Drosophila motor axons recognize and follow a Sidestep-labeled substrate pathway to reach their target fields.
During development of the Drosophila nervous system, migrating motor axons contact and interact with different cell types before reaching their peripheral muscle fields. The axonal attractant Sidestep (Side) is expressed in most of these intermediate targets. Here, we show that motor axons recognize and follow Side-expressing cell surfaces from the ventral nerve cord to their target region. Contact of motor axons with Side-expressing cells induces the down-regulation of Side. In the absence of Side, the interaction with intermediate targets is lost. Misexpression of Side in side mutants strongly attracts motor axons to ectopic sites. We provide evidence that, on motor axons, Beaten path Ia (Beat) functions as a receptor or part of a receptor complex for Side. In beat mutants, motor axons no longer recognize Side-expressing cell surfaces. Furthermore, Beat interacts with Side both genetically and biochemically. These results suggest that the tracing of Side-labeled cell surfaces by Beat-expressing growth cones is a major principle of motor axon guidance in Drosophila.
Siebert
Matthias
M
Westfälische Wilhelms-Universität Münster, Institut für Neurobiologie, Münster, Germany.
Banovic
Daniel
D
Goellner
Bernd
B
Aberle
Hermann
H
D000818:Animals; D001369:Axons / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D020439:Growth Cones / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009046:Motor Neurons / Q000378:metabolism*; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D011984:Sensory Receptor Cells / Q000378:metabolism
D029721:Drosophila Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C103224:beat-Ia protein, Drosophila; C425543:side protein, Drosophila