Figure 4.

Dynamic expression in neural stem/progenitor cells. Hes1 expression oscillates with a period of ∼2–3 h in neural progenitor cells. In these cells, Ngn2 and Dll1 expression also oscillates. Hes1 protein expression exhibits an inverse correlation with Ngn2 protein and Dll1 mRNA expression. In contrast, the expression of Ngn2 and Dll1 is sustained in post-mitotic neurons, which lose Hes1 expression. It is likely that Dll1 oscillation periodically activates Notch signaling between neighboring cells. This reciprocal regulation is particularly important for the maintenance of neural stem/progenitor cells before the formation of neurons.