Immunolocalization of B-50 (GAP-43) in the mouse olfactory bulb: predominant presence in preterminal axons.
Because the growth-associated protein B-50 (GAP-43) has been implicated in neurite outgrowth as well as in synaptic plasticity, we studied its light and electron microscopical distribution in the mouse olfactory bulb, an area of the nervous system which exhibits a high degree of synaptic plasticity. Immunofluorescent staining with monospecific affinity-purified anti-B-50 antibodies revealed that B-50 is most abundantly expressed in the olfactory nerve fibre layer and the granule cell layer neuropil, while little staining was observed in the external plexiform layer and in cell bodies. B-50 is absent from dendrites and myelinated axons as indicated by double labelling with monoclonal antibodies against microtubule-associated protein 2 and the large neurofilament protein, respectively. Using post-embedding immunogold labelling on ultrathin Lowicryl sections, B-50 was found to be highly concentrated in presumed growth cones in the olfactory nerve fibre layer and in thin unmyelinated axons and presynaptic terminals in the granule cell layer neuropil. Near background immunolabelling was seen in perikarya, dendrites and myelinated axons. In view of the implication of B-50 in plasticity-related phenomena, its abundance in the thin unmyelinated preterminal axons suggests that these are potential sites of extrasynaptic plasticity.
Ramakers
G J
GJ
Rudolf Magnus Institute, University of Utrecht, The Netherlands.
Verhaagen
J
J
Oestreicher
A B
AB
Margolis
F L
FL
van Bergen en Henegouwen
P M
PM
Gispen
W H
WH
D000818:Animals; D001369:Axons / Q000737:chemistry*; D015415:Biomarkers / Q000737:chemistry; D003712:Dendrites / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D019922:GAP-43 Protein; D006133:Growth Substances / Q000032:analysis*; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000032:analysis*; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000032:analysis; D009411:Nerve Endings; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009830:Olfactory Bulb / Q000737:chemistry*; D051842:Olfactory Marker Protein
D015415:Biomarkers; D019922:GAP-43 Protein; D006133:Growth Substances; D008562:Membrane Glycoproteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D051842:Olfactory Marker Protein; C497598:Omp protein, mouse