GMF-beta is a 17-kDa brain-specific protein that was isolated from bovine brain homogenate as a substance inducing the maturation of normal neurons as well as glial cells, and at first, it was considered to be a neurotrophic factor. The amino acid sequence of GMFB is highly conserved among many species, suggesting that it plays basic roles across many species. The expression of GMF-b is largely limited to the brain, especially the glial cells and some neurons. Schwann cells of the distal segment of the transected nerve express GMF-b, and this induction of GMF-b coincides with the temporal expression of nerve growth factor receptors in the cell.