In the mammalian central nervous system, a complexcircuit of neurons contributes to higher behaviors.Each region of the brain has a unique function derivedfrom various types of neurons. Several neuralprecursor cell lines have been established from basalganglia of fetal brain. In this study, hippocampalneural precursor cell lines were established from thehippocampus of p53(-/-) embryos. By means ofintegration of a MycER regulatable oncoprotein intop53(-/-) neural precursor cells, several immortallines were established from embryonic hippocampalprimordium, with bFGF and estrogen continuouslysupplied for activation of the MycER protein. A dualluciferase study demonstrated that the MycER proteinblocked the expression of a glial cell marker protein,GFAP, probably contributing to the persistent celldivision of the immortalized neural precursor cells.These cell lines differentiate into neuronal and glialcell types after withdrawal of bFGF. The phenotype ofthe hippocampal cell lines differed from that of thebasal ganglia cell lines as observed in a clonaldensity culture. This result implies that each regionof the brain has a unique developmental program, thatmay be imprinted in each of the neural precursor cells.