title: beta-Catenin-dependent Wnt signalling controls the epithelial organisation of somites through the activation of paraxis.
abstract: The regulation of cell adhesion in epithelia is a fundamental process governing morphogenesis in embryos and a key step in the progression of invasive cancers. Here, we have analysed the molecular pathways controlling the epithelial organisation of somites. Somites are mesodermal epithelial structures of vertebrate embryos that undergo several changes in cell adhesion during early embryonic life. We show that Wnt6 in the ectoderm overlaying the somites, but not Wnt1 in the neighbouring neural tube, is the most likely candidate molecule responsible for the maintenance of the epithelial structure of the dorsal compartment of the somite: the dermomyotome. We characterised the signalling pathway that mediates Wnt6 activity. Our experiments suggest that the Wnt receptor molecule Frizzled7 probably transduces the Wnt6 signal. Intracellularly, this leads to the activation of the beta-catenin/LEF1-dependent pathway. Finally, we demonstrate that the bHLH transcription factor paraxis, which was previously shown to be a major player in the epithelial organisation of somites, is a target of the beta-catenin signal. We conclude that beta-catenin activity, initiated by Wnt6 and mediated by paraxis, is required for the maintenance of the epithelial structure of somites.
authors.affiliation: Laboratoire de Génétique et de Physiologie du Développement (LGPD (IBDM), CNRS UMR 6545. Université de la Méditerranée, Campus de Luminy, case 907, 13288 Marseille, Cedex 09, France. c.linker@ucl.ac.uk
authors.forename: Claudia
authors.initials: C
authors.lastname: Linker
authors.forename: Cynthia
authors.initials: C
authors.lastname: Lesbros
authors.forename: Jérôme
authors.initials: J
authors.lastname: Gros
authors.forename: Laura W
authors.initials: LW
authors.lastname: Burrus
authors.forename: Alan
authors.initials: A
authors.lastname: Rawls
authors.forename: Christophe
authors.initials: C
authors.lastname: Marcelle
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002642:Chick Embryo; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D015398:Signal Transduction; D019170:Somites / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D051153:Wnt Proteins; D051155:Wnt1 Protein; D014981:Xenopus; D029867:Xenopus Proteins; D051176:beta Catenin
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029867:Xenopus Proteins; D051176:beta Catenin; C495266:CTNNB1 protein, Xenopus; C495267:CTNNB1 protein, mouse; C093234:Tcf15 protein, mouse; C495246:Wnt1 protein, mouse