Abstract
BackgroundBoth 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.ResultsHere, 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.ConclusionsThese data suggested that dynamic change of DNA methylation modification is associated with gonadal differentiation.
Highlights
DNA cytosine methylation (DNA methylation) is a major epigenetic modification that plays vital roles in animal development
The results suggested that Foxa1 could bind foxhead-box to activate the dnmt3aa promoter, foxhead-box a and b could not work independently, and mutation of any of them resulted in an obvious decrease of the promoter activity
A 150 bp DNA region from anti-Foxa1 antibody precipitates was amplified in testis. Another DNA fragment in distinct genomic region was used as a control to exclude the possibility of nonspecific binding to the dnmt3aa promoter region (Fig. 4a, b). These results suggested that Foxa1 can bind to foxhead box a and b in the dnmt3aa promoter and activate the promoter activity in testis
Summary
DNA cytosine methylation (DNA methylation) is a major epigenetic modification that plays vital roles in animal development. In the female germline cells, de novo DNA methylation occurred in arrested oocytes in meiotic prophase I. DNA methylation marks in sperms were quickly erased in the zygote by active demethylation mechanism [5], in contrast, the methylation marks in oocytes were lost via passive dilution through cell division [1]. 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. DNA methylation regulation mechanism underlying the gonadal differentiation remains unclear
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