title: Electron microscopic immunocytochemistry of GAP-43 within proximal and chronically denervated distal stumps of transected peripheral nerve.
abstract: Growth-associated protein, GAP-43 was initially described as a neuron-specific molecule thought to play a critical role in axonal growth and regeneration. However, it is also expressed in vitro in certain CNS glia, Schwann cell precursors and non-myelinating Schwann cells. In this paper, we report the subcellular localization of GAP-43 in vivo in chronically-denervated Schwann cells in the distal stumps of previously transected rat sciatic nerve. We have used a progressive lowering of temperature method combined with the non-polar acrylic resin Lowicryl HM20 and a post-embedding labelling regime to visualize the distribution of GAP-43, S-100 (marker for Schwann cells), RT97 and NF68 (markers for different subunits of the neurofilament molecule). We report that (1) the smallest calibre regrowing axons were GAP-43-positive, sometimes NF68-positive but always RT97-negative; (2) regenerating myelinated axons and larger unmyelinated axons (> 0.7 microns diameter) were NF68-positive, RT97-positive but GAP-43-negative; (3) cytoplasmic processes within Schwann cell basal lamina tubes in the distal stumps were S-100-positive, GAP-43-positive but RT97- and NF68-negative. The similar localization of GAP-43 within regrowing axons and denervated Schwann cells suggests that GAP-43 may function similarly in both situations, and may thus be involved in motility and/or elongation of axons and Schwann cells during regeneration.
authors.affiliation: Division of Anatomy and Cell Biology, United Medical and Dental Schools, London, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Hall
authors.forename: A P
authors.initials: AP
authors.lastname: Kent
authors.forename: R
authors.initials: R
authors.lastname: Curtis
authors.forename: D
authors.initials: D
authors.lastname: Robertson
mesh_terms: D000818:Animals; D001369:Axons / Q000737:chemistry / Q000502:physiology; D002467:Cell Nucleus / Q000737:chemistry; D003593:Cytoplasm / Q000737:chemistry; D003714:Denervation; D019922:GAP-43 Protein; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000032:analysis*; D008854:Microscopy, Electron; D009416:Nerve Regeneration; D009419:Nerve Tissue Proteins / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000737:chemistry* / Q000648:ultrastructure; D012584:Sciatic Nerve / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins