Furrows form in cells stuck in anaphase (top) but not metaphase.


Think of cell division, and you probably imagine two phases occurring in successive order: first mitosis, then cytokinesis. But unlike in yeast, mitosis in animal cells does not have to come to completion for cytokinesis to commence. Rather, what is important is the inactivation of the mitotic spindle checkpoint, according to new results from Brad Shuster and David Burgess (Boston College, Boston, MA).

Shuster and Burgess have revisited an old experiment, which demonstrated that cytokinesis could be initiated prematurely in embryonic animal cells by shortening the distance between the spindle poles and the cell cortex. “In the old experiments,” says Burgess, “they did not have the ability to image chromosomes, and so they did not know the stage of mitosis when furrows were initiated.” Now, armed with better imaging tools, the authors have determined that furrow formation can be initiated by manipulating the spindle only after the chromosomes begin to separate. Cells arrested in anaphase, but not those in metaphase, could initiate cytokinesis.This effect may be mediated by the release of a positive effector of cytokinesis or by inhibition of a negative regulator. This factor acts locally, as arresting one of a pair of spindles within the same cytoplasm did not prevent the second from forming a furrow. Yet, a secondary furrow could not form between the two spindle sets, indicating that the component at the metaphase aster dominates. It is possible that a proteolytic effector of the anaphase promoting complex degrades an inhibitor of cytokinesis. ▪


Shuster, C., and D. Burgess.
Curr. Biol.