title: A secretory cell type develops alongside multiciliated cells, ionocytes and goblet cells, and provides a protective, anti-infective function in the frog embryonic mucociliary epidermis.
abstract: The larval epidermis of Xenopus is a bilayered epithelium, which is an excellent model system for the study of the development and function of mucosal and mucociliary epithelia. Goblet cells develop in the outer layer while multiciliated cells and ionocytes sequentially intercalate from the inner to the outer layer. Here, we identify and characterise a fourth cell type, the small secretory cell (SSC). We show that the development of these cells is controlled by the transcription factor Foxa1 and that they intercalate into the outer layer of the epidermis relatively late, at the same time as embryonic hatching. Ultrastructural and molecular characterisation shows that these cells have an abundance of large apical secretory vesicles, which contain highly glycosylated material, positive for binding of the lectin, peanut agglutinin, and an antibody to the carbohydrate epitope, HNK-1. By specifically depleting SSCs, we show that these cells are crucial for protecting the embryo against bacterial infection. Mass spectrometry studies show that SSCs secrete a glycoprotein similar to Otogelin, which may form the structural component of a mucus-like protective layer, over the surface of the embryo, and several potential antimicrobial substances. Our study completes the characterisation of all the epidermal cell types in the early tadpole epidermis and reinforces the suitability of this system for the in vivo study of complex epithelia, including investigation of innate immune defences.
authors.affiliation: Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
authors.forename: Eamon
authors.initials: E
authors.lastname: Dubaissi
authors.forename: Karine
authors.initials: K
authors.lastname: Rousseau
authors.forename: Robert
authors.initials: R
authors.lastname: Lea
authors.forename: Ximena
authors.initials: X
authors.lastname: Soto
authors.forename: Siddarth
authors.initials: S
authors.lastname: Nardeosingh
authors.forename: Axel
authors.initials: A
authors.lastname: Schweickert
authors.forename: Enrique
authors.initials: E
authors.lastname: Amaya
authors.forename: David J
authors.initials: DJ
authors.lastname: Thornton
authors.forename: Nancy
authors.initials: N
authors.lastname: Papalopulu
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002923:Cilia / Q000276:immunology; D004625:Embryo, Nonmammalian; D004817:Epidermis / Q000196:embryology* / Q000276:immunology* / Q000378:metabolism; D006023:Glycoproteins / Q000032:analysis / Q000378:metabolism; D020397:Goblet Cells / Q000276:immunology*; D051541:Hepatocyte Nuclear Factor 3-alpha / Q000502:physiology; D007113:Immunity, Innate / Q000502:physiology*; D007477:Ions / Q000378:metabolism; D007814:Larva; D009093:Mucus / Q000737:chemistry / Q000378:metabolism; D055571:Secretory Pathway / Q000276:immunology; D022142:Secretory Vesicles / Q000276:immunology / Q000378:metabolism; D014981:Xenopus / Q000196:embryology* / Q000276:immunology / Q000382:microbiology*
chemical_list: D006023:Glycoproteins; D051541:Hepatocyte Nuclear Factor 3-alpha; D007477:Ions
keywords: FoxA1; Infection; Mucins; Mucociliary; Otogelin; Xenopus epidermis