Analysis of mechanisms regulating self-renewal and neural differentiation of neural stem cells derived from primate embryonic stem cells

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We have reported that neural differentiation of mouse and monkey embryonic stem (ES) cell can be efficiently induced by Neural Stem Sphere (NSS) method. In the first stage of the method, the NSS was formed from a colony of ES cells by culture in astrocyte-conditioned medium under free-floating conditions. Here we analyzed changes in gene expression during the formation of NSSs from mouse and monkey ES cell colonies by quantitative real-time RT-PCR and found that expression of ES cell markers was down-regulated by the culture. In contrast, expression of an epiblast marker, a neuroectodermal marker, neural stem cell markers and neuronal markers became marked sequentially during the culture. However, expression of an early mesoderm marker, a primitive endodermal marker and an epidermal marker was low and did not significantly increase throughout the culture. In the second stage of the method, culturing the spheres on an adhesive substrate in ACM promoted neurogenesis. These results suggest that mouse and primate ES cells can unidirectionally differentiate into neurons via neural stem cells by the NSS method. We applied the NSS method to human ES cells which were supplied from Kyoto University and demonstrated that human ES cells could be efficiently differentiated into neurons by the method. We examined gene expression and protein profiling during differentiation of mouse embryonic stem (ES) cells into neurons via neural stem cells by microarray-based hybridization and proteomic analysis, and we could identified some genes and proteins with known and unknown biological functions. Neural stem cells prepared from the NSS were demonstrated to be induced to differentiate into astrocytes by withdrawing fibroblast growth factor-2 from the medium without any additional instruction.