A genetic analysis of axon guidance in the C elegans pharynx

Dev Biol. 2003 Aug 1;260(1):158-75. doi: 10.1016/s0012-1606(03)00238-0.


We wish to understand how the trajectories of the twenty pharyngeal neurons of C. elegans are established. In this study we focused on the two bilateral M2 pharyngeal motorneurons, which each have their cell body located in the posterior bulb and send one axon through the isthmus and into the metacorpus. We used a GFP reporter to visualize these neurons in cell-autonomous and cell-non-autonomous axon guidance mutant backgrounds, as well as other mutant classes. Our main findings are: 1). Mutants with impaired growth cone functions, such as unc-6, unc-51, unc-73 and sax-3, often exhibit abnormal terminations and inappropriate trajectories at the distal ends of the M2 axons, i.e. within the metacorpus; and 2). Growth cone function mutants never exhibit abnormalities in the proximal part of the M2 neuron trajectories, i.e. between the cell body and the metacorpus. Our results suggest that the proximal and distal trajectories are established using distinct mechanisms, including a growth cone-independent process to establish the proximal trajectory. We isolated five novel mutants in a screen for worms exhibiting abnormal morphology of the M2 neurons. These mutants define a new gene class designated mnm (M neuron morphology abnormal).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Autoantigens / genetics
  • Autoantigens / metabolism
  • Axons / physiology*
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / growth & development
  • Caenorhabditis elegans / physiology
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Genes, Helminth
  • Genes, Reporter
  • Green Fluorescent Proteins
  • Growth Cones / physiology
  • Kinetics
  • Luminescent Proteins / metabolism
  • Models, Biological
  • Motor Neurons / cytology
  • Motor Neurons / physiology
  • Mutagenesis
  • Mutation
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Pharynx / cytology
  • Pharynx / physiology*
  • Recombinant Fusion Proteins / metabolism
  • Transgenes


  • Autoantigens
  • Caenorhabditis elegans Proteins
  • Luminescent Proteins
  • Nerve Tissue Proteins
  • Recombinant Fusion Proteins
  • ric-19 protein, C elegans
  • Green Fluorescent Proteins