Differential functions of the C. elegans FGF receptor in axon outgrowth and maintenance of axon position.
Wiring of the nervous system requires that axons navigate to their targets and maintain their correct positions in axon fascicles after termination of axon outgrowth. We show here that the C. elegans fibroblast growth factor receptor (FGFR), EGL-15, affects both processes in fundamentally distinct manners. FGF-dependent activation of the EGL-15 tyrosine kinase and subsequently the GTPase LET-60/ras is required within epidermal cells, the substratum for most outgrowing axon, for appropriate outgrowth of specific axon classes to their target area. In contrast, genetic elimination of the FGFR isoform EGL-15(5A), defined by the inclusion of an alternative extracellular interimmunoglobulin domain, has no consequence for axon outgrowth but leads to a failure to postembryonically maintain axon position within defined axon fascicles. An engineered, secreted form of EGL-15(5A) containing only its ectodomain is sufficient for maintenance of axon position, thus providing novel insights into receptor tyrosine kinase function and the process of maintaining axon position.
Bülow
Hannes E
HE
Department of Biochemistry and Molecular Biophysics, Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
Boulin
Thomas
T
Hobert
Oliver
O
D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology*; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology; D009154:Mutation; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; C112493:EGL-15 protein, C elegans; D017468:Receptors, Fibroblast Growth Factor