FGFR3 expression during development and regeneration of the chick inner ear sensory epithelia

Several studies suggest fibroblast growth factor receptor 3 (FGFR3) plays a role in the development of the auditory epithelium in mammals. We undertoo k a study of FGFR3 in the developing and mature chicken inner ear and durin g regeneration of this epithelium to determine whether FGFR3 shows a simila r pattern of expression in birds. FGFR3 mRNA is highly expressed in most su pport cells in the mature chick basilar papilla but not in vestibular organ s of the chick. The gene is expressed early in the development of the basil ar papilla. Gentamicin treatment sufficient to destroy hair cells in the ba silar papilla causes a rapid, transient downregulation of FGFR3 mRNA in the region of damage. In the initial stages of hair cell regeneration, the sup port cells that reenter the mitotic cycle in the basilar papilla do not exp ress detectable levels of FGFR3 mRNA. However, once the hair cells have reg enerated in this region, the levels of FGFR3 mRNA and protein expression ra pidly return to approximate those in the undamaged epithelium. These result s indicate that FGFR3 expression changes after drug-induced hair cell damag e to the basilar papilla in an opposite way to that found in the mammalian cochlea and may be involved in regulating the proliferation of support cell s. (C) 2001 Academic Press.