Quantitative analysis of cytoskeletal reorganization during epithelial tissue sealing by large-volume electron tomography

• Published in: Nature cell biology Vol. 17; no. 5; pp. 605 - 614
• Main Authors: Eltsov, Mikhail, Dubé, Nadia, Yu, Zhou, Pasakarnis, Laurynas, Haselmann-Weiss, Uta, Brunner, Damian, Frangakis, Achilleas S.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2015; Nature Publishing Group
• Subjects: 14/1; 14/19; 14/28; 14/35; 631/136/1660/2127; 631/136/334/1582/715; 631/1647/245; 631/80/128; Actins - metabolism; Animals; Animals, Genetically Modified; Biophysics; Cancer Research; Cell Biology; Cell research; Cellular control mechanisms; Cytoskeleton; Cytoskeleton - metabolism; Cytoskeleton - ultrastructure; Developmental Biology; Drosophila melanogaster - embryology; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila melanogaster - ultrastructure; Electron Microscope Tomography; Embryos; Epithelium - embryology; Epithelium - metabolism; Epithelium - ultrastructure; Genes, Reporter; Image Processing, Computer-Assisted; Imaging, Three-Dimensional; Life Sciences; Luminescent Proteins - biosynthesis; Luminescent Proteins - genetics; Methods; Microscopy; Microscopy, Confocal; Microscopy, Fluorescence; Microscopy, Video; Microtubules - ultrastructure; Molecular biology; Observations; Pseudopodia - ultrastructure; Quantitative analysis; Spina bifida; Stem Cells; Tomography; Germany
• ISSN: 1465-7392; 1476-4679
• DOI: 10.1038/ncb3159

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. Using large-volume correlative electron tomography, Brunner and colleagues show that microtubules provide forces for the sealing of the epidermis during dorsal closure in Drosophila .