title: Complementary chimeric isoforms reveal Dscam1 binding specificity in vivo.
abstract: Dscam1 potentially encodes 19,008 ectodomains of a cell recognition molecule of the immunoglobulin (Ig) superfamily through alternative splicing. Each ectodomain, comprising a unique combination of three variable (Ig) domains, exhibits isoform-specific homophilic binding in vitro. Although we have proposed that the ability of Dscam1 isoforms to distinguish between one another is crucial for neural circuit assembly, via a process called self-avoidance, whether recognition specificity is essential in vivo has not been addressed. Here we tackle this issue by assessing the function of Dscam1 isoforms with altered binding specificities. We generated pairs of chimeric isoforms that bind to each other (heterophilic) but not to themselves (homophilic). These isoforms failed to support self-avoidance or did so poorly. By contrast, coexpression of complementary isoforms within the same neuron restored self-avoidance. These data establish that recognition between Dscam1 isoforms on neurites of the same cell provides the molecular basis for self-avoidance.
authors.affiliation: Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Goran
authors.initials: G
authors.lastname: Ahlsen
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.forename: Lawrence
authors.initials: L
authors.lastname: Shapiro
authors.forename: S Lawrence
authors.initials: SL
authors.lastname: Zipursky
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015703:Antigens, CD / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000235:genetics*; D002450:Cell Communication / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster; D004797:Enzyme-Linked Immunosorbent Assay; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007136:Immunoglobulins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D050506:Mutant Chimeric Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D014461:Ultracentrifugation / Q000379:methods
chemical_list: D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins; C491736:Dscam1 protein, Drosophila; D007136:Immunoglobulins; D050506:Mutant Chimeric Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins