Figure 3.

Evidence that the ER is continuous during mitosis. Blastomeres expressing GFP-KDEL in interphase or metaphase were repetitively bleached using a FLIP protocol. The top panels show the blastomeres before bleaching. The cells were subjected to nine bleach cycles. The confocal microscope was set at 3.1 s per scan. Each cycle consisted of three bleaching scans at high zoom with high laser intensity, followed by one imaging scan at low zoom with low laser intensity, followed by a 10-s wait period. The duration of each cycle was ∼20 s. The total elapsed time for the nine cycles was 2 min 51 s. The middle panels were taken after the fourth bleach (1 min 12 s), and the bottom panels were taken after the ninth bleach (2 min 51 s). The rectangles show the regions that were bleached. Because fluorescence throughout the cell was bleached by this protocol, it is likely that the GFP KDEL is present in a continuous compartment throughout the cell. Bar, 10 μm.