Effects of DRD2/ANKK1 gene variations and clinical factors on aripiprazole efficacy in schizophrenic patients

OBJECTIVES: Aripiprazole, a novel antipsychotic agent, acts as a partial agonist at dopamine D2 receptors (DRD2). We investigate whether its efficacy is predictable by DRD2/ANKK1 gene polymorphisms and clinical factors in Han Chinese hospitalized patients with acutely exacerbated schizophrenia. METHOD: After hospitalization, the patients (n=128) were given aripiprazole for up to 4 weeks. They were genotyped for four functional DRD2/ANKK1 polymorphisms: -141 Ins/Del, Ser311Cys, C957T, and TaqIA. Clinical factors such as gender, age, illness duration, education level, diagnostic subtype, and medication dosage were also recorded. Psychopathology was measured biweekly with the positive and negative syndrome scale (PANSS). The effects of genetic and clinical factors on PANSS performance upon aripiprazole treatment were analyzed by a mixed modeling approach (SAS Proc MIXED). RESULTS: Compared to the patients with TaqI A2/A2 genotype, A1 carriers are associated with superior therapeutic response on positive symptoms after 4-week aripiprazole treatment. Regarding the C957T polymorphism, patients with C/C genotype were associated with poor aripiprazole response for excitement symptoms when compared with T/T patients. The other two polymorphisms, -141 Ins/Del, and Ser311Cys, have no significant effects on PANSS performance. The clinical factors including medication dosage, illness duration, and diagnostic subtype could influence PANSS performance upon aripiprazole treatment. CONCLUSION: This study suggests that DRD2/ANKK1 gene variations and some clinical factors may predict individual response to aripiprazole.     

多巴胺D3受体基因Ser9Gly多态性与阿立哌唑及利培酮治疗效应的关联研究

目的比较阿立哌唑与利培酮治疗女性首发精神分裂症患者的疗效和血浆催乳素水平变化及其与多巴胺D3受体(DRD3)基因Ser9Gly(rs6280)多态性的关联。方法选择完成8周阿立哌唑或利培酮治疗的女性首发精神分裂症患者各60例,于治疗前和治疗8周后分别评测阳性与阴性症状量表(positive and negativesymptom scale,PANSS)。采用放射免疫法检测血浆催乳素水平,DNA测序技术检测DRD3基因Ser9Gly多态性,分析DRD3基因Ser9Gly多态性与两药疗效及血浆催乳素变化的关联。结果治疗8周后,两组PANSS减分率的差异无统计学意义[(59.79±23.48)vs.(63.30±22.66),P>0.05],但利培酮组血浆催乳素的变化值高于阿立哌唑组[(26.92±9.48)vs.(-25.25±8.07),P<0.05]。利培酮组中C等位基因携带者的血浆催乳素的增加明显高于未携带者[(52.48±27.01)ng/mL vs(36.07±17.46),P<0.05];而阿立哌唑组中未见此差异[(-23.27±8.36)vs.TT(-26.05±8.11),P>0.05]。两组8周后PANSS减分率(%)与DRD3基因Ser9Gly的差异均无统计学意义:阿立哌唑组[CC+CT(57.83±19.94)vs.TT(56.84±18.46),P>0.05];利培酮组[CC+CT(53.94±21.08)vs.TT(60.38±19.37),P>0.05]。结论阿立哌唑治疗女性首发精神分裂症疗效与利培酮相当,但引起血浆催乳素水平变化的幅度较小;利培酮引起血浆催乳素水平增加可能与DRD3基因Ser9Gly多态性有关联。     

多巴胺D3受体基因多态性与精神分裂症

目的:探讨沈阳地区汉族人群中多巴胺D3受体基因(DRD3)第一外显子第9密码子A→G单核苷酸置换多态性(Ser9Gly多态)与精神分裂症的关联。方法:采用聚合酶链反应-限制性内切酶片断长度多态性(PCR-RFLP)技术对70例精神分裂症患者、94名健康对照者进行基因分型鉴定。比较患者组与对照组DRD3多态性分布频率、精神分裂症早发组与非早发组基因分布频率差异,并与其他国家人群进行比较。结果:患者组与对照组之间等位基因分布无明显差异,早发组与非早发组亦未发现明显差异,而该位点等位基因分布频率与巴西、英国人群有明显差异。结论:研究人群中未发现DRD3基因Ser9Gly多态与精神分裂症存在明显关联。     

多巴胺D_3受体基因多态性与精神分裂症临床表型

目的：探讨多巴胺D3受体（DRD3）基因多态性与精神分裂症临床表型的关系。方法：对73个精神分裂症核心家系83例精神分裂症患者（患者组）及其146名父母（父母组）应用聚合酶链反应、限制性内切酶消化方法、琼脂糖凝胶电泳结合紫外凝胶成像系统检测DRD3基因中的3个位点（Ser9Gly、Ala38Thr和-205A/G）的多态性;采用阳性与阴性症状量表（PANSS）评定精神分裂症临床表型。结果：两组DRD3基因中3个位点的基因型分布及等位基因的频率分布差异无显著性;但在患者组中,对Ser9Gly位点3种基因型（Ser9Ser、Ser9Gly和Gly9Gly）进行分组比较时,Gly9Gly组的PANSS抑郁因子评分明显高于Ser9Ser组和Ser9Gly组,3组间比较,差异有显著性（P=0.042）。对Ala38Thr位点3种基因型（Ala38Ala、Ala38Thr和Thr38Thr）进行分组比较,PANSS总分及各因子分在Ala38Ala、Ala38Thr和Thr38Thr组间差异均无显著性。对-205A/G位点3种基因型（A/A、A/G和G/G）进行分组比较,G/G组的PANSS反应缺乏因子评分明显高于A/A组和A/G组,3组间比较,差异有显著性（P=0.048）。结论：DRD3基因变异可能与精神分裂症的病理症状有关。     

多巴胺D3受体基因多态性与精神分裂症亚型及利培酮疗效相关性分析

目的探讨多巴胺D3受体(dopamine D3 receptor,DRD3)基因第一外显子丝氨酸9甘氨酸(Ser9Gly)多态性与精神分裂症临床亚型、药物疗效的关联.方法 241 例汉族首发精神分裂症患者,采用限制性片段长度多态性(restriction fragment length polymorphism,RFLP)技术测定基因型.分析判断基因多态性与精神分裂症的临床亚型、药物疗效的关联. 结果精神分裂症各亚型Ser9Gly等位基因分布存在显著性差异(p <0.05).利培酮疗效不同的患者间Ser9Gly等位基因多态性均无显著性差异. 结论 DRD3受体基因第一外显子Ser9Gly多态性可能与精神分裂症亚型相关,而与患者对药物的反应不相关.     

The COMT and DRD3 genes interacted in bipolar I but not bipolar II disorder

Abstract

Objectives. Clarifying the association between bipolar I and bipolar II disorders at the genetic level is essential for improving our understanding of them. In this study, we evaluated the hypothesis that the dopaminergic polymorphisms are risk factors for bipolar disorders. We examined the association between the catechol-O-methyltransferase (COMT) Val158Met and dopamine D3 receptor (DRD3) Ser9Gly polymorphisms and bipolar I and II disorders, as well as possible interactions between these genes. Methods. Seven hundred and eleven participants were recruited: 205 with bipolar I, 270 with bipolar II, and 236 healthy controls. The genotypes of the COMT Val158Met and DRD3 Ser9Gly polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis. Results. Logistic regression analyses showed a statistically significant main effect for the Met/Met genotype of the COMT Val158Met polymorphism (P=0.032) and a significant interaction effect for the Met/Met genotype of the COMT Val158Met and Ser/Ser genotypes of the DRD3 Ser9Gly polymorphism (P=0.001) predicted bipolar I patients. However, there was no association between the COMT Val158Met or DRD3 Ser9Gly and bipolar II. Conclusions. We provide initial evidence that the COMT Val158Met and DRD3 Ser9Gly genotypes interact in bipolar I and bipolar II disorders and that bipolar I and bipolar II are genetically distinct.     

Genetic variants of D2 but not D3 or D4 dopamine receptor gene are associated with rapid onset and poor prognosis of methamphetamine psychosis

D2-like receptors are key targets for methamphetamine in the CNS, and their activation is an initial and indispensable effect in the induction of dependence and psychosis. It is possible that genetic variants of D2-like receptors may affect individual susceptibility to methamphetamine dependence and psychosis. To test this hypothesis, 6 putatively functional polymorphisms of D2-like receptors, −141C Ins/Del, Ser311Cys and TaqIA of the DRD2 gene, Ser9Gly of the DRD3 gene, and −521C>T and a variable number of tandem repeats in exon 3 of the DRD4 gene, were analyzed in 202 patients with methamphetamine dependence and/or psychosis and 243 healthy controls in a Japanese population. No polymorphism examined showed significant association with methamphetamine dependence, but two polymorphisms of DRD2 were associated with the clinical course and prognosis of methamphetamine psychosis. The A1/A1 homozygote of DRD2 was a negative risk factor for a poorer prognosis of psychosis that continues for more than 1 month after the discontinuance of methamphetamine abuse and the beginning of treatment with neuroleptics (p = 0.04, odds ratio (OR) = 0.42, 95% CI; 0.27–0.65) and the complication of spontaneous relapse of methamphetamine psychosis after remission (p = 0.014, OR = 0.34, 95% CI; 0.22–0.54). The genotype of −141C Del positive (Del/Del and Del/Ins) was at risk for rapid onset of methamphetamine psychosis that develops into a psychotic state within 3 years after initiation of methamphetamine abuse (p = 0.00037, OR = 3.62, 95% CI 2.48–5.28). These findings revealed that genetic variants of DRD2, but not DRD3 or DRD4, confer individual risks for rapid onset, prolonged duration, and spontaneous relapse of methamphetamine psychosis.     

Interaction of the DRD3 and BDNF gene variants in subtyped bipolar disorder

Objectives

Bipolar disorder is a severe mental disorder with prominent genetic etiologic factors. Dopaminergic dysfunction has been implicated in the pathogenesis of bipolar disorder, which suggests that the dopamine D3 receptor gene (DRD3) is a strong candidate gene. The brain-derived neurotrophic factor (BDNF) gene has been implicated in the etiology of bipolar disorder. We examined the association between the BDNF Val66Met and DRD3 Ser9Gly polymorphisms with two subtypes of bipolar disorder: bipolar-I and -II. Because BDNF regulates DRD3 expression (1), we also examined possible interactions between these genes.

Methods

We recruited 964 participants: 268 with bipolar-I, 436 with bipolar-II, and 260 healthy controls. The genotypes of the BDNF Val66Met and DRD3 Ser9Gly polymorphisms were determined using polymerase chain reactions plus restriction fragment length polymorphism analysis.

Results

Logistic regression analysis showed a significant main effect for the Val/Val genotype of the BDNF Val66Met polymorphism (P = 0.020), which predicted bipolar-II patients. Significant interaction effects for the BDNF Val66Met Val/Val genotype and both DRD3 Ser9Gly Ser/Ser and Ser/Gly genotypes were found only in bipolar-II patients (P = 0.027 and 0.006, respectively).

Conclusion

We provide initial evidence that the BDNF Val66Met and DRD3 Ser9Gly genotypes interact only in bipolar-II disorder and that bipolar-I and bipolar-II may be genetically distinct.     

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.     

A psycho-genetic study of associations between the symptoms of binge eating disorder and those of attention deficit (hyperactivity) disorder

Objective

Some recent studies have reported intriguingly strong correlations between ADHD and obesity. This study examined whether ADHD symptoms were more pronounced in adults with symptoms of binge eating disorder (BE) than in their non-binging obese counterparts, and whether the links were stronger with inattentive vs impulsive/hyperactive symptoms. We also assessed the role of the dopamine D3 receptor in ADHD symptoms since the DRD3 gene has been associated with impulsivity and drug addiction - both relevant features of ADHD.

Methods

A case (BE: n = 60) double-control (normal weight: n = 61 and obese: n = 60) design was employed. Assessments of both childhood and adults ADHD symptoms were made, as well as genotyping of seven markers of DRD3 including the functional Ser9Gly polymorphism.

Results

Three DRD3 genotypes, including Ser/Ser, had significantly elevated scores on the hyperactive/impulsive symptom scale. In turn, the four ADHD symptom scales were all significantly elevated in the BE and obese groups, who did not differ from each other, compared to those with normal weight.

Conclusions

Results indicated a role for the D3 receptor in the manifestation of the hyperactive/impulsive symptoms of ADHD, and that symptoms of ADHD are significantly, but not differentially, elevated in obese adults with and without binge eating. Our findings suggest that ADHD screening in adults seeking treatment for obesity, including those with BE, may be warranted as methods used to treat ADHD may help some to better manage overeating and other factors contributing to weight gain.     

DRD3 Ser9Gly variant is not associated with essential tremor in a series of Italian patients

Background: Essential tremor (ET) is the most common movement disorder worldwide. Three susceptibility loci on chromosomes 3q13, 2p24.1, and 6p23 have been reported, but no causative genes were found. The Ser9Gly variant of dopamine D3 receptor (DRD3) receptor was found associated to ET in a French and US population. Methods: A case–control study to evaluate the association between the Ser9Gly variant and ET was performed in a cohort of 116 Italian patients with familial ET and in 158 normal controls. Results: No significant difference in allele and genotype frequencies was found between the two groups. Conclusions: These results do not support an association between DRD3 Ser9Gly and susceptibility to ET in Italian patients.     

Novel, replicated associations between dopamine D3 receptor gene polymorphisms and schizophrenia in two independent samples.

BACKGROUND: Meta-analyses have suggested an association between schizophrenia (SZ) and a coding polymorphism (rs6280/Ser9Gly) at the dopamine D3 receptor gene (DRD3), but results have been inconsistent. Because most studies have evaluated only rs6280, the inconsistencies might reflect associations with other variants. METHODS: We analyzed polymorphisms spanning 109kb in two independent samples (United States: 13 single nucleotide polymorphisms (SNPs), 331 cases, 151 trios, 274 control subjects; India: 11 SNPs, 141 trios). RESULTS: In the U.S. samples, significant associations were detected with eight SNPs, including rs6280 (p = .001, odds ratio: 1.5). Consistent associations in the case-control and family-based analyses were detected with a common haplotype spanning intron 1 to the 3' region of the gene (rs324029-rs7625282-rs324030-rs2134655-rs10934254; case-control, p = .002; transmission disequilibrium test [TDT], p = .0009; global p-values = .002 and .007, respectively). In the Indian sample, one SNP was associated (rs10934254, p = .03). Moreover, over-transmission of the same common haplotype as the U.S. sample was observed in this cohort (TDT, p = .005; global test, p = .009). Ser9Gly (rs6280) was associated with SZ against this haplotype background but not other haplotypes. CONCLUSIONS: These data suggest previous inconsistencies might have resulted from associations with other DRD3 variants. A liability locus might be in linkage disequilibrium (LD) with or carried against, an associated haplotype 3' to rs6280. Comprehensive SNP evaluation in larger samples is needed.     

Association between dopamine-related polymorphisms and plasma concentrations of prolactin during risperidone treatment in schizophrenic patients

Hyperprolactinemia is an inevitable consequence of treatment with antipsychotic agents to some extent because prolactin response to antipsychotics is related to dopamine blockade. Recent studies have suggested that polymorphisms of the dopamine receptors are associated with therapeutic response to antipsychotics. Thus, we studied the effects of major polymorphisms of dopamine-related genes on plasma concentration of prolactin. Subjects were 174 schizophrenic patients (68 males, 106 females) receiving 3 mg twice daily of risperidone for at least 4 weeks. Sample collections were conducted 12 h after the bedtime dosing. Five dopamine-related polymorphisms (Taq1A, -141C ins/del for DRD2, Ser9Gly for DRD3, 48 bp VNTR for DRD4, Val158Met for COMT) were identified. The mean (+/-SD) plasma concentration of prolactin in females was significantly higher than males (54.3+/-27.2 ng/ml versus 126.8+/-70.2 ng/ml, p<0.001). No dopamine-related polymorphisms differed the plasma concentration of prolactin in males or females. Multiple regression analyses including plasma drug concentration and age revealed that plasma concentration of prolactin correlated with gender (standardized partial correlation coefficients (beta)=0.551, p<0.001) and negatively with age (standardized beta=-0.202, p<0.01). No correlations were found between prolactin concentration and dopamine-related polymorphisms. These findings suggest that plasma prolactin concentrations in females are much higher than in males but the dopamine-related variants are not predominantly associated with plasma concentration of prolactin.     

Motor complications in patients form the German Competence Network on Parkinson's disease and the DRD3 Ser9Gly polymorphism

In addition to levodopa treatment and disease duration, genetic predisposition might contribute to the development of medication‐related complications in Parkinson's disease (PD). As recent observations indicate the dopamine D₃ receptor (DRD3) to modulate both therapeutic action of levodopa and dyskinesia, we reappraised the impact of the DRD3 Ser9Gly polymorphism on development of motor complications in a large scale association study based on the gene bank of the German Competence Network on Parkinson's disease. Stepwise regression analysis revealed no effect of DRD3 Ser9Gly on chorea, dystonia, or motor fluctuations in PD, despite incorporating established clinical risk factors to avoid overlooking an effect of genotype. Duration of PD was confirmed as the most important clinical risk factor, followed by age of disease onset and female sex. Additional studies incorporating grading of motor complications, and combinations of risk genotypes, are warranted. © 2009 Movement Disorder Society     

Genetic polymorphisms in the dopamine-2 receptor (DRD2), dopamine-3 receptor (DRD3), and dopamine transporter (SLC6A3) genes in schizophrenia: Data from an association study

Objective

To investigate the association between dopaminergic polymorphisms [DRD2 −141C Ins/Del, DRD3 Ser9Gly, and SLC6A3 VNTR] and schizophrenia.

Methods

Two hundred and eighty-eight outpatients with schizophrenia (DSM-IV criteria) [mean age (SD) = 36.4 (12.4), 60.1% males] and 421 unrelated healthy controls [mean age (SD) = 40.6 (11.3), 51.3% males] from a homogeneous Spanish Caucasian population were genotyped using standard methods.

Results

There was a significant difference in genotype distribution for the DRD2 −141C Ins/Del polymorphism [(χ² (2) = 12.35, corrected p = 0.012]. The − 141C Del allele was more common in patients than in controls [0.19 vs. 0.13; χ² (1) = 9.14, corrected p = 0.018, OR (95% CI) = 1.57 (1.17–2.10)]. Genotype and allele distributions for DRD3 Ser9Gly and SLC6A3 VNTR polymorphisms were similar in both groups. However, there was tentative evidence of an interaction effect between DRD3 Ser9Gly and SLC6A3 VNTR [Wald = 9.56 (4), p = 0.049]. Compared to the SLC6A3 10/10 genotype category, the risk of schizophrenia was halved among those with 9/10 [OR = 0.51 (95% CI = 0.30–0.89), p = 0.017]. This protective effect was only present in combination with DRD3 Ser/Ser genotype because of the significant interaction between 9/10 and both Ser/Gly [OR = 2.45 (95% CI = 1.16–5.17), p = 0.019] and Gly/Gly [OR = 3.80 (95% CI = 1.24–11.63), p = 0.019].

Conclusions

This study provides evidence that a genetic variant in the DRD2 gene and possible interaction between DRD3 and SLC6A3 genes are associated with schizophrenia. These findings warrant examination in replication studies.     

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.     

The association of genotypic combination of the DRD3 and BDNF polymorphisms on the adhesio interthalamica and medial temporal lobe structures

Abnormal neurodevelopment in midline structures such as the adhesio interthalamica (AI), as well as in the medial temporal lobe structures has been implicated in schizophrenia, while its genetic mechanism is unknown. This magnetic resonance imaging study investigated the effect of the genotypic combination of the dopamine D3 receptor (DRD3) Ser9Gly and brain-derived neurotrophic factor (BDNF) Val66Met polymorphisms on the AI length and volumetric measures of the medial temporal lobe structures (amygdala, hippocampus, and parahippocampal gyrus) in 33 schizophrenia patients and 29 healthy controls. The subjects with a combination of the Ser/Ser genotype of DRD3 and Met-containing genotypes of BDNF (high-risk combination) had a shorter AI than those without it in the healthy controls, but not in the schizophrenia patients. The subjects carrying the high-risk combination had a smaller posterior hippocampus than those without it for both diagnostic groups. These genotypic combination effects on brain morphology were not explained by the independent effect of each polymorphism. These findings suggest the effect of gene-gene interaction between the DRD3 and BDNF variations on brain morphology in midline and medial temporal lobe structures, but do not support its specific role in the pathogenesis of schizophrenia.     

Polymorphisms of DRD4 and DRD3 and risk of avoidant and obsessive personality traits and disorders

We investigated whether polymorphisms of the dopamine D4 receptor (DRD4) and polymorphisms of the dopamine D3 receptor (DRD3) were associated with personality disorder symptomatology rather than with personality traits such as novelty seeking. DNA was obtained from 145 depressed patients in a clinical trial. These patients were assessed for the presence of personality disorder symptoms and disorders. The 2-repeat allele of the DRD4 exon III polymorphism was associated with increased rates of avoidant and obsessive personality disorder symptomatology. The T,T genotype of the DRD4 -521 C>T polymorphism was also associated with increased rates of avoidant and obsessive personality disorder symptomatology. The Gly9,Gly9 genotype of the DRD3 Ser9Gly polymorphism was associated with increased rates of obsessive personality disorder symptomatology. None of these three polymorphisms were associated with novelty seeking or other temperament traits on the Temperament and Character Inventory. Our results suggest that genetic polymorphisms of DRD4 and DRD3 may well be associated with personality traits, and that conflicting findings to date may arise from the problem of phenotype definition.     

Association of the Ser9Gly polymorphism in the dopamine D3 receptor gene with tardive dyskinesia in Korean schizophrenics

Tardive dyskinesia (TD) is usually regarded as one of the most serious side-effects of the long-term usage of neuroleptics due to its high prevalence and potentially irreversible nature. Previously, several genetic polymorphisms were investigated for an association with TD in various ethnic populations. Among them, the Ser9Gly variant in the MscI restriction site of the dopamine D3 receptor gene was reported to be associated with TD. We have investigated the association of Ser9Gly polymorphism of the dopamine D3 receptor gene with TD in Korean schizophrenics. The frequencies of the genotypes of Ser/Ser, Ser/Gly and Gly/Gly in 54 schizophrenic patients without TD were 21 (38.9%), 33 (61.1%) and 0 (0%), while the corresponding frequencies in 59 schizophrenic patients with TD were 25 (42.4%), 28 (47.5%) and 6 (10.1%). We have found a significant genotypic association of the Gly/Gly genotype with TD in Korean schizophrenics (P = 0.028, two-tailed Fisher's exact test). However, there was no significant allelic association of the Ser9Gly allele with TD (chi2 = 0.288, d.f. = 1, P = 0.591) and there was no significant difference in the Abnormal Involuntary Movement Scale score between the three genotypic groups (P = 0.071, anova). In conclusion, we suggest that Gly/Gly homozygotes in the MscI polymorphic site of the dopamine D3 receptor gene may cause some change in the function of the dopamine D3 receptor and may be involved the pathogenesis of TD.     

Investigation of the genetic interaction between BDNF and DRD3 genes in suicidical behaviour in psychiatric disorders

Objectives. Suicide is a serious public health concern, and it is partly genetic. The brain-derived neurotrophic factor (BDNF) gene has been a strong candidate in genetic studies of suicide (Dwivedi et al., Arch Gen Psychiatry 2010;60:804–815; Zai et al., Prog Neuropsychopharmacol Biol Psychiatry 2012;34:1412–1418) and BDNF regulates the expression of the dopamine D₃ receptor. Objective. We examined the role of the BDNF and DRD3 genes in suicide. Methods. We analysed four tag single-nucleotide polymorphisms (SNPs) in BDNF and 15 SNPs in the D₃ receptor gene DRD3 for possible association with suicide attempt history in our Canadian sample of Schizophrenia (SCZ) patients of European ancestry (N = 188). Results. In this sample, we found a possible interaction between the BDNF Val66Met and DRD3 Ser9Gly SNPs in increasing the risk of suicide attempt(s) in our SCZ sample. Specifically, a larger proportion of SCZ patients who were carrying at least one copy of the minor allele at each of the Val66Met and Ser9Gly functional markers have attempted suicides compared to patients with other genotypes (Bonferroni P < 0.05). However, we could not replicate this finding in samples from other psychiatric populations. Conclusions. Taken together, the results from the present study suggest that an interaction between BDNF and DRD3 may not play a major role in the risk for suicide attempt, though further studies, especially in SCZ, are required.