The general goal of the project is to study neuronal differentiation in the mammalian nervous system by generating markers for molecules expressed by neurons early in their development. These markers will then be used to follow the expression of early-expressed molecules in vivo and in vitro. The study has two main objectives: 1) To identify antigens expressed by early postmitotic neurons. 2) To examine the developmental regulation of the expression of identified molecules. These experiments are designed to generate reagents with which to identify specific cell classes and developmentally significant changes in neurons. Such reagents could then be used to follow normal and abnormal neural development and to test hypotheses of developmental mechanisms. The long term goal of these experiments is to obtain a molecular description of developmental events which could be used to assay the effects of teratogenic or genetic insult on neural development.