Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, 266071, Qingdao, China.
Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao, China.
Fish Physiol Biochem. 2021 Oct;47(5):1341-1352. doi: 10.1007/s10695-021-00986-x. Epub 2021 Jul 15.
DNA methylation and histone methylation are two types of the most important epigenetic modifications. However, research on their differential expression in gonads of male and female fish is limited. In this study, we examined the characteristics of DNA methylation and tri-methylation of lysine 4 of histone H3 (H3K4me3) modification profiles in the gonads of the wild-type and meio-gynogenetic olive flounders Paralichthys olivaceus. Enzyme-linked immunosorbent assay (ELISA) analysis revealed that the global DNA methylation level was higher in the testis than in the ovary. Real-time quantitative PCR (qPCR) results indicated that maintenance DNA methyltransferase gene dnmt1 and de novo DNA methyltransferase gene dnmt3a are highly expressed in the ovary, while DNA demethyltransferase genes tets are highly expressed in the testis. The inconsistency of DNA methylation and methyltransferase genes in the gonads might associate with the differential distribution in the testis. 5-mC mainly located in the spermatids of the testis was shown with immunohistochemistry (IHC). Furtherly, dnmt3a and tets are mainly located in spermatocytes and oocytes with in situ hybridization (ISH) analysis. As for H3K4me3, total level is higher in the ovary detected with western blot assay. IHC results showed that the signals of H3K4me3 in Sertoli cells of the testis were stronger than those in spermatocytes and spermatids. Methyltransferase gene kmt2b and demethylase genes kdm5a and kdm5c also exhibit much higher expression in the testis with qPCR, and ISH stronger signals of kmt2b and kdm5s were detected in spermatocytes. These results implied that DNA methylation and H3K4me3 are involved in the flounder sex differences and gametogenesis.
DNA 甲基化和组蛋白甲基化是两种最重要的表观遗传修饰类型。然而，关于它们在雌雄鱼类性腺中差异表达的研究有限。在这项研究中，我们研究了野生型和雌核发育橄榄鲆性腺中 DNA 甲基化和组蛋白 H3 赖氨酸 4 三甲基化（H3K4me3）修饰谱的特征。酶联免疫吸附测定（ELISA）分析显示，睾丸中的全基因组 DNA 甲基化水平高于卵巢。实时定量 PCR（qPCR）结果表明，维持性 DNA 甲基转移酶基因 dnmt1 和从头合成性 DNA 甲基转移酶基因 dnmt3a 在卵巢中高表达，而 DNA 去甲基化酶基因 tets 在睾丸中高表达。性腺中 DNA 甲基化和甲基转移酶基因的不一致性可能与睾丸中的差异分布有关。免疫组织化学（IHC）显示，5-mC 主要位于睾丸的精母细胞中。进一步的原位杂交（ISH）分析表明，dnmt3a 和 tets 主要位于精母细胞和卵母细胞中。至于 H3K4me3，western blot 检测显示卵巢中总水平较高。IHC 结果显示，睾丸支持细胞中的 H3K4me3 信号强于精母细胞和精细胞。qPCR 显示甲基转移酶基因 kmt2b 和去甲基酶基因 kdm5a 和 kdm5c 在睾丸中表达水平更高，ISH 检测到 kmt2b 和 kdm5s 的信号在精母细胞中更强。这些结果表明，DNA 甲基化和 H3K4me3 参与了鲆鱼的性别差异和配子发生。
