DEVELOPMENTAL EXPRESSION AND FUNCTIONAL-CHARACTERIZATION OF THE 4C5 ANTIGEN IN THE POSTNATAL CEREBELLAR CORTEX

The monoclonal antibody 4C5 recognizes a neuron-specific surface antig en (4C5 antigen) in the CNS and PNS of the rat. In the present study w e investigated the expression of 4C5 antigen in the developing cerebel lum of the rat and the functional role of this molecule during cerebel lar morphogenesis. Immunoblotting and immunohistochemistry in sections of cerebellar cortex revealed an age-dependent decrease in the expres sion of the 4C5 antigen, In cerebellar primary cell cultures, 4C5 immu noreactivity was detected both on granule and on Purkinje neurons, Gra nule cell migration was inhibited in cerebellar explants derived from 8-day-old rats and cultured for 2 days in the presence of antibodies a gainst the 4C5 antigen. Electron microscope immunocytochemistry reveal ed that in 8-day-old rat cerebellum, 4C5 immunoreactivity was localize d on the cell bodies of granule neurons in the external and internal g ranular layers and on parallel fibers in the developing molecular laye r as well as at contact sites between these cellular elements. It was not detected on Bergmann glia. These results suggest strongly that the 4C5 antigen is involved in granule cell migration during cerebellar d evelopment, possibly via neuron-neuron interactions.