Rs1076560, a functional variant of the dopamine D2 receptor gene, confers risk of schizophrenia in Han Chinese

Association Study Between DRD2, DRD3 Genetic Polymorphisms and Adverse Reactions in Chinese Patients on Amisulpride Treatment

OBJECTIVE

To determine if the cardiac function and "endocrinium" of Chinese patients are associated with dopamine D2 (DRD2) (rs6276) and DRD3 (rs6280, rs963468) genetic polymorphisms when treated with amisulpride.

METHODS

This study enrolled 148 patients with schizophrenia who took amisulpride orally for 8 weeks. DRD2 (rs6276) and DRD3 (rs6280, rs963468) genetic polymorphisms were detected with TaqMan-MGB allelic discrimination.

RESULTS

Analysis by multivariate covariance analysis (MANCOVA) showed that after adjusting for age, gender, and the baseline level, the increase in the level of aspartate aminotransferase (AST) and creatine kinase (CK) in the rs6276 AG group was higher than that in the AA and GG groups. Similarly, the changed estradiol (E2) level in rs6276 GG and rs963468 GG groups was higher than that in the other two groups. Adjusting for covariates, the increased triglyceride (TG) level in rs6276 GG and rs963468 GG groups was the highest among their different genotype groups. The increase in the level of "AST" in the rs6280 TT group was higher than that in the CC and CT groups upon adjusting for covariates. Similarly, MANCOVA showed that the increase in the level of "CK" in the rs6280 CT group was higher than that in the CC and CT groups. Besides, the increased level of "PRL" in the rs6280 CC group and rs963468 GG group was higher than that in their other two genotypes groups.

CONCLUSION

DRD2 (rs6276) and DRD3 (rs6280, rs963468) polymorphisms can affect amisulpride tolerability since they are associated with the observed adverse reactions, including cardiac dysfunction and endocrine disorders in Chinese patients with schizophrenia.

Working memory deficits in children with schizophrenia and its mechanism, susceptibility genes, and improvement: A literature review

The negative influence on the cognitive ability of schizophrenia is one of the issues widely discussed in recent years. Working memory deficits are thought to be a core cognitive symptom of schizophrenia and lead to poorer social functions and worse academic performance. Previous studies have confirmed that working memory deficits tend to appear in the prodromal phase of schizophrenia. Therefore, considering that children with schizophrenia have better brain plasticity, it is critical to explore the development of their working memory. Although the research in this field developed gradually in recent years, few researchers have summarized these findings. The current study aims to review the recent studies from both behavior and neuroimaging aspects to summarize the working memory deficits of children with schizophrenia and to discuss the pathogenic factors such as genetic susceptibility. In addition, this study put forward some practicable interventions to improve cognitive symptoms of schizophrenia from psychological and neural perspectives.

Dopamine Receptor DRD2 Gene rs1076560, Personality Traits and Anxiety in the Polysubstance Use Disorder

Development of an addiction is conditioned by many factors. The dopaminergic system has been shown to be the key element in this process. In this paper, we analyzed the influence of dopamine receptor 2 polymorphism rs1076560 in two groups—polysubstance-dependent male patients (n = 299) and the controls matched for age (n = 301). In both groups, we applied the same questionnaires for testing—Mini-international neuropsychiatric interview, the NEO Five-Factor Inventory, and the State–Trait Anxiety Inventory. The real-time PCR method was used for genotyping. When we compared the controls with the case group subjects, we observed significantly higher scores in the second group on both the state and trait scales of anxiety, as well as on the Neuroticism and Openness scales of the NEO-FFI; and lower scores on the scales of Extraversion and Agreeability of the NEO-FFI. The model 2 × 3 factorial ANOVA of the addicted subjects and controls was performed, and the DRD2 rs1076560 variant interaction was found for the anxiety state and trait scales, and for the NEO-FFI Neuroticism scale. The observed associations allow noticing that analysis of psychological factors in combination with genetic data opens new possibilities in addiction research.

No association between polymorphisms in the promoter region of dopamine receptor D2 gene and schizophrenia in the northern Chinese Han population: A case-control study

BACKGROUND

Epidemiological studies found that genetic factors are among the causes of schizophrenia, exclusively the genes involved in the dopamine system. Prior to this, the role of dopamine receptor D2 (DRD2) gene promoter polymorphisms and schizophrenia has been studied extensively, but there are still some uncertainties about these associations. The present study is focusing on the association between the DRD2 gene promoter region polymorphisms and schizophrenia in the northern Chinese Han population.

METHODS

We sequenced 2,111-bp fragment of DRD2 gene promoter region in 306 schizophrenic patients and 324 healthy controls to find association between DRD2 and schizophrenia. SPSS version 18 0.0 was used to calculate odds ratios (OR), 95% confidence intervals (CIs).The Hardy-Weinberg equilibrium test and the confirmation of haplotypes were calculated using Haploview version 4.1. The association of schizophrenic risk of DRD2 genotypes, alleles, and haplotypes between case and control groups was calculated using the chi-squared test. PS program was used to calculate the Power analysis.

RESULTS

The genotype frequencies of rs7116768 (p = 0.025) and rs1799732 (p = 0.042) were associated meagerly. After Bonferroni correction, there was no association found between DRD2 gene promoter region with schizophrenia risk in the northern Chinese Han population.

CONCLUSIONS

In this study, we did not find any significant difference between schizophrenia and the polymorphisms of DRD2 gene promoter region. A more forceful conclusion remains to be verified by further confirmatory experiments.

Exploring the moderating effects of dopaminergic polymorphisms and childhood adversity on brain morphology in schizophrenia-spectrum disorders

Genetic and environmental etiologies may contribute to schizophrenia and its associated neurobiological profile. We examined the interaction between dopaminergic polymorphisms, childhood adversity and diagnosis (schizophrenia/schizoaffective disorder) on dopamine-related brain structures. Childhood adversity histories and structural MRI data were obtained from 249 (153 schizophrenia/schizoaffective, 96 controls) participants registered in the Australian Schizophrenia Research Bank. Polymorphisms in DRD2 and COMT were genotyped and a dopaminergic risk allelic load (RAL) was calculated. Regression analysis was used to test the main and interaction effects of RAL, childhood adversity and diagnosis on volumes of dopamine-related brain structures (caudate, putamen, nucleus accumbens, dorsolateral prefrontal cortex and hippocampus). A schizophrenia/schizoaffective diagnosis showed significant main effects on bilateral hippocampus, left dorsolateral prefrontal cortex and bilateral putamen volumes. RAL showed a significant main effect on left putamen volumes. Furthermore, across the whole sample, a significant two-way interaction between dopaminergic RAL and childhood adversity was found for left putamen volumes. No brain structure volumes were predicted by a three-way interaction that included diagnosis. Our finding suggests the left putamen may be particularly sensitive to dopaminergic gene-environment interactions regardless of diagnosis. However, larger studies are needed to assess whether these interactions are more or less pronounced in those with schizophrenia/schizoaffective disorders.

Genome-Wide Supported Risk Variants in MIR137, CACNA1C, CSMD1, DRD2, and GRM3 Contribute to Schizophrenia Susceptibility in Pakistani Population

OBJECTIVE

Schizophrenia is a chronic neuropsychiatric disease afflicting around 1.1% of the population worldwide. Recently, MIR137, CACNA1C, CSMD1, DRD2, and GRM3 have been reported as the most robustly emerging candidates involved in the etiology of schizophrenia. In this case control study, we performed an association analysis of rs1625579 (MIR137), rs1006737, rs4765905 (CACNA1C), rs10503253 (CSMD1), rs1076560 (DRD2), rs12704290, rs6465084, and rs148754219 (GRM3) in Pakistani population.

METHODS

Schizophrenia was diagnosed on the basis of the Diagnostic and Statistical Manual of Mental Disorders 4th ed (DSM-IV). Detailed clinical information, family history of all patients and healthy controls were collected. RFLP based case control association study was performed in a Pakistani cohort of 508 schizophrenia patients and 300 healthy control subjects. Alleles and genotype frequencies were calculated using SPSS.

RESULTS

A significant difference in the genotype and allele frequencies for rs4765905, rs1076560 and rs6465084 were found between the patients and controls (p=0.000).

CONCLUSION

This study provides substantial evidence supporting the role of CACNA1C, GRM3 and DRD2 as schizophrenia susceptibility genes in Pakistani population.

No association between dopamine D3 receptor gene Ser9Gly polymorphism (rs6280) and risk of schizophrenia: an updated meta-analysis

OBJECTIVE

Ser9Gly (rs6280) is a functional single-nucleotide polymorphism (SNP) in the dopamine receptor D3 (DRD3) gene that may be associated with schizophrenia. We performed a meta-analysis to determine whether Ser9Gly influences the risk of schizophrenia and examined the relationship between the Ser9Gly SNP and the etiology of schizophrenia.

METHODS

Case-control studies were retrieved from literature databases in accordance with established inclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between Ser9Gly and schizophrenia. Subgroup analysis and sensitivity analysis were also performed.

RESULTS

Seventy-three studies comprising 10,634 patients with schizophrenia (cases) and 11,258 controls were included in this meta-analysis. Summary results indicated no association between Ser9Gly and risk of schizophrenia. In the dominant genetic model, the pooled OR using a random effects model was 0.950 (95% CI, 0.847-1.064; P=0.374).

CONCLUSION

Results of this meta-analysis suggest that the Ser9Gly SNP is not associated with schizophrenia. These data provide possible avenues for future case-control studies related to schizophrenia.

A splicing-regulatory polymorphism in DRD2 disrupts ZRANB2 binding, impairs cognitive functioning and increases risk for schizophrenia in six Han Chinese samples

The rs1076560 polymorphism of DRD2 (encoding dopamine receptor D2) is associated with alternative splicing and cognitive functioning; however, a mechanistic relationship to schizophrenia has not been shown. Here, we demonstrate that rs1076560(T) imparts a small but reliable risk for schizophrenia in a sample of 616 affected families and five independent replication samples totaling 4017 affected and 4704 unaffected individuals (odds ratio=1.1; P=0.004). rs1076560(T) was associated with impaired verbal fluency and comprehension in schizophrenia but improved performance among healthy comparison subjects. rs1076560(T) also associated with lower D2 short isoform expression in postmortem brain. rs1076560(T) disrupted a binding site for the splicing factor ZRANB2, diminished binding affinity between DRD2 pre-mRNA and ZRANB2 and abolished the ability of ZRANB2 to modulate short:long isoform-expression ratios of DRD2 minigenes in cell culture. Collectively, this work implicates rs1076560(T) as one possible risk factor for schizophrenia in the Han Chinese population, and suggests molecular mechanisms by which it may exert such influence.

Assessment of functional tag single nucleotide polymorphisms within the DRD2 gene as risk factors for post-traumatic stress disorder in the Han Chinese population

BACKGROUND

Gene variations related to the dopaminergic pathway have been implicated in a number of neuropsychiatric disorders, including post-traumatic stress disorder (PTSD). Dopamine D2 receptor (DRD2) has been shown to significantly contribute to neuropsychiatric disorders and may specifically contribute to predisposition to PTSD. This study aimed to evaluate the association of polymorphisms within the entire DRD2 gene with PTSD in a case-control study.

MATERIALS AND METHODS

A total of 834 unrelated Han Chinese adults, including 497 healthy volunteers and 337 patients with PTSD, were used in this study. Fifteen tag single-nucleotide polymorphisms (tSNPs) were selected spanning the entire DRD2 gene through the construction of haplotype bins. Genotypes were gathered using an improved multiplex ligation detection reaction (iMLDR) technique. Allelic frequencies and clinical characteristics were compared in two independent Han Chinese populations. Moreover, the functionality of the rs2075652 and rs7131056 polymorphisms were assessed by measuring transcriptional enhancer activities.

RESULTS

Fifteen tag SNPs were identified in the Han Chinese population and all were common SNPs. Among 15 tSNPs, two of them (rs2075652 and rs7131056) significantly associated with PTSD. PTSD individuals were more likely to carry the rs2075652A and rs7131056A allele compared to the controls (P<0.05). The haplotype GTGATCGCGCAGGCG, had a risk effect on PTSD occurrence (OR=1.75, 95% CI: 1.24-2.48, P=0.002). Additionally, the rs2075652 polymorphism contained intronic enhancer activities.

CONCLUSIONS

The rs2075652 and rs7131056 polymorphisms, and the haplotype GTGATCGCGCAGGCG within the DRD2 gene, may be potential markers to predict susceptibility to PTSD.

The significant association of Taq1A genotypes in DRD2/ANKK1 with smoking cessation in a large-scale meta-analysis of Caucasian populations

Although a number of studies have analyzed the relation between the DRD2/ANKK1 gene Taq1A polymorphism and smoking cessation, the results remain controversial. The primary objective of the present study was to determine whether this variant indeed has any effect on smoking cessation. The A1-dominant model that considers A1/* (*=A1 or A2) and A2/A2 as two genotypes and compares their frequencies in current and former smokers was applied. A total of 22 studies with 11,075 subjects were included in the meta-analyses. Considering the potential influence of between-study heterogeneity, we conducted stratified meta-analyses with the Comprehensive Meta-Analysis statistical software (version 2.0). Results based on either cross-sectional or longitudinal studies consistently showed a statistically significant association between Taq1A A1/* genotypes and smoking cessation. Further, a more significant association of the variant with smoking cessation was detected when both types of studies were combined. However, there was marginal evidence of heterogeneity among studies (I(2)=33.9%; P=0.06). By excluding other ethnicities and subjects with cancer, the meta-analysis on the basis of 9487 Caucasians demonstrated that Taq1A A1/* genotypes indeed were significantly associated with smoking cessation under both the fixed- and random-effects models (pooled OR 1.22; 95% CI 1.11-1.34; P=3.9 × 10(-5) for both models). No evidence of between-study heterogeneity or publication bias was observed. Thus, we conclude that the polymorphism of Taq1A has an important role in the process of abstaining from smoking, and smokers carrying A2/A2 genotype have a higher likelihood of smoking cessation than those who carry A1/A1 or A1/A2.

Interactions of genetic variants reveal inverse modulation patterns of dopamine system on brain gray matter volume and resting-state functional connectivity in healthy young adults

Different genotypic combinations of COMT and DRD2 can generate multiple subgroups with different levels of dopamine signaling. Its modulations on brain properties can be investigated by analyzing the combined gene effects of COMT and DRD2. However, the inherent association between modulation patterns of the dopamine system on structural and functional properties of the brain remains unknown. In 294 healthy young adults, we investigated both additive and non-additive interactions of COMT and DRD2 on gray matter volume (GMV) and resting-state functional connectivity (rsFC) using a voxel-based analysis. We found a significant non-additive COMT × DRD2 interaction in the right dorsal anterior cingulate cortex (dACC), exhibiting an inverted U-shape modulation by dopamine signaling. We also found a significant non-additive COMT × DRD2 interaction in the rsFC between the right dACC and precuneus, displaying a U-shape modulation by dopamine signaling. Moreover, this rsFC was negatively correlated with the GMV of the right dACC. Although the additive interaction did not pass corrections for multiple comparisons, we also found a trend towards an inverse modulation pattern and a negative correlation between the GMV and rsFC of the right inferior frontal gyrus. No genotypic differences were detected in any assessments of the cognition, mood and personality. These findings suggest that healthy young adults without optimal dopamine signaling may maintain their normal behavioral performance via a functional compensatory mechanism in response to structural deficit due to genetic variation.

Updated findings of the association and functional studies of DRD2/ANKK1 variants with addictions

Both nicotine and alcohol addictions are severe public health hazards worldwide. Various twin and family studies have demonstrated that genetic factors contribute to vulnerability to these addictions; however, the susceptibility genes and the variants underlying them remain largely unknown. Of susceptibility genes investigated for addictions, DRD2 has received much attention. Considering new evidence supporting the association of DRD2 and its adjacent gene ankyrin repeat and kinase domain containing 1 (ANKK1) with various addictions, in this paper, we provide an updated view of the involvement of variants in DRD2 and ANKK1 in the etiology of nicotine dependence (ND) and alcohol dependence (AD) based on linkage, association, and molecular studies. This evidence shows that both genes are significantly associated with addictions; however the association with ANKK1 appears to be stronger. Thus, both more replication studies in independent samples and functional studies of some of these variants are warranted.

Common polymorphisms in dopamine-related genes combine to produce a 'schizophrenia-like' prefrontal hypoactivity

Individual changes in dopamine-related genes influence prefrontal activity during cognitive-affective processes; however, the extent to which common genetic variations combine to influence prefrontal activity is unknown. We assessed catechol-O-methyltransferase (COMT) Val108/158Met (rs4680) and dopamine D2 receptor (DRD2) G-T (rs2283265) single nucleotide polymorphisms and functional magnetic resonance imaging during an emotional response inhibition test in 43 healthy adults and 27 people with schizophrenia to determine the extent to which COMT Val108/158Met and DRD2 G-T polymorphisms combine to influence prefrontal response to cognitive-affective challenges. We found an increased number of cognitive-deficit risk alleles in these two dopamine-regulating genes predict reduced prefrontal activation during response inhibition in healthy adults, mimicking schizophrenia-like prefrontal hypoactivity. Our study provides evidence that functionally related genes can combine to produce a disease-like endophenotype.

Schizophrenia thalamus imaging: low benzamide binding to dopamine D2 receptors suggests fewer D2Short receptors and fewer presynaptic terminals

The dopamine D2 receptor continues to be the major target for the treatment of schizophrenia and is one of many genes genetically associated with this disease. Recent data show that fewer short forms of the D2 receptor protein are synthesized if there is a genetic variant in the D2 receptor (with a T in rs 1076560 in intron 6). At the same time, at least six publications report that the binding of radioactive benzamides is reduced in the schizophrenia thalamus. A review of the benzamide pharmacology of the short and long forms of the D2 receptor shows that benzamides have a 2.4-fold higher affinity for the D2Short receptor relative to the D2Long form. Hence, the reduced amount of benzamide binding to the D2 receptors in the schizophrenia thalamus suggests that there is a reduced amount of D2Short receptors in this diseased region, and may possibly also mean fewer presynaptic terminals because that is where D2Short receptors mostly reside. If so, fewer presynaptic dopamine terminals in various brain regions may be the basis of the known behavioural dopamine supersensitivity in schizophrenia.

Genetic variants of the BDNF and DRD3 genes in bipolar disorder comorbid with anxiety disorder

BACKGROUND

The high comorbidity rate between bipolar disorder (BP) and anxiety disorder (AD) has been studied in depth. This comorbidity is not as high in Han Chinese in Taiwan. Therefore, we explored the genetic effects BP comorbid with AD.

METHODS

We recruited 1316 participants: 286 with BP-I, 681 with BP-II, and 349 healthy Controls. Genotypes of the BDNF Val66Met and DRD3 Ser9Gly polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

RESULTS

The DRD3 Ser9Gly polymorphism was associated with BP-II comorbid with AD (BPII(+AD)), and the BDNF Val66Met polymorphism was associated with BP-I comorbid with AD (BPI(+AD)). An interaction between the Val/Val genotype of the BDNF Val66Met and Gly/Gly polymorphism of the DRD3 Ser9Gly was found in BPII(+AD), but not in BP-II not comorbid with AD (BPI(-AD)) compared with healthy Controls.

LIMITATION

The low comorbidity rate of AD in both BP subtypes, especially BP-I, limit generalizing our findings.

CONCLUSION

The involvement of the dopaminergic pathway in AD was confirmed, particularly with BP-II rather than BP-I. Because the Val/Val genotype of the BDNF Val66Met polymorphism, rather than the other two polymorphisms, has been associated with anxiety, it seems to affect BP-I comorbid with AD without the involvement of the DRD3 Seg9Gly polymorphism, but may modify the involvement of DRD3 Gly/Gly in BP-II comorbid with AD.

The dopamine receptor D2 (DRD2) SNP rs1076560 is associated with opioid addiction

The risk for drug addiction is partially heritable. Genes of the dopamine system are likely candidates to harbour risk variants, as dopamine neurotransmission is involved in mediating the rewarding effects of drugs of abuse. One functional single nucleotide polymorphism in dopamine receptor D2 (DRD2), rs1076560, is involved in regulating splicing of the gene and alters the ratio of DRD2 isoforms located pre- and postsynaptically. rs1076560 has been previously associated with cocaine abuse and we set out to confirm this association in a sample of European American (EA) (n = 336) and African American (AA) (n = 1034) cocaine addicts and EA (n = 656) and AA (n = 668) controls. We also analysed the role of rs1076560 in opioid dependence by genotyping EA (n = 1041) and AA (n = 284) opioid addicts. rs1076560 was found to be nominally associated with opioid dependence in EAs (p = 0.02, OR = 1.27) and AAs (p = 0.03, OR = 1.43). When both opioid-addicted ancestral samples were combined, rs1076560 was significantly associated with increased risk for drug dependence (p = 0.0038, OR = 1.29). This association remained significant after correction for multiple testing. No association was found with cocaine dependence. These data demonstrate the importance of dopamine gene variants in the risk for opioid dependence and highlight a functional polymorphism that warrants further study.