MOLECULAR-CLONING AND DIFFERENTIAL EXPRESSION PATTERNS OF AVIAN GLUTAMATE-RECEPTOR MESSENGER-RNAS

We have identified and studied potential ionotropic glutamate receptor genes in pigeon brain. Three cDNA clones exhibit significant amino ac id sequence identity to members of a rodent ligand-gated ion channel f amily. One of them, GluP-II, encodes a full-length AMPA-sensitive glut amate receptor GluR2 (GluR-B) homologue, whereas the other two partial clones, designated as GluP-III and -IV, are nearly identical to roden t GluR3 (GluR-C) and GluR4 (GluR-D) receptor subunits. Northern analys is demonstrated that the avian genes are widely expressed in the brain . Within the brain regions analyzed by in situ hybridization histochem istry, the three avian GluR subunits showed distinct and regionally sp ecific mRNA expression patterns in the adult. Most of the differences in their expression were observed in cell types of the telencephalon, certain thalamic nuclei, the optic tectum, and the cerebellar cortex. A particularly striking finding was the expression of GluP-II in Golgi epithelial/Bergmann glial cells. in contrast, Bergmann glial cells in rat cerebellum do not express GluR2 (GluR-B) subunit genes. Immunorea ctivity for a monoclonal sequence-specific antipeptide antibody was wi despread and most prominent in Purkinje cell perikarya and their dendr ites, neuronal cell bodies of the ectostriatum, and the deep optic tec tum. These results demonstrate the existence of multiple subunits of t he ionotropic glutamate receptor channel family in avians. Excitatory amino acid receptor genes appear to be highly conserved during evoluti on.