title: Model of myosin node aggregation into a contractile ring: the effect of local alignment.
abstract: Actomyosin bundles frequently form through aggregation of membrane-bound myosin clusters. One such example is the formation of the contractile ring in fission yeast from a broad band of cortical nodes. Nodes are macromolecular complexes containing several dozens of myosin-II molecules and a few formin dimers. The condensation of a broad band of nodes into the contractile ring has been previously described by a search, capture, pull and release (SCPR) model. In SCPR, a random search process mediated by actin filaments nucleated by formins leads to transient actomyosin connections among nodes that pull one another into a ring. The SCPR model reproduces the transport of nodes over long distances and predicts observed clump-formation instabilities in mutants. However, the model does not generate transient linear elements and meshwork structures as observed in some wild-type and mutant cells during ring assembly. As a minimal model of node alignment, we added short-range aligning forces to the SCPR model representing currently unresolved mechanisms that may involve structural components, cross-linking and bundling proteins. We studied the effect of the local node alignment mechanism on ring formation numerically. We varied the new parameters and found viable rings for a realistic range of values. Morphologically, transient structures that form during ring assembly resemble those observed in experiments with wild-type and cdc25-22 cells. Our work supports a hierarchical process of ring self-organization involving components drawn together from distant parts of the cell followed by progressive stabilization.
authors.affiliation: Department of Physics, Lehigh University, Bethlehem, PA 18015, USA.
authors.forename: Nikola
authors.initials: N
authors.lastname: Ojkic
authors.forename: Jian-Qiu
authors.initials: JQ
authors.lastname: Wu
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Vavylonis
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D048749:Cytokinesis / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism*; D008954:Models, Biological; D056004:Molecular Dynamics Simulation; D009154:Mutation / Q000235:genetics; D009218:Myosins / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000166:cytology* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029702:Schizosaccharomyces pombe Proteins; D000205:Actomyosin; D009218:Myosins