title: Epithelial organization and cyst lumen expansion require efficient Sec13-Sec31-driven secretion.
abstract: Epithelial morphogenesis is directed by interactions with the underlying extracellular matrix. Secretion of collagen and other matrix components requires efficient coat complex II (COPII) vesicle formation at the endoplasmic reticulum. Here, we show that suppression of the outer layer COPII component, Sec13, in zebrafish embryos results in a disorganized gut epithelium. In human intestinal epithelial cells (Caco-2), Sec13 depletion causes defective epithelial polarity and organization on permeable supports. Defects are seen in the ability of cells to adhere to the substrate, form a monolayer and form intercellular junctions. When embedded in a three-dimensional matrix, Sec13-depleted Caco-2 cells form cysts but, unlike controls, are defective in lumen expansion. Incorporation of primary fibroblasts within the three-dimensional culture substantially restores normal morphogenesis. We conclude that efficient COPII-dependent secretion, notably assembly of Sec13-Sec31, is required to drive epithelial morphogenesis in both two- and three-dimensional cultures in vitro, as well as in vivo. Our results provide insight into the role of COPII in epithelial morphogenesis and have implications for the interpretation of epithelial polarity and organization assays in cell culture.
authors.affiliation: Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD,  UK.
authors.forename: Anna K
authors.initials: AK
authors.lastname: Townley
authors.forename: Katy
authors.initials: K
authors.lastname: Schmidt
authors.forename: Lorna
authors.initials: L
authors.lastname: Hodgson
authors.forename: David J
authors.initials: DJ
authors.lastname: Stephens
mesh_terms: D000818:Animals; D001483:Base Sequence; D022181:COP-Coated Vesicles / Q000502:physiology; D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D018920:Coculture Techniques; D005109:Extracellular Matrix / Q000502:physiology; D055785:Gene Knockdown Techniques; D006801:Humans; D007413:Intestinal Mucosa / Q000196:embryology* / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009024:Morphogenesis; D034741:RNA, Small Interfering / Q000235:genetics; D033921:Vesicular Transport Proteins / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000502:physiology; D029961:Zebrafish Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D034741:RNA, Small Interfering; C507456:SEC13 protein, human; C507455:SEC31A protein, human; D033921:Vesicular Transport Proteins; D029961:Zebrafish Proteins