Effect of DNA Methylation Modification on Expression Level of Cyp17a1 in Ovary of Spotted Scat(Scatophagus argus)
[Objective]The aim of this study is to analyze the effect of DNA methylation modification on the expression of Cyp17a1 in the ovary of Scatophagus argus,and to better understand the mechanism of gene expression regulation related to ovarian development and maturation.[Methods]The experimental S.argus included individuals with ovaries at different stages(Ⅲ and IV)and 2-years-old females treated with dietary estradiol[0(control),50 and 100 μg/g]for 30 d.The distribution of CpG dinucleotide sites were analyzed and CpG islands of the Cyp17a1 gene were predicated by MethPrimer software.The CpG enriched region of Cyp17a1 was selected to determine the level of DNA methylation modification in the ovaries of individuals at different developmental stages and individuals fed with estradiol.In addition,the level of Cyp17a1 gene expression in these fish was investigated using quantitative real-time PCR.[Results]There are no CpG islands within the 2000 bp after the translation initiation site(TIS)and the region containing five CpG sites in exon 1(106,116,129,148 and 203 bp after the TIS)was selected to determine the level of DNA methylation modification.The DNA methylation modification level of Cyp17a1 exon 1 was significantly higher in the stage Ⅲ ovaries of the fish than in the stage IV ovaries(P<0.05),which was negatively correlated with its mRNA expression level.Methylation levels at the 116,129 and 203 bp sites showed significant developmental differences,whereas the differences at the 106 and 148 bp sites were not significant(P>0.05).After the estradiol treatment,there was no significant change(P>0.05)in the level of Cyp17a1 mRNA and DNA methylation modification in the region of exon 1 in the ovary,but the level of DNA methylation at the 148 and 203 bp sites after the TIS was increased significantly in the estrogen-treated fish(P<0.05).[Conclusion]The methylation level of the CpG enriched region in the first exon of Cyp17a1 in S.argus stageⅢandⅣovaries is negatively correlated with gene expression.Dietary E2 can up-regulate the methylation levels of the first exon of at 148 and 205 bp of Cyp17a1,suggesting that methylation modification is involved in the regulation of Cyp17a1 expression in S.argus.
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