title: Competition for actin between two distinct F-actin networks defines a bistable switch for cell polarization.
abstract: Symmetry-breaking polarization enables functional plasticity of cells and tissues and is yet not well understood. Here we show that epithelial cells, hard-wired to maintain a static morphology and to preserve tissue organization, can spontaneously switch to a migratory polarized phenotype after relaxation of the actomyosin cytoskeleton. We find that myosin II engages actin in the formation of cortical actomyosin bundles and thus makes it unavailable for deployment in the process of dendritic growth normally driving cell motility. Under low-contractility regimes, epithelial cells polarize in a front-back manner owing to the emergence of actin retrograde flows powered by dendritic polymerization of actin. Coupled to cell movement, the flows transport myosin II from the front to the back of the cell, where the motor locally 'locks' actin in contractile bundles. This polarization mechanism could be employed by embryonic and cancer epithelial cells in microenvironments where high-contractility-driven cell motion is inefficient.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.|Department of Microbiology &Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur Boston, Massachusetts 02115, USA.
authors.forename: Alexis J
authors.initials: AJ
authors.lastname: Lomakin
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California, Davis, 1 Shields Avenue Davis, California 95616, USA.|Department of Mathematics, University of California, Davis, 1 Shields Avenue Davis, California 95616, USA.
authors.forename: Kun-Chun
authors.initials: KC
authors.lastname: Lee
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.
authors.forename: Sangyoon J
authors.identifier: http://orcid.org/0000-0002-1384-665X
authors.initials: SJ
authors.lastname: Han
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.
authors.forename: Duyen A
authors.initials: DA
authors.lastname: Bui
authors.affiliation: National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, 1800 E. Paul Dirac Drive Tallahassee, Florida 32310, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Davidson
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California, Davis, 1 Shields Avenue Davis, California 95616, USA.|Department of Mathematics, University of California, Davis, 1 Shields Avenue Davis, California 95616, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Mogilner
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.
authors.forename: Gaudenz
authors.initials: G
authors.lastname: Danuser
mesh_terms: D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism*; D000465:Algorithms; D000818:Animals; D001667:Binding, Competitive; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology*; D061985:Madin Darby Canine Kidney Cells; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D024462:Myosin Type II / Q000235:genetics / Q000378:metabolism; D058105:Polymerization; D034622:RNA Interference; D014741:Video Recording
chemical_list: D000199:Actins; D000205:Actomyosin; D024462:Myosin Type II