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.
Center for Cell Dynamics, Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA. wmbement@wisc.edu
William M
WM
Bement
Hélène A
HA
Benink
George
G
von Dassow
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D002970:Cleavage Stage, Ovum / Q000166:cytology / Q000502:physiology; D048749:Cytokinesis / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008540:Meiosis / Q000502:physiology; D008870:Microtubules / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012617:Sea Urchins; D013045:Species Specificity; D008941:Spindle Apparatus / Q000378:metabolism; D013215:Starfish; D047270:Strongylocentrotus purpuratus; D014982:Xenopus laevis; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; D009218:Myosins; D020742:rhoA GTP-Binding Protein