The molecular and functional properties of neurotransmitter ligand-gated ion channels in glial cells were studied, in order to understand their regulation and function in the brain. Studies were carried out to: A. characterize the physiological and molecular properties of glutamate- gated ion channels in glia and B. to clone a glutamate receptor gene and analyze its 5' regulatory region in order to understand its transcriptional regulation in glia. A. Physiological and molecular properties. Primary cultures of rat oligodendrocyte progenitors (O-2A) and the primary cell line CG-4, derived from rat O-2A cells, were used as a model system. CG-4 and primary O-2A cells develop to oligodendrocytes in vitro similarly to O- 2A progenitors in vivo. In both types of cultures, the intermediate filament protein nestin, highly expressed in neuroepithelial cells in vivo, is found at the O-2A stage, but down-regulated in differentiated oligodendrocytes. A similar downregulation of nestin expression was also demonstrated in oligodendrocytes in vivo. Kainate- and AMPA-preferring glutamate receptors are co-expressed in cells of the oligodendrocyte lineage. Intracellular Ca2+ transients, due to transmembrane influx of the divalent cations, and immediate early gene (NFI-A and c-fos) transcription are regulated by glutamate receptors in cells of the oligodendrocyte lineage. Genes encoding kainate-preferring glutamate receptor subunits are expressed very early in neural development (embryonic day 10 rat embryos) and in undifferentiated, nestin-positive multi-potential precursors of the rat neural tube. B. Glutamate receptor genes and analysis of their 5' regulatory region. Genes encoding kainate receptor subunits are highly expressed in cells of the oligodendrocyte lineage, as determined by Northern blot and RT-PCR analysis of total RNA. The cloning of one of these subunit genes (GRIK5, which encodes the kainate-preferring subunit KA2) was accomplished. Two kb of the 5' regulatory region of the rat GRIK5 were sequenced and analyzed, as well as their transcriptional potential in oligodendrocyte progenitors of the CG-4 cell line. The chromosomal and subchromosomal localization of GRIK4 (encoding the kainate preferring subunit KA1) and GRIK5 was determined in mouse, rat and human by interspecific backcross mapping, Southern analysis of cell hybrid panels and fluorescence in situ hybridization. In all three species, GRIK4 and GRIK5 were found to map on separate chromosomes.
| Gallo, V; Ghiani, C A (2000) Glutamate receptors in glia: new cells, new inputs and new functions. Trends Pharmacol Sci 21:252-8 |
| Ghiani, C A; Yuan, X; Eisen, A M et al. (1999) Voltage-activated K+ channels and membrane depolarization regulate accumulation of the cyclin-dependent kinase inhibitors p27(Kip1) and p21(CIP1) in glial progenitor cells. J Neurosci 19:5380-92 |
