Novel regional and developmental NMDA receptor expression patterns uncovered in NR2C subunit-beta-galactosidase knock-in mice.

NMDA receptor "knock-in" mice were generated by inserting the nuclear beta-galactosidase reporter at the NR2C subunit translation initiation site. Novel cell types and dynamic patterns of NR2C expression were identified using these mice, which were unnoticed before because reagents that specifically recognize NR2C-containing receptors are non-existent. We identified a transition zone from NR2C-expressing neurons to astrocytes in an area connecting the retrosplenial cortex and hippocampus. We demonstrate that NR2C is expressed in a subset of S100beta-positive/GFAP-negative glial cells in the striatum, olfactory bulb and cerebral cortex. We also demonstrate novel areas of neuronal expression such as retrosplenial cortex, thalamus, pontine and vestibular nuclei. In addition, we show that during cerebellar development NR2C is expressed in transient caudal-rostral gradients and parasagittal bands in subsets of granule cells residing in the internal granular layer, further demonstrating heterogeneity of granule neurons. These results point to novel functions of NR2C-containing NMDA receptors.