Fibroblast growth factor 8A (FGF-8A) is a member of the fibroblast growth factor (FGF) family and is an isoform of FGF-8. FGF-8A binds the FGF receptor (FGFR) and activates Ras/MAPK signaling (Hulstrand and Houston). The FGF family possesses broad mitogenic and cell survival activities (Folkman and Klagsbrun; Kimelman and Kirschner) and is involved in a variety of biological processes, including cell proliferation, differentiation, survival, and apoptosis (Folkman and Klagsbrun; Klagsbrun; Rifkin and Moscatelli). FGF-8 RNA is spliced to produce 4 protein isoforms in humans: FGF-8A, FGF-8B, FGF-8E, and FGF-8F. The functional differences are not fully understood; however, studies in zebrafish and Xenopus show that FGF-8A is required for endoderm morphogenesis and neurogenesis (Choe and Crump; Hulstrand and Houston).