Determination of the genomic structure and mutation screening in schizophrenic individuals for five subunits of the N-methyl-D-aspartate glutamate receptor

Abstract

The glutamatergic system is the major excitatory neurotransmitter system in the CNS. Glutamate receptors, and in particular N-methyl-D-aspartate (NMDA) receptors, have been proposed as mediators of many common neuropsychiatric phenotypes including cognition, psychosis, and degeneration. We have reconstructed the genomic structure of all five genes encoding NMDA receptors in silico. We screened each for sequence variation and estimated the allele frequencies of all detected SNPs in pooled samples of 184 UK Caucasian schizophrenics and 184 UK Caucasian blood donor controls. Only a single non-synonymous polymorphism was found indicating extreme selection pressure. The rarity of non-synonymous changes suggests that such variants are unlikely to make a common contribution to common phenotypes. We found a further 26 polymorphisms within exonic or adjacent intronic sequences. The minor alleles of most of these have a relatively high frequency (63% above 0.2). These SNPs will therefore be suitable for studying neuropsychiatric phenotypes that are putatively related to NMDA dysfunction. Pooled analysis provided no support for association between any of the GRIN genes and schizophrenia.

Follow-up of genetic linkage findings on chromosome 16p13: evidence of association of N-methyl-D aspartate glutamate receptor 2A gene polymorphism with ADHD

“…To confirm these markers were not appreciably enriched in the ADHD sample, we initially genotyped all six polymorphisms in pooled samples of 100 UK Caucasian ADHD cases in DNA pools. 15 All fragments were amplified using primers and conditions described by Williams et al 2 This analysis confirmed that the minor alleles for three of the variants were at frequencies below the resolution of the pooling method, which empirically, we have found to be o2%. The other three SNPs were genotyped in the original association sample (n ¼ 161 families) by single nucleotide primer extension using a fluorescence polarisation (FP) assay 16 based upon AcycloPrimet reagents (Perkin Elmer Life Science Products, Boston, MA, USA) according to the manufacturer's recommendations.…”

“…2 This sample has power of 0.8 to detect alleles with a frequency of 0.05 in the sampled population. As we have previously shown 2 that the allele frequencies at GRIN2A are the same in schizophrenics and the general population, our power estimate of 0.8 to detect alleles with a frequency of 0.05 in the general population applies.…”

“…Given this, genes encoding glutamate receptors represent candidate genes of interest for neuropsychiatric disorders. 2 There are two classes of glutamate receptor, ionotropic and metabotropic. Ionotropic receptors are further classified based on their binding to a range of ligands into N-methyl D-aspartate receptors (NMDA), alpha-amino-3 hydroxy-5-methyl-4-isoxazole propionate receptors (AMPA), kainate (KA) and delta receptors.…”

The molecular genetics of schizophrenia: new findings promise new insights

“…With recent developments in genome analysis and the recent publication of a working draft of the human genome sequence, 80 these data are being rapidly extended to other systems including the glutamatergic, GABAergic, and genes involved in neuromodula-tion and neurodevelopment. 81 It is impossible for us to present the results of the many candidate gene studies that have been published or reported at meetings. However, for the reasons outlined, the overwhelming number of negative reports cannot be considered as definitive exclusions of small genetic effects.…”

Association study between the NMDA receptor 2B subunit gene (GRIN2B) and schizophrenia: A HuGE review and meta-analysis

“…1 teria. One reference 16 was excluded for insufficient and equivocal data, one reference 17 was excluded for association with clozapine, and one reference 18 was excluded on the grounds of being a linkage study. Finally, six references 5,19 -23 met our criteria for inclusion.…”