title: Receptor tyrosine phosphatases regulate axon guidance across the midline of the Drosophila embryo.
abstract: Neural receptor-linked protein tyrosine phosphatases (RPTPs) are required for guidance of motoneuron and photoreceptor growth cones in Drosophila. These phosphatases have not been implicated in growth cone responses to specific guidance cues, however, so it is unknown which aspects of axonal pathfinding are controlled by their activities. Three RPTPs, known as DLAR, DPTP69D, and DPTP99A, have been genetically characterized thus far. Here we report the isolation of mutations in the fourth neural RPTP, DPTP10D. The analysis of double mutant phenotypes shows that DPTP10D and DPTP69D are necessary for repulsion of growth cones from the midline of the embryonic central nervous system. Repulsion is thought to be triggered by binding of the secreted protein Slit, which is expressed by midline glia, to Roundabout (Robo) receptors on growth cones. Robo repulsion is downregulated by the Commissureless (Comm) protein, allowing axons to cross the midline. Here we show that the Rptp mutations genetically interact with robo, slit and comm. The nature of these interactions suggests that DPTP10D and DPTP69D are positive regulators of Slit/Roundabout repulsive signaling. We also show that elimination of all four neural RPTPs converts most noncrossing longitudinal pathways into commissures that cross the midline, indicating that tyrosine phosphorylation controls the manner in which growth cones respond to midline signals.
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Sun
authors.forename: S
authors.initials: S
authors.lastname: Bahri
authors.forename: A
authors.initials: A
authors.lastname: Schmid
authors.forename: W
authors.initials: W
authors.lastname: Chia
authors.forename: K
authors.initials: K
authors.lastname: Zinn
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure; D002874:Chromosome Mapping; D004330:Drosophila / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics; D017344:Genes, Insect; D020439:Growth Cones / Q000648:ultrastructure; D019476:Insect Proteins / Q000378:metabolism*; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009420:Nervous System / Q000196:embryology* / Q000201:enzymology*; D010641:Phenotype; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D019476:Insect Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D011505:Protein-Tyrosine Kinases