The expression pattern of Errfi1 by E2 and P4 in the uterus. Total RNA used for the RT-PCR assays was prepared from wild-type mice that were treated with P4, E2, E2 plus P4, or vehicle (sesame oil [Veh]) for 4 h, 16 h, and 40 h. The results represent the mean ± SEM of three independent RNA sets. *P < 0.05 and **P < 0.01.