title: An astral simulacrum of the central spindle accounts for normal, spindle-less, and anucleate cytokinesis in echinoderm embryos.
abstract: Cytokinesis in animal cells depends on spindle-derived spatial cues that culminate in Rho activation, and thereby actomyosin assembly, in a narrow equatorial band. Although the nature, origin, and variety of such cues have long been obscure, one component is certainly the Rho activator Ect2. Here we describe the behavior and function of Ect2 in echinoderm embryos, showing that Ect2 migrates from spindle midzone to astral microtubules in anaphase and that Ect2 shapes the pattern of Rho activation in incipient furrows. Our key finding is that Ect2 and its binding partner Cyk4 accumulate not only at normal furrows, but also at furrows that form in the absence of associated spindle, midzone, or chromosomes. In all these cases, the cell assembles essentially the same cytokinetic signaling ensemble—opposed astral microtubules decorated with Ect2 and Cyk4. We conclude that if multiple signals contribute to furrow induction in echinoderm embryos, they likely converge on the same signaling ensemble on an analogous cytoskeletal scaffold.
authors.affiliation: Oregon Institute of Marine Biology, Charleston, OR 97420 Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms EN6 3LD, United Kingdom.
authors.forename: Kuan-Chung
authors.initials: KC
authors.lastname: Su
authors.affiliation: Oregon Institute of Marine Biology, Charleston, OR 97420 Laboratory of Cell and Molecular Biology, University of Wisconsin, Madison, WI 53706.
authors.forename: William M
authors.initials: WM
authors.lastname: Bement
authors.affiliation: Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms EN6 3LD, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Petronczki
authors.affiliation: Oregon Institute of Marine Biology, Charleston, OR 97420 dassow@uoregon.edu.
authors.forename: George
authors.initials: G
authors.lastname: von Dassow
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000502:physiology; D048749:Cytokinesis; D003599:Cytoskeleton / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D047270:Strongylocentrotus purpuratus / Q000166:cytology*
chemical_list: D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; C485184:enhanced green fluorescent protein; C104434:spindlin; D049452:Green Fluorescent Proteins