Otx2 is an intrinsic determinant of the embryonic stem cell state and is required for transition to a stable epiblast stem cell condition

Mouse embryonic stem cells (ESCs) represent the naive ground state of the preimplantation epiblast and epiblast stem cells (EpiSCs) represent the primed state of the postimplantation epiblast. Studies have revealed that the ESC state is maintained by a dynamic mechanism characterized by cell-to-cell spontaneous and reversible differences in sensitivity to self-renewal and susceptibility to differentiation. This metastable condition ensures indefinite self-renewal and, at the same time, predisposes ESCs for differentiation to EpiSCs. Despite considerable advances, the molecular mechanism controlling the ESC state and pluripotency transition from ESCs to EpiSCs have not been fully elucidated. Here we show that Otx2, a transcription factor essential for brain development, plays a crucial role in ESCs and EpiSCs. Otx2 is required to maintain the ESC metastable state by antagonizing ground state pluripotency and promoting commitment to differentiation. Furthermore, Otx2 is required for ESC transition into EpiSCs and, subsequently, to stabilize the EpiSC state by suppressing, in pluripotent cells, the mesendoderm-to-neural fate switch in cooperation with BMP4 and Fgf2. However, according to its central role in neural development and differentiation, Otx2 is crucially required for the specification of ESC-derived neural precursors fated to generate telencephalic and mesencephalic neurons. We propose that Otx2 is a novel intrinsic determinant controlling the functional integrity of ESCs and EpiSCs.