Investigations on the role of Blimp1 in pluripotency and reprogramming

Blimp1 (Prdm1), the key determinant of primordial germ cells (PGC), plays a combinatorial role with Prdm14 during PGC specification from postimplantation epiblast cells. They together initiate epigenetic reprogramming in early germ cells towards an underlying pluripotent state, which is equivalent to embryonic stem cells (ESC). Whereas Prdm14 alone can promote reprogramming and is important for the propagation of the pluripotent state, it is not known if Blimp1 is similarly involved. Using a genetic approach, we demonstrate that Blimp1 is dispensable for the derivation and maintenance of ESC and postimplantation epiblast stem cells (EpiSC). Notably, Blimp1 is also dispensable for reprogramming EpiSC to ESC. Thus, while Blimp1 is obligatory for PGC specification, it is not required for the reversion of EpiSC to ESC, and for their maintenance thereafter. This study suggests that reprogramming, including that of somatic cells to ESC, may not entail an obligatory route through Blimp1 positive PGC-like state. Comparison of gene expression between Blimp1 null and heterozygous ESC, EpiSC and rESC (plus ESC grown in 2i/LIF conditions)