We focused our examination on SNP markers in the region of the alternatively spliced exons 9, 17 and 18, the intron 13 region containing the complementary sequence required for RNA editing and the glutamine-to-arginine coding change in exon 13 (Barbon & Barlati 2000) and the 3’UTR (Figure 1). To provide sufficient statistical power to detect an association to phenotype, we focused on SNPs with minor allele frequencies >10%. Six tag SNPs were identified using the Tagger algorithm (de Bakker et al. 2005) incorporated in the HapMap CEPH European ancestry dataset release 21a based on the NCBI B35 assembly covering the 100kb 3’ region of GRIK1 extending from the distal portion of intron 7 to 30 kb 3’ of exon 17 (chromosome 21 position 29,800,000–29,900,000). These six Tag SNPs captured 27 of 29 known SNPs genotyped in the CEPH sample with an average R2 of 0.927. Two recombination hot spots are annotated in the HapMap dataset in this genomic interval and occur in the proximal region of intron 9, approximately 15kb distal to the alternatively spliced exon 9. We also examined rs2832407, midway between these recombination hot spots.
