Figure 5.

Maintenance of neural stem/progenitor cells by the mutual activation of Notch signaling. Ngn2 and Dll1 oscillations are regulated by Hes1 oscillation in neural stem/progenitor cells. Ngn2 oscillation may be advantageous for the maintenance/proliferation of neural stem/progenitor cells during the early stages of development, because it induces Dll1 expression and activates Notch signaling without promoting neuronal differentiation. A salt-and-pepper pattern induced by lateral inhibition is just a snapshot of oscillatory expression. The precise interactive regulation among Dll1-positive and -negative cells remains to be determined.