title: An integrative toy model of cell flattening, spreading, and ruffling.
abstract: BACKGROUND
  The processes of cell spreading and crawling are frequently associated with mysterious waves and ruffling cycles of the leading edge.
  
  
  OBJECTIVE
  To develop a physical model that can account for these phenomena based on a few simple and plausible rules governing adhesion, contractility, polymerization of cytoskeleton, and membrane tension.
  
  
  METHODS
  Extension of a continuum mechanical model of phagocytosis [J Cell Sci. (2006);119(Pt 9):1903-13] adding a simple coupling between membrane curvature and cytoskeletal polymerization.
  
  
  RESULTS
  We show that our generalized model has just the right nonlinearity needed for triggering of stochastic/chaotic cycles of ruffling similar to those that are observed in real cells.
  
  
  CONCLUSIONS
  The cycles are caused by a branching instability at the leading edge that leads to bifurcations of protrusion into forward moving lamellipodium and upward and rearward folding ruffles. The amplitude of the instability is modulated by the surface tension, with higher tension stabilizing against ruffling (but inhibiting protrusion) and lower tension promoting ruffling and protrusion.
authors.affiliation: Biomedical Engineering Department, Boston University, Boston, MA, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Herant
authors.affiliation: Biomedical Engineering Department, Boston University, Boston, MA, USA.
authors.forename: Micah
authors.initials: M
authors.lastname: Dembo
mesh_terms: D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology; D008954:Models, Biological; D010587:Phagocytosis / Q000502:physiology
keywords: Cell motility; cell mechanics; cytoskeleton; lamella; membrane curvature; membrane tension