title: The molecular basis of self-avoidance.
abstract: Self-avoidance, the tendency of neurites of the same cell to selectively avoid each other, is a property of both vertebrate and invertebrate neurons. In Drosophila, self-avoidance is mediated by a large family of cell recognition molecules of the immunoglobulin superfamily encoded, via alternative splicing, by the Dscam1 locus. Dscam1 promotes self-avoidance in dendrites, axons, and prospective postsynaptic elements. Expression analysis suggests that each neuron expresses a unique combination of isoforms. Identical isoforms on sister neurites exhibit isoform-specific homophilic recognition and elicit repulsion between processes, thereby promoting self-avoidance. Although any isoform can promote self-avoidance, thousands are necessary to ensure that neurites readily discriminate between self and nonself. Recent studies indicate that a large family of cadherins in the mouse, i.e., the clustered protocadherins, functions in an analogous fashion to promote self-avoidance. These studies argue for the evolution of a common molecular strategy for self-avoidance.
authors.affiliation: Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California-Los Angeles, CA 90095-1662, USA. lzipursky@mednet.ucla.edu
authors.forename: S Lawrence
authors.initials: SL
authors.lastname: Zipursky
authors.forename: Wesley B
authors.initials: WB
authors.lastname: Grueber
mesh_terms: D000818:Animals; D005075:Biological Evolution; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication / Q000502:physiology*; D003712:Dendrites / Q000502:physiology; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D007136:Immunoglobulins / Q000235:genetics / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*
chemical_list: D015820:Cadherins; D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins; C491736:Dscam1 protein, Drosophila; D007136:Immunoglobulins