A variety of cellular interactions in the developing nervous system are thought to be mediated by macromolecules which neurons have on their surfaces or which they secrete into the extracellular space. Recent work with cultures of dissociated sympathetic neurons has described a number of candidates for such intercellular signals. These are surface-bound and secreted molecules, identified by isotopic labeling or with monoclonal, antibodies, which are enriched in either adrenergic or cholinergic sympathetic neurons. Such molecules are thus potentially involved in functions or interactions specific to one of these two phenotypes. Since certain sensory neurons are known to exert trophic influences on their targets it is proposed to examine neuronal cultures from various sensory ganglia with the same methods to see if different classes of sensory neurons also secrete characteristic families of glycoproteins. The functional roles of the glycoproteins and glycolipids of interest are being investigated by producing antibodies against them. The antibodies are then added to cultured sympathetic neurons, either chronically or in acute incubations, and the effect on neuronal survival, growth and differentiation determined. In such experiments, certain of the monoclonal antibodies already produced against sympathetic neuron surface membranes of have been found to selectively decrease or enhance the development of specific neuronal properties such as transmitter synthesis or release. The new monoclonals to be generated agaist phenotype-specific molecules as well as the rest of the present monoclonal library (greater than 100 clones) will be similarly examined for effects on neuronal development. The antibodies will also be tested for their ability to disrupt previously studied cellular interactions such as neuron-induced receptor clustering on myotubes, and Schwann cell mitosis induced by contact with axons. Another method being employed for assessing antigen function is to use the antibodies to generate mutant PC12 cell lines which are then tested for deficiencies in the various assays. Selected antigens will be localized in vivo by immunocytochemical methods and, ultimately, antigen function in normal development will be assessed by antibody injections in developing rats.
