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Long astral microtubules uncouple mitotic spindles from the cytokinetic furrow.

TitleLong astral microtubules uncouple mitotic spindles from the cytokinetic furrow.
Publication TypeJournal Article
Year of Publication2010
AuthorsRankin KE, Wordeman L
JournalThe Journal of cell biology
Date Published2010 Jul 12
KeywordsAnaphase, Biological Clocks, Cytokinesis, HeLa Cells, Humans, Kinesin, Microtubules, Myosin Type II, Paclitaxel, Spindle Apparatus, Tubulin Modulators

<p>Astral microtubules (MTs) are known to be important for cleavage furrow induction and spindle positioning, and loss of astral MTs has been reported to increase cortical contractility. To investigate the effect of excess astral MT activity, we depleted the MT depolymerizer mitotic centromere-associated kinesin (MCAK) from HeLa cells to produce ultra-long, astral MTs during mitosis. MCAK depletion promoted dramatic spindle rocking in early anaphase, wherein the entire mitotic spindle oscillated along the spindle axis from one proto-daughter cell to the other, driven by oscillations of cortical nonmuscle myosin II. The effect was phenocopied by taxol treatment. Live imaging revealed that cortical actin partially vacates the polar cortex in favor of the equatorial cortex during anaphase. We propose that this renders the polar actin cortex vulnerable to rupture during normal contractile activity and that long astral MTs enlarge the blebs. Excessively large blebs displace mitotic spindle position by cytoplasmic flow, triggering the oscillations as the blebs resolve.</p>

Alternate JournalJ. Cell Biol.