Glial cell-derived neurotrophic factor (GDNF) is a neurotrophic factor that is a member of the TGF-β superfamily. GDNF is founding member of the GDNF family of ligands, which to date include GDNF, neurturin (NTN), persephin (PSP) and artemin (ART). GDNF is a glycosylated disulfide-linked homodimeric protein of ~15 kDa. Mature rat and human GDNF share 93% sequence homology with strong species cross-reactivity. GDNF promotes survival of various neuronal cells in central and peripheral nervous systems and different stages of development including motoneurons, midbrain dopaminergic neurons, Purkinje cells, and sympathetic neurons. Cells known to express GDNF include Sertoli cells, type 1 astrocytes, Schwann cells, neurons, pinealocytes, and skeletal muscle cells. In addition, exogenously applied GDNF has been shown to rescue damaged facial motor neurons in vivo.