Figure 7.

Dynamics of GFP-Mad2 in syncytial embryonic mitoses. (A–C) Selected frames of TLSC acquisitions describing the behavior of GFP-Mad2 and mRFP-Nup107 during three consecutive embryonic cleavage cycles: interphase #10 to prometaphase #11 (A), interphase #11 to metaphase #12 (B), and interphase #12 to interphase #13 (C). Best focal plane of a 4.0 μm z-stack is shown for each time frame. Bar, 10 μm. Time is in minutes:seconds. In each cycle, accumulation of Mad2 in the reforming nuclei begins only once a continuous perinuclear Nup107 staining is observed (arrowheads and open arrows). Note the presence of a fraction of GFP-Mad2 in between the two reforming nuclei (seen in A and C). Arrows point to the NE localization of GFP-Mad2 in interphase nuclei of cycles #12 (B and C), and #13 (C), and black arrowheads to prophase cells, revealing its dissociation from the NE before mRFP-Nup107. (D) Photobleaching analysis of GFP-Mad2 in embryonic nuclei. Small regions (outlined in white in the first frames) within three or four nuclei of interphases #10, #11, or #12 were bleached. Images are in pseudocolor to facilitate the visualization of differences in fluorescence intensity. Bars, 10 μm. Note that the fluorescence signal at the NE of interphase nuclei of cycles #10, #11, and #12 becomes clearly detectable after bleaching the intranuclear pool (postbleach) and is of similar intensity in all three interphase cycles (compare nuclei 2 in the three series).