Cell-surface antigens of developing rat cerebellar neurons: identification with monoclonal antibodies

Three monoclonal antibodies (Mab's), named 3C5.59, 3G5.34, and 3G6.41, that recognize cell-surface antigens found on embryonic and postnatal neurons were selected for study from among a group generated against adult rat synaptic plasma membranes (SPM's). Immunofluorescence staining with these 3 antibodies showed strong reactivity of the processes and much weaker staining of the cell bodies of the small neurons cultured from early postnatal rat cerebella. Mab 3G6.41 also reacted with flat astrocyte-like cells cultured from cerebellum. In contrast Mab's 3C5.59 and 3G5.34 appeared to specifically recognize only the neurons in these cultures. In situ staining of cryostat sections with 3G5.34 and 3G6.41 demonstrated immunoreactivity that was predominantly localized to the molecular layer of the cerebellum in the early postnatal through adult stages, in agreement with the strong staining of neurites seen in primary neuronal cultures. Quantitative analysis of Mab binding to particulate protein preparations from various tissues of the adult rat indicated that each of the antigens is restricted to the nervous system in the adult. Binding studies also indicated that each antigen was enriched approximately 1.5-fold in the SPM fractions compared to total particulate fractions from cerebellum. All 3 Mab's recognize membrane-bound molecules that can be solubilized by non-ionic detergent. Mab 3G6.41 immunoprecipitated two polypeptides of 140,000 and 185,000 apparent molecular weight from detergent-solubilized cerebellar cells that were surface-iodinated in culture. These antibodies should prove useful in the further analysis of the expression and function of individual cell surface antigens during the differentiation of cerebellar granule cells.