title: Extrinsic and intrinsic mechanisms directing epithelial cell sheet replacement during Drosophila metamorphosis.
abstract: The fusion of epithelial sheets is an essential morphogenetic event. Here, we study the development of the abdomen of Drosophila as a model of bounded epithelia expansion and uncover a complex multistep process for the generation of the adult epidermis from histoblasts, founder cells that replace the larval cells during metamorphosis. We find that histoblasts experience a biphasic cell cycle and emit apical projections that direct their invasive planar intercalation in between larval cells. Coordinately, the larval cells extrude from the epithelia by apical constriction of an actomyosin ring and as a consequence die by apoptosis and are removed by circulating haemocytes. We demonstrate that the proliferation of histoblasts and the death of larval cells are triggered by two independent extrinsic Ecdysone hormonal pulses. Finally, we show that histoblast spreading and the death of larval cells depend on a mutual exchange of signals and are non-autonomous processes.
authors.affiliation: Instituto de Biología Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, Parc Cientific de Barcelona, Josep Samitier 1-5, Barcelona 08028, Spain.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Ninov
authors.forename: Dominic A
authors.initials: DA
authors.lastname: Chiarelli
authors.forename: Enrique
authors.initials: E
authors.lastname: Martín-Blanco
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D002450:Cell Communication; D002453:Cell Cycle; D016923:Cell Death; D049109:Cell Proliferation; D004330:Drosophila / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism; D004440:Ecdysone / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D017344:Genes, Insect; D005838:Genotype; D007814:Larva / Q000166:cytology / Q000254:growth & development; D008675:Metamorphosis, Biological; D009218:Myosins / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000199:Actins; D029721:Drosophila Proteins; D004440:Ecdysone; D009218:Myosins