No association of dopamine D2 receptor molecular variant Cys311 and schizophrenia in Chinese patients

Genetic variants in dopamine receptors influence on heterodimerization in the context of antipsychotic drug action

Human dopamine D2 receptor (D₂R) gene has polymorphic variants, three of them alter its amino acid sequence: Val96Ala, Pro310Ser and Ser311Cys. Their functional role never became the object of extensive studies, even though there are some evidence that they correlate with schizophrenia. The present work reviews data indicating that these mutations play a role in dimer formation with dopamine D1 receptor (D₁R), with the strongest effect observed for Ser311Cys variant. Similarly, the affinity for antipsychotic drugs of this genetic variant depends on whether it is expressed together with D₁R or not. Better understanding of altered ability of genetic variants of D₂R to form dimers with D₁R, as well as of altered affinity for antipsychotic drugs, depending on the absence or presence of the second dopamine receptor is of great importance-since these two receptors are not always co-expressed in the same cell. It may well be that targeting new compounds toward the D₁R-D₂R dimers, which the most probably form under conditions of excessive dopamine release, will result in antipsychotic drugs devoid of serious side effects.

Identification of genetic correlates of response to Risperidone: Findings of a multicentric schizophrenia study from India

Risperidone is most commonly used as an antipsychotic in India for treatment of schizophrenia. However, the response to treatment with risperidone is affected by many factors, genetic factors being one of them. So, we attempted to evaluate the association between dopamine D2 (DRD2) receptor, serotonergic (5HT2A) receptor and CYP2D6 gene polymorphisms and response to treatment with risperidone in persons with schizophrenia from North India. It was a multicentric 12-weeks prospective study, undertaken in patients diagnosed with schizophrenia according to International Classification of Diseases 10th revision, Diagnostic Criteria for Research module (ICD-10 DCR). Patients were treated with incremental dosages of risperidone. Nine gene polymorphisms from three genes viz. DRD2, 5-HT2A and CYP2D6 along with socio-demographical and clinical variables were analyzed to ascertain the association in response to risperidone treatment. The change in the Positive and Negative Syndrome Scale (PANSS) was used to measure the outcome. Significant differences in the frequencies of single nucleotide proteins (SNPs) rs180498 (Taq1D) and rs 6305 (C516T) polymorphisms were found amongst the groups defined according to percent decline in PANSS. The CYP2D6*4 polymorphism differed significantly when drop outs were excluded from analysis. Presence of DRD2 Taq 1 D2D2 and 5-HT2A C516T CT genotypes in patients were more likely to be associated with non-response to risperidone. Ser311Cys (rs1801028) mutation was absent in the North Indian patients suffering from schizophrenia.

Associations between dopamine D2 receptor gene polymorphisms and schizophrenia risk: a PRISMA compliant meta-analysis

OBJECTIVE

To determine the relationships between dopamine D2 receptor gene polymorphisms and the risk of schizophrenia using meta-analysis.

METHOD

The PubMed, Embase, and China National Knowledge Infrastructure databases were searched to identify relevant literature published up to February 2016. The allele contrast model was used. Stata software was used for statistical analysis, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated to evaluate the associations between dopamine D2 receptor gene polymorphisms and the risk of schizophrenia. Meta-regression and publication bias, trim-and-fill, subgroup, sensitivity, cumulative, and fail-safe number analyses were also performed.

RESULTS

This meta-analysis included 81 studies. The rs1801028 and rs1799732 were associated with schizophrenia risk among Asians (P=0.04, OR =1.25, 95% CI =1.01-1.55; P<0.01, OR =0.76, 95% CI =0.63-0.92, respectively), while the rs6277 was associated with schizophrenia risk in Caucasians (P<0.01, OR=0.72, 95% CI =0.66-0.79). The rs1800497 was also associated with schizophrenia risk in population-based controls (P<0.01, OR =0.84, 95% CI =0.72-0.97). The rs6275, rs1079597, and rs1800498 were not associated with schizophrenia risk. In addition, meta-regression indicated that the controls may be sources of heterogeneity for the rs1801028 single-nucleotide polymorphism (SNP), while ethnicity may be sources of heterogeneity for the rs6277 SNP. Publication bias was significant for the rs1801028 SNP, and this result changed after the publication bias was adjusted using the trim-and-fill method.

CONCLUSION

This meta-analysis demonstrated that the rs1801028 may be a risk factor for susceptibility to schizophrenia among Asians, while the rs1799732 may be a protective factor for that population. Large-sample studies are necessary to verify the results of this meta-analysis.

The role of C957T, TaqI and Ser311Cys polymorphisms of the DRD2 gene in schizophrenia: systematic review and meta-analysis

Background

The association between the dopamine D2 receptor (DRD2) gene and schizophrenia has been studied though no conclusive outcomes have been attained. The aim of this study was to perform a systematic review and meta-analysis to explore the relation between three polymorphisms of the DRD2 gene (C957T, TaqI and Ser311Cys) and schizophrenia.

Methods

The search was made in PubMed and EBSCO databases (up to February 2016). The systematic review included 34 case–control association studies (34 for C957T, 16 for TaqI and 36 for Ser311Cys). The association analysis comprised the allelic, additive, dominant, and recessive genetic models. The meta-analysis was performed following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement.

Results

The meta-analysis showed that TaqI (additive model: OR 0.57, 95% CI 0.30–1.14) and C957T (additive model: OR 0.75, 95% OR 0.58–0.97, recessive model: OR 0.79, 95% CI 0.64–0.98) exert a protective effect against developing schizophrenia. However, the sub-analysis for the C957T variant showed that this polymorphism exhibits a risk factor effect on Chinese individuals (allelic model: OR 1.33, 95% CI 1.04–1.70).

Conclusion

Our meta-analysis suggests an association of the DRD2 gene and the risk for schizophrenia, given that TaqI and C957T polymorphisms presented a protective effect against schizophrenia, and in the sub-analyses the C957T variant increased the risk for this disorder in the Chinese population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12993-016-0114-z) contains supplementary material, which is available to authorized users.

Association between DRD2 (rs1799732 and rs1801028) and ANKK1 (rs1800497) polymorphisms and schizophrenia: a meta-analysis

The role of dopamine D2 receptor (DRD2) polymorphisms in schizophrenia remains controversial. We performed a meta-analysis to determine whether DRD2 polymorphisms influence the risk of schizophrenia and examined the relationship between rs1799732, rs1801028, and rs1800rs028 an23381d rs1800497 genetic variants and the etiology of schizophrenia. Relevant case-control studies were retrieved by database searches and selected according to established inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, sensitivity analysis, and cumulative meta-analysis were performed. A total of 76 studies with 16096 cases and 18965 controls were included. Specifically, 24 studies with 6075 cases and 6643 controls involved rs1799732, 36 studies with 8043 cases and 10194 controls involved rs1801028 and 16 studies with 1978 cases and 2128 controls involved rs1800497. No significant associations were observed between rs1799732 and rs1800rs732 and rs1800497 and schizophrenia. The rs1801028 locus was associated with schizophrenia, with a pooled OR of 1.221 (95% CI = 1.037-1.438, P = 0.016). This meta-analysis indicates that the rs1801028 locus may be associated with schizophrenia. These data provide possible references for future case-control studies related to schizophrenia.

Association of DRD2 gene polymorphisms with mood disorders: a meta-analysis

BACKGROUND

In the past few decades, a number of studies have investigated the association of dopamine D2 receptor (DRD2) gene polymorphisms with mood disorders, but the findings are not always consistent. The aim of our study was to assess the association between DRD2 gene polymorphisms and mood disorders by using a meta-analysis.

METHODS

Data were collected from the following electronic databases: PubMed, Elsevier Science Direct, Cochrane Library, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, and Wanfang, with the last report up to June 2010. Meta-analysis was performed in a fixed/random effect model by using the software Review Manager 4.2.

RESULTS

We identified 19 separate studies using search, but only 14 separate studies (2157 cases and 3272 controls) were included in the current study. Meta-analysis was performed for three DRD2 gene polymorphisms (-141Cins/del, Ser311/Cys311, and TaqI A1). We performed meta-analysis in overall, Caucasian, and Asian populations. We also performed disease-specific meta-analysis in unipolar disorder and bipolar disorder. We found no association between DRD2 gene -141Cins/del polymorphism and mood disorders in overall and Caucasian populations (P>0.05). We also found no association between DRD2 gene Ser311/Cys311 polymorphism and mood disorders in overall, Caucasian, and Asian populations (P>0.05). An association of DRD2 gene TaqI A1 polymorphism with mood disorders was found in overall population, and the individuals with A1A1 genotype were more susceptible to mood disorders in comparison to those with A2A1 and A2A2 genotypes (OR=1.84, 95% CI=1.07-3.17, P=0.03).

LIMITATION

Meta-analysis is retrospective research that is subject to the methodological deficiencies of the included studies.

CONCLUSION

This meta-analysis suggests that mood disorders may be associated with DRD2 gene TaqI A1 polymorphism, but not -141Cins/del and Ser311/Cys311.

Association of dopamine receptor polymorphisms with schizophrenia and antipsychotic response in a South Indian population

BACKGROUND

Alterations in the dopamine transmission and receptor density are hypothesized in the pathophysiology of schizophrenia but ethnic disparities are reported to exist in disease association and therapeutic response to psychotropic medication. Antipsychotics have higher binding affinity to D2 subtype of dopamine receptor. DRD2 Cys311, TaqIB1 and TaqIA1 variants are considered to have either reduced affinity for dopamine and hypo-dopaminergic activity.

METHODS

We examined the role of Taq1B, Taq1D, S311C, H313H and Taq1A polymorphisms of DRD2 gene in schizophrenia and antipsychotic treatment response in 213 patients and 196 controls from a homogenous South Indian population. A more detailed genotype phenotype association analysis was carried out to understand the disease in terms of its socio-cultural factors.

RESULTS

H313HTT genotype was found to be associated with schizophrenia (P = 0.004) while TaqIB1B1 genotype was significantly associated with higher psychopathology score. When treatment response was considered H313HCC, TaqIA2A2 and Taq1D1D1 had higher mean improvement scores. TaqID1D1 and H313HTT genotype were found to be significantly higher in responders than in nonresponder group. Distinct shift in the LD patterns of responder and non-responder group was observed. Certain symptoms were characteristic of our patient population. Following medication the scores and presentation of these symptoms tend to vary in the responder and non-responder groups.

CONCLUSION

Based on genotype phenotype correlations it can be suggested that certain polymorphisms can be defined for their critical functions in disease and their role in treatment response in South Indian population. The present study suggests that in addition to ethnic bias, socio-cultural factors should also be considered while evaluating genotype phenotype correlations, in association and treatment response to complex disorders like schizophrenia.

The Cys allele of the DRD2 Ser311Cys polymorphism has a dominant effect on risk for schizophrenia: evidence from fixed- and random-effects meta-analyses

Previously we derived independent estimates of the effect of the dopamine D2 receptor (DRD2) Ser311Cys polymorphism on risk for schizophrenia using fixed- and random-effects meta-analyses. Both analyses identified a significant association between the Cys allele and schizophrenia, but neither included all available data. Furthermore, genotype data were not evaluated in either analysis, thus precluding any determination of the mode of inheritance. The present study was conducted to resolve discrepancies between the existing meta-analyses, and provide more comprehensive and accurate estimates of the nature and magnitude of the influence of the Ser311Cys polymorphism on risk for schizophrenia. All discrepancies between the two sets of previously meta-analyzed studies were identified and resolved to the mutual satisfaction of the authors, and the final dataset was analyzed independently by fixed- and random-effects meta-analyses. A total of 27 samples, comprising 3,707 schizophrenia patients and 5,363 control subjects, were included in the analyses of allelic association, while smaller numbers of studies and subjects were included in each of the genotypic association analyses. A significant effect of the Cys allele was observed under both fixed-effects (odds ratio [OR] = 1.4; P = 0.002) and random-effects (OR = 1.4; P = 0.007) models. Cys/Ser heterozygotes were at elevated risk for schizophrenia when compared to Ser/Ser homozygotes (fixed- and random-effects OR = 1.4, p(s) or= 0.948). There was no evidence of heterogeneity, excessive influence of any single study, or publication bias in any of the analyses, suggesting that the effect of this DRD2 polymorphism on schizophrenia risk is reliable and uniform across populations, and our estimates of its magnitude are robust and accurate.

Meta-analysis identifies an association between the dopamine D2 receptor gene and schizophrenia

The D2 subtype of dopamine receptor has been widely implicated in the pathogenesis of schizophrenia. Early evidence supporting an association between the Cys311Ser polymorphism of the D2 receptor gene (DRD2) and schizophrenia was subsequently refuted and, eventually, dismissed. From all 24 published case-control studies, we calculated a pooled estimate of this association. The pooled odds ratio was 1.3 for the Cys allele, which was highly significant (P=0.007). The odds ratio derived from each study was unrelated to the ethnicity or gender composition of the sample, or the age of the control group. There was no evidence of publication bias or excessive influence attributable to any given study. Although more family-based studies are needed to confirm this relation, our results provide strong evidence that DRD2 influences susceptibility to schizophrenia.

Dopamine D2 receptor gene Ser311Cys variant and schizophrenia: association study and meta-analysis

An association has been reported between a dopamine D(2) receptor gene (DRD2) Ser311Cys variant and schizophrenia. In a replication attempt, Swedish patients with schizophrenia (n = 173) and control subjects (n = 236) were assessed for the DRD2 Ser311Cys variant. Schizophrenic patients displayed higher Cys311 allele frequencies than control subjects (4.0 vs. 0.8%, chi(2) = 9.49, df = 1, P = 0.002; odds ratio (OR) 4.93, 95% confidence interval (95% CI) 1.61-15.12). The association was detected only in men. The results were supported by a meta-analysis of all published case-control studies comprising a total of 9,152 subjects (chi(2) = 11.37, df = 1, P < 0.001; OR 1.43, 95% CI 1.16-1.78). The present results support the involvement of the DRD2 gene in the pathogenesis of schizophrenia.

Relationship between adverse effects of antipsychotic treatment and dopamine D(2) receptor polymorphisms in patients with schizophrenia

Extrapyramidal adverse symptoms (EPS) represent a major type of adverse events in treatment with typical antipsychotic drugs which share high affinity to the dopamine D(2) receptor (DRD2). Genetic variants of this receptor may modulate the therapeutic response and the severity of adverse symptoms of antipsychotics. We analyzed nine known polymorphisms of the DRD2 in 665 schizophrenic patients with European Caucasian ethnic background and compared the intensity of acute dystonia, extrapyramidal symptoms, akathisia, and tardive dyskinesia between carriers of different DRD2 genotypes. In a subgroup of 40 patients with most severe extrapyramidal symptoms we sequenced the coding region including the exon-intron junctions of the DRD2 gene. Functionally relevant DRD2 amino acid variants (Ser(310), Cys(311)) were rare or were not found at all (Ala(96)). Complete sequence analysis of sufferers from the most severe adverse effects revealed two new intronic polymorphisms and a silent polymorphism in exon 7, but no new amino acid variants beyond those which are already known. We found no significant association between these polymorphisms and the intensity of the different types of adverse neurologic effects of the antipsychotics. These results were obtained by correlating adverse events with each of the nine single nucleotide polymorphisms and by correlation with the estimated haplotypes. In conclusion, genetic variations in the DRD2 gene were no major predictors of the individually variable adverse effects from antipsychotic treatment in Caucasian schizophrenic patients.

Mutation analysis of the human NR4A2 gene, an essential gene for midbrain dopaminergic neurogenesis, in schizophrenic patients

Recent studies have revealed that an orphan receptor gene of the steroid/thyroid hormone nuclear receptor superfamily, the Nurr1 gene, is essential for the neurogenesis and differentiation of dopaminergic neurons in the midbrain of mice. Transgenic mice lacking the Nurr1 gene soon die after birth and are devoid of dopaminergic neurons in the midbrain. Heterozygous mice survive postnatally without obvious locomotor deficits; however, they have increased vulnerability to dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In view of the importance of dopamine neurotransmission in brain function, we were interested to know if the human homologous gene of murine Nurr1, the NR4A2 gene, may play a role in the pathogenesis of schizophrenia. We systematically sequenced all the exons of the human NR4A2 gene to search for molecular variants in a cohort of Chinese schizophrenic patients from Taiwan. Two molecular variants were identified: a G-insertion in intron 6 (designated IVS6 + 17 [see text] + 18insG), and a G-deletion in the untranslated exon 1 (designated c.-469delG). The IVS6 + 17 [see text] + 18insG is a polymorphic one; further case control study, however, did not reveal association of this polymorphism with schizophrenia. The c.-469delG is a rare variant found in two unrelated patients among 177 schizophrenic patients, but not in 130 nonpsychotic controls. The result suggests that the c.-469delG and possibly other variants of the NR4A2 gene may be of relevance to the complex factors involved in the pathogenesis of schizophrenia.

Genetic variations and polymorphisms of G protein-coupled receptors: functional and therapeutic implications

G protein-coupled receptors (GPCRs) represent a major class of proteins in the genome of many species, including humans. In addition to the mapping of a number of human disorders to regions of the genome containing GPCRs, a growing body of literature has documented frequently occurring variations (i.e. polymorphisms) in GPCR loci. In this article, we use a domain-based approach to systematically examine examples of genetic variation in the coding and noncoding regions of GPCR loci. Data to date indicate that residues in GPCRs are involved in ligand binding and coupling to G proteins and that regulation can be altered by polymorphisms. Studies of GPCR polymorphisms have also uncovered the functional importance of residues not previously implicated from other approaches that are involved in the function of GPCRs. We predict that studies of GPCR polymorphisms will have a significant impact on medicine and pharmacology, in particular, by providing new means to subclassify patients in terms of both diagnosis and treatment.

Association and excess of transmission of a DRD2 haplotype in a sample of French schizophrenic patients

The gene which codes for dopamine receptor D2 (DRD2) is considered as one of the most relevant candidate genes in schizophrenia. Previous genetic studies focusing on this gene gave conflicting results, potentially because of the differences in methodology (linkage versus association studies), and the different loci analyzed (the DRD2 gene having many polymorphisms). We used a progressive strategy with three different approaches (case/control, haplotype relative risk and transmission disequilibrium test) and investigated two genetic polymorphisms (TaqI B1/B2 and TaqI A1/A2, spanning the coding region of the DRD2 gene) in 50 patients with DSM-IV diagnoses of schizophrenia, in their 100 parents and in 50 healthy, matched controls. Firstly, we found a significant excess of the two alleles (B2 and A2) in the schizophrenic group compared to unaffected controls. Secondly, we found an excess of transmission from the parents to their affected children, using the haplotype relative risk design applied to the B2A2 haplotype. Finally, the transmission disequilibrium test showed evidence for linkage between B2A2 haplotype and schizophrenia. The significant excess of the B2A2 haplotype in schizophrenic patients is specifically observed in a subsample of patients with a disease onset occurring after 20 years of age. As the haplotype contains nearly the entire DRD2 gene, we found convergent evidence in our sample for a significant role of the DRD2 gene in the risk for schizophrenia. This haplotype may be more specifically involved in the disorder's onset at a later age in some patients, or, alternatively, may be implicated as a modifying factor acting on age of onset.

Dopamine receptor D2 Ser/Cys 311 variant is associated with delusion and disorganization symptomatology in major psychoses

The D2 receptor (DRD2) is a binding site of many psychoactive drugs and it has been proposed as a genetic risk factor for psychiatric disorders. The aim of this investigation was to study the DRD2 S311C variant in major psychoses. We studied 1182 inpatients with diagnoses of bipolar disorder (n = 480), major depressive disorder (n = 269), schizophrenia (n = 366), delusional disorder (n = 44), psychotic disorder not otherwise specified (n = 23) and 267 healthy controls. Eight hundred and eighty-seven subjects were also scored for their lifetime symptomatology using the the Operational Criteria checklist for psychotic illness (OPCRIT). DRD2 variants were not associated with affected subjects even when possible confounders like gender and onset were considered. When we considered the 887 subjects with the symptomatologic analysis, we observed a significant association of the DRD2 S311C variant with both delusion and disorganization features. The association was present independently from diagnoses. Our results do not show that coding variants of the DRD2 S311C play a major role in conferring susceptibility to major psychoses, but they may be connected with disorganized and delusional symptomatology independently from diagnoses.

Dopamine receptor D2 Ser/Cys311 variant associated with disorganized symptomatology of schizophrenia

The dopamine D2 receptor gene has been proposed as a genetic risk factor for schizophrenia (Arinami et al., 1994). However, a number of replications failed to confirm the initial report. The finding of a stronger association considering schizophrenics with the absence of negative symptoms (Arinami et al., 1996) suggested that the influence of DRD2 variants should be analyzed more at the level of symptoms rather than syndromes. One hundred and four inpatients affected by schizophrenia (n = 99) and delusional disorder (n = 5) (DSM IV) were assessed at admission by the Operational Criteria for Psychotic Illness (OPCRIT) and were typed for DRD2 variants using polymerase chain reaction (PCR) techniques. Subjects with the S311C variant presented a higher score on the 'Disorganization' factor (P = 0.012). Consideration of possible stratification effects such as sex and age of onset did not reveal any deviation from the whole sample. In conclusion, our preliminary report suggests that the DRD2 S311C variant may be a liability factor for disorganized symptoms among schizophrenics or for a subtype of schizophrenia characterized by highly disorganized symptomatology.

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.

No association of the Ser/Cys311 DRD2 molecular variant with schizophrenia using a classical case control study and the haplotype relative risk

Arinami et al. (1994) reported an association between the Ser311/Cys311 variant of the DRD2 gene and schizophrenia in a Japanese population. We did not find statistically significant differences in the distribution of the allele frequencies between schizophrenics (103) and controls (97) in a case-control sample (chi 2 = 2.07; p = 0.150) or in 64 nuclear families with the haplotype relative risk (HRR) design (chi 2 = 0.13; p = 0.718). Our results seem to exclude a main involvement of this variant of the dopamine D2 receptor gene in the etiopathogenesis of schizophrenia.