Immunoelectron microscopic localization of neural cell adhesion molecules (L1, N-CAM, and myelin-associated glycoprotein) in regenerating adult mouse sciatic nerve

R. Martini, Melitta Camartin

Research output: Contribution to journalArticlepeer-review

303 Scopus citations

Abstract

The localization of the neural cell adhesion molecules L1, N-CAM, and the myelin-associated glycoprotein was studied by pre- and postembedding staining procedures at the light and electron microscopic levels in transected and crushed adult mouse sciatic nerve. During the first 2-6 d after transection, myelinated and nonmyelinated axons degenerated in the distal part of the proximal stump close to the transection site and over the entire length of the distal part of the transected nerve. During this time, regrowing axons were seen only in the proximal, but not in the distal nerve stump. In most cases L1 and N-CAM remained detectable at cell contacts between nonmyelinating Schwann cells and degenerating axons as long as these were still morphologically intact. Similarly, myelin-associated glycoprotein remained detectable in the periaxonal area of the degenerating myelinated axons. During and after degeneration of axons, nonmyelinating Schwann cells formed slender processes which were L1 and N-CAM positive. They resembled small-diameter axons but could be unequivocally identified as Schwann cells by chronical denervation. Unlike the nonmyelinating Schwann cells, only few myelinating ones expressed L1 and N-CAM. At the cut ends of the nerve stumps a cap developed (more at the proximal than at the distal stump) that contained S-100-negative and fibronectin-positive fibroblast-like cells. Most of these cells were N-CAM positive but always L1 negative. Growth cones and regrowing axons expressed N-CAM and L1 at contact sites with these cells. Regrowing axons of small diameter were L1 and N-CAM positive where they made contact with each other or with Schwann cells, while large-diameter axons were only poorly antigen positive or completely negative. 14 d after transection, when regrowing axons were seen in the distal part of the transected nerve, regrowing axons made L1- and N-CAM-positive contacts with Schwann cells. When contacting basement membrane, axons were rarely found to express L1 and N-CAM. Most, if not all, Schwann cells associated with degenerating myelin expressed L1 and N-CAM. In crushed nerves, the immunostaining pattern was essentially the same as in the cut nerve. During formation of myelin, the sequence of adhesion molecule expression was the same as during development: L1 disappeared and N-CAM was reduced on myelinating Schwann cells and axons after the Schwann cell process had turned ~1.5 loops around the axon. Myelin-associated glycoprotein then appeared both periaxonally and on the turning loops of Schwann cells in the uncompacted myelin. We infer from these observations that L1 and N-CAM are involved in supporting axon regrowth on the surface of Schwann and fibroblast-like cells, and that, after the initial contacts between axons and Schwann cells, regulation of adhesion molecule expression during regeneration in many ways recapitulates development.

Original languageEnglish (US)
Pages (from-to)1735-1746
Number of pages12
JournalJournal of Cell Biology
Volume106
Issue number5
DOIs
StatePublished - 1988

All Science Journal Classification (ASJC) codes

  • Cell Biology

Fingerprint Dive into the research topics of 'Immunoelectron microscopic localization of neural cell adhesion molecules (L1, N-CAM, and myelin-associated glycoprotein) in regenerating adult mouse sciatic nerve'. Together they form a unique fingerprint.

Cite this