Roles of fibroblast growth factor 2 during innervation of the avian inner ear

The importance of individual members of the fibroblast growth factor gene f amily during innervation of the vertebrate inner ear is not clearly defined . Here we address the role of fibroblast growth factor 2 (FGF-2 or basic FG F) during development of the chicken inner ear. We found that FGF-2 stimula ted survival of isolated cochlear and vestibular neurons during distinct ph ases of inner ear innervation. The potential neurotrophic role of FGF-2 was confirmed by its expression in the corresponding sensory epithelia and the detection of one of its high-affinity receptors in inner ear neurons. Fina lly, we have analysed the potential of the amplicon system based on defecti ve herpes simplex virus type 1 (HSV-I) vectors to express FGF-2 in cochlear neurons. Overexpression of FGF-2 in cochlear neurons resulted in neuronal differentiation demonstrating the presence of biologically active growth fa ctor. This study underlines the potential of FGF-2 to control innervation a nd development of sensory epithelia in the avian inner ear. Furthermore, am plicon vectors may provide a useful tool to analyse gene function in isolat ed neurons of the vertebrate inner ear.