title: Mechanical detection of a long-range actin network emanating from a biomimetic cortex.
abstract: Actin is ubiquitous globular protein that polymerizes into filaments and forms networks that participate in the force generation of eukaryotic cells. Such forces are used for cell motility, cytokinesis, and tissue remodeling. Among those actin networks, we focus on the actin cortex, a dense branched network beneath the plasma membrane that is of particular importance for the mechanical properties of the cell. Here we reproduce the cellular cortex by activating actin filament growth on a solid surface. We unveil the existence of a sparse actin network that emanates from the surface and extends over a distance that is at least 10 times larger than the cortex itself. We call this sparse actin network the "actin cloud" and characterize its mechanical properties with optical tweezers. We show, both experimentally and theoretically, that the actin cloud is mechanically relevant and that it should be taken into account because it can sustain forces as high as several picoNewtons (pN). In particular, it is known that in plant cells, actin networks similar to the actin cloud have a role in positioning the nucleus; in large oocytes, they play a role in driving chromosome movement. Recent evidence shows that such networks even prevent granule condensation in large cells.
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Université Paris Diderot, Sorbonne Paris Cité, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bussonnier
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
authors.forename: Kevin
authors.initials: K
authors.lastname: Carvalho
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Université Paris Diderot, Sorbonne Paris Cité, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
authors.forename: Joël
authors.initials: J
authors.lastname: Lemière
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Joanny
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Sykes
authors.affiliation: Institut Curie, Centre de Recherche, Paris, France; Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, UMR 168, Paris, France; Centre National de la Recherche Scientifique, UMR168, Paris, France. Electronic address: timo.betz@curie.fr.
authors.forename: Timo
authors.initials: T
authors.lastname: Betz
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins / Q000737:chemistry; D001696:Biomechanical Phenomena; D040761:Biomimetic Materials / Q000737:chemistry; D055119:Elastic Modulus; D008954:Models, Biological; D017711:Nonlinear Dynamics; D052898:Optical Tweezers; D011137:Polystyrenes / Q000737:chemistry
chemical_list: D000199:Actins; D011137:Polystyrenes