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. Author manuscript; available in PMC: 2016 Mar 16.
Published in final edited form as: Curr Biol. 2015 Mar 5;25(6):811–816. doi: 10.1016/j.cub.2015.01.053

Figure 1. Mitotic Cyclins, but Not the SAC, Dictate Timing of Anaphase Onset.

Figure 1

(A) Schematic showing that checkpoint release by the first aligned spindle hurries the slower prometaphases into anaphase in a syncytium.

(B–G) Mitotic progress was visualized in real time by following H2AvD-GFP produced from a transgene (B, D–G), or from injected mRNA (C). Frames from videos at the indicated times (min:s) show mitosis 13 beginning at prometaphase. The time lapse to the beginning of chromosome separation reveals the timing of metaphase-anaphase in the different genotypes and injected embryos. Scale bar, 5 mμ.

(H) Comparison of metaphase duration. SAC-deficient embryos did not differ significantly from wild-type (unpaired t test, control versus mad2p: p = 0.0752; control versus mad2p+bubR1ΔKEN: p = 0.0929). Changing the levels of particular cyclins had a cyclin-type-specific effect on metaphase duration. No obvious metaphase was seen in Cyclin A- and B-depleted embryos (star), whereas a prolonged metaphase was observed when the level of Cyclin A and B was increased by mRNA injection (unpaired t test, p < 0.0001). Knockdown of Cyclin B3 extended metaphase (unpaired t test, p < 0.0001), and Cyclin B3 mRNA injection slightly shortened metaphase (unpaired t test, p = 0.0124). Error bars represent the SD.