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  • The EMBO Journal (2000) 19, 4463 - 4472
  • doi:10.1093/emboj/19.17.4463

Amalgam is a ligand for the transmembrane receptor neurotactin and is required for neurotactin-mediated cell adhesion and axon fasciculation in Drosophila

F. Frémion1,5, I. Darboux2,5, M. Diano1, R. Hipeau-Jacquotte3, M.A. Seeger4 and M. Piovant1

  1. Laboratoire de Génétique et de Physiologie du Développement, IBDM, CNRS/INSERM/Université de la Méditerranée/A.P. de Marseille, Parc Scientifique de Luminy Case 907, 13288 Marseille, Cedex 9, France
  2. Present address: Laboratoire de Biologie des Invertébrés, Centre de Recherches d'Antibes–INRA, 123, Boulevard Francis Meilland, BP 2078, 06606 Antibes Cedex, France
  3. Present address: Centre d'Océanologie de Marseille, Station Marine d'Endoume, Rue Batterie des Lions, 13007 Marseille France
  4. Department of Molecular Genetics and the Neurobiotechnology Center, The Ohio State University, Rightmire Hall, 1060 Carmack Road, Columbus, OH 43210, USA
  5. F.Frémion and I.Darboux contributed equally to this work

Correspondence to:

M. Piovant, E-mail: piovant@ibdm.univ-mrs.fr

Received 4 February 2000; Accepted 11 July 2000; Revised 11 July 2000

Neurotactin (NRT), a member of the cholinesterase-homologous protein family, is a heterophilic cell adhesion molecule that is required for proper axon guidance during Drosophila development. In this study, we identify amalgam (AMA), a member of the immunoglobulin superfamily, as a ligand for the NRT receptor. Using transfected Schneider 2 cells and embryonic primary cultures, we demonstrate that AMA is a secreted protein. Furthermore, AMA is necessary for NRT-expressing cells both to aggregate with themselves and to associate with embryonic primary culture cells. Aggregation assays performed with truncated NRT molecules reveal that the integrity of the cholinesterase-like extracellular domain was not required either for AMA binding or for adhesion, with only amino acids 347–482 of the extracellular domain being necessary for both activities. Moreover, the NRT cytoplasmic domain is required for NRT-mediated adhesion, although not for AMA binding. Using an ama-deficient stock, we find that ama function is not essential for viability. Pupae deficient for ama do exhibit defasciculation defects of the ocellar nerves similar to those found in nrt mutants.

  • Keywords:

    • amalgam,
    • axon fasciculation,
    • cell adhesion,
    • Drosophila,
    • neurotactin