Mechanisms driving the transition from oocyte to embryo: The role of the mRNA decay activator ZFP36L2.

项目摘要 全球转录沉默是一种高度保守的进化事件，对于从完全 将卵母细胞分化为全能胚胎。尽管它对所有动物的发育都很重要，但这 关键的全基因组事件仍然知之甚少。我们最近发现，全球卵母细胞 转录沉默依赖于信使核糖核酸衰变激活剂。卵母细胞特异性缺失Zfp36l2-an RNA- 结合蛋白在富含AU的元素介导的mRNA衰变中具有公认的作用-防止卵母细胞 经历全球转录沉默。Zfp36l2缺陷的卵母细胞发育不全， 成熟和受精缺陷导致女性完全不孕。单细胞RNA序列分析 发现Zfp36l2调控着许多在染色质修饰中起中心作用的转录调节因子 以及转录起始和延伸。这种失调导致组蛋白不能积聚。 与沉默的、有能力的状态相关的甲基化标记。我们的结果定义了卵母细胞的关键作用 MRNA衰变激活剂下调转录激活物，导致组蛋白甲基化，全球 转录沉默与卵母细胞向胚胎转化的能力。这些发现有力地指出了 一种模型，在该模型中，卵母细胞中的整体转录沉默是由信使核糖核酸衰变所介导的。这样做的目的是 建议既揭示Zfp36l2导致全球变暖的机制(S) 在卵母细胞中转录沉默，并利用这种独特的基因提供的洞察力 模型系统研究Zfp36l2依赖的染色质修饰对全球 转录沉默与卵母细胞向胚胎的成功转化。确定信使核糖核酸的作用 在导致全球转录沉默的过程中，我们将确定Zfp36l2在 并测试这些因子在介导整体转录沉默和卵母细胞中的作用 发展能力。我们将确定Zfp36l2在染色质修饰中的作用，包括 组蛋白H3和DNA甲基化，并测试这些修饰在全球转录沉默中的作用 卵母细胞。最后，我们将测试Zfp36l2依赖的染色质修饰是否在卵母细胞中建立 采取行动在卵母细胞到胚胎的转变过程中保持全球转录沉默和/或为 在新形成的胚胎中激活新的转录。

Project Summary Global transcriptional silencing is a highly conserved evolutionary event central to the transition from the fully differentiated oocyte to the totipotent embryo. Despite its importance in the development of all animals, this pivotal genome-wide event remains poorly understood. We have recently discovered that oocyte global transcriptional silencing depends on an mRNA decay activator. Oocyte-specific loss of ZFP36L2—an RNA- binding protein with a well-established role in AU-rich element-mediated mRNA decay—prevents oocytes from undergoing global transcriptional silencing. ZFP36L2-deficient oocytes are developmentally incompetent, with defects in maturation and fertilization leading to complete female infertility. Single cell RNA-seq analysis revealed that ZFP36L2 regulates scores of transcription regulators with central roles in chromatin modification and transcription initiation and elongation. This dysregulation resulted in failure to accumulate histone methylation marks associated with the silent, competent state. Our results define a critical role for an oocyte mRNA decay activator in the downregulation of transcription activators, leading to histone methylation, global transcriptional silencing and competence to transition from oocyte to embryo. These findings strongly point to a model in which global transcriptional silencing in the oocyte is mediated by mRNA decay. The goals of this proposal are to both uncover the mechanism(s) by which mRNA decay by ZFP36L2 brings about global transcriptional silencing in the oocyte and to take advantage of the insights provided by this unique genetic model system to investigate the role of ZFP36L2-dependent chromatin modifications critical for global transcriptional silencing and the successful transition from oocyte to embryo. To determine the role of mRNA decay in bringing about global transcriptional silencing, we will identify the direct targets of ZFP36L2 in the oocyte genome-wide and test the role of these factors in mediating global transcriptional silencing and oocyte developmental competence. We will determine the role of ZFP36L2 in chromatin modification, including histone H3 and DNA methylation, and test the role of these modifications in global transcriptional silencing in the oocyte. Finally, we will test whether ZFP36L2-dependent chromatin modifications established in the oocyte act to maintain global transcriptional silencing over the oocyte-to-embryo transition and/or set the stage for activation of new transcription in the newly formed embryo.