Adult rat otic placode-derived neurons and sensory epithelium express all four erbB receptors: A role in regulating vestibular ganglion neuron viability

The erbB receptor family consists of erbB1/epidermal growth factor receptor , erbB2/neu, erbB3, and erbB4, all of which have been implicated in cell pr oliferation, differentiation, and survival in several tissues. In the nervo us system, these family members can function in a trophic capacity for cert ain subpopulations of neurons and some types of non-neuronal cells. Vestibu lar sensory epithelial cells and vestibular ganglion neurons are derived fr om ectodermal otic placode and are essential components of the peripheral v estibular system, the sensory system for balance. Recent studies in mammals suggest that certain ligands of the epidermal growth factor receptor can i nduce proliferation of vestibular sensory epithelial cells. We now show tha t vestibular ganglion neurons and vestibular sensory epithelial cells expre ss all four erbB receptors in adult rats. Cultured vestibular ganglion neur ons also expressed all four erbB family members and were therefore used to analyze the effects of modulating erbB signaling on differentiated vestibul ar ganglion neurons. Transforming growth factor-alpha (a ligand for epiderm al growth factor receptor) and sensory and motor neuron-derived factor (a l igand for erbB3 and erbB4) promoted vestibular ganglion neuron viability, w hereas epidermal growth factor (another ligand for epidermal growth factor receptor) did not. Glial growth factor 2 (another ligand for erbB3 and erbB 4) and an antibody that blocks erbB2/neu-mediated signaling inhibited vesti bular ganglion neuron viability. Collectively, these observations indicate that erbB signaling regulates the viability of differentiated otic placode- derived cells in mammals and suggest that exogenous modulation of erbB sign aling in peripheral vestibular tissues may prove therapeutically useful in peripheral vestibular disorders.