Microtubules are required for completion of cytokinesis in sea urchin eggs

Completion of cytokinesis, abscission, has been studied little despite the intensive studies of the onset and contractile mechanism of the earlier pha ses of division. It has been well documented that microtubule (MT) disrupti on before furrow stimulation prevents furrowing, while MT disruption after furrow stimulation allows division to proceed. We have confirmed those find ings using the MT inhibitors, nocodazole and demecolcine. In addition, we h ave found that MT disruption after furrow stimulation but before completion of division prevents abscission as evidenced by the observation that prosp ective daughter cells in MT-disrupted eggs maintain electrical continuity. Continued observation of eggs revealed that the furrow in MT-disrupted eggs did not result in abscission, but rather held steady until the time when c ontrols underwent second cleavage, at which point the furrows regressed. Th ese findings extend the recent reports that MTs are required for completion of division in mammalian tissue culture cells and frog eggs, to invertebra tes, suggesting a common mechanism of abscission for animal cells. (C) 1999 Academic Press.