title: Quantitative analysis of cytoskeletal reorganization during epithelial tissue sealing by large-volume electron tomography.
abstract: The closure of epidermal openings is an essential biological process that causes major developmental problems such as spina bifida in humans if it goes awry. At present, the mechanism of closure remains elusive. Therefore, we reconstructed a model closure event, dorsal closure in fly embryos, by large-volume correlative electron tomography. We present a comprehensive, quantitative analysis of the cytoskeletal reorganization, enabling separated epidermal cells to seal the epithelium. After establishing contact through actin-driven exploratory filopodia, cells use a single lamella to generate 'roof tile'-like overlaps. These shorten to produce the force, 'zipping' the tissue closed. The shortening overlaps lack detectable actin filament ensembles but are crowded with microtubules. Cortical accumulation of shrinking microtubule ends suggests a force generation mechanism in which cortical motors pull on microtubule ends as for mitotic spindle positioning. In addition, microtubules orient filopodia and lamellae before zipping. Our 4D electron microscopy picture describes an entire developmental process and provides fundamental insight into epidermal closure.
authors.affiliation: 1] Goethe University Frankfurt, Buchmann Institute for Molecular Life Sciences and Institute for Biophysics, Max-von-Laue Str. 15 60438 Frankfurt am Main, Germany [2] Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany [3] Electron Microscopy Core Facility, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Eltsov
authors.affiliation: 1] Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany [2] University of Zurich, Institute of Molecular Life Sciences, Winterthurerstr. 190, 8057 Zurich, Switzerland [3] Institut de recherches cliniques de Montréal (IRCM), 110 avenue des Pins Ouest, Montréal (Québec), H2W 1R7, Canada.
authors.forename: Nadia
authors.initials: N
authors.lastname: Dubé
authors.affiliation: Goethe University Frankfurt, Buchmann Institute for Molecular Life Sciences and Institute for Biophysics, Max-von-Laue Str. 15 60438 Frankfurt am Main, Germany.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Yu
authors.affiliation: University of Zurich, Institute of Molecular Life Sciences, Winterthurerstr. 190, 8057 Zurich, Switzerland.
authors.forename: Laurynas
authors.initials: L
authors.lastname: Pasakarnis
authors.affiliation: Electron Microscopy Core Facility, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Haselmann-Weiss
authors.affiliation: 1] Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany [2] University of Zurich, Institute of Molecular Life Sciences, Winterthurerstr. 190, 8057 Zurich, Switzerland.
authors.forename: Damian
authors.initials: D
authors.lastname: Brunner
authors.affiliation: Goethe University Frankfurt, Buchmann Institute for Molecular Life Sciences and Institute for Biophysics, Max-von-Laue Str. 15 60438 Frankfurt am Main, Germany.
authors.forename: Achilleas S
authors.initials: AS
authors.lastname: Frangakis
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D055032:Electron Microscope Tomography; D004848:Epithelium / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure*; D017930:Genes, Reporter; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008870:Microtubules / Q000648:ultrastructure; D011554:Pseudopodia / Q000648:ultrastructure
chemical_list: D000199:Actins; D008164:Luminescent Proteins