Fibroblast growth factor 9 is also known as FGF9, GAF, HBFG-9, SYNS3, and is a member of the fibroblast growth factor (FGF) family. FGF family members 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. FGF9 is also a mitogen for oligodendrocyte type 2 astrocyte progenitor cells, smooth muscle cells, pheochromocytoma PC12 cells, and BALB/3T3 fibroblasts. However, unlike FGF acidic and basic, FGF9 has no effect on human umbilical vein endothelial cells, and it has been demonstrated that FGF9 binds preferentially to the IIIc form of FGFR3. Although no typical signal sequence was found in FGF9, it is secreted efficiently after synthesis not in a conventional manner. In nervous system, FGF9 is produced mainly by neurons and may plays an important role in CNS development. FGF9 has been shown to interact with Fibroblast growth factor receptor 3.