Mechanisms Linking Global Transcriptional Silencing and Zygotic Gene Activation During the Oocyte-to-Embryo Transition in Mammals

哺乳动物卵母细胞到胚胎转变过程中全局转录沉默和合子基因激活的联系机制

• 批准号: 10221758
• 负责人: Katherine Lee
• 金额: $ 3.93万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-02 至 2023-08-01
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10221758
• 关键词: Binding; Biological Assay; Biological Models; Biology; Cells; Competence; Data; Deposition; Development; Down-Regulation; Elements; Embryo; Epigenetic Process; Event; Failure; Female infertility; Fertilization; Gene Activation; Gene Silencing; Genes; Genetic Models; Genetic Transcription; Genome; Goals; Growth; Histones; Human; Infertility; Inherited; Knock-out; Knowledge; Laboratories; Link; Lysine; Mammals; Mediating; Messenger RNA; Methylation; Modeling; Oocytes; Pattern; Play; Publishing; RNA Polymerase II; RNA-Binding Proteins; Role; Technology; Testing; Totipotent; Transcriptional Regulation; ZFP36L2 gene; chromatin modification; cooking; demethylation; embryo cell; experimental study; histone demethylase; histone methylation; insight; mRNA Decay; mRNA Transcript Degradation; prevent; promoter; recruit; single-cell RNA sequencing; stem cell technology; stem cells

Abstract Remarkably, the dynamic transition from the fully differentiated oocyte to the totipotent embryo occurs in the complete absence of de novo transcription. Transcription is globally silenced during the final stages of oocyte growth and does not significantly resume until the zygotic genome activation (ZGA) in the late 2-cell embryo stage. Although critical for development from worms to humans, how transcriptional silencing is achieved on a global scale and subsequently reactivated without new transcription across the oocyte-to- embryo transition remains poorly understood. A deeper understanding of the mechanisms underlying these developmental transitions is critical for advances in stem cell technologies and infertility therapies. We have recently discovered (Dumdie et al., Dev Cell, 2018) that oocyte global transcriptional silencing depends on the mRNA decay activator ZFP36L2—an RNA-binding protein with a well-established role in AU-rich element-mediated mRNA decay. Oocyte-specific loss of ZFP36L2 prevents oocytes from undergoing global transcriptional silencing and leads to complete female infertility. Single-cell RNA-seq revealed that ZFP36L2 downregulates mRNAs encoding factors regulating transcription and chromatin modification, including a specific group of mRNAs encoding histone lysine demethylases (KDMs) targeting histones H3K4 and H3K9. We showed that ZFP36L2 can bind and degrade these KDM mRNAs, suggesting a direct role for ZFP36L2-mediated mRNA decay in regulating histone methylation. Consistent with this, Zfp36l2 knockout resulted in the failure to accumulate H3K4 and H3K9 methylation associated with the transcriptionally silent, developmentally competent oocyte state. Together, these results define a critical role for an mRNA decay activator in oocyte developmental competence and suggest a model in which mRNA decay by ZPF36L2 serves as a developmental switch to downregulate transcriptional regulators, trigger wide-spread shifts in epigenetic marks, bring about global transcriptional silencing, and set the stage for a successful transition from oocyte to embryo. The goal of this proposal is to test each stage of this model—to dissect the specific mechanism(s) by which ZFP36L2-dependent mRNA decay contributes to chromatin modifications in the oocyte; to investigate the role of these chromatin modifications in bringing about global transcriptional silencing; and to uncover the contribution of histone methylation in the oocyte to transcription reactivation in the newly formed embryo.

摘要 值得注意的是，从完全分化的卵母细胞到全能胚胎的动态转变发生在 完全没有从头转录。转录在最后阶段被全局静默 卵母细胞生长，直到合子基因组激活(ZGA)后2-细胞才能显著恢复 胚胎期。尽管对从蠕虫到人类的发育至关重要，但转录沉默是如何 在全球范围内实现，随后在没有新的跨卵母细胞到- 胚胎移植仍然知之甚少。对这些问题背后的机制有更深入的了解 发育转变对于干细胞技术和不孕不育疗法的进步至关重要。我们有 最近发现(Dumdie等人，Dev Cell，2018)卵母细胞的全局转录沉默依赖于 信使核糖核酸衰变激活因子Zfp36l2--一种在富含AU中具有广泛作用的RNA结合蛋白 元素介导的信使核糖核酸衰变。卵母细胞特异性缺失Zfp36l2阻止卵母细胞经历 转录沉默并导致女性完全不孕。单细胞rna-seq显示 Zfp36l2下调编码转录和染色质修饰因子的mRNAs， 包括编码组蛋白赖氨酸去甲基酶(KDM)的一组特定的mRNAs，其靶向组蛋白 H3K4和H3K9。我们发现Zfp36l2可以结合和降解这些KDM mRNAs，这表明 Zfp36l2介导的mRNA衰变在调控组蛋白甲基化中的作用与此一致，Zfp36l2 基因敲除导致H3K4和H3K9甲基化积累失败 转录沉默，有发育能力的卵母细胞状态。总之，这些结果定义了一个关键的 MRNA衰变激活剂在卵母细胞发育能力中的作用并提出一个模型 ZPF36L2的mRNA降解是下调转录调控的发育开关， 触发表观遗传标记的广泛转移，带来全球转录沉默，并为 成功地从卵母细胞过渡到胚胎。这项提案的目标是测试这一过程的每一个阶段 模型-剖析Zfp36l2依赖的信使核糖核酸衰变的具体机制(S) 卵母细胞中的染色质修饰；研究这些染色质修饰在将 关于整体转录沉默；以及揭示卵母细胞中组蛋白甲基化对 在新形成的胚胎中转录重新激活。