Interspecies cross-complementation of Ccnb3^−/− oocytes. (A) Ccnb3^−/− oocytes were injected with the indicated mRNA, induced to enter meiosis I, and scored for PB extrusion. n: number of oocytes from three independent experiments; number of oocytes analyzed and percentage of PB extrusion: 46 Ccnb3^−/− sham injected oocytes (0% PBs), 48 Ccnb3^−/− oocytes injected with mRNA coding for X. laevis cyclin B3 (85.41%), 20 Ccnb3^−/− oocytes with D. rerio cyclin B3 mRNA (60%), and 53 Ccnb3^−/− oocytes with D. melanogaster cyclin B3 mRNA (92.45%). (B) Selected time frames of collapsed z-sections (12 sections, 3-µm steps) from a representative spinning disk confocal movie of Ccnb3^−/− sham-injected oocytes, and Ccnb3^−/− oocytes injected with X. laevis cyclin B3 mRNA. Before live imaging, oocytes were incubated with SiR-DNA. Top panel shows the DIC channel and bottom panel shows siR-DNA staining in far-red. Time points after GVBD are indicated as hours:minutes. Scale bar: 20 µm. White asterisks: PBs. n: number of oocytes from three independent experiments.