[Polymorphic markers of the dopamine D4 receptor gene promoter region and personality traits in mentally healthy individuals from the Russian population].

The dopamine receptor gene D4 is a highly polymorphic gene, which, according to a number of studies, is associated with the personality traits characterizing human activity. Earlier, a VNTR polymorphic marker in exon 3 and single-nucleotide polymorphism in the promoter region were shown to be associated with novelty seeking. However, these results were not supported by all subsequent studies, which suggest a possible effect of other polymorphic regions of this gene. The aim of the present work was studying the effect of gene DRD4 on activity-related human personality traits in Russians, using in association analysis three polymorphic markers of this gene (-809 G/A, -616 C/G, and -521 C/T) and psychological traits assessed by various tests. Genotyping and psychological examination were conducted in 220 mentally healthy subjects (131 individuals lacking hereditary load of psychic diseases and 89 relatives of patients with psychoses). In Russians, allele frequencies of all markers proved to have no significant difference from the corresponding estimates for European populations. The markers examined were in linkage equilibrium. We have found a significant contribution of genotypes -521 C/T and -809 G/A to the expression of extraversion (Eysenck Personality Inventory (EPI), P = 0.0016) and variation of scores of the Social Introversion scale (Minnesota Multiphase Personality Inventory (MMPI), P = 0.0085). Genotypes -521 C/T and -616 C/G had a joint effect on scores on the Hypomania scale (P = 0.04), while their effect on extraversion was recorded as a trend (P = 0.054). Thus, the results of this study in general support the evidence by other authors showing association of polymorphism at the DRD4 gene promoter to personality traits. We have shown that the traits in question were mainly related to social activity. A reduction in social activity is associated largely with the T(-521 C/T) allele, characterized by low transcription rate.