title: serpentine and vermiform encode matrix proteins with chitin binding and deacetylation domains that limit tracheal tube length in Drosophila.
abstract: Many organs contain epithelial tubes that transport gases or liquids . Proper tube size and shape is crucial for organ function, but the mechanisms controlling tube diameter and length are poorly understood. Recent studies of tracheal (respiratory) tube morphogenesis in Drosophila show that chitin synthesis genes produce an expanding chitin cylinder in the apical (luminal) extracellular matrix (ECM) that coordinates the dilation of the surrounding epithelium . Here, we describe two genes involved in chitin modification, serpentine (serp) and vermiform (verm), mutations in which cause excessively long and tortuous tracheal tubes. The genes encode similar proteins with an LDL-receptor ligand binding motif and chitin binding and deacetylation domains. Both proteins are expressed and secreted during tube expansion and localize throughout the lumen in a chitin-dependent manner. Unlike previously characterized chitin pathway genes, serp and verm are not required for chitin synthesis or secretion but rather for its normal fibrillar structure. The mutations also affect structural properties of another chitinous matrix, epidermal cuticle. Our work demonstrates that chitin and the matrix proteins Serp and Verm limit tube elongation, and it suggests that tube length is controlled independently of diameter by modulating physical properties of the chitin ECM, presumably by N-deacetylation of chitin and conversion to chitosan.
authors.affiliation: Bayreuther Zentrum für Molekulare Biowissenschaften, Department of Genetics, University of Bayreuth, D-95440 Bayreuth, Germany. stefan.luschnig@uni-bayreuth.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Luschnig
authors.forename: Tilmann
authors.initials: T
authors.lastname: Bätz
authors.forename: Kristina
authors.initials: K
authors.lastname: Armbruster
authors.forename: Mark A
authors.initials: MA
authors.lastname: Krasnow
mesh_terms: D000581:Amidohydrolases / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D016764:Cell Polarity; D002686:Chitin / Q000378:metabolism*; D004330:Drosophila / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D009024:Morphogenesis; D005810:Multigene Family; D017434:Protein Structure, Tertiary; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D014132:Trachea / Q000166:cytology / Q000196:embryology*
chemical_list: D029721:Drosophila Proteins; D016326:Extracellular Matrix Proteins; D002686:Chitin; D000581:Amidohydrolases; C509513:serp protein, Drosophila; C509514:verm protein, Drosophila; C019866:chitin deacetylase