title: Direct laser manipulation reveals the mechanics of cell contacts in vivo.
abstract: Cell-generated forces produce a variety of tissue movements and tissue shape changes. The cytoskeletal elements that underlie these dynamics act at cell-cell and cell-ECM contacts to apply local forces on adhesive structures. In epithelia, force imbalance at cell contacts induces cell shape changes, such as apical constriction or polarized junction remodeling, driving tissue morphogenesis. The dynamics of these processes are well-characterized; however, the mechanical basis of cell shape changes is largely unknown because of a lack of mechanical measurements in vivo. We have developed an approach combining optical tweezers with light-sheet microscopy to probe the mechanical properties of epithelial cell junctions in the early Drosophila embryo. We show that optical trapping can efficiently deform cell-cell interfaces and measure tension at cell junctions, which is on the order of 100 pN. We show that tension at cell junctions equilibrates over a few seconds, a short timescale compared with the contractile events that drive morphogenetic movements. We also show that tension increases along cell interfaces during early tissue morphogenesis and becomes anisotropic as cells intercalate during germ-band extension. By performing pull-and-release experiments, we identify time-dependent properties of junctional mechanics consistent with a simple viscoelastic model. Integrating this constitutive law into a tissue-scale model, we predict quantitatively how local deformations propagate throughout the tissue.
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Biologie du Développement de Marseille, IBDM UMR7288, 13009 Marseille, France.
authors.forename: Kapil
authors.initials: K
authors.lastname: Bambardekar
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Biologie du Développement de Marseille, IBDM UMR7288, 13009 Marseille, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Clément
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Biologie du Développement de Marseille, IBDM UMR7288, 13009 Marseille, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Blanc
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Biologie du Développement de Marseille, IBDM UMR7288, 13009 Marseille, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Chardès
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Biologie du Développement de Marseille, IBDM UMR7288, 13009 Marseille, France pierre-francois.lenne@univ-amu.fr.
authors.forename: Pierre-François
authors.initials: PF
authors.lastname: Lenne
mesh_terms: D000818:Animals; D002450:Cell Communication; D004330:Drosophila / Q000196:embryology; D007834:Lasers; D052898:Optical Tweezers
keywords: Myosin-II; cell mechanics; light-sheet microscopy; optical tweezers; tissue morphogenesis