Findings suggest that phenotypic impacts of IR were not mediated by global shifts in the DNA methylome in our study.
