胚胎着床的表观遗传调控机制

Embryo implantation, a crucial early pregnancy event determining the success of term pregnancy, is precisely regulated by ovarian estrogen and progesterone, as well as locally produced signaling molecules at the maternal-fetal interface. However, it remained largely unknown regarding the transcriptional regulatory mechanism, via which various signaling molecules and functional genes are spatiotemporally activated or silenced. In this respect, EZH1/2 and PR-Set7, the methyltransferases for histone H3K27 and H4K20, are likely to be potential vital players during early pregnancy. To address how these histone methylation events participate in regulating the process of implantation and decidualization, we will employ uterine selective transgenic and knockout mouse models as well as human clinical endometrial samples, to accordingly investigate: ⑴ the spatiotemporal expression pattern of EZH1, EZH2 and PR-Set7 in the periimplantation uterus; ⑵ the physiological role of H3K27 and H4K20 methylation during embryo implantation and decidualization; ⑶ the involvement of H3K27 and H4K20 methylation during the establishment of endometrial receptivity and decidual transformation in humans; ⑷ novel underlying mechanisms of EZH1/2 and PR-Set7 governing embryo implantation. It is hoped that a better understanding on epigenetic regulatory aspects of embryo implantation will help us to reveal the pathological seeds of early pregnancy loss in humans.

胚胎着床是决定妊娠成功与否的关键环节，受雌孕激素和母胎界面局部产生的信号分子的精确调控，但诸多关键功能基因在植入进程中时空特异性开启与关闭的转录调控机制仍远未阐明。我们推测EZH1/2和PR-Set7介导的H3K27和H4K20甲基化修饰可能在胚胎着床中起核心的转录调控作用，提出关键科学问题“组蛋白甲基化修饰调控胚胎着床和蜕膜发育的分子机制是什么”，拟利用子宫特异性敲除或过表达小鼠模型和人类临床资源，系统研究：⑴EZH1/2和PR-Set7在围植入期子宫中的动态表达模式；⑵H3K27和H4K20甲基化修饰在胚胎着床和子宫蜕膜发育中的调节作用；⑶H3K27和H4K20甲基化修饰在人子宫内膜接受态建立和蜕膜发育中的作用机制；⑷EZH1/2和PR-Set7调控胚胎着床的新机制，力争揭示胚胎着床的表观转录调控分子机制，为实现从源头上揭示早期妊娠失败等不良妊娠结局的诱发机制提供理论基础和新思路。

胚胎着床是决定妊娠成功与否的关键环节，受雌孕激素和母胎界面局部产生的信号分子的精确调控，但诸多关键功能基因在植入进程中时空特异性开启与关闭的转录调控机制仍远未阐明。本项目主要解决的关键科学问题是“组蛋白甲基化修饰调控胚胎着床和蜕膜发育的分子机制是什么”，我们利用转基因和子宫特异性敲除小鼠模型，结合子宫细胞培养研究了（1）Ezh1、Ezh2、Prs-et7、WT1以及表观修饰相关的底物H3K27Me3和H4K20Me1在围植入期子宫中的动态表达模式，在出生后子宫发育的关键时间窗口内检测Pr-set7及其参与修饰的H4K20Me1的动态变化；（2）Prs-et7对子宫发育的影响；（3）Ezh对胚胎植入的影响；（4）WT1对胚胎植入的影响。我们发现：（1）子宫特异性敲除Pr-set7造成子宫上皮细胞的大量凋亡和腺体发生障碍，并提出腺体发育的“上皮细胞数目阈值”假说，Pr-set7缺失子宫基质细胞的增殖也明显减弱；（2）子宫中特异性敲除Ezh2导致子宫接受态建立的异常，蜕膜分化异常，蜕膜细胞中Wnt信号配体表达增多，活性氧（ROS）水平上升，NK细胞数量减少等，最终造成胚胎发育停滞以及妊娠的失败；（3）WT1的子宫特异敲除导致胚胎植入失败和雌孕激素响应的异常。本研究揭示了胚胎着床过程中Ezh和Pr-set7等介导的的表观遗传调控机制，为实现从源头上揭示早期妊娠失败等不良妊娠结局的诱发机制提供理论基础和新思路。