Temperature effects on global DNA methylation and gene expression during larval development in the European sea bass

Abstract

The environmental information received during early development may be integrated into the genome via epigenetic mechanisms and may have short- or long-term consequences on the phenotype. Fish larvae are susceptible to environmental influences due to direct exposure to the water environment. One-year-old European sea bass (Dicentrarchus labrax) exposed to high temperature (HT) during the early development had higher levels of DNA methylation in the promoter of gonadal aromatase (Navarro-Martín et al. 2011. PLoS Genetics 7(12): e1002447). In this study, we focused on the effects of temperature on global DNA methylation and expression of key genes during the early life of sea bass. We considered two periods of temperature treatment: (1) from 0 to 15 days post fertilization (dpf) and (2) from 20 to 60 dpf, at the beginning and end of the thermosensitive period, respectively. In (1), we conducted a dose (temperature)-response experiment and a time-series of switches between low (LT) and HT. We used MSAP to detect global changes in DNA methylation. We found that there were statistically significant differences in global DNA methylation between groups subjected to increasing temperature during the first 15 days of life, while in contrast no statistically significant differences were detected after the second period of treatment. Furthermore, there was, in general, an upregulation of gene expression, with a mean fold change of 12.216 times in the HT group. The expression of enzymes with a key role in DNA methylation establishment and maintenance, dnmt1 and dnmt3, was found significantly higher in the HT group during the first period when compared to the second one. These experiments illustrate the importance of the environmental conditions during the first 15 dpf of sea bass in evoking changes on DNA methylation and gene expression which will probably have enduring phenotypic consequences