The MuvB complex safeguards embryonic stem cell identity through regulation of the cell cycle machinery.

Increasing evidences indicate that unlimited capacity for self-renewal and pluripotency, two unique properties of embryonic stem cells (ESCs), are intrinsically linked to cell cycle control. However, the precise mechanisms coordinating cell fate decisions and cell cycle regulation remain to be fully explored. Here, using CRISPR/Cas9-mediated genome editing, we show that in ESCs, deficiency of components of the cell cycle regulatory MuvB complex Lin54 or Lin52, but not Lin9 or Lin37, triggers G2/M arrest, loss of pluripotency, and spontaneous differentiation. Further dissection of these phenotypes demonstrated that this cell cycle arrest is accompanied by the gradual activation of mesoendodermal lineage-specifying genes. Strikingly, the abnormalities observed in Lin54-null ESCs were partially but significantly rescued by ectopic coexpression of genes encoding G2/M proteins Cyclin B1 and Cdk1. Thus, our study provides new insights into the mechanisms by which the MuvB complex determines cell fate through regulation of the cell cycle machinery.