The role of an astrocyte surface molecule in neuronal migration in the developing rat cerebellum.

We have shown previously that the MAb 1A1 recognizes a cell surface glycoprotein with adhesive properties expressed exclusively on astrocytes in the rat central nervous system (CNS). In this study, the role of this molecule in neuronal migration in the developing rat cerebellum was investigated by antibody perturbation experiments. The MAb 1A1 binds to the surface of cultured radial Bergmann glia, a subclass of astrocytes known to guide the migration of postmitotic neurons by cell-cell contact, but does not bind to neurons in the cerebellum. The antibody does not bind to tissue sections for immunohistochemical studies. However, by immunoprecipitation the level of this antigen increases by about twofold between Postnatal Day 1 (P1) and P20 followed by a decrease to the P1 level at P35. In addition, the number of 1A1+ Bergmann glia also increases from 33 to 78% between P1 and P7 in dissociated cell cultures. Monovalent fragments of the MAb 1A1 inhibit the adhesion of neurons to Bergmann glia by about 50% in dissociated cultures of the P7 cerebellum. In addition, the migration of neurons on Bergmann glia was assessed in microexplant cultures of the P7 cerebellar cortex after 3 days in vitro. In these experiments the MAb 1A1 blocks the migration of neurons by 60%. These findings suggest that the 1A1 molecule might play a role in glial-guided neuronal migration in the developing cerebellum.