Fig. 9. A hypothetical model for the function of Notch signaling during mouse ENS development. The NCCs begin to express Sox10 when they detach from the neural tube at around E8.5. After arriving at the foregut (E9.5), a subset of the NCCs begins to express Mash1. In turn, Mash1 suppresses Sox10 expression, and Mash1-positive cells then eventually produce neurons. The remaining NCCs continue to express Sox10 to maintain the pool of ENS progenitors. Notch signaling might be required for the continuous expression of Sox10 by suppressing Mash1. TC cells, transient catecholaminergic cells (see Discussion).