NeuroD is a basic helix-loop-helix (bHLH) transcription factor that is expressed in the pancreas, central and peripheral nervous systems during embryonic development (Naya et al., 1997;Miyata et. al., 1999;Liu et al., 2000;Kim et al., 2001). Deletion of the NeuroD gene in mice results in deafness and head tilting/circling behavior due to the loss of cochlear and vestibular neurons respectively (Liu et al., 2000;Kim et. al., 2001). The aim of this study is to examine the role of NeuroD in the development of the afferent neurons of the cochlea and vestibular organs. Previous results from studies in Xenopus indicate that NeuroD is capable of converting epidermal cells into neurons, but the ability of this gene to specify cochlear and/or vestibular neurons during inner ear development is unknown (Lee et. al., 1995). The proposed experiments will (1): determine whether expression of NeuroD is sufficient for cochlear and/or vestibular neuron development, and (2): determine whether interfering with NeuroD expression can alter neuronal development and/or pathfinding. PUBLIC HEALTH RELEVANCE: These data will further elucidate the role of NeuroD in the development of inner ear neurons. In addition, characterization of the molecular pathways involved in early development of inner ear neurons should assist in clinical strategies to regenerate cochlear and vestibular neurons in the human ear.