title: PlexinA3 restricts spinal exit points and branching of trunk motor nerves in embryonic zebrafish.
abstract: The pioneering primary motor axons in the zebrafish trunk are guided by multiple cues along their pathways. Plexins are receptor components for semaphorins that influence motor axon growth and path finding. We cloned plexinA3 in zebrafish and localized plexinA3 mRNA in primary motor neurons during axon outgrowth. Antisense morpholino knock-down led to substantial errors in motor axon growth. Errors comprised aberrant branching of primary motor nerves as well as additional exit points of axons from the spinal cord. Excessively branched and supernumerary nerves were found in both ventral and dorsal pathways of motor axons. The trunk environment and several other types of axons, including trigeminal axons, were not detectably affected by plexinA3 knock-down. RNA overexpression rescued all morpholino effects. Synergistic effects of combined morpholino injections indicate interactions of plexinA3 with semaphorin3A homologs. Thus, plexinA3 is a crucial receptor for axon guidance cues in primary motor neurons.
authors.affiliation: Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, Australia.
authors.forename: Julia
authors.initials: J
authors.lastname: Feldner
authors.forename: Michell M
authors.initials: MM
authors.lastname: Reimer
authors.forename: Jörn
authors.initials: J
authors.lastname: Schweitzer
authors.forename: Björn
authors.initials: B
authors.lastname: Wendik
authors.forename: Dirk
authors.initials: D
authors.lastname: Meyer
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Catherina G
authors.initials: CG
authors.lastname: Becker
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D009046:Motor Neurons / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D013116:Spinal Cord / Q000196:embryology* / Q000378:metabolism*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D008562:Membrane Glycoproteins; C097871:PLXNA3 protein, human; C524494:Plxna3 protein, zebrafish; D011956:Receptors, Cell Surface; D029961:Zebrafish Proteins