Fig. 2.

BubR1-depletion induces a prometaphase I arrest. (A) Timeline of PBE for uninjected controls, Mad2-depleted and BubR1-depleted oocytes. Oocytes were scored for the presence of polar bodies at 6 h, 7 h , 8 h, 9 h and 10 h post-GVBD. Note the contrasting effects of Mad2- and BubR1-depletion on PBE. (B) PBE is inhibited after BubR1-depletion. PBE rates were determined at 10 h and 20 h post-GVBD. Note that prometaphase I arrest is robust after BubR1-depleti on so that PBE increases only modestly (from 6% to 11%) during an additional 10 h of culture (from 10 h post-GVBD to 20 h post-GVBD) . Furthermore, co-depletion of Mad2 does not restore PBE rates indicating that MI arrest is not SAC-mediated. Error bars, me an + SEM; N ≥ 3. Asterisks denote a significant difference from uninjected controls (P < 0.0001; Student’s t test). (C) Samples (50 oocytes) of BubR1-depleted oocytes at 2 h, 4 h, 6 h and 8 h post-GVBD were blotted for cyclin B1, securin and actin. (D and E) Control and BubR1-depleted oocytes were immunostained for tubulin and DNA at the times post-GVBD indicated in the figure (n ≥ 15 oocytes per time-point). Note that by 10 h post-GVBD in controls, a polar body (white arrowhead) with associated chromosomes is present.