Neurog1, Neurod1, and Atoh1 are essential for spiral ganglia, cochlear nuclei, and cochlear hair cell development.

We review the molecular basis of three related basic helix-loop-helix (bHLH) genes (, , and ) and upstream regulators , , , , , , and during the development of spiral ganglia, cochlear nuclei, and cochlear hair cells. Neuronal development requires early expression of , followed by its downstream target , which downregulates expression. In contrast, hair cells and cochlear nuclei critically depend on and require and expression for various aspects of development. Several experiments show a partial uncoupling of (spiral ganglia and cochlea) and (cochlear nuclei). In this review, we integrate the cellular and molecular mechanisms that regulate the development of auditory system and provide novel insights into the restoration of hearing loss, beyond the limited generation of lost sensory neurons and hair cells.