title: The PDZ-GEF protein Dizzy regulates the establishment of adherens junctions required for ventral furrow formation in Drosophila.
abstract: The PDZ-GEF protein Dizzy (Dzy) and its downstream GTPase Rap1 have pleiotropic roles during development of the Drosophila embryo. Here, we show that maternally provided Dzy and Rap1 first function during ventral furrow formation (VFF) where they are critical to guarantee rapid apical cell constrictions. Contraction of the apical actomyosin filament system occurs independently of Dzy and Rap1, but loss of Dzy results in a delayed establishment of the apical adherens junction (AJ) belt, whereas in the absence of Rap1 only a fragmentary apical AJ belt is formed in the epithelium. The timely establishment of apical AJs appears to be essential for coupling actomyosin contractions to cell shape change and to assure completion of the ventral furrow. Immediately after VFF, the downregulation of Dzy and Rap1 is necessary to allow normal mesodermal development to continue after the epithelial-to-mesenchymal transition, as overexpression of Dzy or of constitutively active Rap1 compromises mesodermal migration and monolayer formation. We propose that Dzy and Rap1 are crucial factors regulating the dynamics of AJs during gastrulation.
authors.affiliation: Interfakultäres Institut für Zellbiologie, Abteilung Genetik der Tiere, Fachbereich für Biologie, Universität Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen,  Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Spahn
authors.forename: Alice
authors.initials: A
authors.lastname: Ott
authors.forename: Rolf
authors.initials: R
authors.lastname: Reuter
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002465:Cell Movement / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D004625:Embryo, Nonmammalian; D047108:Embryonic Development; D004789:Enzyme Activation; D054262:Gastrulation; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; C514059:PDZ-GEF protein, Drosophila