title: Tenascin-C is involved in motor axon outgrowth in the trunk of developing zebrafish.
abstract: Motor axons in the trunk of the developing zebrafish exit from the ventral spinal cord in one ventral root per hemisegment and grow on a common path toward the region of the horizontal myoseptum, where they select their specific pathways. Tenascin-C, a component of the extracellular matrix, is concentrated in this choice region. Adaxial cells and other myotomal cells express tenascin-C mRNA, suggesting that these cells are the source of tenascin-C protein. Overexpressing an axon repellent fragment containing the cysteine-rich region and the epidermal growth factor-like repeats of tenascin-C led to retarded growth of ventral motor nerves between their spinal exit point and the horizontal myoseptum. Injection of a protein fragment containing the same part of tenascin-C also induced slower growth of motor nerves. Conversely, knock down of tenascin-C protein resulted in abnormal lateral branching of ventral motor nerves. In the zebrafish unplugged mutant, in which axons display pathfinding defects in the region of the horizontal myoseptum, tenascin-C immunoreactivity was not detectable in this region, indicating an abnormal extracellular matrix in unplugged. We conclude that tenascin-C is part of a specialized extracellular matrix in the region of the horizontal myoseptum that influences the growth of motor axons.
authors.affiliation: Zentrum für Molekulare Neurobiologie, Hamburg, Germany.
authors.forename: Jörn
authors.initials: J
authors.lastname: Schweitzer
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Julie
authors.initials: J
authors.lastname: Lefebvre
authors.forename: Michael
authors.initials: M
authors.lastname: Granato
authors.forename: Melitta
authors.initials: M
authors.lastname: Schachner
authors.forename: Catherina G
authors.initials: CG
authors.lastname: Becker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000737:chemistry / Q000378:metabolism*; D002454:Cell Differentiation; D003001:Cloning, Molecular; D003545:Cysteine / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019063:Tenascin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D019063:Tenascin; D004815:Epidermal Growth Factor; D003545:Cysteine