A genome-wide screen reveals new regulators of the 2-cell-like cell state

Abstract: In mammals, only the zygote and blastomeres of the early embryo are fully totipotent. This totipotency is mirrored in vitro by mouse "2-cell-like cells" (2CLCs), which appear at low frequency in cultures of Embryonic Stem cells (ESCs). Because totipotency is incompletely understood, we carried out a genome-wide CRISPR KO screen in mouse ESCs, searching for mutants that reactivate the expression of Dazl, a robust 2-cell-like marker. Using secondary screens, we identify four mutants that reactivate not just Dazl, but also a broader 2-cell-like signature: the E3 ubiquitin ligase adaptor SPOP, the Zinc Finger transcription factor ZBTB14, MCM3AP, a component of the RNA processing complex TREX-2, and the lysine demethylase KDM5C. Functional experiments show how these factors link to known players of the 2 cell-like state. These results extend our knowledge of totipotency, a key phase of organismal life.