Neurotrophin-3 (NT-3), encoded by the NTF3 gene, is a member of the NGF family of neurotrophic factors (also named neurotrophins). The neurotrophin family is comprised of at least four proteins including NGF, BDNF, NT-3, and NT-4/5. These secreted cytokines are synthesized as prepropeptides that are proteolytically processed to generate the mature proteins. Their functions including supporting the survival and differentiation of existing neurons, encouraging the growth and differentiation of new neurons and synapses, are required in both the central and the peripheral nervous systems. NT-4 signals predominantly through the TrkB receptor tyrosine kinase. NTF3-deficient mice generated by gene targeting display severe movement defects of the limbs. The mature peptide of this protein is identical in all mammals examined including human, pig, rat and mouse.