Our current work is aimed at the identification and characterization of the neuroepithelial precursor cell in the embryonic rat. The strategy we have used was first, to identify the major morphological cell classes in the neural tube at the time of neurogenesis using monoclonal antibodies (Hockfield and McKay, 1985). Secondly, we have showed that one of these monoclonal antibodies recognizes neuroepithelial precursor cells in vivo (Frederiksen and McKay, 1985). The third step in this strategy has been to immortalize cell lines from the early nervous system using retroviral transduction of an oncogene. These cell lines have properties of neuroepthelial precursor cells. This proposal focuses on the origin, fate, and function of these cells. These studies are relevant to CNS injury and repair and to two neural diseases, neural tumors and demyelinating disease.