Derivation of intermediate pluripotent stem cells amenable to primordial germ cell specification

Dynamic pluripotent stem cell (PSC) states represent in vitro adaptations of the in vivo pluripotency continuum. Decades of studies have generated a number of PSCs with distinct molecular and phenotypic features. To date, however, no known PSCs have demonstrated direct primordial germ cell (PGC) specification responsiveness, a property unique to the embryonic day 5-6 (E5-6) epiblast in mice. Here, we developed a method that enabled the derivation of intermediate PSCs from mouse blastocysts, which not only shared transcriptional similarity with E5-6 epiblast but were also capable of efficient PGC specification in vitro and germline transmission in vivo. The same culture system supported the derivation of embryonic stem cells (ESCs) from horse blastocysts and transgene-free induced pluripotent stem cells (iPSCs) from horse and human fibroblasts, which could also be directly induced into PGC-like cells in vitro. PGC responsive PSCs are invaluable for studying mammalian pluripotency and early PGC development, and our method may be broadly applicable for the derivation of analogous stem cells from other mammalian species. Note: The supplementary data that support the findings of this study have been deposited into CNSA with accession number CNP0001190.