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PubMed1997

Clinical susceptibility to migraine with aura is modified by dopamine D2 receptor (DRD2) NcoI alleles.

Migraine has a major genetic component. Although most recent scientific studies have focused on the role of 5-hydroxytryptamine and neuropeptides in migraine, dopaminergic systems are also implicated in the pathogenesis. Therefore, the dopamine D2 receptor (DRD2) was analyzed as a candidate gene since antagonists of this receptor have been reported to be effective in the acute treatment of migraine. Individuals with migraine with aura (n = 52) have an increased frequency (0.84) of the DRD2 NcoI C allele (chi-square = 6.47; p < 0.005) compared with control individuals (n = 121; C allele frequency = 0.71). Individuals with migraine without aura (n = 77) showed the same DRD2 T allele frequency (0.70) as the control group. Migraine with aura was present in 27% of the C/C individuals, 16% of the C/T individuals, and 5.2% of the T/T individuals. These data suggest that activation of the DRD2 receptor plays a modifying role in the pathophysiology of migraine with aura. As a result, these data provide a molecular rationale for the documented efficacy of DRD2 antagonists in the treatment of migraine with aura.

Adult↗
PubMed1996

Allele-specific PCR for simultaneous amplification of both alleles of a deletion polymorphism in intron 6 of the human dopamine 2 receptor gene (DRD2).

The human dopamine 2 receptor gene (DRD2) is an important candidate gene for drug addiction and alcoholism. So far, no mutations within the coding region of DRD2 have been found to be associated with addiction disorders. To identify sequence polymorphisms for further haplotype analyses and to analyze the importance of possible intron sequence variations of the human DRD2 gene (>260kb) in greater cohorts and in a routine manner we established an optimized methodological procedure for polymerase chain reaction (PCR) amplification and direct non-radioactive sequencing followed by a bidirectional allele-specific PCR protocol; the latter one allows the simultaneous amplification of several alleles in one reaction tube. Overall, the sequences of the DRD2 introns 3-7 are highly conserved. Nevertheless, in each of the analyzed intron sequences we found substitution variants as well as a one base-pair deletion polymorphism in intron 6. The allele-specific PCR allowed the reliable testing of 95 healthy control individuals and 270 alcoholics for analyzing a possible genetic association of this newly characterized polymorphic DRD2 marker with alcoholism in an ethnically and clinically homogenous group of patients. However, the observed allele frequencies for the 1bp deletion polymorphism were 15.9% for the alcoholics and 15.3% for the controls suggesting no association of the deletion to alcoholism.

Alleles↗
PubMed1999

Family-based association study between bipolar disorder and DRD2, DRD4, DAT, and SERT in Sardinia.

Association analysis of candidate genes may represent a strategy for clarifying the genetic components involved in bipolar disorder. Polymorphism at dopamine receptor genes DRD2, DRD4, and dopamine and serotonin transporter genes (DAT, SERT) has been used in previous association studies. Some authors have reported positive association between certain alleles and bipolar disorder, using the case-control design. In this family-based association study of DRD2, DRD4, DAT, and SERT, the distribution of parental nontransmitted alleles was compared with that of alleles transmitted to 53 Sardinian probands suffering from bipolar disorder. The transmission disequilibrium test (TDT) was used to detect any disproportionate transmission of alleles by heterozygous parents to affected children. No differences were found between the allele distribution of polymorphisms at DRD2, DRD4, DAT, and SERT in probands and parental nontransmitted chromosomes. TDT did not reveal any difference between transmitted and nontransmitted alleles. Our results do not support the hypothesis of a role for DRD2, DRD4, DAT, or SERT in bipolar disorder. Previously reported positive associations between DRD2 or SERT and bipolar disorder were conceivably due to stratification dependent on the case-control design, even though our sample might have failed to detect small associations due to limited power.

Adolescent↗
PubMed1991

No association between an allele at the D2 dopamine receptor gene (DRD2) and alcoholism.

OBJECTIVE: --We attempted to replicate a positive allelic association between the A1 allele of DRD2 (the D2 dopamine receptor locus) and alcoholism that has been reported. DESIGN: --We compared allele frequencies at the previously described Taq I restriction fragment length polymorphism system of DRD2 in alcoholics and random population controls. SUBJECTS: --The alcoholic subjects were 44 unrelated white individuals, diagnosed by direct structured interview to have alcohol dependence (by the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition, criteria). The subjects in our random population control group (N = 68) were also white. RESULTS: --For the control group, allele frequencies at DRD2 were 0.20 (A1) and 0.80 (A2). For the alcoholic group overall, allele frequencies were 0.23 (A1) and 0.77 (A2). There were no significant differences in allele frequencies at the DRD2 locus between alcoholics and controls. The allele frequencies in both groups agreed closely with those observed in most previously described control populations. Subtyping the alcoholic group according to presence or absence of family history of alcoholism, presence or absence of antisocial personality disorder, age of onset, presence or absence of physical withdrawal symptoms, or recent alcohol consumption (as a measure of severity) did not in any case reveal significant differences in allele frequencies. CONCLUSION: --We were not able to replicate the results previously reported. We conclude that our data do not support an allelic association between the A1 allele at DRD2 and alcoholism.

Adult↗
PubMed1998

Association analysis in an evolutionary context: cladistic analysis of the DRD2 locus to test for association with alcoholism.

Previous studies testing the dopamine D2 receptor (DRD2) locus for association with alcoholism have produced conflicting results. Failure to screen controls for substance abuse and failure to assess alcoholics for severity have been proposed as causes for the inability of some studies to detect an association. We have reevaluated the involvement of DRD2 mutations in susceptibility to alcoholism with a cladistics-based association analysis after restricting an alcoholic sample to more severe cases. For the present study we tested 55 alcoholic probands and 80 normal controls for differences in the frequency of six haplotypes at the DRD2 locus. The haplotypes were derived from five di-allelic polymorphisms spanning all but the first exon of the DRD2 gene. A cladogram constructed from the haplotypes provided the evolutionary context for a nested statistical analysis. We found no significant evidence for association of the DRD2 haplotypes analyzed with the more severe alcoholic phenotype.

Alcoholism↗
PubMed1998

European Multicentre Association Study of Schizophrenia: a study of the DRD2 Ser311Cys and DRD3 Ser9Gly polymorphisms.

As part of the European Multicentre Association Study of Schizophrenia (EMASS), we studied polymorphisms in the dopamine DRD2 and DRD3 receptor genes. The EMASS collaboration was established to create a large, statistically powerful sample of schizophrenic patients and controls from different European centres. Previous studies have suggested associations between schizophrenia and the Ser311Cys polymorphism in exon 7 of the dopamine DRD2 receptor gene [Arinami et al., (1994): Lancet 343:703-704] and a polymorphism Ser9gly in exon 1 of the dopamine DRD3 receptor gene [Crocq et al. (1992): J Med Genet 29:858-860]. We tested for these associations in samples of 373 and 413, and 311 and 306 patients and controls, respectively. We found no evidence for allelic association between schizophrenia and the Cys311 variant of the DRD2 receptor gene and no homozygotes for this variant were observed by any group. However, an excess of homozygotes for both alleles of the DRD3 polymorphism was observed in schizophrenic patients (chi2 = 8.54, P = 0.003, odds ratio = 1.64, 95% CI = 1.18-2.29). We also observed a significant excess of the 1-1 (Ser9Ser) genotype (chi2 = 8.13, P = 0.004, odds ratio = 1.7, 95% CI = 1.18-2.4). No evidence of heterogeneity between samples was detected and there was no evidence of an allelic association. These findings suggest that the rare Cys311 variant in exon 7 of the DRD2 receptor gene does not play a role in the pathogenesis of schizophrenia in European populations. Currently, our results do support the previous findings of an association between increased homozygosity of the Ser/Gly variant of the Dopamine D3 receptor gene and schizophrenia.

Alleles↗
PubMed2000

Functional variant in the DRD2 receptor promoter region and subtypes of alcoholism.

Dopaminergic pathway genes are considered as candidate genes for several neuropsychiatric diseases including severe alcoholism. Since 1990, there have been numerous reports of conflicting association studies of the Taq I A allele of the dopamine D2 receptor (DRD2) gene and alcoholism. Functional and structural variations in candidate genes offer more direct evaluation of their role in the development of a disorder. To determine the role of such variations in the DRD2 gene in the development of alcoholism subtypes, we screened a sample of 173 alcoholics and 88 normal controls with the A-241G and -141C Ins/Del variations in the promoter region and C311G variation in exon 7 of the DRD2 gene. Comparison of alcoholics with normal controls for allele frequency differences of these three variations was negative. Allele frequency differences of the two variations in the promoter region between type II alcoholics, alcoholics with medical complications, and normal controls were not significant. There was linkage disequilibrium only between -141 Ins/Del and Taq I D polymorphisms. We conclude that the functional and structural variations in DRD2 gene do not play a major role in the development of alcoholism subtypes in our sample.

Alcoholism↗
PubMed2000

Haplotypes at the DRD2 locus and severe alcoholism.

Association studies of the minor TaqI A allele of the D(2) dopamine receptor (DRD2) gene with alcoholism have produced conflicting findings. Failure to assess alcoholics for severity of their disorder and to screen controls for substance use have been proposed as causes for the discrepant results. In the present study, five diallelic sites spanning the DRD2 gene were determined in combined Caucasian (non-Hispanic) studies of more severe alcoholics (n = 92) and controls screened for substance use (n = 85). The frequency of the minor alleles at the 3'-untranslated site (TaqI A) and two intronic sites (TaqI B and intron 6) of the DRD2 gene were each strongly associated with alcoholism. Moreover, the alcoholics compared with the controls at these three sites had a significantly higher frequency of the minor/major allele heterozygote haplotype combination (A1/A2 B1/B2 T/G) than the major allele homozygote haplotype combination (A2/A2 B2/B2 G/G). However, exon 7 and promoter alleles were not associated with alcoholism. In neither the alcoholics nor in the controls were there departures from Hardy-Weinberg equilibrium at any of the five sites examined. The most significant diallelic composite genotypic disequilibria were found when comparisons were made between TaqI A and TaqI B, TaqI A and intron 6, and TaqI B and intron 6 sites. Weaker but still significant disequilibria were observed when TaqI A and exon 7, TaqI B and exon 7, intron 6 and exon 7, and promoter and exon 7 sites were compared. However, no significant disequilibria were noted when TaqI A and promoter, TaqI B and promoter, and intron 6 and promoter sites were compared. In sum, the study found significant evidence for association of the minor alleles in the untranslated sites of the DRD2 gene and their haplotypes with the more severe alcoholic phenotype.

Adult↗
PubMed2000

Family-based study of DRD2 alleles in alcohol and drug dependence.

Numerous case-control studies have addressed the hypothesis that variant alleles of the dopamine D2 receptor gene (DRD2) increase the liability for alcohol and/or drug dependence, and both positive and negative results have been reported. Because population frequencies of these alleles vary considerably, the conflicting results could be due to population stratification bias. Using the transmission disequilibrium test, the present study examined linkage disequilibrium of alcohol and drug (opioid and/or cocaine) dependence with three DRD2 polymorphic systems: (a) TaqI A, (b) TaqI D, and (c) the functional -141CIns/Del promoter systems. DNA samples were collected from small nuclear families (SNFs), where one or more offspring met DSM-III-R or DSM-IV criteria for alcohol and/or drug dependence. Because positive association between DRD2 alleles and alcohol and/or drug dependence has been reported only in populations of European ancestry, we limited the present study to European Americans (EAs). No evidence for linkage disequilibrium was found for any of the polymorphic systems when examined in relation to any substance dependence, alcohol dependence (with or without drug dependence), or drug dependence (with or without alcohol dependence). These results are consistent with those from a recent family-based study of alcohol dependence. Together, these studies suggest that the conflicting findings from case-control studies of the association between alleles of DRD2 and substance dependence may be attributable to population stratification in some samples.

Alcoholism↗
PubMed2002

Gender-specific molecular heterosis of dopamine D2 receptor gene (DRD2) for smoking in schizophrenia.

We examined the genetic effect of DRD2 A1 allele in 167 Korean schizophrenics in relation to their smoking habit. Although there was no apparent difference in the genotype distributions of DRD2 gene among the female schizophrenics (n = 66), the male counterpart (n = 101) showed significant differences in their genotype distributions. The comparison between male smoking and non-smoking patients showed the difference in genotype distribution (P = 0.010) with a higher prevalence of A1 allele (P = 0.020) and frequency of heterozygotes (P = 0.005), but not frequency of the A1 allele. The A1A2 heterozygotes male showed significantly higher smoking rate compared to the A1A1 or A2A2 homozygotes male, and non-smokers were deficient in heterozygotes. By contrast, among female schizophrenics, the heterozygotes showed a lower smoking rate than homozygotes and there were more heterozygotes in non-smokers. The deviation from Hardy-Weinberg expectations was observed in male and female non-smokers showing quite opposite profiles. Highly significant differences were seen between male and female non-smokers in A1 prevalence (P = 0.001), genotype distribution (P = 0.00011), and frequency of heterozygotes (P = 0.00003), but not in A1 frequency. The analyses from both male and female as one group showing no significant difference in the genotype distributions between smokers and non-smokers could be explained by the gender difference in the genetic effect of DRD2 A1 allele. Our findings present the gender-specific molecular heterosis of DRD2 gene in relation specifically to the smoking status of schizophrenic patients. They indicate the importance of heterosis and gender effects that should be taken into consideration for the association studies.

Alleles↗
PubMed2004

DRD2 -141C insertion/deletion polymorphism is not associated with schizophrenia: results of a meta-analysis.

The gene DRD2, which codes for dopamine receptor D2, has been considered a prime candidate for allelic association testing with schizophrenia based on the strong evidence for involvement of this protein in disease pathophysiology. Recent meta-analyses confirmed a small but reliable association between schizophrenia and the cysteine-coding allele of the Cys311Ser polymorphism of DRD2. In the present study, we sought to determine if another polymorphism (the -141C insertion/deletion) in the same gene, which has been reported to be associated with schizophrenia in several individual studies, would show a similar pattern of association with the disease in a pooled dataset. The pooled odds ratio for the insertion allele obtained from 10 case-control studies was 1.1, which was not significant (P = 0.580); however, there was marked heterogeneity among the findings of individual studies, suggesting that some underlying factor influenced the size of their observed effects. Yet, neither ethnicity, the age of the control group, nor the gender composition of the samples reliably influenced effect size. Because linkage disequilibrium patterns between various DRD2 polymorphisms are not yet known, it remains possible that divergent meta-analytic findings at both commonly examined mutation sites within DRD2 are accurate. Haplotype analysis within this gene would be useful for definitively specifying the role of this gene in the etiology of schizophrenia.

Humans↗
PubMed2005

Association between the DRD2 A1 allele and opium addiction in the Iranian population.

Dysfunction of the central dopaminergic neurotransmission has been suggested to play an important role in the etiology of certain neuropsychiatric disorders such as drug abuse. It has been shown that the dopamine D2 receptor (DRD2) gene dysfunction is associated with multi-drug addiction. Addiction to opium is the most common form of drug abuse in Iran. We studied the allelic association between DRD2 Taq I A polymorphism in 100 opium-dependent Iranian patients and 130 unrelated controls. A 310 bp (base pair) region surrounding Taq I site at the DRD2 locus was amplified by polymerase chain reaction (PCR) and the PCR product was incubated with Taq I restriction enzyme. The A1 allele remained intact while the A2 allele was cut. Significant association was observed between A1 allele and addiction in the patients group (P < 0.0001). Moreover, the frequency of A1A1 genotype was significantly higher in opium users than controls (P < 0.0001). Our result indicates that DRD2 might be involved in the pathophysiology of opium addiction.

Adult↗
PubMed2006

Association between the DRD2 A1 allele and response to methadone and buprenorphine maintenance treatments.

The TaqI A polymorphism (A(1)) of the dopamine D(2) receptor gene (DRD2), although not a specific predictor of opioid dependence, has been strongly associated with high levels of prior heroin use and poor treatment outcomes among methadone maintenance patients. The aims of this study were to confirm these findings via a retrospective analysis of A(1) allele frequency in methadone (n = 46) and buprenorphine (n = 25) patients, and non-opioid-dependent controls (n = 95). Subjects were genotyped at the DRD2 TaqI A locus using PCR amplification followed by TaqI restriction enzyme digestion and gel electrophoresis. For methadone and buprenorphine subjects, heroin use (prior to treatment), treatment outcomes, and withdrawal occurrence were determined from comprehensive case notes. No significant differences in A(1) allele frequency (%) were observed between: methadone (19.6%), buprenorphine (18.0%), and control (17.9%) groups (P > 0.7); successful and poor treatment outcome groups, methadone: 20.0% and 19.2%, respectively (P = 1.0); buprenorphine: 18.4% and 20.0%, respectively (P = 1.0). Also, there were no significant relationships between TaqI A genotype and prior heroin use (P = 0.47). However, among the successful methadone subjects, significantly fewer A(1) allele carriers experienced withdrawal than non-A(1) carriers (P = 0.04). In conclusion, the DRD2 genotype effects did not affect opioid maintenance treatment outcomes. This suggests the need for a further prospective investigation into the role of the DRD2 A(1) allele in heroin use and response to maintenance pharmacotherapies for opioid dependence.

Adult↗
PubMed2004

Identification and characterization of ANKK1: a novel kinase gene closely linked to DRD2 on chromosome band 11q23.1.

The dopamine D2 receptor has been extensively studied in relation to alcoholism, substance abuse, and nicotine dependence. The most frequently examined polymorphism linked to this gene is the Taq1A restriction fragment length polymorphism (RFLP) (dbSNP rs1800497; g.32806C>T in GenBank AF050737.1), which has been associated with a reduction in D2 receptor density, although this is not universally accepted. The Taq1A RFLP lies 10 kB downstream of DRD2 and may therefore fall within a different coding region than the DRD2 gene or within a regulatory region. Within this downstream region, we have identified a novel kinase gene, named ankyrin repeat and kinase domain containing 1 (ANKK1), which contains a single serine/threonine kinase domain and is expressed at low levels in placenta and whole spinal cord RNA. This gene is a member of an extensive family of proteins involved in signal transduction pathways. The DRD2 Taq1A RFLP is a single nucleotide polymorphism (SNP) that causes an amino acid substitution within the 11th ankyrin repeat of ANKK1 (p.Glu713Lys), which, while unlikely to affect structural integrity, may affect substrate-binding specificity. If this is the case, then changes in ANKK1 activity may provide an alternative explanation for previously described associations between the DRD2 Taq1A RFLP and neuropsychiatric disorders such as addiction.

Amino Acid Sequence↗
PubMed1994

Linkage disequilibria at the D2 dopamine receptor locus (DRD2) in alcoholics and controls.

Because of its central role in the neuromodulation of appetitive behaviors, the D2 dopamine receptor gene (DRD2) has received considerable scrutiny as a possible candidate that may affect susceptibility to additive behaviors--especially alcoholism. Association studies that compare the frequencies of anonymous restriction fragment length polymorphisms (RFLPs) in alcoholics and controls have yielded equivocal results, suggesting that any role played by this receptor will account for only part of the variation. Since these RFLPs are not located in coding regions, the hypothesis has been advanced that the association seen in some studies results from linkage disequilibrium between these markers and one or more functional DRD2 alleles that affect susceptibility. To test this hypothesis, we have assayed four DRD2 RFLPs that span coding regions as well as a 3' flanking RFLP in an expanded sample of 88 unrelated Caucasian alcoholics and 89 unrelated race-matched controls. No significant difference for any RFLP frequency between these samples was observed, although for one marker (phD2-244), the alcoholic sample showed a significant departure from the Hardy-Weinberg equilibrium. The pattern of pairwise composite disequilibrium coefficients is broadly similar in the two samples, although when the five-marker haplotype frequencies are compared, a significant difference is revealed. This difference appears to be due to greater linkage disequilibrium of the control sample. These results do not support the involvement of the DRD2 region in the etiology of alcoholism.

Adult↗
PubMed2006

DRD2 C957T polymorphism interacts with the COMT Val158Met polymorphism in human working memory ability.

The C957T polymorphism in the dopamine D2 receptor (DRD2) gene and the Val158Met polymorphism in the Catechol-O-Methyl-Transferase (COMT) gene affect dopamine transmission and have been found to be associated with schizophrenia. Since DRD2 in mice and the COMT gene in humans modulate working memory, we examined the relationship and possible interaction of both polymorphisms to working memory performance in 188 healthy adults. Subjects having the DRD2 C/C allele showed the poorest performance in a word serial position test. Moreover, the effect of the C957T genotype was strengthened when interaction with the COMT Val158Met polymorphism was included in the analysis. We propose that an interaction of the DRD2 C957T and COMT Val158Met may be involved in the generation of some working memory deficits in schizophrenia.

Adolescent↗
PubMed1996

Dopamine D2 receptor gene (DRD2) haplotypes in Caucasians.

The human dopamine D2 receptor gene (DRD2) is considered a candidate gene for neuro-psychiatric diseases. We typed three new DNA sequence variants in DRD2 intron 4, intron 6 and exon 8, in combination with the known TaqI A restriction fragment length polymorphism (RFLP) and exon 7 311Ser/Cys in 106 unrelated psychiatrically healthy Caucasians. Based on the genotypic data we delineated 10 distinct DRD2 haplotypes and their genetic relationship. Our data provide evidence that the Taq A1 allele and the 311Cys variant are components of different groups of haplotypes though both variants have been speculated to be associated with alcoholism or schizophrenia in recent studies. Therefore we conclude that the prior knowledge of the frequencies and genetic relationships of DRD2 haplotypes will lead to the selection of more suitable intragenic markers for future association studies.

Gene Frequency↗
PubMedDate not supplied

Interaction between variation in the D2 dopamine receptor (DRD2) and the neuronal calcium sensor-1 (FREQ) genes in predicting response to nicotine replacement therapy for tobacco dependence.

We have previously demonstrated that a functional dopamine D2 receptor promoter variant (DRD2 -141 Ins/Del) predicts response to nicotine replacement therapy (NRT). The present study extends this finding in the same population of 363 NRT-treated subjects, by examining variation in the gene encoding the neuronal calcium sensor-1 protein (FREQ), which functions to regulate D2 receptor desensitization. The results indicate a statistically significant interaction effect of DRD2-141 and FREQ genotypes on abstinence at the end of the NRT treatment phase; 62% of the smokers with at least one copy of the DRD2 -141 Del allele and two copies of the FREQ rs1054879 A allele were abstinent from smoking, compared to 29-38% abstinence rates for other smokers in the trial. This result suggests that the interaction between variation in the DRD2 and FREQ genes, which both encode components of the D2 dopamine receptor signal transduction pathway, impacts the efficacy of NRT.

Administration, Cutaneous↗