title: Differential adhesion determines the organization of synaptic fascicles in the Drosophila visual system.
abstract: BACKGROUND
  Neuronal circuits in worms, flies, and mammals are organized so as to minimize wiring length for a functional number of synaptic connections, a phenomenon called wiring optimization. However, the molecular mechanisms that establish optimal wiring during development are unknown. We addressed this question by studying the role of N-cadherin in the development of optimally wired neurite fascicles in the peripheral visual system of Drosophila.
  
  
  RESULTS
  Photoreceptor axons surround the dendrites of their postsynaptic targets, called lamina cells, within a concentric fascicle called a cartridge. N-cadherin is expressed at higher levels in lamina cells than in photoreceptors, and all genetic manipulations that invert these relative differences displace lamina cells to the periphery and relocate photoreceptor axon terminals into the center.
  
  
  CONCLUSIONS
  Differential expression of a single cadherin is both necessary and sufficient to determine cartridge structure because it positions the most-adhesive elements that make the most synapses at the core and the less-adhesive elements that make fewer synapses at the periphery. These results suggest a general model by which differential adhesion can be utilized to determine the relative positions of axons and dendrites to establish optimal wiring.
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Tina
authors.initials: T
authors.lastname: Schwabe
authors.affiliation: Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, Halifax, NS B3H 4R2, Canada.
authors.forename: Jolanta A
authors.initials: JA
authors.lastname: Borycz
authors.affiliation: Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, Halifax, NS B3H 4R2, Canada.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Meinertzhagen
authors.affiliation: Department of Neurobiology, Stanford University, Stanford, CA 94305, USA. Electronic address: trc@stanford.edu.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Clandinin
mesh_terms: D000818:Animals; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D007814:Larva / Q000254:growth & development / Q000502:physiology; D016501:Neurites / Q000378:metabolism; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology* / Q000502:physiology; D011679:Pupa / Q000254:growth & development / Q000502:physiology; D013569:Synapses / Q000502:physiology; D014795:Visual Pathways / Q000254:growth & development / Q000502:physiology
chemical_list: C570800:CadN protein, Drosophila; D015820:Cadherins; D029721:Drosophila Proteins