Faculty Opinions recommendation of A microtubule-dependent zone of active RhoA during cleavage plane specification.

Cytokinesis in animal cells results from the assembly and constriction of a circumferential array of actin filaments and myosin-2. Microtubules of the mitotic apparatus determine the position at which the cytokinetic actomyosin array forms, but the molecular mechanisms by which they do so remain unknown. The small GTPase RhoA has previously been implicated in cytokinesis. Using four-dimensional microscopy and a probe for active RhoA, we show that active RhoA concentrates in a precisely bounded zone before cytokinesis and is independent of actin assembly. Cytokinetic RhoA activity zones are common to four echinoderm species, the vertebrate Xenopus laevis, and the highly asymmetric cytokinesis accompanying meiosis. Microtubules direct the formation and placement of the RhoA activity zone, and the zone is repositioned after physical spindle displacement. We conclude that microtubules specify the cytokinetic apparatus via a dynamic zone of local RhoA activity. PMID: 15998801 Funding information This work was supported by: NIGMS NIH HHS, United States Grant ID: GM66050 NIGMS NIH HHS, United States Grant ID: GM52932 NIGMS NIH HHS, United States Grant ID: R01 GM052932 NIGMS NIH HHS, United States Grant ID: P50 GM066050