Association analysis of polymorphisms in the upstream region of the human dopamine D4 receptor gene (DRD4) with schizophrenia and personality traits

The human dopamine D4 receptor (DRD4) is of major interest in molecular studies of schizophrenia and personality traits. We examined the association of schizophrenia and polymorphisms in the upstream region of the DRD4 gene (−768G>A in the negative modulator region; −521C>T, −376C>T, and −291C>T in the cell type-specific promoter region; and −616C>G between the two regions) in 208 schizophrenic patients and 210 normal controls. No significant difference in genotype and allele frequencies was observed between the two groups, indicating that these polymorphisms do not make a major contribution to the pathogenesis of schizophrenia. We also studied the association of polymorphisms in the upstream region and a 48-bp repeat polymorphism in exon III of the DRD4 gene with personality traits in 173 Japanese individuals who completed the temperament and character inventory (TCI). The −768G>A polymorphism was significantly associated with reward dependence (P = 0.044), while no significant association was observed between novelty seeking and polymorphisms in the upstream region or the exon III repeat polymorphism of the DRD4 gene. Received: August 28, 2000 / Accepted: October 25, 2000     

Non-association of dopamine D4 and D2 receptor genes with personality in healthy individuals

Recently, different research groups reported conflicting results with regard to an association of dopamine 4 receptor (DRD4) genotypes and the personality dimension of novelty seeking (NS). High scores for NS seemed to be associated with long alleles of a DRD4 polymorphism. Furthermore, an association between personality traits and the dopamine 2 (DRD2) receptor gene was reported. NS and persistence (PS) high scores seemed to be associated with alleles of DRD2. We examined 109 (78 female and 31 male) normal healthy individuals using Cloninger's Temperament and Character Inventory (TCI) in order to replicate these findings. We genotyped a 48 base pair variable number of tandem repeats (from two to eight repeats) polymorphism in the third exon of DRD4 and a Cys311Ser polymorphism in exon 7 of DRD2. We tested alleles and genotypes of DRD4 (allele 7 absent or present; genotype 4,4 versus 4,7), and Ser/Cys and Cys/Cys genotypes of DRD2 for associations with TCI values. NS and the alleles and genotypes of DRD4 did not show any association. In associating the genotypes of DRD2 with TCI scales (NS, harm avoidance, reward dependence and PS), we also found no association. Recent findings associating NS with DRD4 could not be replicated. With regard to DRD2, we tested a different polymorphism as published recently and could not find an association of TCI scales with the gene. The present results therefore do not provide evidence that the DRD2 and DRD4 receptor genes contribute a common and relevant effect to personality traits.     

Novelty seeking: interaction between parental alcohol use and dopamine D4 receptor gene exon III polymorphism over 17 years

Recent meta-analyses have questioned the association between the dopamine receptor D4 (DRD4) gene polymorphism and the temperament trait of novelty seeking, and proposed an interaction between the polymorphism and other factors. We wanted to test whether parental alcohol use during childhood moderated the effect of an offspring dopamine receptor gene (DRD4) polymorphism on the temperament trait of novelty seeking in adulthood. A population-based sample of children and adolescents (n=2149) and their parents was examined in 1980 and 1983 on parental alcohol use and rearing practices. In 1997, study participants completed the Temperament and Character Inventory for the novelty-seeking temperament trait, and a subsample (n=150) was genotyped for the DRD4 exon III polymorphism. For the participants with the father, but not the mother, reporting more frequent alcohol consumption or drunkenness in examinations 17 and/or 14 years before the novelty-seeking assessment, an association between the short (two- or five-repeat) alleles of the DRD4 gene and extremely high novelty-seeking scores was observed. When the father reported less frequent alcohol consumption or drunkenness, the genotype was not associated with novelty seeking. The association remained after controlling for sex, age, and maternal child-rearing. These results provide preliminary information on gene-environment interaction on the temperament trait of novelty seeking and may partly explain the heterogeneity of findings concerning the association between DRD4 polymorphisms and novelty seeking.     

Functional polymorphism of the GTP cyclohydrolase 1 gene affects the personality trait of novelty seeking in healthy subjects

GTP cyclohydrolase 1 (GCH1) is the initial and rate-limiting enzyme in the biosynthesis of tetrahydrobiopterin, which is an essential cofactor for biosynthetic enzymes of dopamine, serotonin, and nitric oxide. In the present study, the association of functional polymorphism of the GCH1 gene (C+243T, rs841) with personality traits was examined in 902 healthy Japanese subjects. Personality traits were assessed by the Temperament and Character Inventory (TCI), and the GCH1 genotype was detected by a PCR-RFLP method. There were no significant main effects of the GCH1 genotype on the seven TCI dimension scores, but significant interaction effects between the GCH1 genotype and gender were found on the scores of novelty seeking. Post-hoc analysis revealed that males with the C/C genotype had higher scores of novelty seeking than those with the C/T genotype or those with the T/T genotype, while in females the scores of novelty seeking were not different among the genotype groups. The present study thus suggests that the C+243T polymorphism of the GCH1 gene affects the personality trait of novelty seeking in males.     

Allelic variants of dopamine receptor D4 (DRD4) and serotonin receptor 5HT2c (HTR2c) and temperament factors: replication tests

The contribution of genetic factors to personality differences between individuals is evidenced by twin and adoption studies. Ebstein et al. [1996, 1997a, 1997b] reported an association between the long repeat allele of the dopamine D4-exon-III receptor polymorphism and the human personality dimension novelty seeking (NS), between the 5HT2c-ser-23 allele and reward dependence, and an interaction between both receptor polymorphisms and reward dependence. Subsequent replication tests mainly reported controversial results for the association between DRD4-exon-III long repeat and NS. We examined a homogeneous study population of 190 healthy male students of middle European descent, aged between 20 and 30 years using Cloninger's TPQ in order to replicate Ebstein's findings. Using a significance level of 1%, no association between the long repeat of the DRD4-exon-III polymorphism and NS and between the 5HT2c receptor polymorphism and reward dependence was found, but a significant interaction effect of DRD4 and 5HT2c receptor polymorphisms on reward dependence was observed in accordance to Ebstein's report.     

The association of 5-HTTLPR and DRD4 VNTR polymorphisms with affective temperamental traits in healthy volunteers

BACKGROUND: There has been growing evidence that temperamental traits, including affective temperaments, are heritable and associated with genetic polymorphisms. The purpose of the present study was to investigate the possible relationship between affective temperaments and the triallelic serotonin transporter gene-linked polymorphic region (5-HTTLPR) and dopamine receptor D4 (DRD4) polymorphisms in healthy Korean subjects. METHODS: Three hundred thirty-five healthy college students were recruited, and 290 participants with a complete data set (172 males, 118 females) were included in the data analysis. The DNA of the subjects was isolated from whole blood cells, and the 5-HTTLPR and DRD4 variable number of tandem repeats polymorphisms were genotyped using polymerase chain reaction. Participants performed the 110-item version of the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego auto-questionnaire (TEMPS-A) measuring five affective temperamental traits. RESULTS: A significant association was found between the DRD4 polymorphism and the cyclothymic and irritable temperaments in male subjects. No significant association was shown between the 5-HTTLPR gene polymorphisms and affective temperaments. LIMITATION: Our data were collected from a specific group of college students and cannot be generalized easily to other non-clinical populations. In addition, Korean version of the TEMPS-A used in this study has not yet been validated in Korean population. CONCLUSIONS: This study showed a possible association between the DRD4 polymorphism and certain affective temperaments in the Korean male population. The clarification of the biological basis of predisposing temperaments such as cyclothymic temperament might help to understand the pathophysiology and mechanisms of mood disorders.     

Novelty seeking and the dopamine D4 receptor gene (DRD4) revisited in Asians: haplotype characterization and relevance of the 2-repeat allele.

The relationship of the dopamine D4 receptor gene (DRD4) to the behavioral trait of novelty seeking has not been uniformly consistent. A methodological shortcoming in previous studies may relate to the way different DRD4 variants were categorized. Because of evolutionary and functional (e.g., diminished potency to reduce cAMP) similarities between the 2- and 7-repeat (2R, 7R) alleles of the DRD4, we suggest grouping of these two alleles together may facilitate detection of biologically meaningful and reproducible association findings with behavioral traits. We measured novelty seeking with the Tridimensional Personality Questionnaire (TPQ) in a community sample of Caucasian, Korean, and Filipino subjects (N = 171) who were subsequently characterized for the DRD4 variable number of tandem repeats (VNTR). In the Korean sample, those with a 2R and/or 7R allele scored significantly higher on novelty seeking scale (P < 0.05). By contrast, grouping the VNTR alleles by size (2, 3, 4 vs. 5, 6, 7), as has been done in similar studies of Asian subjects, was not significant. Using the extreme discordant phenotype (EDP) strategy in the pooled sample and selecting the individuals within the upper and lower decile, we observed a trend for association with higher novelty seeking in individuals who carry the 2R and/or 7R alleles (P = 0.06). We also confirmed that the 2R allele in the Korean and Filipino subjects was the result of a one-step recombination event between the 4R and 7R alleles. This study suggests that genetic association analyses can benefit by consideration of the shared functional and evolutionary attributes of the DRD4 2R and 7R alleles.     

Association analysis between polymorphisms in the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes with cocaine dependence

Genetic research on cocaine dependence (CD) may help clarify our understanding of the disorder as well as provide novel insights for effective treatment. Since dopamine neurotransmission has been shown to be involved in drug reward, related genes are plausible candidates for susceptibility to CD. The dopamine receptor D₂ (DRD2) protein and dopamine transporter (DAT1) protein play regulatory roles in dopamine neurotransmission. The TaqI A single-nucleotide polymorphism (SNP) in the DRD2 gene and the 3′ variable number tandem repeat (VNTR) polymorphism in the DAT1 gene have been implicated in psychiatric disorders and drug addictions. In this study, we hypothesize that these polymorphisms contribute to increased risk for CD. Cocaine-dependent individuals (n = 347) and unaffected controls (n = 257) of African descent were genotyped for the polymorphisms in the DRD2 and DAT1 genes. We observed no statistically significant differences or trends in allele or genotype frequencies between cases and controls for either of the tested polymorphisms. Our study suggests that there is no association between the DRD2 and DAT1 polymorphisms and CD. However, additional studies using larger sample sizes and clinically homogenous populations are necessary before confidently excluding these variants as contributing genetic risk factors for CD.     

Association between dopamine D4 receptor (DRD4) exon III polymorphism and Neuroticism in the Japanese population

The association between the dopamine D4 receptor (DRD4) exon III polymorphism and personality trait of novelty seeking (NS) has been studied intensively. In the Japanese population, the results of the previous studies did not always coincide. In the present study, we investigated the association between the polymorphism and personality traits evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) in 196 Japanese subjects. A meta-analysis of the present and previous Japanese studies was also conducted regarding NS. As a result, significant association was observed between the polymorphism and personality traits evaluated by using NEO PI-R as a whole (p=0.022, MANCOVA). Subsequent analyses showed a significant association between short alleles (2-4 repeats) and higher scores for Neuroticism or its subscales, Anxiety, Depression, and Vulnerability (p=0.015, 0.039, 0.021, and 0.008, respectively, uncorrected). No other significant difference in the scores for NEO PI-R was observed in the subsequent analyses. Significant association was also observed between the polymorphism and scores for STAI as a whole (p=0.004, MANCOVA). Subsequent analyses did not show significant association, although a weak trend for the relation between the genotype consisting of short alleles and Trait Anxiety was observed (p=0.10, uncorrected). The meta-analysis showed no significant association between the polymorphism and NS. Thus, the present study suggested the association between the short allele of the DRD4 exon III polymorphism and personality trait of Neuroticism in Japanese subjects.     

DRD4 and novelty seeking: results of meta-analyses

Studies of the association between polymorphisms within and near the dopamine D4 receptor (DRD4) gene and novelty seeking (NS) have produced inconsistent results, raising questions about the strength of the relationship and the methodological conditions under which the relationship holds. We conducted three meta-analyses of existing studies to provide formal statistical measures of the strength of the DRD4-NS relationship. Results provided no support for a relationship between NS and the presence of the 7-repeat allele of the VNTR polymorphism. A small positive effect, however, was found for long repeats of the same polymorphism. The most promising findings were obtained for the relationship with the -521 C/T promoter polymorphism, for which the analysis showed an effect size of 0.32. The positive findings are consistent with a polygenic model of influence on fundamental personality dimensions.     

D2 and D4 dopamine receptor polymorphisms and personality

The relationship of various dimensions of temperament, measured by the Tridimensional Personality Questionnaire (TPQ), to polymorphisms of the D₂ dopamine receptor (DRD2) and D₄ dopamine receptor (DRD4) genes was determined in 119 healthy Caucasian boys who had not yet begun to consume alcohol and other drugs of abuse. Total Novelty Seeking score of the TPQ was significantly higher in boys having, in common, all three minor (A1,B1, and Intron 6 1) alleles of the DRD2 compared to boys without any of these alleles. Boys with the DRD4 7 repeat (7R) allele also had a significantly higher Novelty Seeking score than those without this allele. However, the greatest difference in Novelty Seeking score was found when boys having all three minor DRD2 alleles and the DRD4 7R allele were contrasted to those without any of these alleles. Neither the DRD2 nor the DRD4 polymorphisms differentiated total Harm Avoidance score. Whereas subjects having all three minor DRD2 alleles had a significantly higher Reward Dependence 2 (Persistence) score than subjects without any of these alleles, no significant difference in this personality score was found between subjects with and without the DRD4 7R allele. In conclusion, DRD2 and DRD4 polymorphisms individually associate with Novelty Seeking behavior. However, the combined DRD2 and DRD4 polymorphisms contribute more markedly to this behavior than when these two gene polymorphisms are individually considered. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 81:257–267, 1998. © 1998 Wiley-Liss, Inc.     

Association between novelty seeking and dopamine receptor D4 (DRD4) exon III polymorphism in Japanese subjects.

In this study, we investigated the association between dopamine receptor D4 (DRD4) exon III polymorphism and novelty seeking in 69 Japanese women. The group of subjects with long allele (> or =5 repeats) exhibited significantly elevated novelty seeking scores in comparison with subjects lacking the long allele. By contrast, the scores for harm avoidance, reward dependence, and persistence were statistically indistinguishable in the two group of subjects. With regard to the subscales of novelty seeking, the scores for exploratory excitability and extravagance were significantly higher in subjects with the long allele than in subjects lacking the long allele. However, no significant associations with impulsiveness or disorderliness were recognized. Our results suggest that although long alleles of the polymorphic exon III repeats are low in the Japanese population, there is an association between long alleles of DRD4 exon III polymorphism and novelty seeking.     

Personality traits and dopamine receptors (D2 and D4): linkage studies in families of alcoholics

Activation of the mesolimbic dopamine pathway appears to promote drug- and alcohol-seeking behavior in laboratory animals. Results for association and linkage analysis between various alcohol dependence phenotypes and the dopamine receptors have been quite mixed. Similarly, both positive and negative results have been presented concerning dopamine receptor genes and temperament. Cloninger has postulated that the novelty seeking factor from the Tridimensional Personality Questionnaire (TPQ) may be related to the dopamine neurotransmitter system. As novelty seeking is a trait of some importance for substance-dependent individuals, our goal was to test this relationship within a sample of families of alcoholics. No evidence favoring linkage between D2, D4, or DAT1 was found for TPQ novelty seeking. However, the harm-avoidance trait from the TPQ showed evidence for linkage to both the D4 and one of the D2 loci (TaqI A). The Multidimensional Personality Questionnaire (MPQ) was used to provide converging evidence for these results. The TPQ harm-avoidance scale loads heavily on introversion (worry, pessimism, shyness), characteristics that may be especially salient in alcoholic families. Thus, planned comparisons were made between selected MPQ traits measuring the affective dimension (negative affectivity, stress reaction, alienation, and well-being). We find evidence favoring linkage between the D2 and D4 receptor loci and these MPQ traits, with stronger evidence being seen for the D2 polymorphisms. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:634-641, 1999.     

Association between novelty seeking and dopamine receptor D4 (DRD4) exon III polymorphism in Japanese subjects

In this study, we investigated the association between dopamine receptor D4 (DRD4) exon III polymorphism and novelty seeking in 69 Japanese women. The group of subjects with long allele (≥5 repeats) exhibited significantly elevated novelty seeking scores in comparison with subjects lacking the long allele. By contrast, the scores for harm avoidance, reward dependence, and persistence were statistically indistinguishable in the two group of subjects. With regard to the subscales of novelty seeking, the scores for exploratory excitability and extravagance were significantly higher in subjects with the long allele than in subjects lacking the long allele. However, no significant associations with impulsiveness or disorderliness were recognized. Our results suggest that although long alleles of the polymorphic exon III repeats are low in the Japanese population, there is an association between long alleles of DRD4 exon III polymorphism and novelty seeking. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:469–471, 1999. © 1999 Wiley-Liss, Inc.     

Association of serotonin and dopamine gene pathways with behavioral subphenotypes in dementia

Genetic association studies investigating the association between genes of serotonergic and dopaminergic systems and behavioral and psychological symptoms in dementia (BPSD) are contradictory. We have utilized 1008 probable Alzheimer's disease (AD) patients from the UK and used the 12-item Neuropsychiatric Inventory. We applied a multiple indicators-multiple causes (MIMIC) approach to investigate the effect of 11 polymorphisms on the 4 behavioral subphenotypes “psychosis”, “moods”, “agitation”, and “behavioural dyscontrol”. Significant associations were observed between the serotonin transporter gene (SERT) polymorphism STin2 and “psychosis”; the dopamine transporter gene (DAT) 3′ variable number tandem repeats (VNTR) and “agitation”; and the dopamine receptor 4 (DRD4) VNTR and “moods” factors. Direct associations were identified between the dopamine receptor 3 (DRD3) BalI polymorphism and depression; the dopamine receptor 1 (DRD1) and dopamine transporter gene 3′ VNTR polymorphisms and aberrant motor behavior; the DRD4 VNTR and sleep disturbances; and the SERT gene VNTR 5HTTLPR and apathy items. Significant interactions observed between polymorphisms suggested epistatic effects and interactions between polymorphisms and medications highlighted potential treatment response. This multiple indicators multiple causes (MIMIC) model efficiently captured the complexity of the interrelations between genetic variation, behavioral symptoms, and clinical variables.     

Dopamine D4 receptor exon III alleles and variation of novelty seeking in alcoholics

A dysfunction of dopaminergic neurotansmission has been implicated in alcohol-seeking behavior. Recently, a significant association between the seven-repeat allele (DRD4*7R) of a 16 amino acid motif in the third exon of the dopamine D4 receptor gene (DRD4) and the personality trait of novelty seeking has been reported. Our population-based association study tested the hypothesis that the DRD4*7R variant predisposes to high levels of novelty seeking, which may underlie alcohol-seeking behavior. The genotypes of the expressed DRD4 exon III polymorphism were determined in 197 German controls and 252 German alcohol-dependent males, of whom 92 alcoholics completed the tridimensional personality questionnaire. We found no significant differences in the DRD4*7R frequencies between controls and alcoholics, including two subgroups (56 alcoholics with dissocial personality disorder according to ICD-10 and 89 alcoholics with severe withdrawal symptoms) with a high level of novelty seeking. The novelty-seeking scores did not differ significantly between alcoholics (including both subgroups) carrying long alleles with six or more repeats compared with those lacking long alleles. The present results do not provide evidence that the DRD4*7R allele contributes a common and relevant effect to alcohol-seeking behavior in our sample of alcoholics. Am. J. Med. Genet. 74:483–487, 1997. © 1997 Wiley-Liss, Inc.     

A multivariate analysis of 59 candidate genes in personality traits: the temperament and character inventory

Cloninger (Cloninger CR. Neurogenetic adaptive mechanisms in alcoholism. Science 1987: 236: 410-416) proposed three basic personality dimensions for temperament: novelty seeking, harm avoidance, and reward dependence. He suggested that novelty seeking primarily utilized dopamine pathways, harm avoidance utilized serotonin pathways, and reward dependence utilized norepinephrine pathways. Subsequently, one additional temperament dimension (persistence) and three character dimensions (cooperativeness, self-directedness, and self-transcendence) were added to form the temperament and character inventory (TCI). We have utilized a previously described multivariate analysis technique (Comings DE, Gade-Andavolu R, Gonzalez N et al. Comparison of the role of dopamine, serotonin, and noradrenergic genes in ADHD, ODD and conduct disorder. Multivariate regression analysis of 20 genes. Clin Genet 2000: 57: 178-196; Comings DD, Gade-Andavolu R, Gonzalez N et al. Multivariate analysis of associations of 42 genes in ADHD, ODD and conduct disorder. Clin Genet 2000: in press) to examine the relative role of 59 candidate genes in the seven TCI traits and test the hypothesis that specific personality traits were associated with specific genes. While there was some tendency for this to be true, a more important trend was the involvement of different ratios of functionally related groups of genes, and of different genotypes of the same genes, for different traits.     

DRD4 and novelty seeking: Results of meta‐analyses

Studies of the association between polymorphisms within and near the dopamine D4 receptor (DRD4) gene and novelty seeking (NS) have produced inconsistent results, raising questions about the strength of the relationship and the methodological conditions under which the relationship holds. We conducted three meta‐analyses of existing studies to provide formal statistical measures of the strength of the DRD4‐NS relationship. Results provided no support for a relationship between NS and the presence of the 7‐repeat allele of the VNTR polymorphism. A small positive effect, however, was found for long repeats of the same polymorphism. The most promising findings were obtained for the relationship with the ?521 C/T promoter polymorphism, for which the analysis showed an effect size of 0.32. The positive findings are consistent with a polygenic model of influence on fundamental personality dimensions. © 2002 Wiley‐Liss, Inc.     

Investigation of dopamine receptor (DRD4) and dopamine transporter (DAT) polymorphisms for genetic linkage or association to panic disorder

Clinical and animal studies suggest a role for the neurotransmitter dopamine in anxiety states. In humans, one such condition is panic disorder, which is typified by recurrent panic attacks accompanied by anticipatory anxiety. Family, segregation, and twin studies imply a genetic component to the pathophysiology of panic disorder. In this study, we examined the genes for the D4 dopamine receptor (DRD4) and the dopamine transporter (DAT) using three common sequence polymorphisms. Two of these polymorphisms were in DRD4, a 12 base-pair insertion/deletion in exon 1 and a 48 base-pair repeat in exon 3, and the third was a 40 base-pair repeat in the 3' untranslated region of DAT. We employed a family-based design, using 622 individuals in 70 families, as well as 82 haplotype relative risk "trios". Subjects were genotyped at the polymorphic loci, and the data were analyzed for genetic association and linkage. There were no significant differences in allele frequencies or occurrence of genotypes within the triads for any of the three polymorphisms. No significant linkage between the DRD4 or DAT polymorphisms and panic disorder was observed in the multiplex families, using a variety of simulations for dominant and recessive models of inheritance. However, LOD scores of approximately 1.1 and 1.05 were observed for the DAT and DRD4 exon 1 loci, respectively. The results reported here provide little support for the role of these polymorphisms in panic disorder.     

Combination of the serotonin transporter and norepinephrine transporter gene promoter polymorphisms might influence harm avoidance and novelty seeking in healthy females

It has been demonstrated that the interaction between serotonin transporter (5HTT) and norepinephrine transporter (NET) functions affects each transporter function and behavior in studies using knockout mice model. In the present study, we examined the effects of the 5HTT and NET gene promoter polymorphisms on personality traits in 575 Japanese healthy subjects. The 5HTT (long/short, L/S) and NET (-3081 A/T) genotypes were identified by PCR methods, and personality traits were assessed by the Temperament and Character Inventory (TCI). Neither of the two polymorphisms affected any TCI dimension, but the interaction between them had significant effects on harm avoidance and novelty seeking in females. Subsequent analyses showed that the females with the combination of the SS genotype reducing 5HTT function and the TT genotype reducing NET function had higher harm avoidance and lower novelty seeking. The present study suggests that the combination of 5HTT and NET polymorphisms influences harm avoidance and novelty seeking in females.