表观遗传是研究生命与环境相互作用的桥梁。鱼类性别决定和分化是研究表观遗传调控的绝佳案例。本项目组前期发现DNA甲基化在温度介导的半滑舌鳎性别决定和分化过程中发挥重要作用。DNA甲基化与组蛋白甲基化修饰H3K9me2密切相关，常常协同调控基因表达，共同参与生命活动。本研究以H3K9me2与DNA甲基化的交叉对话为切入点，证明EHMT1/2是主要负责H3K9me2的甲基转移酶，利用CUT&Tag技术分析H3K9me2的差异定位，结合DNA甲基化数据，筛选受H3K9me2与DNA甲基化协同调控的关键性别基因。进一步利用RNAi与抑制剂处理，阐明DNA甲基化与H3K9me2协同调控关键性别基因的分子机理。同时，揭示关键性别基因对EHMT1/2及H3K9me2的负反馈调控机制，从而完善性别决定与分化的表观调控信号通路，为深入理解环境介导的鱼类性别调控机制提供新认知。

Epigenetics is an excellent breakthrough for the interaction between lives and the environment. Sex determination and differentiation of fishes are outstanding examples to investigate the mechanism of epigenetic regulation. Our previous research showed that DNA methylation plays an important role in the temperature-regulated sex determination and differentiation of Chinese tongue sole. DNA methylation and H3K9me2 are well-conserved epigenetic marks for transcriptional silencing, and crosstalk with each other in many gene locus. In this study we will focus on the cross-talk of H3K9me2 and DNA methylation. First, we will prove that EHMT1/2 are the methyltransferases mainly responsible for H3K9me2. CUT & Tag sequencing will be performed to detect the enrichment of H3K9me2 at the genome-wide level in tongue sole. Then, we will carry out combined analysis of the genomic H3K9me2 enrichment and DNA methylation data to screen important sex genes that are regulated by both modifications. We will also investigate the epigenetic mechanisms of sex genes expression cooperatively regulated by DNA methylation and H3K9me2 using RNAi and inhibitors. Furthermore, the negative feedback regulation of sex genes on EHMT1/2 and H3K9me2 will be elucidated. This study will provide new insights into the crosstalk of different epigenetic modifications and improve our understanding of epigenetic signal pathways in the temperature-regulated sex determination.