Epigenetics of uterine quiescence

蜕膜是位于胚胎和子宫肌层之间的专门的子宫内膜组织，其功能是 怀孕期间的几个重要功能。在这样做的同时，它还必须保持“静止”，否则就会有风险 胎盘功能受损或引发子宫收缩，从而导致早产。这是静止的 状态已被假定为与任何其他组织的状态相同，因为它将被下列应力废除 破坏组织的动态平衡或完整性。然而，我们最近在老鼠身上的研究表明，蜕膜是独一无二的 因为它主动地使自己处于静止状态，这是因为蜕膜基质细胞(DSCs) H3三甲基赖氨酸27靶向启动子的转录沉默威胁基因 (H3K27me3)，一个抑制性组蛋白标记。这一表观遗传计划影响了一组不同的约800个基因， 我们目前了解的作用是抑制1型免疫和伤口愈合反应。 H3K27me3是由PrC2(多梳抑制物2)产生的，其主要催化亚基是 组蛋白甲基转移酶EZH2(Zust Homolog 2的增强子)。在这里，我们建议解剖妊娠 Ezh2在子宫内有条件缺失的小鼠的表型，长期目标是获得 更深入地了解子宫静止的本质，以及通过 蜕膜基因沉默程序。重要的是，“Ezh2 CKO”小鼠形成着床部位，但它们很短- 活着。我们推测，H3K27me3介导的DSCs基因沉默对怀孕至关重要，因为它 在面对许多潜在的组织压力时，以保护伞的方式强制子宫静止，包括 感染、同种免疫反应、组织损伤，甚至胎盘发育本身。在目标1中，它 最一般地接近Ezh2 CKO表型，我们将确定哪些类型的妊娠并发症 由子宫Ezh2缺乏以及可能引发这些 并发症。目的集中在(1)着床和早期胚胎发育所造成的压力， (2)胎盘发育较晚；(3)全身炎症；(4)直接感染。然后目标2解决了一个 Ezh2CKO蜕膜的一个已经很清楚的方面，即它的收缩α的异常产生-平滑 肌肉肌动蛋白+肌成纤维细胞。我们将确定这些细胞是否对怀孕成功构成威胁，以及 蜕膜基因沉默是否通过颠覆强大的肌成纤维细胞诱导来阻止它们的出现 创伤后激活的生长因子转化生长因子-β的活性。然后，目标3将确定蜕膜基因如何 沉默程序将活化的T细胞和巨噬细胞排除在母胎界面的能力 有助于妊娠成功。总之，这些目标将确立PrC2介导的基因的重要性 蜕膜生物学中的沉默，有助于更好地理解子宫静止的本质，以及 潜在地揭示了以前未被意识到的与人类生殖有关的怀孕威胁。

The decidua, the specialized endometrial tissue positioned between the conceptus and myometrium, performs several important functions during pregnancy. While doing so, it must also remain “quiescent” or else risk compromising placental function or triggering uterine contractions and thus premature delivery. This quiescent state has been assumed to be like that of any other tissue, in that it would be abrogated by stresses that disrupt tissue homeostasis or integrity. However, our recent work in mice suggests that the decidua is unique in that it actively enforces its own quiescence, and that this occurs because decidual stromal cells (DSCs) transcriptionally silence quiescence-threatening genes via targeted promoter accrual of H3 trimethyl lysine 27 (H3K27me3), a repressive histone mark. This epigenetic program impacts a diverse set of ~800 genes, with the effects we currently understand being the suppression of type 1 immunity and wound healing responses. H3K27me3 is generated by PRC2 (Polycomb Repressive Complex 2), whose primary catalytic subunit is the histone methyltransferase EZH2 (Enhancer of Zeste Homolog 2). Here, we propose to dissect the pregnancy phenotype of mice in which Ezh2 is conditionally deleted within the uterus, with the long-term goal of gaining a greater insight into the nature of uterine quiescence and the kinds of threats to pregnancy mitigated by the decidual gene silencing program. Importantly, “Ezh2 cKO” mice form implantations sites, but they are short- lived. We hypothesize that H3K27me3-mediated gene silencing in DSCs is critical to pregnancy because it acts in umbrella fashion to enforce uterine quiescence in the face of many potential tissue stresses, including infection, allo-immune responses, tissue damage, and even placental development itself. In Aim 1, which approaches the Ezh2 cKO phenotype most generally, we will identify the kinds of pregnancy complications that result from uterine Ezh2 deficiency, as well as the kinds of tissue stresses that might trigger these complications. The Aim focuses on the stresses caused by (1) implantation and early embryonic development, (2) later placental development, (3) systemic inflammation, and (4) direct infection. Aim 2 then addresses an aspect of the Ezh2 cKO decidua that is already clear, namely its aberrant generation of contractile α-smooth muscle actin+ myofibroblasts. We will determine whether these cells pose a threat to pregnancy success, and whether the decidual gene silencing prevents their appearance by subverting the potent myofibroblast-inducing activity of TGF-β, a growth factor activated by wounding. Aim 3 will then determine how the decidual gene silencing program's ability to exclude activated T cells and macrophages from the maternal-fetal interface contributes to pregnancy success. Together, these aims will establish the importance of PRC2-mediated gene silencing in decidual biology, provide a greater understanding of the nature of uterine quiescence, and potentially reveal previously unappreciated threats to pregnancy relevant to human reproduction.