Growth Arrest-Specific Protein 7 (GAS7) is expressed primarily in terminalaly differentiated brain cells and predominantly in mature cerebellar Purkinje neurons. GAS7 may play a role in neuronal development by promoting maturation and morphological differentiation of cerebellar neurons. Inhibition of GAS7 production in terminally differentiating cultures of embryonic murine cerebullum impedes neurite outgrowth. The hyper-expression of GAS7 may play an major role in the initiation and development of huaman osteosarcoma.