title: Epithelial polarity proteins regulate Drosophila tracheal tube size in parallel to the luminal matrix pathway.
abstract: Regulation of epithelial tube size is critical for organ function. However, the mechanisms of tube size control remain poorly understood. In the Drosophila trachea, tube dimensions are regulated by a luminal extracellular matrix (ECM). ECM organization requires apical (luminal) secretion of the protein Vermiform (Verm), which depends on the basolateral septate junction (SJ). Here, we show that apical and basolateral epithelial polarity proteins interact to control tracheal tube size independently of the Verm pathway. Mutations in yurt (yrt) and scribble (scrib), which encode SJ-associated polarity proteins, cause an expansion of tracheal tubes but do not disrupt Verm secretion. Reducing activity of the apical polarity protein Crumbs (Crb) suppresses the length defects in yrt but not scrib mutants, suggesting that Yrt acts by negatively regulating Crb. Conversely, Crb overexpression increases tracheal tube dimensions. Reducing crb dosage also rescues tracheal size defects caused by mutations in coracle (cora), which encodes an SJ-associated polarity protein. In addition, crb mutations suppress cora length defects without restoring Verm secretion. Together, these data indicate that Yrt, Cora, Crb, and Scrib operate independently of the Verm pathway. Our data support a model in which Cora and Yrt act through Crb to regulate epithelial tube size.
authors.affiliation: Laval University Cancer Research Center, CRCHUQ-Hôtel-Dieu de Québec, 9 McMahon, Québec, QC G1R 2J6, Canada. patrick.laprise@crhdq.ulaval.ca
authors.forename: Patrick
authors.initials: P
authors.lastname: Laprise
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Paul
authors.forename: Jim
authors.initials: J
authors.lastname: Boulanger
authors.forename: Renée M
authors.initials: RM
authors.lastname: Robbins
authors.forename: Greg J
authors.initials: GJ
authors.lastname: Beitel
authors.forename: Ulrich
authors.initials: U
authors.lastname: Tepass
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D005109:Extracellular Matrix / Q000502:physiology; D017344:Genes, Insect; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D009154:Mutation; D009929:Organ Size; D014132:Trachea / Q000196:embryology*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; D008565:Membrane Proteins; C404683:Scrib protein, Drosophila; D025521:Tumor Suppressor Proteins; C442474:cora protein, Drosophila; C064360:crb protein, Drosophila; C474499:yrt protein, Drosophila