Single-cell RNA sequencing of Zfp36l2 knock-out and floxed GV mouse oocytes.

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. Here, we report the unexpected finding that oocyte global transcriptional silencing depends on an mRNA decay activator. Oocyte-specific loss of ZFP36L2--an RNA-binding protein critical for 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. Examination of differential gene expression in mouse oocytes upon loss of Zfp36l2.全局转录沉默（global transcriptional silencing）是一种高度保守的进化事件，是完全分化的卵母细胞向全能性胚胎转变的核心环节。尽管这一关键的全基因组事件在所有动物的发育中至关重要，但目前对其仍知之甚少。本研究报告了一项意外发现：卵母细胞的全局转录沉默依赖于一种mRNA降解激活因子（mRNA decay activator）。ZFP36L2是一种对AU富集元件（AU-rich element）介导的mRNA降解至关重要的RNA结合蛋白，卵母细胞特异性缺失ZFP36L2会阻止卵母细胞发生全局转录沉默。ZFP36L2缺陷的卵母细胞发育潜能丧失，其成熟与受精过程存在缺陷，最终会导致完全的雌性不育。单细胞RNA测序（single cell RNA-seq）分析显示，ZFP36L2可调控大量在染色质修饰、转录起始与延伸过程中发挥核心作用的转录调控因子。这种调控失调会导致无法积累与沉默且具备发育潜能状态相关的组蛋白甲基化标记。本研究结果阐明了卵母细胞mRNA降解激活因子在下调转录激活因子过程中的关键作用，该过程最终可介导组蛋白甲基化、全局转录沉默以及卵母细胞向胚胎转变所需的发育潜能获得。本数据集涵盖Zfp36l2缺失小鼠卵母细胞的差异基因表达分析内容。