Increase of B-50/GAP-43 immunoreactivity in uninjured muscle nerves of MDX mice.
Lack of dystrophin in mdx mice leads to muscle fibre degeneration followed by the formation of new myofibres. This degeneration-regeneration event occurs in clusters. It is accompanied by inflammation and remodelling of the intramuscular terminal nerve fibres. Since the growth-associated protein B-50/GAP-43 has been shown to be involved in axonal outgrowth and synaptic remodelling following neuronal injury, we have investigated the presence of B-50 in gastrocnemius and quadriceps muscles of mdx mice. Using immunocytochemistry we demonstrate increased presence of B-50 in terminal nerve branches at motor endplates of mdx mice, particularly in the clusters of de- and regenerating myofibres. In comparison, the control mice displayed no B-50 immunoreactivity in nerve fibres contacting motor endplates. Our findings indicate that during axonal remodelling and collateral sprouting the B-50 level in the terminal axon arbours is increased although there is no direct injury to the motoneurons. We suggest that the degenerating target and/or the inflammatory reaction induces the increased B-50 level in the motoaxons. The increased B-50 may be important for sprouting of the nerve fibres and re-establishment of synaptic contacts, and in addition, for maturation and survival of the newly formed myofibres.
Verzè
L
L
Department of Human Anatomy and Physiology, University of Turin, Torino, Italy.
Buffo
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A
Rossi
F
F
Oestreicher
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AB
Gispen
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WH
Strata
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P
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D019922:GAP-43 Protein; D006133:Growth Substances / Q000378:metabolism; D006651:Histocytochemistry; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx / Q000378:metabolism*; D009045:Motor Endplate / Q000378:metabolism*; D009137:Muscular Dystrophy, Animal / Q000378:metabolism*; D009411:Nerve Endings / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D012016:Reference Values
D019922:GAP-43 Protein; D006133:Growth Substances; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D000110:Acetylcholinesterase