title: No association of DRD2, DRD3, and tyrosine hydroxylase gene polymorphisms with personality traits in the Japanese population.
abstract: BACKGROUND
  Dopamine D2 receptor (DRD2) and dopamine D3 receptor (DRD3) genes could be candidates for personality-related genes considering their pharmacological profiles or structures. However, a limited number of studies have investigated the association between these genes and personality traits. In the present study, we investigated the DRD2, DRD3, and tyrosine hydroxylase (TH) genes in relation to personality traits in the Japanese population. Epistasis (gene-gene interaction) among the genes was extensively analyzed, in addition to the analysis based on each gene.
  
  
  METHODS
  The -241A/G, -141C Ins/Del, and Ser311Cys polymorphisms in the DRD2 gene, the Ser9Gly polymorphism of the DRD3 gene, and the Val81Met and PstI site polymorphisms in the TH gene were genotyped in 257 healthy Japanese subjects. Personality traits were evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and the State-Trait Anxiety Inventory (STAI). The associations between gene polymorphisms and the scores for NEO PI-R or Trait Anxiety of STAI were statistically analyzed by one-way analysis of covariance (ANCOVA) adjusting sex and age. Epistasis was assessed using two-way ANCOVA between the polymorphisms of independent two genes.
  
  
  RESULTS
  In the analysis based on each gene, trends for association were observed between State Anxiety and the DRD2 -141C Ins/Del polymorphism (p = 0.031, uncorrected), and between Trait Anxiety and the DRD2 Ser311Cys or TH PstI site polymorphism (p = 0.048 and 0.041, respectively, uncorrected). In epistatic analysis, a trend for interaction was observed on the scores for Neuroticism and Trait Anxiety between the DRD2 -141C Ins/Del and TH Val81Met polymorphisms (p = 0.015 and 0.010, respectively, uncorrected). However, these differences were insignificant after Bonferroni correction.
  
  
  CONCLUSIONS
  The present study did not provide evidence for the association between these dopamine-related genes and personality traits in the Japanese population.
authors.affiliation: Department of Neuropsychiatry, Graduate School of Medicine, University of Tokyo, Tokyo, Japan. hibinoh-tky@umin.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hibino
authors.forename: Mamoru
authors.initials: M
authors.lastname: Tochigi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Otowa
authors.forename: Nobumasa
authors.initials: N
authors.lastname: Kato
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Sasaki