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: 10014626
• 负责人: Katherine Lee
• 金额: $ 3.84万
• 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/10014626
• 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 完全不存在从头转录。转录在最后阶段是全面沉默的， 卵母细胞的生长，并没有显着恢复，直到合子基因组激活（ZGA）在后期2-细胞 胚期虽然从蠕虫到人类的发展至关重要，转录沉默是如何 在全球范围内实现，随后在没有新的转录的情况下重新激活， 胚胎转变仍然知之甚少。更深入地了解这些机制 发育转变对于干细胞技术和不孕症治疗的进步至关重要。我们有 最近发现（Dumdie等人，Dev Cell，2018），卵母细胞全局转录沉默取决于 mRNA衰变激活剂ZFP 36 L2-一种在富含AU的细胞中具有明确作用的RNA结合蛋白， 元件介导的mRNA衰变。卵母细胞特异性ZFP 36 L2的丢失阻止卵母细胞经历全球性的 转录沉默并导致完全的女性不育。单细胞RNA-seq显示， ZFP 36 L2下调编码调节转录和染色质修饰的因子的mRNA， 包括编码靶向组蛋白的组蛋白赖氨酸脱甲基酶（KDM）的特定组的mRNA H3 K4和H3 K9。我们发现ZFP 36 L2可以结合并降解这些KDM mRNA，这表明ZFP 36 L2可以直接抑制KDM mRNA的表达。 ZFP 36 L2介导的mRNA衰减在调节组蛋白甲基化中的作用。与此一致，Zfp 36 l2 基因敲除导致不能积累H3 K4和H3 K9甲基化， 转录沉默，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，并提出了一个模型， ZPF 36 L2引起的mRNA衰减作为发育开关下调转录调节因子， 引发表观遗传标记的广泛变化，带来全球转录沉默， 从卵母细胞到胚胎的成功过渡。本提案的目标是测试此 模型-剖析ZFP 36 L2依赖性mRNA衰变有助于 卵母细胞中的染色质修饰;研究这些染色质修饰在使卵母细胞中的细胞分化中的作用。 关于全球转录沉默;并揭示卵母细胞中组蛋白甲基化的贡献， 在新形成的胚胎中转录再激活。