The PC3 gene is an immediate early gene, induced in PC12 cells by treatment with nerve growth factor. It is one of the two members of a new gene family, with a putative antiproliferative function. PC3 is expressed in the developing rat neural tube with a pattern that correlates with neuronal cell birthday. PC3 is therefore hypothesized to be functionally involved either in the growth arrest of neuronal precursors and PC12 cells, or in an early phase of neuronal commitment, or both, the two processes being tightly related to each other. The aims of this project are: a) to test this hypothesis by altering PC3 expression both in PC12 cells and in neuroepithelial cells in living embryos and then evaluating the effects on both cell proliferation and neuronal differentiation; b) to investigate further the functional role of the PC3 protein by analyzing its subcellular localization and its interactions with other proteins.