Figure 4. .

Erk2 phosphorylation is essential for lipid-induced pluripotency transition. (A and B) Western blot for Erk1/2 and p-Erk1/2 proteins in ESCs cultured in 2iL or 2iLA at passage 3 (A) or for Mek/Erk signaling related proteins in ESCs after switching 2iL to 2iLA (B). m, min; h: hours. (C) qRT-PCR for the naive marker genes Nanog, Prdm14 and formative marker genes Dnmt3b, Pim2 for WT, Erk2^−/−, Erk2-Res ESCs at passage 4 cultured in 2iL or 2iLA. Erk2-Res: Erk2-rescued in the Erk1/2 mutant ESCs (Lentiviral-based shRNA against Erk1 in the Erk2^−/− ESCs). Experiments were repeated three times (n = 3), ns: no significant difference, ^*P < 0.05, ^**P < 0.01, ^***P < 0.001, ^****P< 0.0001, two-tailed t-test was used. (D and E) Schematic illustration of the experimental design and ESC colony morphology change (D), qRT-PCR for the naive marker genes Zfp42, Prdm14, and the formative marker genes Dnmt3b, Pim2 for WT, and Erk2^−/−Erk2-Res (E) after 2i and LIF removal for 72 h. n = 3 experiments.