Myopodia (postsynaptic filopodia) participate in synaptic target recognition

J Neurobiol. 2003 Apr;55(1):31-40. doi: 10.1002/neu.10180.

Abstract

Synaptic partner cells recognize one another by utilizing a variety of molecular cues. Prior to neuromuscular synapse formation, Drosophila embryonic muscles extend dynamic actin-based filopodia called "myopodia." In wild-type animals, myopodia are initially extended randomly from the muscle surface but become gradually restricted to the site of motoneuron innervation, a spatial redistribution we call "clustering." Previous experiments with prospero mutant embryos demonstrated that myopodia clustering does not occur in the absence of motoneuron outgrowth into the muscle field. However, whether myopodia clustering is due to a general signal from passing axons or is a result of the specific interactions between synaptic partners remained to be investigated. Here, we have examined the relationship of myopodia to the specific events of synaptic target recognition, the stable adhesion of synaptic partners. We manipulated the embryonic expression of alphaPS2 integrin and Toll, molecules known to affect synaptic development, to specifically alter synaptic targeting on identified muscles. Then, we used a vital single-cell labeling approach to visualize the behavior of myopodia in these animals. We demonstrate a strong positive correlation between myopodia activity and synaptic target recognition. The frequency of myopodia clustering is lowered in cases where synaptic targeting is disrupted. Myopodia clustering seems to result from the adherence of a subset of myopodia to the innervating growth cone while the rest are eliminated. The data suggest that postsynaptic cells play a dynamic role in the process of synaptic target recognition.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acids / metabolism
  • Animals
  • Drosophila Proteins / deficiency
  • Drosophila Proteins / genetics
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / genetics
  • Embryo, Nonmammalian
  • Gene Deletion
  • Growth Cones / metabolism*
  • Growth Cones / ultrastructure
  • Immunohistochemistry
  • Integrin alpha Chains
  • Integrins / deficiency
  • Integrins / genetics
  • Motor Neurons / metabolism*
  • Motor Neurons / ultrastructure
  • Muscle, Skeletal / embryology*
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / ultrastructure
  • Mutation
  • Neuromuscular Junction / embryology*
  • Neuromuscular Junction / metabolism
  • Pseudopodia / metabolism*
  • Receptors, Cell Surface / deficiency
  • Receptors, Cell Surface / genetics
  • Synapses / physiology*
  • Time Factors
  • Toll-Like Receptors

Substances

  • Amino Acids
  • Drosophila Proteins
  • Integrin alpha Chains
  • Integrins
  • Receptors, Cell Surface
  • Tl protein, Drosophila
  • Toll-Like Receptors
  • dolaisoleucine
  • if protein, Drosophila