Kilens, S. et al. Nat. Commun. 9, 360 (2018).

Standard human pluripotent stem cells (hPSCs) appear to be equivalent in many ways to post-implantation epiblast-derived murine stem cells (so-called epi-SCs). A number of methods are now available to convert hPSCs to a 'naive' state in which they resemble pre-implantation mouse pluripotent stem cells, akin to a true developmental ground state. Kilens et al. developed a method for converting somatic cells directly to naive hPSCs, using overexpression of the four Yamanaka transcription factors (Oct4, Klf4, cMyc and Sox2) in an established 'T2iLGö' naive hPSC medium. The authors stress that to evaluate pluripotency, it is critical to carefully benchmark naive hPSCs against human pre-implantation epiblast cells at the level of the transcriptome, mitochondrial respiration and X-chromosome inactivation status.