Mechanosensilla in the adult abdomen of Drosophila: engrailed and slit help to corral the peripheral sensory axons into segmental bundles.
The abdomen of adult Drosophila bears mechanosensory bristles with axons that connect directly to the CNS, each hemisegment contributing a separate nerve bundle. Here, we alter the amount of Engrailed protein and manipulate the Hedgehog signalling pathway in clones of cells to study their effects on nerve pathfinding within the peripheral nervous system. We find that high levels of Engrailed make the epidermal cells inhospitable to bristle neurons; sensory axons that are too near these cells are either deflected or fail to extend properly or at all. We then searched for the engrailed-dependent agent responsible for these repellent properties. We found slit to be expressed in the P compartment and, using genetic mosaics, present evidence that Slit is the responsible molecule. Blocking the activity of the three Robo genes (putative receptors for Slit) with RNAi supported this hypothesis. We conclude that, during normal development, gradients of Slit protein repel axons away from compartment boundaries - in consequence, the bristles from each segment send their nerves to the CNS in separated sets.
Fabre
Caroline C G
CC
Department of Zoology, University of Cambridge, Cambridge, UK. c.c.g.fabre.03@cantab.net
Casal
José
J
Lawrence
Peter A
PA
D000005:Abdomen / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology; D004330:Drosophila / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D053823:Hedgehog Proteins / Q000235:genetics / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D008465:Mechanoreceptors / Q000502:physiology*; D008959:Models, Neurological; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D055495:Neurogenesis / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000502:physiology; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000072086:Smoothened Receptor; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D000097905:Roundabout Proteins
D048868:Adaptor Proteins, Signal Transducing; D029721:Drosophila Proteins; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D011971:Receptors, Immunologic; D000072086:Smoothened Receptor; D014157:Transcription Factors; D000097905:Roundabout Proteins; C063459:En protein, Drosophila; C099753:dock protein, Drosophila; C070844:ptc protein, Drosophila; C066819:sli protein, Drosophila; C100664:smo protein, Drosophila; C077245:hh protein, Drosophila