Differential inhibition of neurone–neurone, neurone–astrocyte and astrocyte–astrocyte adhesion by L1, L2 and N-CAM antibodies

Abstract

The cell adhesion molecules L1, N-CAM and Ng-CAM have been implicated in cell–cell interactions among developing neural cells^1–4. L1 and N-CAM are structurally and functionally distinct molecular entities and act synergistically in mediating Ca²⁺-independent adhesion between re-aggregating early postnatal cerebellar cells⁵. N-CAM has been reported to be neurone-specific in the chicken and to mediate fasciculation of neurites and of nerve–muscle interactions. L1, which in the central nervous system has been found only on post-mitotic neurones, mediates migration of granule cell neurones in the mouse cerebellar cortex⁶. In view of the molecules' distinct effects on cell interactions, we wondered whether different neural cell types are involved in the actions of each molecule. Here we report that LI antigen promotes neurone–neurone adhesion. N-CAM, which is expressed on both neurones and glia, mediates neurone–neurone, neurone–astrocyte and astrocyte–astrocyte adhesion. The L2 carbohydrate epitope shared between the two adhesion molecules⁷ seems to be involved in neurone–astrocyte and astrocyte–astrocyte adhesion and acts in a more than additive manner in N-CAM-mediated neurone–neurone adhesion.