Characterization of a novel set of membrane antigens associated with axonal growth. II. Expression in the chick central nervous system.

In the preceding paper (Dev. Brain Res., 69 (1992) 215-223), a polyclonal antiserum ('3070') and several monoclonal antibodies (MAbs 4 and 199) were used to define a novel set of laminin-binding membrane antigens in chick brain. These MAbs specifically inhibited attachment of NG108-15 cells to low, but not high amounts of laminin. Here, the immunocytochemical localization of MAb 4 and 3070 antigens was examined in frozen sections of E3-P21 chick brain, with particular reference to retina, optic tectum, cerebellum and spinal cord. Growing axons and migrating nascent neurons were stained transiently, while projection neurons were intensely labelled at all stages. Some interneurons and glial cells were stained faintly; others, apparently not at all. Finally, 3070 antiserum stained neuropil regions in mature brain. Cells in the CNS expressing high levels of MAb 4 antigens corresponded to those which, in rodents, are known to migrate in response to laminin or to synthesize forms of laminin themselves. These data, together with evidence presented elsewhere (J. Comp. Neurol., 313 (1991) 625-642) and in the next paper in this series (Dev. Brain Res., 69 (1992) 277-282), suggest that MAb 4 and 3070 antigens are important in neural development by mediating at least some of the responses of neural cells to laminin--for example, by acting as a laminin receptor guiding axonal outgrowth and neuronal migration, or by involvement in the transport and binding of laminin to the surface of neurons and reactive glial cells.