FoxO transcription factors actuate the formative pluripotency specific gene expression programme

Naive pluripotency is sustained by a self-reinforcing gene regulatory network (GRN) comprising core and naive pluripotency-specific transcription factors (TFs). Upon exiting naive pluripotency, ES cells transition through a formative post-implantation-like pluripotent state, where they acquire competence for lineage-choice. However, the mechanisms underlying disengagement from the naive GRN and initiation of the formative GRN are unclear. Here, we demonstrate that phosphorylated AKT acts as a gatekeeper that prevents nuclear localization of FoxO TFs in naive ESCs. PTEN-mediated reduction of AKT activity upon exit from naive pluripotency allows nuclear entry of FoxO TFs, enforcing a cell fate transition by binding and activating formative pluripotency-specific enhancers. Indeed, FoxO TFs are necessary and sufficient for transition from the naive to the formative pluripotent state. Our work uncovers a pivotal role for FoxO TFs and AKT signalling in mechanisms establishing formative post-implantation pluripotency, a critical early embryonic cell fate transition.