　Using an optogenetic gene expression regulation system, the present invention provides a method for controlling, by using light irradiation to regulate the expression of factors that determine neural differentiation, whether to proliferate and maintain neural precursor cells (NPC), or whether to induce differentiation of neural stem cells into nervous system cells. The present invention is based on: the discovery that neural differentiation factors such as Ascl1, Hes1, and Olig2 are expressed in NPCs periodically in an oscillatory manner but that the expression of any one of these becomes dominant during fate determination; and the structure of gene expression systems in which a target gene can be expressed periodically in an oscillatory manner. In other words, the present invention provides a method for either oscillating the expression of a target factor and maintaining and amplifying NPCs, or inducing sustained expression of the target factor and inducing differentiation into committed nervous system cells by said factor, said method being accomplished by introducing, into NPCs, a nucleic acid which codes a transcriptional activator (GAL4-Vivid-p65 fusion protein; GAVPO) that is activated (dimerized) in response to blue light, and a nucleic acid which links DNA, which codes a target neural differentiation determining factor downstream of a promoter that includes a cis sequence to which the transcriptional activator binds, and a 3'-UTR, which destabilizes mRNA, and by irradiating the NPCs with blue light for short periods of time, changing the cycle.
OPTOGENETIC CONTROL METHOD FOR PROLIFERATION AND DIFFERENTIATION OF STEM CELLS