title: Adaptive rheology and ordering of cell cytoskeleton govern matrix rigidity sensing.
abstract: Matrix rigidity sensing regulates a large variety of cellular processes and has important implications for tissue development and disease. However, how cells probe matrix rigidity, and hence respond to it, remains unclear. Here, we show that rigidity sensing and adaptation emerge naturally from actin cytoskeleton remodelling. Our in vitro experiments and theoretical modelling demonstrate a biphasic rheology of the actin cytoskeleton, which transitions from fluid on soft substrates to solid on stiffer ones. Furthermore, we find that increasing substrate stiffness correlates with the emergence of an orientational order in actin stress fibres, which exhibit an isotropic to nematic transition that we characterize quantitatively in the framework of active matter theory. These findings imply mechanisms mediated by a large-scale reinforcement of actin structures under stress, which could be the mechanical drivers of substrate stiffness-dependent cell shape changes and cell polarity.
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
authors.forename: Mukund
authors.initials: M
authors.lastname: Gupta
authors.affiliation: Institut Jacques Monod (IJM), CNRS UMR 7592, Université Paris Diderot, Paris 75013, France.
authors.forename: Bibhu Ranjan
authors.initials: BR
authors.lastname: Sarangi
authors.affiliation: Institut Jacques Monod (IJM), CNRS UMR 7592, Université Paris Diderot, Paris 75013, France.
authors.forename: Joran
authors.identifier: http://orcid.org/0000-0001-8462-2883
authors.initials: J
authors.lastname: Deschamps
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, 28 Medical Drive, Singapore 117456, Singapore.|Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
authors.forename: Yasaman
authors.initials: Y
authors.lastname: Nematbakhsh
authors.affiliation: Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, Université Paris Diderot, Paris 75013, France.
authors.forename: Andrew
authors.initials: A
authors.lastname: Callan-Jones
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
authors.forename: Felix
authors.initials: F
authors.lastname: Margadant
authors.affiliation: Institut Jacques Monod (IJM), CNRS UMR 7592, Université Paris Diderot, Paris 75013, France.
authors.forename: René-Marc
authors.initials: RM
authors.lastname: Mège
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.|NUS Graduate School for Integrative Sciences and Engineering, 28 Medical Drive, Singapore 117456, Singapore.|Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.|Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
authors.forename: Chwee Teck
authors.initials: CT
authors.lastname: Lim
authors.affiliation: Laboratoire de Physique Thèorique de la Matière Condensée, CNRS/UPMC, 4 place Jussieu, Paris 75005, France.|Laboratoire Jean Perrin, CNRS/UPMC, 4 place Jussieu, Paris 75005, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Voituriez
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.|Institut Jacques Monod (IJM), CNRS UMR 7592, Université Paris Diderot, Paris 75013, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Ladoux
mesh_terms: D000199:Actins / Q000502:physiology*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001696:Biomechanical Phenomena; D003599:Cytoskeleton / Q000502:physiology*; D061252:Feeder Cells; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D051381:Rats; D012212:Rheology / Q000379:methods
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria