Plays an important role in the regulation of embryonic development, cell proliferation, cell differentiation and cell migration. May have a role in glial cell growth and differentiation during development, gliosis during repair and regeneration of brain tissue after damage, differentiation and survival of neuronal cells, and growth stimulation of glial tumors. Monomer. Homodimer. Interacts with FGFR1, FGFR2, FGFR3 and FGFR4. Affinity between fibroblast growth factors (FGFs) and their receptors is increased by heparan sulfate glycosaminoglycans that function as coreceptors. Glial cells. Three molecular species were found (30 kDa, 29 kDa and 25 kDa), cleaved at Leu-4, Val-13 and Ser-34 respectively. The smaller ones might be products of proteolytic digestion. Furthermore, there may be a functional signal sequence in the 30 kDa species which is uncleavable in the secretion step. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. Biochemical analysis of the Asn-99 mutation reveals a significantly impaired FGF signaling, as evidenced by diminished activity of the MAPK1/MAPK2 pathway and decreases CTNNB1 and MYC expression when compared with wild-type protein. Binding of mutant protein to the receptor FGFR3 is severely impaired, although homodimerization of mutant to itself or wild-type is not detectably affected, providing a basis for the observed defective FGF9 signaling. Belongs to the heparin-binding growth factors family.