Howard Hughes Medical Institute, Boston, MA, USA.
Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.
Nat Cell Biol. 2019 Jul;21(7):835-844. doi: 10.1038/s41556-019-0343-0. Epub 2019 Jun 17.
Totipotency refers to the ability of a cell to generate all of the cell types of an organism. Unlike pluripotency, the establishment of totipotency is poorly understood. In mouse embryonic stem cells, Dux drives a small percentage of cells into a totipotent state by expressing 2-cell-embryo-specific transcripts. To understand how this transition takes place, we performed single-cell RNA-seq, which revealed a two-step transcriptional reprogramming process characterized by downregulation of pluripotent genes in the first step and upregulation of the 2-cell-embryo-specific elements in the second step. To identify factors controlling the transition, we performed a CRISPR-Cas9-mediated screen, which revealed Myc and Dnmt1 as two factors preventing the transition. Mechanistic studies demonstrate that Myc prevents downregulation of pluripotent genes in the first step, while Dnmt1 impedes 2-cell-embryo-specific gene activation in the second step. Collectively, the findings of our study reveal insights into the establishment and regulation of the totipotent state in mouse embryonic stem cells.
全能性是指细胞生成生物体所有细胞类型的能力。与多能性不同，全能性的建立还了解甚少。在小鼠胚胎干细胞中，Dux 通过表达 2 细胞胚胎特异性转录本，将一小部分细胞驱动进入全能性状态。为了了解这种转变是如何发生的，我们进行了单细胞 RNA-seq 分析，结果揭示了一个两步转录重编程过程，其特征是第一步中多能性基因下调，第二步中 2 细胞胚胎特异性元件上调。为了鉴定控制这种转变的因素，我们进行了 CRISPR-Cas9 介导的筛选，结果显示 Myc 和 Dnmt1 是阻止这种转变的两个因素。机制研究表明，Myc 阻止了第一步中多能性基因的下调，而 Dnmt1 则阻碍了第二步中 2 细胞胚胎特异性基因的激活。总的来说，本研究的结果揭示了小鼠胚胎干细胞中全能性状态建立和调控的新见解。
