CpG methylation of <i>dmrt1</i> and <i>cyp19a</i> promoters in relation to their sexual dimorphic expression in the Japanese flounder <i>Paralichthys olivaceus</i>

<jats:p>To better understand the effects of <jats:styled-content style="fixed-case">DNA</jats:styled-content> methylation on the expression patterns of <jats:italic>dmrt1</jats:italic> (Doublesex and Mab‐3‐related transcription factor 1) and <jats:italic>cyp19a</jats:italic> (Cytochrome <jats:styled-content style="fixed-case">P450</jats:styled-content> 19a) in the Japanese flounder <jats:italic>Paralichthys olivaceus</jats:italic>, quantitative expressions, cellular distributions and cytosine‐p‐guanine (CpG) methylation patterns of these two genes in the gonads were analysed. The results showed that <jats:italic>P. olivaceus dmrt1</jats:italic> expression was 70 times higher in the testis than in the ovary (<jats:italic>P</jats:italic> < 0·05). Its <jats:styled-content style="fixed-case">mRNA</jats:styled-content> was detected clearly in spermatocytes and Sertoli cells of the testis, but weakly in the ovary. <jats:italic>Paralichthys olivaceus cyp19a</jats:italic> expression was 40 times higher in the ovary than in the testis (<jats:italic>P</jats:italic> < 0·01). Its <jats:styled-content style="fixed-case">mRNA</jats:styled-content> was detected clearly in follicular cells of the ovary, but weakly in spermatocytes of the testis. The <jats:italic>dmrt1</jats:italic> promoter <jats:styled-content style="fixed-case">CpGs</jats:styled-content> were not methylated in the testis, whereas 57·69% were methylated in the ovary. For the <jats:italic>cyp19a</jats:italic> promoter <jats:styled-content style="fixed-case">CpGs</jats:styled-content>, 97·5% were methylated in the testis and 73·33% were methylated in the ovary. These findings demonstrate that <jats:italic>P. olivaceus dmrt1</jats:italic> and <jats:italic>cyp19a</jats:italic> are sex‐related genes with sexual dimorphic expression, <jats:styled-content style="fixed-case">CpG</jats:styled-content> methylation levels of the two genes are consistent with their expression quantities, and this epigenetic modification can influence the differential expression of genes in the gonads of <jats:italic>P. olivaceus</jats:italic>.</jats:p>