title: Dscam2 mediates axonal tiling in the Drosophila visual system.
abstract: Sensory processing centres in both the vertebrate and the invertebrate brain are often organized into reiterated columns, thus facilitating an internal topographic representation of the external world. Cells within each column are arranged in a stereotyped fashion and form precise patterns of synaptic connections within discrete layers. These connections are largely confined to a single column, thereby preserving the spatial information from the periphery. Other neurons integrate this information by connecting to multiple columns. Restricting axons to columns is conceptually similar to tiling. Axons and dendrites of neighbouring neurons of the same class use tiling to form complete, yet non-overlapping, receptive fields. It is thought that, at the molecular level, cell-surface proteins mediate tiling through contact-dependent repulsive interactions, but proteins serving this function have not yet been identified. Here we show that the immunoglobulin superfamily member Dscam2 restricts the connections formed by L1 lamina neurons to columns in the Drosophila visual system. Our data support a model in which Dscam2 homophilic interactions mediate repulsion between neurites of L1 cells in neighbouring columns. We propose that Dscam2 is a tiling receptor for L1 neurons.
authors.affiliation: Howard Hughes Medical Institute, Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095, USA.
authors.forename: S Sean
authors.initials: SS
authors.lastname: Millard
authors.forename: John J
authors.initials: JJ
authors.lastname: Flanagan
authors.forename: Kartik S
authors.initials: KS
authors.lastname: Pappu
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: S Lawrence
authors.initials: SL
authors.lastname: Zipursky
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology* / Q000196:embryology* / Q000502:physiology; D008969:Molecular Sequence Data; D019006:Neural Cell Adhesion Molecules; D011485:Protein Binding; D014785:Vision, Ocular / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*
chemical_list: D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins; C491736:Dscam1 protein, Drosophila; C520675:Dscam2 protein, Drosophila; D019006:Neural Cell Adhesion Molecules