The interaction of nerves with muscles, particularly at neuromuscular junctions, is one of the most extensively studied areas of neurophysiology. From the point of view of developmental biology, however, little is known about the cellular and molecular events that lead to formation of these junctions 1,2. In previous investigations of cell-cell adhesion in the chick embryo, we identified a molecule on the surface of essentially all nerve cells, called neural cell adhesion molecule (N-CAM)3,4, that appears to be a ligand in the formation of cell-cell bonds5. N-CAM is involved in a variety of developmental processes including neurite fasciculation and the formation of plexiform and cell layers in retinal tissue6-8. We report here that N-CAM antigenic determinants are also present on chick embryo skeletal muscle cells. This observation raised the possibility that N-CAM is involved in adhesion between nerve and muscle cells. In model systems set up to explore this possibility, we observed that myoblasts will adhere in vitro to nerve cells from retina, and that this adhesion can be inhibited by F(ab′) fragments of antibodies against N-CAM. In addition, membrane vesicles obtained from chick embryo brain or artificial vesicles5 reconstituted from lipid and affinity-purified N-CAM9 bound to the surface of myoblasts and myotubes; this binding was also blocked by anti-N-CAM F(ab′). These results suggest that the N-CAM adhesion system can facilitate nerve-muscle as well as nerve-nerve interactions in vitro.
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