The guanine nucleotide exchange factor trio mediates axonal development in the Drosophila embryo

Neuron. 2000 Apr;26(1):93-106. doi: 10.1016/s0896-6273(00)81141-1.


Recent analysis of Rho subfamily GTPases in Drosophila revealed roles for Rac and Cdc42 during axonogenesis. Here, we describe the identification and characterization of the Drosophila counterpart of Trio, a guanine nucleotide exchange factor (GEF) that associates with the receptor phosphatase LAR and regulates GTPase activation in vertebrate cells. Mutants deficient in trio activity display defects in both central and peripheral axon pathways reminiscent of phenotypes observed in embryos deficient in small GTPase function. Double mutant analysis shows that trio interacts with Rac in a dose-sensitive manner but not with Rho. Moreover, reduction of trio activity potentiates the phenotype of mutations in the LAR homolog Dlar, suggesting that these proteins collaborate in orchestrating the cytoskeletal events that underlie normal axonogenesis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / metabolism*
  • Drosophila / embryology
  • Drosophila / genetics
  • Drosophila Proteins*
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Motor Neurons / metabolism
  • Oligochaeta / genetics
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Retina / embryology
  • Retina / metabolism*
  • rac GTP-Binding Proteins / genetics
  • rac GTP-Binding Proteins / metabolism*
  • rho GTP-Binding Proteins / genetics
  • rho GTP-Binding Proteins / metabolism*


  • Drosophila Proteins
  • Guanine Nucleotide Exchange Factors
  • Phosphoproteins
  • Protein Serine-Threonine Kinases
  • trio protein, Drosophila
  • rac GTP-Binding Proteins
  • rho GTP-Binding Proteins