title: Phase geometries of two-dimensional excitable waves govern self-organized morphodynamics of amoeboid cells.
abstract: In both randomly moving Dictyostelium and mammalian cells, phosphatidylinositol (3,4,5)-trisphosphate and F-actin are known to propagate as waves at the membrane and act to push out the protruding edge. To date, however, the relationship between the wave geometry and the patterns of amoeboid shape change remains elusive. Here, by using phase map analysis, we show that morphology dynamics of randomly moving Dictyostelium discoideum cells can be characterized by the number, topology, and position of spatial phase singularities, i.e., points that represent organizing centers of rotating waves. A single isolated singularity near the cellular edge induced a rotational protrusion, whereas a pair of singularities supported a symmetric extension. These singularities appeared by strong phase resetting due to de novo nucleation at the back of preexisting waves. Analysis of a theoretical model indicated excitability of the system that is governed by positive feedback from phosphatidylinositol (3,4,5)-trisphosphate to PI3-kinase activation, and we showed experimentally that this requires F-actin. Furthermore, by incorporating membrane deformation into the model, we demonstrated that geometries of competing waves explain most of the observed semiperiodic changes in amoeboid morphology.
authors.affiliation: Graduate School of Arts and Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Taniguchi
authors.forename: Shuji
authors.initials: S
authors.lastname: Ishihara
authors.forename: Takehiko
authors.initials: T
authors.lastname: Oonuki
authors.forename: Mai
authors.initials: M
authors.lastname: Honda-Kitahara
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Kaneko
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sawai
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D004023:Dictyostelium / Q000166:cytology* / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D015800:Protozoan Proteins / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D019869:Phosphatidylinositol 3-Kinases