title: Spatial discontinuity of optomotor-blind expression in the Drosophila wing imaginal disc disrupts epithelial architecture and promotes cell sorting.
abstract: BACKGROUND
  Decapentaplegic (Dpp) is one of the best characterized morphogens, required for dorso-ventral patterning of the Drosophila embryo and for anterior-posterior (A/P) patterning of the wing imaginal disc. In the larval wing pouch, the Dpp target gene optomotor-blind (omb) is generally assumed to be expressed in a step function above a certain threshold of Dpp signaling activity.
  
  
  RESULTS
  We show that the transcription factor Omb forms, in fact, a symmetrical gradient on both sides of the A/P compartment boundary. Disruptions of the Omb gradient lead to a re-organization of the epithelial cytoskeleton and to a retraction of cells toward the basal membrane suggesting that the Omb gradient is required for correct epithelial morphology. Moreover, by analysing the shape of omb gain- and loss-of-function clones, we find that Omb promotes cell sorting along the A/P axis in a concentration-dependent manner.
  
  
  CONCLUSIONS
  Our findings show that Omb distribution in the wing imaginal disc is described by a gradient rather than a step function. Graded Omb expression is necessary for normal cell morphogenesis and cell affinity and sharp spatial discontinuities must be avoided to allow normal wing development.
authors.affiliation: Department of Entomology, China Agricultural University, Beijing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Shen
authors.forename: Christian
authors.initials: C
authors.lastname: Dahmann
authors.forename: Gert O
authors.initials: GO
authors.lastname: Pflugfelder
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000378:metabolism; D014921:Wings, Animal / Q000196:embryology
chemical_list: D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D020825:T-Box Domain Proteins; C064196:dpp protein, Drosophila; C072962:bi protein, Drosophila