title: Geometry and network connectivity govern the mechanics of stress fibers.
abstract: Actomyosin stress fibers (SFs) play key roles in driving polarized motility and generating traction forces, yet little is known about how tension borne by an individual SF is governed by SF geometry and its connectivity to other cytoskeletal elements. We now address this question by combining single-cell micropatterning with subcellular laser ablation to probe the mechanics of single, geometrically defined SFs. The retraction length of geometrically isolated SFs after cutting depends strongly on SF length, demonstrating that longer SFs dissipate more energy upon incision. Furthermore, when cell geometry and adhesive spacing are fixed, cell-to-cell heterogeneities in SF dissipated elastic energy can be predicted from varying degrees of physical integration with the surrounding network. We apply genetic, pharmacological, and computational approaches to demonstrate a causal and quantitative relationship between SF connectivity and mechanics for patterned cells and show that similar relationships hold for nonpatterned cells allowed to form cell-cell contacts in monolayer culture. Remarkably, dissipation of a single SF within a monolayer induces cytoskeletal rearrangements in cells long distances away. Finally, stimulation of cell migration leads to characteristic changes in network connectivity that promote SF bundling at the cell rear. Our findings demonstrate that SFs influence and are influenced by the networks in which they reside. Such higher order network interactions contribute in unexpected ways to cell mechanics and motility.
authors.affiliation: Department of Bioengineering, University of California, Berkeley, CA 94720.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA 94720.
authors.forename: Elena
authors.initials: E
authors.lastname: Kassianidou
authors.affiliation: Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany.|BioQuant--Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Brand
authors.affiliation: Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany.|BioQuant--Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Ulrich S
authors.identifier: 0000-0003-1483-640X
authors.initials: US
authors.lastname: Schwarz
authors.affiliation: Department of Bioengineering, University of California, Berkeley, CA 94720; skumar@berkeley.edu.|UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley, CA 94720.|Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000205:Actomyosin / Q000737:chemistry*; D002465:Cell Movement; D016764:Cell Polarity; D003599:Cytoskeleton / Q000737:chemistry*; D008962:Models, Theoretical; D059010:Single-Cell Analysis / Q000379:methods; D022502:Stress Fibers / Q000737:chemistry*; D013314:Stress, Mechanical
chemical_list: D000205:Actomyosin
keywords: actin; active cable model; cell migration; cytoskeleton; myosin