title: How to make a static cytokinetic furrow out of traveling excitable waves.
abstract: Emergence of the cytokinetic Rho zone that orchestrates formation and ingression of the cleavage furrow had been explained previously via microtubule-dependent cortical concentration of Ect2, a guanine nucleotide exchange factor for Rho. The results of a recent publication now demonstrate that, en route from resting cortex to fully established furrow, there lies a regime of cortical excitability in which Rho activity and F-actin play the roles of the prototypical activator and inhibitor, respectively. This cortical excitability is manifest as dramatic traveling waves on the cortex of oocytes and embryos of frogs and starfish. These waves are initiated by autocatalytic activation of Rho at the wave front and extinguished by F-actin-dependent inhibition at their back. It is still unclear how propagating excitable Rho-actin waves give rise to the stable co-existence of Rho activity and F-actin density in the static cleavage furrow during cytokinesis. It is possible that some central spindle-associated signaling molecule simply turns off the inhibition of Rho activity by F-actin. However, mathematical modeling suggests a distinct scenario in which local "re-wiring" of the Rho-actin coupling in the furrow is no longer necessary. Instead, the model predicts that the continuously rising level of Ect2 produces in the furrow a qualitatively new stable steady state that replaces excitability and brings about the stable co-existence of high Rho activity and dense F-actin despite the continuing inhibition of Rho by F-actin.
authors.affiliation: a Centre for Systems and Synthetic Biology, Cell Biology Institute, School of Biological Sciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Goryachev
authors.affiliation: a Centre for Systems and Synthetic Biology, Cell Biology Institute, School of Biological Sciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Marcin
authors.initials: M
authors.lastname: Leda
authors.affiliation: b Department of Molecular , Cellular and Developmental Biology, University of Michigan , Ann-Arbor , MI , USA.
authors.forename: Ann L
authors.initials: AL
authors.lastname: Miller
authors.affiliation: c Oregon Institute of Marine Biology, University of Oregon , Charleston , OR , USA.
authors.forename: George
authors.initials: G
authors.lastname: von Dassow
authors.affiliation: d Laboratory of Cell and Molecular Biology, Graduate Program in Cell and Molecular Biology, University of Wisconsin-Madison , Madison , WI , USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Bement
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D048749:Cytokinesis; D006801:Humans; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D020741:rho GTP-Binding Proteins
keywords: Ect2; F-actin; Rho small GTPases; Rho zone; activator-inhibitor coupling; cytokinesis; excitable dynamics; guanine nucleotide exchange factor; traveling waves