GENOMIC ORGANIZATION, PROMOTER ANALYSIS, AND CHROMOSOMAL LOCALIZATIONOF THE GENE FOR THE MOUSE GLIAL HIGH-AFFINITY GLUTAMATE TRANSPORTER SLC1A3

The mouse gene encoding glial high-affinity, Na+-dependent glutamate t ransporter Slc1a3 (GluT-1/GLAST) was isolated, and its structural orga nization was characterized. The gene appeared to exist as a single cop y in the mouse genome and comprised 10 exons spanning more than 56 kil obases. The transcription initiation sites were mapped to positions 50 3, which is the first transcriptional point (defined as +1), 128 (+376 ), and 64 (+440) basepairs upstream of the 3'-end of exon 1 by primer extension. The 5'-flanking region of the mouse GluT-1 gene had a typic al CCAAT box and a GC box but lacked a TATA box. These features of the promoter region were characteristic of housekeeping genes. The fusion plasmids containing approximately 4 kb of the 5'-flanking region (-38 30 to +450) and the firefly luciferase gene induced a significant luci ferase activity when transfected into COS-1 cells. Distal deletion of the 5'-flanking region, leaving 619 bp (-169 to +450), resulted in a m arked decrease in luciferase activity in COS-1 cells, suggesting that a CCAAT box, which was positioned at -200, is necessary for the expres sion of this gene. In situ hybridization localized this gene to mouse chromosome 15A2. These structural features will lead to a better under standing of the regulatory mechanism of the expression of the GluT-1 g ene by ischemia and will also provide a basis for future evolutionary comparisons with other neurotransmitter transporters. (C) 1996 Academi c Press, Inc.