Distribution of the neural antigen BSP-2 in the cerebellum during development

The monoclonal antibody anti-BSP-2 recognizes three glycosylated peptide chains of 180,000, 140,000 and 120,000 daltons in extracts from adult mouse forebrain and cerebellum. In extracts of embryonic or neonatal brain, it recognizes a different form, migrating as a broad band of higher molecular weight on SDS polyacrylamide gels. This report describes the distribution of the antigen BSP-2 in developing mouse cerebella using a sensitive immunoperoxidase technique at the electron microscope level. As early as 3 days after birth the antigen can be detected on the surface of all cerebellar neurons, including neuroblasts in the external granular layer, basket and stellate neurons and Purkinje cells. In addition, radial glial fibres (astrocytes) terminating on the pial surface contain BSP-2. At later stages a pronounced surface labelling of parallel fibres is observed. Migrating granule cell perikaryal membranes possess the glycoprotein. The results are discussed in relation to the apparent identity of BSP-2 and the cell adhesion molecule N-CAM and its physiological properties.