The asynchrony in the exit from naive pluripotency cannot be explained by differences in the cell cycle phase
Development is characterized by consecutive cell state transitions that build on each other and ultimately lead to the generation of the numerous different cell types found in the organism. During each of these transitions, cells change their gene expression profiles and take on new identities. Cell state transitions have to be tightly coordinated with proliferation to ensure simultaneous growth and differentiation. The exit from naive pluripotency is an ideal model system for studying the temporal coordination of proliferation and differentiation. Individual cells initiate differentiation earlier compared to others, thereby leading to an asynchronous exit from naive pluripotency. One of the major differences among the cells of the starting population of mouse embryonic stem cells (mESCs) is the cell cycle status, and could therefore be an underlying cause of the differences in the onset of the exit from naive pluripotency. However, through comprehensive analysis including single cell RNA sequencing (scRNA-seq), cell cycle synchronization, and perturbation experiments, we demonstrate here that the cell cycle phase at the initiation of differentiation does not influence the timing of the exit from naive pluripotency.