title: Crumbs is required to achieve proper organ size control during Drosophila head development.
abstract: Crumbs (Crb) is a conserved apical polarity determinant required for zonula adherens specification and remodelling during Drosophila development. Interestingly, crb function in maintaining apicobasal polarity appears largely dispensable in primary epithelia such as the imaginal discs. Here, we show that crb function is not required for maintaining epithelial integrity during the morphogenesis of the Drosophila head and eye. However, although crb mutant heads are properly developed, they are also significantly larger than their wild-type counterparts. We demonstrate that in the eye, this is caused by an increase in cell proliferation that can be attributed to an increase in ligand-dependent Notch (N) signalling. Moreover, we show that in crb mutant cells, ectopic N activity correlates with an increase in N and Delta endocytosis. These data indicate a role for Crb in modulating endocytosis at the apical epithelial plasma membrane, which we demonstrate is independent of Crb function in apicobasal polarity. Overall, our work reveals a novel function for Crb in limiting ligand-dependent transactivation of the N receptor at the epithelial cell membrane.
authors.affiliation: MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, University College London, London, UK.
authors.forename: Emily C N
authors.initials: EC
authors.lastname: Richardson
authors.forename: Franck
authors.initials: F
authors.lastname: Pichaud
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D004705:Endocytosis; D005123:Eye / Q000254:growth & development; D017344:Genes, Insect; D006257:Head / Q000254:growth & development; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D009929:Organ Size; D010641:Phenotype; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology; D051880:Receptors, Notch / Q000502:physiology; D015398:Signal Transduction; D014921:Wings, Animal / Q000254:growth & development
chemical_list: D017931:DNA Primers; D029721:Drosophila Proteins; D008565:Membrane Proteins; C497759:N protein, Drosophila; D051880:Receptors, Notch; C064360:crb protein, Drosophila