Metastable pluripotent states in NOD mouse derived ES cells

Embryonic stem (ES) cells are isolated from the inner cell mass (ICM) of developing blastocysts, whereas epiblast stem cells (EpiSCs) are derived from the post-implantation epiblast and are characterized by a restricted developmental potential. Although certain mouse strains, such as the non-obese diabetic (NOD) mice, are considered “non-permissive” for ES cell derivation, they retain the capacity to generate EpiSCs. Using the NOD strain as a model, we characterized the stability of pluripotent states in cells generated by ICM explantation or direct in vitro reprogramming. We find that ES-like NOD stem cells can be captured in both approaches by providing exogenous constitutive expression of Klf4 or c-Myc transcription factors or small molecules that can replace these factors during in vitro reprogramming. The fully pluripotent NOD ES and iPS cells appear “metastable”, as the cells acquire an alternative EpiSC-like identity after removal of the exogenous factors, while reintroduction of these factors converts the cells back to ICM-like pluripotency. Our findings suggest that stem cells from different genetic backgrounds can assume distinct states of pluripotency in vitro, the stability of which is regulated by endogenous genetic determinants and can be modified by the continuous presence of defined exogenous factors. Gene expression profiling was performed in mouse ES, EpiSC and EpiSC-like cell lines.