title: Tubulogenesis in a simple cell cord requires the formation of bi-apical cells through two discrete Par domains.
abstract: Apico-basal polarization is a crucial step in the de novo formation of biological tubes. In Ciona notochord, tubulogenesis occurs in a single file of cells in the absence of cell proliferation. This configuration presents a unique challenge for the formation of a continuous lumen. Here, we show that this geometric configuration is associated with a novel polarization strategy: the generation of bipolar epithelial cells possessing two apical/luminal domains instead of one, as in the conventional epithelium. At the molecular level, cells establish two discrete Par3/Par6/aPKC patches, and form two sets of tight junctions, in opposite points of the cells. The key molecule controlling the formation of both domains is Par3. Changing the position of the cells within the organ fundamentally changes their polarity and the number of apical domains they develop. These results reveal a new mechanism for tubulogenesis from the simplest cell arrangement, which occurs in other developmental contexts, including vertebrate vascular anastomosis.
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgt. 55, N-5008 Bergen, Norway.
authors.forename: Elsa
authors.initials: E
authors.lastname: Denker
authors.forename: Ivana
authors.initials: I
authors.lastname: Bocina
authors.forename: Di
authors.initials: D
authors.lastname: Jiang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D016764:Cell Polarity; D002938:Ciona intestinalis / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D015536:Down-Regulation; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism; D007814:Larva / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D009024:Morphogenesis; D009672:Notochord / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D008565:Membrane Proteins; C115015:PKC-3 protein; D011493:Protein Kinase C
keywords: Apico-basal polarity; Bipolarity; Par3; Tubulogenesis