title: Measurement of cortical elasticity in Drosophila melanogaster embryos using ferrofluids.
abstract: Many models of morphogenesis are forced to assume specific mechanical properties of cells, because the actual mechanical properties of living tissues are largely unknown. Here, we measure the rheology of epithelial cells in the cellularizing Drosophila embryo by injecting magnetic particles and studying their response to external actuation. We establish that, on timescales relevant to epithelial morphogenesis, the cytoplasm is predominantly viscous, whereas the cellular cortex is elastic. The timescale of elastic stress relaxation has a lower bound of 4 min, which is comparable to the time required for internalization of the ventral furrow during gastrulation. The cytoplasm was measured to be ∼103-fold as viscous as water. We show that elasticity depends on the actin cytoskeleton and conclude by discussing how these results relate to existing mechanical models of morphogenesis.
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544.|Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544.|Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Doubrovinski
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544.
authors.forename: Michael
authors.initials: M
authors.lastname: Swan
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544.
authors.forename: Oleg
authors.initials: O
authors.lastname: Polyakov
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544; efw@princeton.edu.|Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544.
authors.forename: Eric F
authors.initials: EF
authors.lastname: Wieschaus
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000187:drug effects / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D004331:Drosophila melanogaster / Q000196:embryology*; D004548:Elasticity; D004625:Embryo, Nonmammalian / Q000502:physiology* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000502:physiology*; D054262:Gastrulation / Q000502:physiology; D015726:Giant Cells / Q000502:physiology; D008280:Magnetics; D058185:Magnetite Nanoparticles; D059346:Magnets; D008845:Microinjections; D008954:Models, Biological; D009024:Morphogenesis; D012212:Rheology; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D058185:Magnetite Nanoparticles
keywords: cell rheology; embryology; gastrulation