title: Rac1 controls epithelial tube length through the apical secretion and polarity pathways.
abstract: The morphometric parameters of epithelial tubes are critical to the physiology and homeostasis of most organs. In addition, many human diseases are associated with tube-size defects. Here, we show that Rac1 limits epithelial tube elongation in the developing fly trachea by promoting Rab5-dependent endocytosis of the apical determinant Crumbs. Rac1 is also involved in a positive feedback loop with the septate junction protein Coracle. Thereby, Rac1 precludes paracellular diffusion and contributes to the septate junction-dependent secretion of the chitin-modifying enzymes Vermiform and Serpentine, which restrict epithelial tube length independently of Crumbs. Thus, Rac1 is a critical component of two important pathways controlling epithelial tube morphogenesis.
authors.affiliation: Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada Centre de recherche sur le cancer, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada CRCHU de Québec, axe oncologie, 9 McMahon, Québec, Québec G1R 3S3,Canada.
authors.forename: Kévin
authors.initials: K
authors.lastname: Sollier
authors.affiliation: Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada Centre de recherche sur le cancer, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada CRCHU de Québec, axe oncologie, 9 McMahon, Québec, Québec G1R 3S3,Canada.
authors.forename: Helori-Mael
authors.initials: HM
authors.lastname: Gaudé
authors.affiliation: Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada Centre de recherche sur le cancer, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada CRCHU de Québec, axe oncologie, 9 McMahon, Québec, Québec G1R 3S3,Canada.
authors.forename: François J-M
authors.initials: FJ
authors.lastname: Chartier
authors.affiliation: Département de Biologie Moléculaire, Biochimie Médicale et Pathologie, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada Centre de recherche sur le cancer, Université Laval, 9 McMahon, Québec, Québec G1R 3S3, Canada CRCHU de Québec, axe oncologie, 9 McMahon, Québec, Québec G1R 3S3,Canada Patrick.Laprise@crhdq.ulaval.ca.
authors.forename: Patrick
authors.initials: P
authors.lastname: Laprise
keywords: Coracle; Crumbs; Drosophila trachea; Epithelial polarity; Epithelial tube morphogenesis; Rac1; Septate junction