The first-cell-fate coordinator KLF5 induces multiple cell fate transitions from epiblast stem cells
During early embryogenesis, Kruppel-like factor KLF5 is expressed in inner cell mass (ICM), trophectoderm (TE), and primordial germ cell (PGC). It is wellknow to be essential for specifying the TE fate, as well as redundantly with KLF2/4 for specifying the ICM fate during the first fate segregation. Here, we aimed to clarify whether KLF5 regulates these three fates in vitro. We firstly validated the necessity of KLF5 in mouse trophoblast stem cells (TSCs) and PGC-like cells. Mechanistically, we showed that KLF5 is deeply integrated into the transcriptional networks of ICM, TE and PGC in a context-dependent manner. Furthermore, KLF5 is almost the only factor capable of driving TSC fate from primed epiblast stem cells. It could also induce a transition from the primed to naive state just in the absence of WNT signaling. During this transition, KLF5 generates PGC-like cells, concomitantly. Taken together, our work supports KLF5 as a powerful and versatile specifier in both early embryonic lineage determination and in vitro cell fate reprogramming.