FIG. 2.

Mad2 is essential for colchicine-invoked SAC function. gfp-cdc20 mad2^+/+, gfp-cdc20 mad2^EY (mad2^−/− null mutant), and gfp-mad2 mad2^EY embryos were treated with colchicine by microinjection. Time-lapse confocal images were taken before (01, 07, and 13) or after (02 to 06, 08 to 12, and 14 to 18) injection. GFP-Cdc20 or GFP-Mad2 kinetochore signals were used as cell cycle progression markers. (Top row) The arrows indicate the arrested kinetochores in images 02 to 06. The area marked by an arrow in image 01 indicates that before colchicine treatment, GFP-Cdc20 was excluded from the late-interphase nucleus. (Middle row) In the absence of endogenous Mad2, GFP-Cdc20 signals continued to oscillate in and out of the nucleus and on and off the kinetochores in the presence of colchicine (indicated by arrows in images 07 to 12). Separation of daughter nuclei failed in image 10. (Bottom row) Arrowheads in images 14 to 18 indicate arrested kinetochores with accumulated GFP-Mad2 fusion proteins. The arrowhead in image 13 indicates GFP-Mad2 accumulation in a late-interphase nucleus. Bar = 5 mm.