Response windows of FGF and MAPK inhibitors in differentiating ES cells. (A) FGF1 at 40 ng/ml was applied to 46C ES cells on individual days (D1, D2, D3, D4) or from day 1 through 4 (D1-4). (B) Derived GFP+ cells were analyzed by FACS on day 6. Independent experiments done in triplicate are illustrated. (C) As the indicated experimental conditions, the induction of Sox1-GFP+ cells on day 6 was shown in (D) after FACS analysis. SP600125 and U0126, 10 μM and 5 μM, respectively.