Highlights d Rabbit PGCs are specified at the posterior epiblast of the bilaminar disc embryo d Rabbit pluripotent state is characteristic of many mammalian disc-shaped epiblast d PGC-like cells induced from pluripotent cells are like in vivo nascent rabbit PGCs d SOX17 is a critical PGC specifier in rabbits as in humans and non-rodent mammals

No abstract

Murine animal models from genetically modified pluripotent stem cells (PSCs) are essential for functional genomics and biomedical research, which require germline transmission for the establishment of colonies. However, the quality of PSCs, and donor-host cell competition in chimeras often present strong barriers for germline transmission. Here, we report efficient germline transmission of recalcitrant PSCs via blastocyst complementation, a method to compensate for missing tissues or organs in genetically modified animals via blastocyst injection of PSCs. We show that blastocysts from germline-deficient Prdm14 knockout rats provide a niche for the development of gametes originating entirely from the donor PSCs without any detriment to somatic development. We demonstrate the potential of this approach by creating PSC-derived Pax2/Pax8 double mutant anephric rats, and rescuing germline transmission of a PSC carrying a mouse artificial chromosome. Furthermore, we generate mouse PSC-derived functional spermatids in rats, which provides a proof-of-principle for the generation of xenogenic gametes in vivo. We believe this approach will become a useful system for generating PSC-derived germ cells in the future.

The in vitro generation of germ cells from pluripotent stem cells (PSCs) can have a substantial effect on future reproductive medicine and animal breeding. A decade ago, in vitro gametogenesis was established in the mouse. However, induction of primordial germ cell–like cells (PGCLCs) to produce gametes has not been achieved in any other species. Here, we demonstrate the induction of functional PGCLCs from rat PSCs. We show that epiblast-like cells in floating aggregates form rat PGCLCs. The gonadal somatic cells support maturation and epigenetic reprogramming of the PGCLCs. When rat PGCLCs are transplanted into the seminiferous tubules of germline-less rats, functional spermatids—that is, those capable of siring viable offspring—are generated. Insights from our rat model will elucidate conserved and divergent mechanisms essential for the broad applicability of in vitro gametogenesis.

Primordial germ cells (PGCs), the founder cells of the germline, are specified in pre-gastrulating embryos in mammals, and subsequently migrate towards gonads to mature into functional gametes. Here, we investigated PGC development in rats, by genetically modifying Prdm14, a unique marker and a critical PGC transcriptional regulator. We trace PGC development in rats, for the first time, from specification until sex determination stage in fetal gonads using Prdm14 H2BVenus knock-in rats. We uncover that Prdm14’s crucial role in PGC specification is conserved between rat and mice, by analyzing Prdm14 deficient rat embryos. Notably, loss of Prdm14 completely abrogates the PGC program: failure in maintenance and/or activation of germ cell markers and pluripotency genes. Finally, we profile the transcriptome of the postimplantation epiblast and all PGC stages in rat, to reveal enrichment of distinct gene sets at each transition point, thereby providing an accurate transcriptional time-line for rat PGC development. Thus, the novel genetically modified rats and data sets obtained in this study will advance our knowledge on conserved vs species-specific features for germline development in mammals.