Glial cell-line-derived neurtrophic factor(GDNF) , neurturin(NTN) and persephin (PSP) define a new family of neurotrophic factors which are distant members of the transforming growth factor-β(TGF-β) superfamily and play widely physiological roles in vivo. Recent studies have revealed the existence of a novel family of multicomponent receptors for GDNF family, composed of distinct glycosyl-phosphatidylinositol(GPI)-linked cell surface proteins and a shared transmembrane tyrosine kinase receptor, Ret.