Comparison of two cell surface molecules involved in neural cell adhesion.

Two cell surface molecules found in mouse brain, N‐CAM and the L1 antigen, were compared in terms of their cell adhesion function, polypeptide structures, antigenic determinants and distribution in cerebellar tissue. Fab fragments of polyclonal antibodies to either N‐CAM or L1 antigen only partially inhibited the rate of calcium‐independent aggregation of neuroblastoma N2A cells, whereas complete and more efficient inhibition was obtained when they were used in combination. Despite the functional similarity, comparison of the electrophoretic behaviour of the purified molecules and of their proteolytic fragments shows that the L1 antigen polypeptide is distinct from that of N‐CAM. In addition, no antigenic cross‐reactivity was detected between the two molecules. In cryostat sections of cerebellum from young post‐natal mice, N‐CAM was found to be present in all cell and neurite layers, whereas L1 antigen was expressed only in regions containing post‐mitotic cells. These results indicate that two chemically and histochemically distinct cell surface polypeptides can contribute to the calcium‐independent adhesiveness of neural cells, and suggest that their differential expression might cause adhesive specificity among cells of developing neural tissues.