Divergent roles of KLF4 and TFCP2L1 in ground-state naive pluripotency and human primordial germ cell development

During development, human primordial germ cells (hPGCs) transition through a transcriptional and epigenetic state similar to pre-implantation epiblast cells called naive ground-state pluripotency. Diagnostic transcription factors that define this state include TFAP2C, KLF4, and TFCP2L1, with TFAP2C necessary for both establishment of the naive-like state in hPGC-like cells (hPGCLCs) as well as establishment and self-renewal of naive human embryonic stem cells (hESCs). Here, we show that KLF4 and TFCP2L1 are not required for hPGC specification or establishment of the naive-like state in hPGCLCs. Instead, KLF4 and TFCP2L1 are each required for reversion of primed hESCs to the self-renewing naive ground state. Additionally, TFCP2L1 but not KLF4 function after hPGC specification in the proliferation of the hPGCLC population. H1_hESC_WT_derived_hPGCLCs and H1_hESC_KLF4KO_derived_hPGCLCs at passage numbers 65 and 68