title: WNT/beta-catenin signalling and epithelial patterning in the homoscleromorph sponge Oscarella.
abstract: Sponges branch basally in the metazoan phylogenetic tree and are thus well positioned to provide insights into the evolution of mechanisms controlling animal development, likely to remain active in adult sponges. Of the four sponge clades, the Homoscleromorpha are of particular interest as they alone show the "true" epithelial organization seen in other metazoan phyla (the Eumetazoa). We have examined the deployment in sponges of Wnt signalling pathway components, since this pathway is an important regulator of many developmental patterning processes. We identified a reduced repertoire of three divergent Wnt ligand genes in the recently-sequenced Amphimedon queenslandica (demosponge) genome and two Wnts from our EST collection from the homoscleromorph Oscarella lobularis, along with well-conserved genes for intracellular pathway components (beta-catenin, GSK3beta). Remarkably, the two O. lobularis Wnt genes showed complementary expression patterns in relation to the evenly spaced ostia (canal openings) of the exopinacoderm (ectoderm), highly reminiscent of Wnt expression during skin appendage formation in vertebrates. Furthermore, experimental activation of the Wnt/beta-catenin pathway using GSK3beta inhibitors provoked formation of ectopic ostia, as has been shown for epithelial appendages in Eumetazoa. We thus suggest that deployment of Wnt signalling is a common and perhaps ancient feature of metazoan epithelial patterning and morphogenesis.
authors.affiliation: Centre d'Océanologie de Marseille, Aix-Marseille Université, CNRS-UMR 6540, Station marine d'Endoume, Marseille, France. pascal.lapebie@univmed.fr
authors.forename: Pascal
authors.initials: P
authors.lastname: Lapébie
authors.forename: Eve
authors.initials: E
authors.lastname: Gazave
authors.forename: Alexander
authors.initials: A
authors.lastname: Ereskovsky
authors.forename: Romain
authors.initials: R
authors.lastname: Derelle
authors.forename: Chantal
authors.initials: C
authors.lastname: Bézac
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Renard
authors.forename: Evelyn
authors.initials: E
authors.lastname: Houliston
authors.forename: Carole
authors.initials: C
authors.lastname: Borchiellini
mesh_terms: D000818:Animals; D019521:Body Patterning; D004848:Epithelium / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D017403:In Situ Hybridization; D008024:Ligands; D016013:Likelihood Functions; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D010802:Phylogeny; D011161:Porifera; D015398:Signal Transduction; D013997:Time Factors; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D008024:Ligands; D051153:Wnt Proteins; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3