DNA methylation modification is associated with gonadal differentiation in Monopterus albus.

Both testis and ovary can be produced sequentially in an individual with the same genome when sex reversal occurs in the teleost Monopterus albus, and epigenetic modification is supposed to be involved in gonadal differentiation. However, DNA methylation regulation mechanism underlying the gonadal differentiation remains unclear. Here, we used liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) to simultaneously determine endogenous levels of both 5-methyl-2'-deoxycytidine (m5dC) and 5-hydroxymethyl-2'-deoxycytidine (hm5dC) during gonadal differentiation. Overall DNA methylation level was upregulated from ovary to testis via ovotestis. As a de novo methylase, dnmt3aa expression was also upregulated in the process. Notably, we determined transcription factor Foxa1 for dnmt3aa gene expression. Site-specific mutations and chromatin immunoprecipitation showed that Foxa1 can bind to and activate the dnmt3aa promoter. Furthermore, DNA methylation levels of key genes foxl2 (forkhead box L2) and cyp19a1a (cytochrome P450, family 19, subfamily A, polypeptide 1a) in regulation of female hormone synthesis were consistently upregulated during gonadal differentiation. These data suggested that dynamic change of DNA methylation modification is associated with gonadal differentiation.