Association between tridimensional personality questionnaire (TPQ) traits and three functional polymorphisms: Dopamine receptor D4 (DRD4), serotonin transporter promoter region (5-HTTLPR) and catechol O-methyltransferase (COMT)

Dopamine D4 receptor (DRD4), serotonin transporter promoter regulatory region (5-HTTLPR) and catechol O-methyltransferase (COMT) polymorphisms were examined for association with TPQ personality factors in 455 subjects. Significant interactions were observed by multivariate analysis, (COMT x 5-HTTLPR: Hotelling's Trace = 2.3, P = 0.02) and by subsequent univariate 3-way ANOVA when Novelty Seeking (NS) was the dependent variable: 5-HTTLPR x D4DR (F = 6.18, P = 0.03) and COMT x 5-HTTLPR (F = 4.42, P = 0.03). In the absence of the short 5-HTTLPR allele and in the presence of the high enzyme activity COMT val/val genotype, NS scores are higher in the presence of the DRD4 seven-repeat allele. The effect of these three polymorphisms on NS was also examined using a within-families design. Siblings who shared identical genotype groups for all three polymorphisms (COMT, DRD4 and 5-HTTLPR) had significantly correlated NS scores (intraclass coefficient = 0.39, F= 2.26, P = 0.008, n = 49) whereas sibs with dissimilar genotypes in at least one polymorphism showed no significant correlation for NS scores (intraclass coefficient = 0.177, F = 1.43, P = 0.09, n =110). Similar interactions were also observed between these three polymorphisms and Novelty Seeking when the 150 independently recruited and non-related subjects were analyzed. The current results are consistent with two earlier reports in which we demonstrated an interaction between the 5-HTTLPR and DRD4 polymorphisms in 2-week-old neonates, in the same children assessed again at 2 months of age and in adults.