Person:

Fu, Xudong

Totipotency refers to the ability of a cell to generate all the cell types of an organism. Unlike pluripotency, the establishment of totipotency is poorly understood. In mouse embryonic stem cells (mESCs), Dux drives a small percentage of cells into a totipotent state by expressing 2-cell-embyro-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 down-regulation of pluripotent genes in the first step, while Dnmt1 impedes 2 cell embryo-specific gene activation in the second step. Collectively, our study reveals insights into establishment and regulation of totipotent state in mESCs.