Fibroblast Growth Factor-6 (FGF-6) is a cytokine belonging to the heparin-binding member of the FGF family. Members of this family possess broad mitogenic and cell survival activities, and are involved in a variety of biological processes, including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion. FGF-6 binds and signals through the FGF receptors: FGFR1 and FGFR4. It is also required for normal muscle regeneration. In vivo high concentration of recombinant FGF-6 up-regulates and down-regulates FGFR1 and FGFR4, respectively, as FGFR1 promotes the proliferation while FGFR4 promotes the differentiation in the muscle. FGF6 gene displayed oncogenic transforming activity when transfected into mammalian cells. Despite the function in muscle protection against mechanical damage, FGF6 overexpresses in developmental heart and regulates osteoblasts and osteoclasts for bone remodeling.