GMFB,Glia maturation factor beta,is a nerve growth factor implicated in nervous system development. It was reported that GMF-beta promotes the phenotypic expression of glia and neurons and inhibits the proliferation of their respective tumors in culture cells. GMF-beta protein is specific to the brain where it is expressed in glial cells (mainly astrocytes) and insome neurons. Higher levels of GMFB were found in the central nervous system,except for the spinal cord,and in thymus and colon.