Expression of neurturin, GDNF, and GDNF family-receptor mRNA in the developing and mature mouse

The GDNF family of neurotrophic factors currently has four members: neurturin (NRTN), glial cell line-derived neurotrophic factor (GDNF), persephin, and artemin. These proteins are potent survival factors for several populations of central and peripheral neurons. The receptors for these factors are complexes that include the Ret tyrosine kinase receptor and a GPI-linked, ligand-hinding component called GDNF family receptor α 1-4 (GFRα1-4). We have used in situ hybridization to study the mRNA expression of NRTN, GDNF, Ret, GFRαl, and GFRα2 during embryonic development and in the adult mouse. GDNF receptors were prominently expressed during embryonic development in the nervous system, the urogenital system, the digestive system, the respiratory system, and in developing skin, bone, muscle, and endocrine glands. In some regions, incomplete receptor complexes were expressed suggesting that other, as yet unidentified, receptor components exist or that receptor complexes are formed in trans. NRTN and GDNF were expressed in many trigeminal targets during embryonic development including the nasal epithelium, the teeth, and the whisker follicles. NRTN and GDNF were also expressed in the developing limbs and urogenital system. In the embryo, GDNF factors and receptors were expressed at several sites of mesenchyme/epithelial induction, including the kidney, tooth, and submandibular gland. This expression pattern is consistent with the possibility that the GDNF factors function in inductive processes during embryonic development and with the recently discovered role of NRTN as a necessary trophic factor for the development of some parasympathetic neurons. In the mature animal, receptor expression was more limited than in the embryo. In the adult mouse, NRTN was most prominently expressed in the gut, prostate testicle, and oviduct; GDNF was most prominently expressed in the ovary.