Determining the position of the cell division plane

Abstract

Proper positioning of the cell division plane during mitosis is essential for determining the size and position of the two daughter cells--a critical step during development and cell differentiation. A bipolar microtubule array has been proposed to be a minimum requirement for furrow positioning in mammalian cells, with furrows forming at the site of microtubule plus-end overlap between the spindle poles. Observations in other species have suggested, however, that this may not be true. Here we show, by inducing mammalian tissue cells with monopolar spindles to enter anaphase, that furrow formation in cultured mammalian cells does not require a bipolar spindle. Unexpectedly, cytokinesis occurs at high frequency in monopolar cells. Division always occurs at a cortical position distal to the chromosomes. Analysis of microtubules during cytokinesis in cells with monopolar and bipolar spindles shows that a subpopulation of stable microtubules extends past chromosomes and binds to the cell cortex at the site of furrow formation. Our data are consistent with a model in which chromosomes supply microtubules with factors that promote microtubule stability and furrowing.

Dissecting the Role of Rho-mediated Signaling in Contractile Ring Formation

“…It has been reported that furrows are formed near the site of high numbers of stabilized microtubules (Canman et al, 2003). We demonstrate that the bundled microtubules lead to accumulation of Rho-mediated signaling molecules and cause ectopic furrowing.…”

Rho GTPase activity zones and transient contractile arrays

“…(59) Further, there is good reason to believe that stable microtubules may somehow signal cytokinetic apparatus establishment. (60) Meanwhile, astral microtubules penetrate the polar cortex in echinoderm embryonic cells sooner and more densely than the equatorial cortex. Treatment of echinoderm blastomeres with low doses of nocodazole results in wider-and sloppier-thannormal Rho zones, which sometimes fail to furrow; likewise, physically restricting access to the cortex by astral microtubules leads to broad, poorly developed Rho activity zones.…”

A cytokinesis furrow is positioned by two consecutive signals

“…We also shifted the first furrow using monopolar spindles, as it has been shown that either an isolated aster or a monopolar spindle is sufficient to specify a cleavage plane 4,13 . To generate monopolar spindles, we repeated ASS and subsequently disintegrated the separated aster using the ultraviolet laser ( Fig.…”