Expression of mouse fibroblast growth factor and fibroblast growth factor receptor genes during early inner ear development.

The inner ear, which mediates hearing and equilibrium, develops from an ectodermal placode located adjacent to the developing hindbrain. Induction of the placode and its subsequent morphogenesis and differentiation into the inner ear epithelium and its sensory neurons, involves signalling interactions within and between otic and non-otic tissues. Several members of the fibroblast growth factor (FGF) family play important roles at various stages of otic development; however, there are additional family members that have not been evaluated. In this study, we surveyed the expression patterns of 18 mouse Fgf and 3 Fgf receptor (Fgfr) genes during early otic development. Two members of the Fgf family, Fgf4 and Fgf16, and all three tested members of the Fgfr family, Fgfr2c, Fgfr3c, and Fgfr4, were expressed in tissues relevant to inner ear development. Fgf4 transcripts were expressed in the preplacodal and placodal ectoderm, suggesting potential roles in placode induction and/or maintenance. Fgf16 was expressed in the posterior otic cup and vesicle, suggesting roles in otic cell fate decisions and/or axis formation.