Isoforms of receptors of fibroblast growth factors.

The breadth and scope of Fibroblast Growth Factor signaling is immense, with documentation of its role in almost every organism and system studied so far. FGF ligands signal through a family of four distinct tyrosine kinase receptors, the FGF receptors (FGFRs). One contribution to the diversity of function and signaling of FGFs and their receptors arises from the numerous alternative splicing variants that have been documented in the FGFR literature. The present review discusses the types and roles of alternatively spliced variants of the FGFR family members and the significant impact of alternative splicing on the physiological functions of five broad classes of FGFR isoforms. Some characterized known regulatory mechanisms of alternative splicing and future directions in studies of FGFR alternative splicing are also discussed. Presence, absence, and/or the combination of specific exons within each FGFR protein impart upon each individual isoform its unique function and expression pattern during normal function and in diseased states (e.g., in cancers and birth defects). A better understanding of the diversity of FGF signaling in different developmental contexts and diseased states can be achieved through increased knowledge of the presence of specific FGFR isoforms and their impact on downstream signaling and functions. Modern high-throughput techniques afford an opportunity to explore the distribution and function of isoforms of FGFR during development and in diseases.