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 naive epiblast of the preimplantation embryo. It has been proposed that 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 naive embryonic stem cells (ESCs) recapitulate the molecular and functional properties of the naive epiblast, including the capacity to acquire a formative state and differentiate. However, the network of regulators and functional relevance of formative transition remain unresolved. Here we observe that differentiating ESCs transiently activate a distinct transcriptional program consistent with a formative state, after whose completion cells are irreversibly committed to differentiate. To our surprise, we observed that Esrrb, a pivotal naive pluripotency factor, is both sufficient and required to activate the formative program. Mechanistically, in naive cells ESRRB occupies both naive and formative gene loci. During formative transition ESRRB binding at naive genes is lost, while binding on formative genes is consolidated. Finally, when both naive and formative transcriptional programs are inactivated, ESRRB occupancy is mostly lost and cells irreversibly commit to differentiate. Genetic inactivation of Esrrb leads to failure to induce the appropriate formative program, which functionally results in severely impaired PGC specification and accelerated spontaneous mesendoderm differentiation. Thus, Esrrb is critical for activating the formative transition and consequently for executing timely and unbiased multilineage differentiation of murine pluripotent cells. We propose that similar in-built differentiation circuits might be found in other species and stem cell types.