No association detected between a D3 receptor gene-expressed variant and schizophrenia

No association between the Ser9Gly polymorphism of the dopamine receptor D3 gene and schizophrenia: a meta-analysis of family-based association studies

BACKGROUND

Previous studies found that Ser9Gly (rs6280) might be involved in the occurrence of schizophrenia. However, no consist conclusion has yet been achieved. Compared to the case-control study, the family-based study took into account stratification bias. Thus, we conducted a meta-analysis of family-based studies to measure a pooled effect size of the association between Ser9Gly and the risk of schizophrenia.

METHODS

The relevant family-based studies were screened using the electronic databases by the inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to measure the correction between Ser9Gly polymorphism and schizophrenia susceptibility. Subgroup analysis was performed by stratification of ethnicity (i.e., East Asian, Caucasian, and other populations). Additionally, publication bias was evaluated by the funnel plot.

RESULTS

After literature searching, a total of 13 family-based association studies were included, which contained 11 transmission disequilibrium test (TDT) studies with 1219 informative meiosis and 5 haplotype-based haplotype relative risk (HRR) studies. No statistical significance of the heterogeneity was detected in TDT and HRR studies. Thus, the pooled effect size was calculated under the fixed effect model. The results found that the association was significantly protective in East Asian in TDT studies (204 informative meiosis, OR = 0.744, 95% CI = 0.564-0.980, Z-value = - 2.104, p = 0.035).

CONCLUSIONS

The meta-analysis based on the family study found a protective association of Ser9Gly in East Asian. In future, large sample molecular epidemiology studies are needed to validate our findings.

The Ser9Gly polymorphism of the dopamine D3 receptor gene and risk of schizophrenia: an association study and a large meta-analysis

Dopamine D3 receptor (DRD3) binds antipsychotic drugs and is abundant in the limbic system of the brain. It has been shown to play important roles in schizophrenia. A number of studies investigated the Ser9Gly polymorphism of the DRD3 gene to test its possible association with schizophrenia; however, the results were inconsistent. Our study aims to further evaluate the possible association between the Ser9Gly polymorphism and schizophrenia using a case-control association study within the Han Chinese population as well as a meta-analysis covering all previous studies. Our study, based on 329 schizophrenic patients and 288 controls, found no significant difference in the genotype or allele distributions of Ser9Gly polymorphism, the meta-analysis showed that the Ser9Gly polymorphism was not associated with Schizophrenia. Our study does not support the contention that the Ser9Gly polymorphism of the DRD3 gene plays a major role in schizophrenia in the Chinese population.

No association between the DRD3 Ser9Gly polymorphism and schizophrenia

OBJECTIVE

To investigate the association between a Ser9Gly polymorphism of the dopamine D3 receptor gene (DRD3) and schizophrenia.

METHODS

408 schizophrenic patients and 172 control subjects were compared with regard to their DRD3 Ser9Gly genotypic and allelic frequencies. In addition, we carried out a family-based association study including 183 pedigrees (472 subjects) using the transmission disequilibrium test (TDT).

RESULTS

No significant differences of genotype or homozygosity distribution were identified between patients and controls. When patients were stratified according to gender, response to treatment, age at onset, no significant differences were observed. Neither allele A (Ser), or G (Gly) were preferentially transmitted from parents to affected offspring.

CONCLUSION

The hypothesis that the DRD3 Ser9Gly polymorphism plays a predisposing role in schizophrenia is not supported by this study.

No association between the Ser9Gly polymorphism of the dopamine D3 receptor gene and schizophrenia in a Spanish sample

This study aims to further evaluate the controversial association between the Ser9Gly polymorphism in codon 9 of the D3 dopamine receptor gene (DRD3) and schizophrenia in psychiatric inpatients acutely hospitalized in two general hospitals in Madrid, Spain. The Ser9Gly polymorphism of the DRD3 was examined in 178 schizophrenic patients, 286 patients with other psychiatric diagnoses, and 132 controls recruited. Genotype frequencies were in Hardy-Weinberg equilibrium. No association was found between schizophrenia and the Ser9Gly polymorphism of the D3 dopamine receptor gene.

Family association study between DRD2 and DRD3 gene polymorphisms and schizophrenia in a Portuguese population

Schizophrenia is a highly heritable condition, as demonstrated in family, twin and adoption studies. Candidate genes from the dopaminergic system have long been hypothesized to be involved in the etiology of this disorder. In the present study, we investigated the genetic association between polymorphisms in the D2 and D3 dopamine receptor (DRD2, DRD3) genes and schizophrenia. We examined 90 trios from Portugal, and negative results were obtained from association studies with both Haplotype Relative Risk (HRR) and Transmission Disequilibrium Test (TDT), as well as TRANSMIT. Therefore, we conclude that neither the DRD2 nor the DRD3 gene polymorphisms investigated are associated with schizophrenia in our sample.

Dopamine D3 receptor gene Ser9Gly variant and schizophrenia: association study and meta-analysis

OBJECTIVE

To further evaluate the controversial putative association between a Ser9Gly variant in the first exon of the dopamine D3 receptor gene (DRD3) and schizophrenia.

METHODS

Swedish patients with schizophrenia ( n=156) and control subjects ( n=463) were assessed for the DRD3 Ser9Gly variant. Meta-analyses including previous and the present Swedish case-control results were performed.

RESULTS

No significant difference between the Swedish patients and controls were found, but there was an association between DRD3 Ser9Gly Ser/Ser and homozygous genotypes and response to anti-psychotic drugs. This finding was supported by an incomplete meta-analysis. In a meta-analysis of all case-control studies comprising 8761 subjects the association between DRD3 Ser9Gly homozygosity and schizophrenia ( =4.96, degree of freedom=1, p <0.05, odds ratio=1.10, 95% confidence interval=1.01-1.20) persisted. However, the previously proposed association between the Ser/Ser genotype and schizophrenia was not significant (chi2 =2.71, degree of freedom=1, p>0.05, odds ratio=1.08, 95% confidence interval=0.99-1.17).

CONCLUSIONS

Whereas the present Swedish case-control analysis did not yield any evidence for association with the diagnosis, the present meta-analysis suggests that the DRD3 gene confer susceptibility to schizophrenia. Reasons for the discrepancies between prior studies are discussed.

Polymorphisms in dopamine receptors: what do they tell us?

Many genetic studies have focussed on dopamine receptors and their relationship to neuropsychiatric disease. Schizophrenia, bipolar disorder, and substance abuse have been the most studied, but no conclusive linkage or association has been found. The possible influence of dopamine receptor variants on drug response has not received as much attention. While there is some evidence that polymorphisms and mutations in dopamine receptors can alter functional activity and pharmacological profiles, no conclusive data link these gene variants to drug response or disease. The lack of unequivocal findings may be related, in part, to the subtle changes in receptor pharmacology that these polymorphisms and mutations mediate. These subtle effects may be obscured by the influence of genes controlling drug metabolism and kinetics. Further insight into the pharmacogenetics of dopamine receptors may require not just more studies, but novel approaches to the study of complex genetic traits and diseases.

Localization of genes modulating the predisposition to schizophrenia: a revision

The genetics of schizophrenia or bipolar affective disorder has advanced greatly at the molecular level since the introduction of probes for the localization of specific genes. Research on gene candidates for susceptibility to schizophrenia can broadly be divided into two types, i.e., linkage studies, where a gene is found near a specific DNA marker on a specific chromosome, and association studies, when a condition is associated with a specific allele of a specific gene. This review covers a decade of publications in this area, from the 1988 works of Bassett et al. and Sherrington et al. on a gene localized on the long arm of chromosome 5 at the 5q11-13 loci, to the 1997 work of Lin et al. pointing to the 13q14.1-q32 loci of chromosome 13 and to the 1998 work of Wright et al. on an HLA DRB1 gene locus on chromosome 6 at 6p21-3. The most replicated loci were those in the long arm of chromosome 22 (22q12-q13.1) and on the short arm of chromosome 6 (6p24-22). In this critical review of the molecular genetic studies involved in the localization of genes which modulate the predisposition to schizophrenia the high variability in the results obtained by different workers suggests that multiple loci are involved in the predisposition to this illness.

DRD3 and DAT1 genes in schizophrenia: an association study

OBJECTIVE

To investigate the role of the dopamine receptor 3 (DRD3) and transporter 1 (DAT1) genes in schizophrenia or in modulating its phenotype.

METHODS

a Ser9Gly polymorphism in codon 9 of the DRD3 and a VNTR polymorphism in the DAT1genes were examined in two groups of schizophrenic patients, one of excellent neuroleptic responders (N=42) and one of nonresponders (N=64). A group of healthy volunteers screened for major psychiatric disorders was also included (N=89). In addition, age at onset of psychotic symptoms, attention performance and family loading for schizophrenia spectrum disorders were compared between patients with different genotypes in the DRD3 and DAT1 genes.

RESULTS

No significant differences in the allelic distribution of the DRD3 and DAT1 polymorphisms were detected between schizophrenic patients and controls. A trend toward an excess of DRD3 genotype Gly/Gly was observed in neuroleptic nonresponder schizophrenic patients compared to controls (chi(2)=3. 30, df=1, p=0.07). No significant differences in age at onset of psychotic symptoms, attention task performance or family loading for schizophrenia spectrum disorders were observed between groups with different DRD3 and DAT1 genotypes.

CONCLUSION

These results do not support the role of either of these genes in increasing susceptibility to schizophrenia or in modulating its phenotype in the studied population.

Possible implications of the dopamine D(3) receptor in schizophrenia and in antipsychotic drug actions

The D(3) receptor may represent an important target for antipsychotic drugs which all bind with high affinity and do not induce upon repeated administration either tolerance or receptor upregulation. The D(3) receptor is localized in brain areas, namely the nucleus accumbens and cerebral cortex, implicated in neural circuits believed to display defective functioning in schizophrenia. Overexpression of the D(3) receptor, which accounts for the behavioral sensitization to levodopa in a rodent model of Parkinson's disease, might also be responsible for the sensitization to dopamine agonists observed in schizophrenia. The appearance of the D(3) receptor during brain development, early in proliferating neuroepithelia and later in neurons from limbic areas, suggests further studies to assess its participation in the neurodevelopmental disorders of schizophrenia. Finally, meta-analysis of approximately 30 studies comprising over 2500 patients indicate that a polymorphism in the coding sequence of the D(3) receptor is associated with a small but significant enhancement of vulnerability to the disease.

COMT and DRD3 polymorphisms, environmental exposures, and personality traits related to common mental disorders

In a community sample of 2,327 Caucasians, we tested the hypotheses that polymorphisms in the COMT and DRD3 genes are associated with personality traits conferring vulnerability to anxiety, depression, or alcohol misuse, or with current symptoms of these; and that the association is stronger in persons who also have been exposed to stressor experiences. To conserve resources and to allow replication, the genetic analysis was undertaken in two stages. For the COMT polymorphism, no statistically significant associations were found in the first sample of 862 persons. The remainder of the sample was therefore not analysed for that gene. For the DRD3 polymorphism, those in the first sample with at least one of the Ser(9) alleles had significantly higher scores in neuroticism (p=0.006) and behavioral inhibition (p=0.003). There was a trend, failing to meet the 1% significance criterion, for those with this genotype also to have higher depression and anxiety. The groups did not differ in alcohol use. In persons with the Ser(9) allele who were also exposed to stressors, there was a higher level of depression at the 5% level; and the depression level was higher in homozygotes. But when the remainder of the sample (1,465) was analysed, none of the associations reached statistical significance. We conclude that neither the COMT nor DRD3 polymorphisms are associated with anxiety, depression, or alcohol abuse. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:102-107, 2000

Association study of schizophrenia among Indian families

A putative association of schizophrenia with a Msc I restriction fragment length polymorphism at the dopamine D3 receptor gene locus (DRD3) was tested among Indian families, using haplotype relative risk analysis and the transmission disequilibrium test (n=66 families and 58 sets of transmissions, respectively). A significant association either with homozygosity or with allele 1 at the biallelic polymporphism could not be detected.