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

项目摘要 全局转录沉默是一个高度保守的进化事件，对于从完全转录沉默到完全转录沉默的转变至关重要。 分化的卵母细胞发育为全能胚胎。尽管它在所有动物的发展中很重要， 关键的全基因组事件仍然知之甚少。我们最近发现，卵母细胞全球 转录沉默依赖于mRNA衰变激活剂。ZFP 36 L2-一种RNA-的卵母细胞特异性丢失 结合蛋白在富含AU的元件介导的mRNA衰变中具有明确的作用， 正在经历全面的转录沉默ZFP 36 L2缺陷卵母细胞发育不全， 导致女性完全不育的成熟和受精缺陷。单细胞RNA测序分析 ZFP 36 L2调节大量转录调节因子，在染色质修饰中起核心作用 以及转录起始和延伸。这种失调导致了组蛋白的积累失败， 甲基化标记与沉默，有能力的状态有关。我们的研究结果定义了卵母细胞的关键作用 mRNA衰变激活因子在下调转录激活因子中，导致组蛋白甲基化，全球 转录沉默和从卵母细胞向胚胎过渡的能力。这些发现有力地表明， 一个模型，其中卵母细胞中的整体转录沉默是由mRNA衰变介导的。这个的目标 我们的建议是揭示ZFP 36 L2引起的mRNA衰减导致全球性的细胞凋亡的机制。 转录沉默的卵母细胞，并利用这种独特的遗传学提供的见解， 模型系统，以研究ZFP 36 L2依赖性染色质修饰的作用， 转录沉默和从卵母细胞到胚胎的成功过渡。为了确定mRNA的作用 我们将鉴定ZFP 36 L2在细胞中的直接靶点， 卵母细胞全基因组和测试的作用，这些因素介导的全球转录沉默和卵母细胞 发展能力我们将确定ZFP 36 L2在染色质修饰中的作用，包括 组蛋白H3和DNA甲基化，并测试这些修饰在整体转录沉默中的作用， 卵母细胞最后，我们将测试卵母细胞中是否建立了ZFP 36 L2依赖的染色质修饰， 在卵母细胞到胚胎的转变过程中维持整体转录沉默和/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.