Hedgehog and Notch signaling in enteric nervous system development.

The enteric nervous system (ENS) in mammals is derived from a small pool of progenitor cells, namely enteric neural crest cells (NCCs). These precursor cells proliferate extensively to expand, migrate over a long distance to fully colonize the developing gut and differentiate into millions of neurons and glia to form a functional ENS for regulating the complex behaviors of the gut. This developmental process relies on a precise regulation of the neuronal and glial differentiation and requires an appropriate balance between the migration, proliferation and differentiation of enteric NCCs and their progeny. Hedgehog (Hh) and Notch signalings are essential for almost every aspect of ENS development, and they confer both the long- and short-range signals to coordinate these seemingly diverse cellular processes. In this review, we summarize the roles of Hh and Notch signaling, particularly in the context of gut organogenesis and ENS development and emphasize how combinatory Hh and Notch signaling renders functional diversity as well as specificity.