Fibroblast growth factor 8 (FGF-8) is a member of the fibroblast growth factor family. It is discovered as a growth factor essential for the androgen--dependent growth of mouse mammary carcinoma cells. Mouse FGF-8b shares 100% aa identity with human FGF-8b. FGF-8 is widely expressed during embryogenesis, and mediates epithelial--mesenchymal transitions. It plays an important role in the regulation of embryonic development, cell proliferation, cell differentiation and cell migration. It is required for normal brain, eye, ear, limb development during embryogenesis and normal development of the gonadotropin-releasing hormone (GnRH) neuronal system.