FGF signaling in ear development and innervation

The 22 mammalian fibroblast growth factors (FGFs) acting through seven main receptor tyrosine kinase isoforms play roles in controlling the growth, differentiation, motility, and survival of cells during development. A variety of experimental approaches have begun to reveal the ways in which FGF signaling is used to control the development of the outer, middle, and inner ears. Structurally related groups of FGFs have similar receptor binding specificity in vitro and in cultured cells. For some aspects of ear development, both the relevant FGF ligand and receptor is known. In other cases, only one member of the pair has been determined, but plausible candidates can be proposed based on expression data. Despite the large number of distinct roles for FGF signaling that have been uncovered in the developing auditory system to date, it is clear that we have only begun to scratch the surface of this topic. Future studies aimed at uncovering redundant functions of FGFs and unraveling the later functions of FGFs that are required for early stages of development will help in defining the full complement of roles for FGF signaling in otic development. © 2003 Elsevier Inc. All rights reserved.