Reconstitution of the mouse germ-cell specification pathway in culture by pluripotent stem cells

The generation of properly functioning gametes in vitro, a key goal in developmental/reproductive biology, requires multi-step reconstitutions of complex germ cell development. Based on the logic of primordial germ cell (PGC)-specification, we demonstrate here the generation of PGC-like cells (PGCLCs) in mice with robust capacity for spermatogenesis from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) through epiblast-like cells (EpiLCs), a cellular state highly similar to pre-gastrulating epiblasts, but distinct from epiblast stem cells (EpiSCs). The global transcription profiles, epigenetic reprogramming, and cellular dynamics during PGCLC induction from EpiLCs are a meticulous capture of those associated with PGC specification from the epiblasts. Furthermore, we identify Integrin-beta 3 and SSEA1 as markers that purify PGCLCs with spermatogenic capacity free from tumorigenic undifferentiated cells. With the reconstitution of PGC specification pathway from the naive inner cell mass state, our study defines a paradigm for the essential step of in vitro gametogenesis.