Esrrb conveys naïve pluripotent cells through the formative transcriptional program

Pluripotency is the potential of a single cell to give rise to all embryonic lineages and first emerges in the naïve epiblast of the preimplantation embryo. Upon implantation, epiblast cells transit to a formative phase, which is preparatory for their differentiation into all somatic lineages and primordial germ cells (PGCs). Murine naïve embryonic stem cells (ESCs) recapitulate the molecular and functional properties of the naïve epiblast, including the capacity to acquire a formative state and differentiate. However, the transition to the formative state, and its functional relevance, is still heavily investigated. Here we observed that Esrrb, a pivotal naïve pluripotency factor, is both required and sufficient to activate formative genes. In naïve cells ESRRB occupies both naïve and formative gene loci. During the formative transition, however, ESRRB binding becomes consolidated on formative genes. Subsequently, ESRRB occupancy is mostly lost, and the formative transcriptional program is inactivated. Functionally, genetic inactivation of Esrrb leads to impaired PGC specification, spontaneous expression of mesendoderm and trophectoderm markers, and inability to generate Formative Stem (FS) cells. Moreover, the 3D organisation in a polarised epithelium with a central lumen, as observed in the formative epiblast, is impaired in the absence of Esrrb. Thus, Esrrb is critical for activating the formative transition and consequently for executing timely and unbiased multilineage differentiation and self-organisation of murine pluripotent cells.