Regulation of mobilization by PGE₂/EP4 signal. (A) CFU-Cs mobilized in EP4^+/+ and EP4^−/− mice treated with PGE₂ (n = 3 for PBS/BSA group and n = 6-10 for G-CSF group). (B) CFU-Cs mobilized in EP4 chimeric mice treated with PGE₂ (n = 6-12). Data are represented as mean ± SEM. *P < .05; ***P < .001. n.s., not significant.