Meeting Abstract
DNA methylation, a well-studied epigenetic mark, is important for gene regulation and is vulnerable to early-life exposure to environmental challenges. In this context, the present study aimed at evaluating the combined effects of heat stress and copper (Cu) exposure on DNA methylation during early zebrafish (Danio rerio) embryogenesis. Zebrafish embryos were exposed to 325 µg Cu/L from fertilization to 4 hours post fertilization (hpf) (when remethylation of the zygotic genome is restored) at either 26.5 °C or 34 °C, followed by incubation within clean water at 26.5 °C to 96 hpf. Overall, significant decreased survival rate and delayed embryo hatching were observed following exposure to high temperature and Cu from fertilization to 4 hpf. Quantitative real-time PCR assays showed a significant increase (45 %) in the metallothionein 2 (mt2) mRNA expression in 96 hpf larvae following Cu exposure, independently of heat stress. Despite alterations in mt2 mRNA expression, we did not observe any significant change in the DNA methylation levels of seven CpG sites located in the promoter region of mt2 gene in 96 hpf zebrafish larvae by using pyrosequencing. All CpG positions were hypomethylated (on average between 2.0 and 6.3 %). The methylation levels of individual CpG sites located in other mt2 gene regions (e.g., the first intron) are being analyzed, as well as global DNA methylation using the LUminometric Methylation Assay. Our preliminary results suggest that further research is needed to better understand the effects of environmental stressors and the role of epigenetic mechanisms within susceptible windows of early vertebrate development.
