Cell division and differentiation after egg fertilization are critical steps in the development of embryos from single cells to multicellular individuals and are regulated by DNA methylation via its effects on gene expression. However, the mechanisms by which DNA methylation regulates these processes in insects remain unclear. Here, we studied the impacts of DNA methylation on early embryonic development in Bombyx mori. Genome methylation and transcriptome analysis of early embryos showed that DNA methylation events mainly occurred in the 5' region of protein metabolism-related genes. The transcription factor gene zinc finger protein 615 ( ZnF615) was methylated by DNA methyltransferase 1 (Dnmt1) to be up-regulated and bind to protein metabolism-related genes. Dnmt1 RNA interference (RNAi) revealed that DNA methylation mainly regulated the expression of nonmethylated nutrient metabolism-related genes through ZnF615. The same sites in the ZnF615 gene were methylated in ovaries and embryos. Knockout of ZnF615 using CRISPR/Cas9 gene editing decreased the hatching rate and egg number to levels similar to that of Dnmt1 knockout. Analysis of the ZnF615 methylation rate revealed that the DNA methylation pattern in the parent ovary was maintained and doubled in the offspring embryo. Thus, Dnmt1-mediated intragenic DNA methylation of the transcription factor ZnF615 enhances its expression to ensure ovarian and embryonic development.
细胞分裂和分化是胚胎从受精卵发育成多细胞个体的重要步骤，DNA甲基化通过调控基因表达而影响胚胎发育的过程。然而，昆虫DNA甲基化调控胚胎发育的机制仍不清楚。该文研究了DNA甲基化对家蚕早期胚胎的影响。早期胚胎的DNA甲基化组和转录组分析表明，5-甲基胞嘧啶（5mC）主要发生在蛋白质代谢相关基因的基因体5’端区域。DNA甲基转移酶1（Dnmt1）催化转录因子锌指蛋白615（ ZnF615）基因的甲基化修饰，从而使 ZnF615表达上调，并结合到蛋白质代谢相关基因而调控这些基因的表达。 Dnmt1 RNAi显示DNA甲基化介导ZnF615调控了非甲基化修饰的胚胎发育所需的营养代谢相关基因的表达。卵巢和胚胎中的 ZnF615基因的5mC位点相同。与 Dnmt1敲除类似，敲除 ZnF615也可以降低家蚕的胚胎孵化率和卵巢的产卵数。对 ZnF615基因甲基化率的分析表明，亲本的卵巢和后代胚胎中的 ZnF615基因的5mC位点相同，但5mC比率加倍。因此，该研究结果证明了Dnmt1促进转录因子 ZnF615的基因内DNA甲基化，增强了其表达而确保了家蚕卵巢和胚胎发育。.
Keywords: DNA methylation; Embryonic development; Epigenetic; Transcriptional regulation.