No 1.5 glass

For live-cell experiments, all cells were grown on MatTek glass bottom dishes with No. 1.5 glass (MatTek Corporation, Ashland, MA). At the time of imaging, cell medium was replaced with L-15 medium supplemented with 4.5 g/l glucose (high glucose). All live cell experiments were performed on a Nikon Eclipse Ti inverted microscope (Nikon instruments Inc, NY, USA) equipped with phase-contrast trans-illumination, transmitted light shutter, ProScan automated stage (Prior Scientific, Cambridge, UK), CoolSNAP HQ2 CCD camera (Photometrics, AZ, USA), Lumen200PRO light source (Prior Scientific, Cambridge, UK), and a temperature and humidity controlled incubator (Tokai Hit, Japan). For 24 hr and 72 hr live cell phase contrast videos, images were acquired every 6 min through a 20X/0.3 NA A Plan corrected phase contrast objective for the duration of the experiment. Time-lapse videos were analyzed using NIS Elements AR software (Nikon Instruments Inc, NY, USA) to determine the nature of division (bipolar, tripolar, tetrapolar) at anaphase and the subsequent number of daughter cells formed after cytokinesis.

Cells were grown on glass bottom dishes with No. 1.5 glass (MatTek Corporation, Ashland, MA). Immediately prior to imaging, cell medium was replaced with L-15 media (Gibco) supplemented with 4.5 g/L glucose. All live-cell experiments were performed on the same Nikon Eclipse Ti inverted microscope (Nikon Instruments Inc.) described earlier (“Preparation of chromosome spreads and chromosome counting”) with a temperature and humidity-controlled incubator (Tokai Hit, Japan). For live-cell phase contrast videos, images were acquired every 3 min using a 20X/0.3 NA A Plan corrected phase contrast objective for at least 6 h. Videos were analyzed with NIS Elements to determine mitotic duration, or the time from cell rounding to anaphase onset. In some cells, especially the larger 4N groups, nuclear envelope breakdown (NEBD) could also be observed and typically coincided with the beginning of cell rounding. For analysis of prometaphase and metaphase duration, only cells with visible metaphase plates were used for analysis. Prometaphase-metaphase transition was recorded as the time a metaphase plate could be seen at the spindle equator.