Study on GRIA2, GRIA3 and GRIA4 genes highlights a positive association between schizophrenia and GRIA3 in female patients.

Impairment of glutamatergic neurotransmission is one of the major hypotheses proposed to explain the neurobiology of schizophrenia. Therefore, the genes involved in the glutamate neurotransmitter system could be considered potential candidate genes for schizophrenia susceptibility. A systematic study on alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor genes has been carried out and the results obtained from the analysis on GRIA2, GRIA3 and GRIA4 are reported. No evidence of association with schizophrenia was found for the GRIA2 and GRIA4 genes; strong evidence of association with schizophrenia was found for GRIA3. This X-linked gene showed a different behavior in the two genders; a positive association with schizophrenia was observed among females but not in males. Female carriers of rs1034428 A allele were found to have a 2.19-fold higher risk of developing schizophrenia compared to non-carriers and 3.28-fold higher risk for developing a non-paranoid phenotype. The analysis at the haplotype level showed that susceptibility to schizophrenia was associated with the specific haplotype rs989638-rs1034428-rs2227098 CAC (P = 0.0008). We conclude that, of the three AMPA genes analyzed here, only GRIA3 seems to be involved in the pathogenesis of schizophrenia, but only in females.

Mitochondrial DNA haplogroups and age at onset of schizophrenia.

A number of studies support a possible link between mitochondrial dysfunction and schizophrenia. To test the hypothesis of a direct contribution of mitochondrial DNA (mt-DNA) in susceptibility to DSM-IV-TR-schizophrenia, we looked for differences in the frequency distribution of the major European haplogroups (hgs) in 142 patients and 190 controls both of Italian origin. A subgroup of patients (N = 37) and healthy counterparts (N = 41) was also analyzed for possible differences in the relative amount of mt-DNA versus nuclear-DNA in blood cells. Patients and controls were comparable for hg frequency distribution and the relative levels of mt-DNA even after stratification by gender and schizophrenia subtype. However, patients harboring the hg J-T showed an anticipated onset of the disorder. These results indicate that the J-T hg of mt-DNA may have a modulator effect on deeper determinants of schizophrenia.

Glutamate AMPA receptor subunit 1 gene (GRIA1) and DSM-IV-TR schizophrenia: a pilot case-control association study in an Italian sample.

Glutamatergic dysfunction is one of the major hypotheses for the pathogenesis of schizophrenia. The GRIA1 gene encodes for one (GluR1) of the four (GluR1-4) ionotropic AMPA receptor subunits. GRIA1 is a good candidate gene for susceptibility to schizophrenia since it maps in 5q33, a region where the presence of susceptibility loci has been suggested by independent genome-wide scans and because its expression has been found to be decreased in the brain of some schizophrenia patients. We present data from a case-control association study on the Italian population with eight polymorphisms spanning the whole GRIA1 gene. Single-locus analysis revealed a significantly different allele distribution in cases and in controls of two SNPs (rs707176, 0.41 vs. 0.31, P = 0.009; rs2963944, 0.41 vs. 0.30, P = 0.007), and one microsatellite (rs10631988, allele 9: 0.40 vs. 0.29, P = 0.004). Haplotype analysis showed an increased frequency of a specific haplotype for these markers (C09CC, 0.39 vs. 0.28, P = 0.009). Therefore our data indicate that GRIA1 may be involved in susceptibility to DSM-IV-TR schizophrenia.