Fig. 4.

Temporal expression profiles of endogenous core clock genes in RA-induced differentiation culture using EB5 ES cells. Dbp:luc stably transfected EB5 ES cells were used for Taqman quantitative PCR analysis. All ES cells and Day 5 and Day 14 samples were cultured under the same conditions for bioluminescence monitoring analysis. Day 5 and Day 14 samples were differentiated by 1 μM of RA for 5 days and 14 days, respectively. Compared with ES cells, the expression levels of mPer2 and mClock genes were significantly higher (P < 0.001) and mCry1 expression was significantly lower (P < 0.001) on Day 5. In contrast, the expression levels of all analyzed clock genes were similar on Day 5 and Day 14. Data are mean ± SEM of three independently cultured dishes under each condition. *P < 0.05, **P < 0.01; n.s., not significant.