Meiotic maturation of OoMastl^−/− oocytes. (A) Comparison of the kinetics of GVBD after release from dbcAMP. The total numbers of oocytes used (n) are indicated. (B) Representative images of immunostaining for DNA, CREST, and spindle showing normal progression to metaphase I in OoMastl^−/− oocytes. Oocytes were cultured for the indicated periods after GVBD and were fixed. 30 oocytes were analyzed for each time point. (C) Kinetics of PBE. Oocytes that had undergone GVBD within 2 h after release into dbcAMP-free M16 medium were selected (at time = 0) and cultured further. PBE was scored at 1-h intervals. The numbers of oocytes examined are indicated (n). (D) Comparable PBE rates of the ovulated oocytes collected at 16 h after hCG. The numbers of oocytes used (n) are shown. All of the experiments were repeated at least three times, and representative results are shown. (E) Western blots showing the timing of securin degradation and Cdc20 level during oocyte maturation. Lysate from 100 oocytes was loaded in each lane. The levels of β-actin were used as a control. The same β-actin panel is presented again in Fig. 3 B, which shows the expression of other proteins of interest in the same cell lysates.