Epigenetic effect of temperature, sex, parent-specific genetic background and their interactions on gonadal genes related to sex determination of the European sea bass (Dicentrarchus labrax)

Abstract

The European sea bass is a gonochoristic species whose sex ratio is determined by both genetic and environmental factors contributing to the resulting sex-balanced wild populations. Exposure to high temperature of juveniles during a thermosensitive period has been shown to induce masculinisation of genotypic females with intratesticular oocytes. However, the epigenetic molecular mechanism regulating key sex-related genes remain unclear. We prepared a Multiplex Bisulfite Sequencing (MBS) library including 99 gonadal samples which was designed for the analysis of promoter region of target genes. The analysis of differential DNA methylation profiles was focused on a panel of 10 genes related to sex determination and gonadal differentiation in juvenile fish reared at high or low temperatures during the thermosensitive period (TSP) from previously genotyped progeny. The statistical analysis of our results determined gene-specific epigenetic effect of temperature, sex, genetic background and interaction of such factors on gonadal genes. Therefore, it is suggested that gonadal gene expression of sea bass are highly plastic and sensitive to environmental cues. Furthermore, DNA methylation might play a role in high temperature-induced masculinisation of genotype femalesby lower methylation on promoters of core genes involved in testis developmentas well ashypermethylation of master genes related to differentiation of ovaries. Finally, sensitivity to the epigenetic mechanism could be dependent on the methylome epigenetically inherited through the male parent