2.2. Embryonic stem cell derivation and culture

The Tet‐On‐OSKM/Oct4‐GFP mouse ESC line was derived from the blastocysts obtained from crossbreeding of the above DOX‐OSKM mice and Oct4‐GFP mice according to standard procedures. The cells were derived and further cultured in 2iL medium on the mitomycin‐c treated mouse embryonic fibroblast (MEF) cells (feeder cells). The detail components of slightly modified N2B27 medium 14 were listed in Table S1. The 2iL medium 14 contained N2B27 medium with the addition of PD0325901 (Stemgent, 04‐0006), CHIR99021 (Stemgent, 04‐0004), and LIF (Millipore, ESG1007). ESCs cultured in 2iL medium were switched into three different types of medium: N2B27 with 2i and LIF as the 2iL group, N2B27 with 2 μg/mL DOX (Sigma‐Aldrich) as the OSKM group, and N2B27 as the N2B27 group.