title: Guidance of postural motoneurons requires MAPK/ERK signaling downstream of fibroblast growth factor receptor 1.
abstract: Identification of intracellular signaling pathways necessary for appropriate axon guidance is challenging because many CNS populations used to study these events contain multiple cell types. Here, we resolve this issue by using mouse embryonic stem (ES) cells that were directed to differentiate into a population of motoneurons that exclusively innervate epaxial muscles [medial median motor column (MMCm) motoneurons]. These ES cell-derived MMCm motoneurons, like their endogenous counterparts, express fibroblast growth factor receptor 1 (FGFR1) and selectively extend axons toward the epaxial trophin FGF8. Unlike wild-type MMCm motoneurons, FGFR1(-/-) MMCm motoneurons show guidance defects when transplanted into the neural tube of chick embryos. Furthermore, activation of FGFR1 selectively signals through mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) for appropriate guidance in vitro, whereas overexpression of constitutively active MAPK/ERK in transplanted, or endogenous chick, MMCm cells causes guidance defects in vivo. These results indicate that MAPK/ERK activation downstream of FGFR1 is necessary for MMCm motor axon guidance and that ES cell-derived neurons provide an important tool for dissecting intracellular pathways required for axon guidance.
authors.affiliation: Department of Anatomy and Neurobiology, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 1X5.
authors.forename: Prabakaran
authors.initials: P
authors.lastname: Soundararajan
authors.forename: James P
authors.initials: JP
authors.lastname: Fawcett
authors.forename: Victor F
authors.initials: VF
authors.lastname: Rafuse
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D002642:Chick Embryo; D053595:Embryonic Stem Cells; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005121:Extremities / Q000254:growth & development / Q000294:innervation / Q000502:physiology; D051524:Fibroblast Growth Factor 8 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009046:Motor Neurons / Q000502:physiology*; D054259:Neural Tube / Q000254:growth & development / Q000502:physiology; D011187:Posture / Q000502:physiology*; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D033581:Stem Cell Transplantation
chemical_list: D051524:Fibroblast Growth Factor 8; D051496:Receptor, Fibroblast Growth Factor, Type 1; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases
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