Dopamine neurotransmissin is thought to play a relevant role in behavioral reinforcement system. Polymorphism of the genes involved in dopamine system has been reported for association with ...psychological traits related to impulsive and sensation seeking behaviors. The study was aimed at a search for association of catechol-O-metyltransferase (COMT) and dopamine receptor D4 (DRD4) gene polymorphism with personality traits in Russian population. A sample comprised 130 subjects. It was found that carriers of the Met/Met COMT genotype had higher scores of novelty seeking as compared to those with the Val/Val and Met/Met genotypes. The association was observed in women only. In the presence of the C allele of the DRD4 gene, females with the Met/Met genotype demonstrated higher scores on extraversion and hypomania. The results are consistent with the current theoretical concepts on the regulation of dopamine neurotransmission in the brain.
The synaptosomal-associated protein (SNAP-25) plays an integral role in synaptic transmission and in memory consolidation in the hippocampus. Recently an association between SNAP-25 gene polymorphism ...and cognitive ability has been reported in two independent studies of healthy people and patients with schizophrenia. Authors carried out an association study of MnlI SNAP-25 polymorphism and performance on neurocognitive tests measuring verbal memory, attention/executive functions in 66 patients with major psychosis, 75 their relatives and 136 controls. MANCOVA revealed a significant effect of group (small er, Cyrillic=0,00001) and genotype (small er, Cyrillic=0,012) as well as an interaction effect between group and genotype (small er, Cyrillic=0,02) on the performance on neurocognitive tests. Carriers of the TT genotype performed worse on the most tasks compared to other genotypes. The similar character of the MnlI SNAP-25 polymorphism effect on the variability of neurocognitive traits in all groups suggests the relationship between this gene and general cognitive ability.
The changes of P300 parameters (lower amplitude and increased latency) are thought to be the most prominent phenomena of schizophrenia. A role of gene polymorphism in P300 generation was supported by ...several associative studies in psychiatrically well subjects and patients with mental disorders. We studied P300 parameters and the following polymorphisms: T102C for the serotonin receptor type 2A (5-HTR2A) gene, the 5-HTTLPR for the serotonin transporter gene, -809G/A, -616G/C N -52C/T SNPs in the promoter region of the dopamine D4 receptor (DRD4) gene and the Val158Met polymorphism of the catechol-O-methyltransferase (COMT) in 74 patients with schizophrenia and spectrum disorders and 71 their first-degree relatives. No association was found between serotonergic system genes and P300. The -809G/A DRD4 gene polymorphism was related to amplitude in all frontal leads (p=0,01) in patients. In relatives, an association was observed between -521C/T DRD4 variants and latency (p=0,005) as well as between the COMT gene polymorphism and P300 amplitude (p=0,004) at the central lead. Thus, the genes involved in dopaminergic system play a role in P300 generation both in patients with schizophrenia and spectrum disorders and their relatives.
A vast body of associative studies reported a role of highly polymorphic dopamine receptor DRD4 gene in regulation of emotional processes and development of mental disorders. The present study ...addresses allele, genotype and haplotype distribution of 3 polymorphic DRD4 markers (-809G/A, -616G/C N -521C/T) in Russian patients with schizophrenia spectrum disorders and their relation to the disease and personality traits. A sample included 151 patients with iCD-10 diagnosis of schizophrenia, schizoaffective psychosis and schizotypal personality disorders, 89 their first-degree non-psychotic relatives and 131 mentally healthy individuals. No differences in allele and genotype frequency was found between the patients and the controls. Transmission disiquilibrium test (TDT) did not reveal a preferential transmission of either allele from parents to proband. The 521C/T N -616G/C markers were linked to the disease when the EH program has been used in the analysis. Patients with the GG (-809G/A) and GG (-616G/C) genotypes had higher scores on the Hypomania scale (MMPI) comparing to the GA(-809G/A)+AA(-809G/A) and GC(-616G/C)+CC(-616G/C) genotypes but the association did not reach a level of significance (p = 0.06). The results confirmed the literature reports on the relation of the DRD4 gene to schizophrenia and personality traits related to social activity.
