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。     

A transmission disequilibrium test of the Ser9/Gly dopamine D3 receptor gene polymorphism in adult attention-deficit hyperactivity disorder

Convincing data support the hypothesis that genetic factors are involved in the etiology of attention-deficit hyperactivity disorder (ADHD). Various lines of evidence have shown that the dopamine system plays a crucial role in the pathophysiology of ADHD. The dopamine D3 receptor gene (DRD3) represents a promising candidate to examine in ADHD. Animal studies have shown that DRD3 mRNA is highly expressed in the ventral striatum suggesting an involvement of this receptor in the control of motor behaviour. Manipulation of DRD3 in rodents has led to a mouse model with nonfunctional D3 receptors that displays hyperactive behaviour in various environmental conditions. Furthermore, administration of 7-OH-DPAT, a dopaminergic agonist that binds preferentially to D3 receptors exerts an inhibitory effect on locomotor activity while D3 antagonists induce hyperactivity. Among various polymorphisms described for DRD3, the BalI polymorphism is most interesting because it codes for an aminoacid substitution in the N-terminus of the receptor. The receptor products of the two alleles (Ser/Gly) exhibit differential affinity for dopamine. To determine if DRD3 Ser9/Gly is involved in the susceptibility to ADHD we genotyped 39 adults with ADHD and their respective parents (trios). Adult ADHD represents a promising phenotype for studying the genetic component of the disorder. In fact, a recent family study has shown that relatives of adult ADHD patients have a higher rate of ADHD compared to relatives of children with ADHD suggesting a stronger genetic component for the adult version. The results of genotyping in the 39 trios analyzed with the transmission disequilibrium test showed no excess of transmission for DRD3 MscI/BalI alleles (χ²=0.360; DF=1; P=0.54). This result, although from a relatively small sample, indicates that it is unlikely that DRD3 is playing a major role in the etiology of ADHD in our sample.     

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.     

Mutation and association analysis of the 5' region of the dopamine D3 receptor gene in schizophrenia patients: identification of the Ala38Thr polymorphism and suggested association between DRD3 haplotypes and schizophrenia

Although the association between the Ser9Gly polymorphism of the dopamine D3 receptor gene (DRD3) and schizophrenia has been investigated by many research groups, it is not known whether the Ser9Gly polymorphism alone or a variation in linkage disequilibrium may effect susceptibility to schizophrenia. We searched the 5' region of the DRD3 gene and found three novel polymorphisms: -712G/C, -205A/G, and Ala38Thr. The Ala38Thr polymorphism is located in the first transmembrane region and is conserved in the monkey, mouse, and rat. Case-control comparisons in 153 Japanese schizophrenia patients and 122 Japanese controls did not suggest an association between Ala38Thr and schizophrenia. However, there was a marginally significant association between the Ser9 allele of the Ser9Gly polymorphisms and schizophrenia (P = 0.02). Furthermore, there was a highly significant association between haplotypes of the -712G/C, -205A/G, and Ser9Gly polymorphisms and schizophrenia (P = 0.0007, corrected P = 0.007). These positive findings were replicated in an additional 99 Japanese schizophrenia patients and 132 controls (P = 0.04 and 0.0004, respectively). The most allelic differences of the Ser9Gly polymorphism between patient and control groups arose from the chromosome carrying specific alleles of the other three polymorphisms. This study indicates unknown variant(s) in linkage disequilibrium with the DRD3 haplotypes associated with schizophrenia.     

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.     

Association between the ionotropic glutamate receptor kainate3 (GRIK3) Ser310Ala polymorphism and schizophrenia in the Indian population

Various studies have been done to check the status of glutamate receptor gene in the pathogenesis of schizophrenia. The T928G (Ser310Ala) polymorphism of ionotropic glutamate receptor kainate 3 gene (GRIK3) and its positive association with schizophrenia was reported in Caucasians, whereas no association of this polymorphism with schizophrenia was shown in two other populations, Chinese and Japanese. However, no literature is available regarding the prevalence of this polymorphism and its association with schizophrenia in the Indian population. As genetic susceptibility profiles in India are often different from those of white Caucasians or Orientals, we investigated the status of Ser310Ala polymorphism of GRIK3 in 100 schizophrenic patients and 100 healthy controls in the Indian population by the PCR-RFLP (restriction fragment length polymorphism) method. A statistically significant difference in the genotype and allelic distributions (P<0.000001 and P=0.01, respectively) of Ser310Ala polymorphism was found in schizophrenics than in control, considering Ala-allele as being associated with the disease (OR=1.7, 95% CI=1.137–2.540). Our study suggests a potential role for GRIK3 for susceptibility to schizophrenia in Indian population.     

Allelic variation in the human prodynorphin gene promoter and schizophrenia

Experimental and clinical studies suggest an involvement of the opioid neuropeptide system in schizophrenia. In particular, the prodynorphin (PDYN), the precursor of the dynorphin opioid peptides, has been shown to play an important role in several aspects of human mental diseases. Recently, a functional polymorphism in the promoter of PDYN gene has been described. We studied the possible relationship between this polymorphism and schizophrenia and we found no significant difference in allelic and genotype distributions between schizophrenic patients and control subjects. However, we observed a significant interactive effect with the receptor 3 of dopamine gene (DRD3); in particular, the frequency of subjects carrying PDYN allele 3 being also homozygotes for DRD3 Gly allele (of Ser9Gly polymorphism) was significantly greater in patients than controls. We conclude that PDYN gene polymorphism alone does not alter the risk for schizophrenia but, by an epistatic interaction with the Gly allele of DRD3 gene, may contribute to the susceptibility to this disorder.     

Association between dopamine D3 receptor gene polymorphisms and schizophrenia in an isolate population

There are several lines of evidence implicating the dopamine D3 receptor in the pathophysiology of schizophrenia. The Ser9Gly polymorphism of the dopamine D3 receptor gene (DRD3) has been the most extensively investigated DRD3 variant in connection with the disease but results have been inconclusive. Recent reports indicate that the Ser9Gly polymorphism is in linkage disequilibrium with other markers, but association studies between DRD3 haplotypes and schizophrenia have had mixed results. Genetic heterogeneity may be one of the causes of contradicting results. In order to clarify the role of DRD3 alterations in the aetiology of disease, we have investigated three D3 genetic variants (Ser9Gly, -205-G/A, -7685-G/C) in a sample of patients with schizophrenia or schizoaffective disorder (N=118) and controls (N=162) recruited from a human isolate from Navarra (Northern Spain) of Basque origin. Although no association was found between the Ser9Gly or the -205-A/G polymorphisms and disease, an excess of allele -7685-C was observed in patients (p=0.002 after correction for multiple analyses). Haplotype analysis shows the three markers to be in strong linkage disequilibrium (p<0.0001) and strongly associated with disease (p<1x 10(-5)). These results may suggest that these polymorphisms exert a combined or synergistic effect on susceptibility to schizophrenia, or are in linkage with an unknown causative factor. However, further replication in independent samples is required.     

Meta-analysis of the influence of DRD3 Ser9Gly variant on susceptibility for essential tremor

The dopamine D3 receptor (DRD3) Ser9Gly variant has attracted more attention since the variant was observed to be associated with risk of essential tremor (ET). A number of association studies concerning the DRD3 Ser9Gly variant and ET susceptibility have been conducted in various populations. However, some results were contradictory. To derive a more precise estimation of the relationship between the DRD3 Ser9Gly variant and the genetic risk of ET, we performed a comprehensive meta-analysis which included seven case–control studies. The meta-analysis was conducted in four genetic models: dominant, recessive, heterozygous, and homozygous. The odds ratio and 95% confidence intervals were used as the measure of association. The combined results of overall analysis showed a lack of association of the DRD3 Ser9Gly variant and ET, regardless of the genetic model of Ser9Gly. Publication bias and heterogeneity were absent in most analyses. In conclusion, the present meta-analysis does not support the notion that the DRD3 Ser9Gly variant is a genetic risk factor for ET.     

Association study of a (TG)n dinucleotide repeat at chromosome 15q13.3 and schizophrenia in the Chinese population

Linkage studies have suggested that chromosome 15q13–q14 may harbor a susceptibility locus for schizophrenia. In the current study, the association between a (TG)n dinucleotide repeat polymorphism at D15S976 and schizophrenia was investigated using two independent samples from the Han Chinese population. In a population-based study, no significant difference was found between the genotype and allele frequency distributions in schizophrenia patients and control subjects. In a family-based study, no significant transmission disequilibrium from heterozygous parents to affected offspring was observed. Further analysis of the parent-of-origin effect found nominally significant allele-wise transmission disequilibrium through maternal transmissions, while 157bp and 159bp alleles showed significant individual allelic transmission disequilibrium from heterozygous mothers to affected offspring. Our results did not support the hypothesis that the (TG)n dinucleotide repeat polymorphism plays a major role in schizophrenia susceptibility in the Chinese population. Further studies are needed to elucidate the putative parent-of-origin effect and its role in schizophrenia susceptibility.     

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。     

Brain-derived neurotrophic factor gene C-270T and Val66Met functional polymorphisms and risk of schizophrenia: a moderate-scale population-based study and meta-analysis

BACKGROUND: Lines of evidence have suggested that the brain-derived neurotrophic factor (BDNF) gene may be involved in the pathogenesis of schizophrenia. Two common functional polymorphisms C-270T and Val66Met within the BDNF gene were first reported by Kunugi et al. [Kunugi, H., Nanko, S., Hirasawa, H., Kato, N., Nabika, T., Kobayashi, S., 2003. Brain-derived neurotrophic factor gene and schizophrenia: polymorphism screening and association analysis. Schizophr. Res. 62, 281-283.] and pls expand this too: Hong et al. (2003) to be significantly associated with schizophrenia. However, subsequently several studies obtained conflicting results. METHODS: We compared the allele/genotype frequencies of the C-270T and Val66Met polymorphisms and the haplotype frequencies at the two polymorphisms in a moderate independent patient-control sample from the Han Chinese population. Two systematic meta-analyses were performed to assess the collective evidence for association across studies for each of the two polymorphisms. RESULTS: No statistically significant differences were found in allele or genotype or haplotype frequencies between patient and normal control subjects for either of the two polymorphisms. On the other hand, the meta-analysis of all published population-based association studies showed statistically significant evidence for heterogeneity among each of the two polymorphisms. Stratification of the studies by ethnicity of the samples yielded no significant evidence for an association with the polymorphisms in the Caucasian population (for C-270T polymorphism: pooled OR(Caucasian)=0.736, 95% CI=0.476-1.139, p=0.169; for Val66Met polymorphism: pooled OR(Caucasian)=1.027, 95% CI=0.796-1.325, p=0.835), nor in the Asian population (for C-270T polymorphism: pooled OR(Asian)=0.445, 95% CI=0.144-1.373, p=0.159; for Val66Met polymorphism: pooled OR(Asian)=0.962, 95% CI=0.820-1.128, p=0.635). CONCLUSIONS: Our population-based study and meta-analysis demonstrate that the BDNF C-270T and Val66Met polymorphisms do not play major roles in the susceptibility to schizophrenia in either Caucasian or Asian populations. But we can not rule out the possibility that other polymorphisms with the BDNF gene are involved in the pathophysiology of schizophrenia.     

Effects of the DRD3 Ser9Gly polymorphism on aripiprazole efficacy in schizophrenic patients as modified by clinical factors

Aripiprazole, a novel antipsychotic agent, has a unique pharmacological action (partial agonist) on the dopamine neurotransmission system. Aripiprazole has high affinity for dopamine D2 and D3 receptors (DRD2 and DRD3). We investigated whether the efficacy of aripiprazole can be predicted by a functional DRD3 gene polymorphism Ser9Gly (rs6280) as modified by clinical factors in Han Chinese hospitalized patients with acutely exacerbated schizophrenia. After hospitalization, the patients (n = 128) were given aripiprazole for up to four weeks. Patients were genotyped for DRD3 Ser9Gly polymorphism by Restriction Fragment Length Polymorphism (RFLP) method. Clinical factors such as gender, age, duration of illness, education level, diagnostic subtype and medication dosage were recorded. Psychopathology was measured biweekly with the Positive and Negative Syndrome Scale (PANSS). The effects of genetic and clinical factors on PANSS performance after aripiprazole treatment were analyzed by a mixed model regression approach (SAS Proc MIXED). We found that, although the Ser carriers have numerically larger score reductions when compared with non-carriers in almost all PANSS dimensions, the difference of their effects are statically not significant. However, the clinical factors, including dosage of aripiprazole, age, duration of illness, and diagnostic subtype could influence PANSS performance after aripiprazole treatment. This study suggests that DRD3 Ser9Gly polymorphism may not contribute significantly to inter-individual differences in therapeutic efficacy of aripiprazole, but some clinical factors may predict treatment efficacy.     

Positive association between SIAT8B and schizophrenia in the Chinese Han population

The Sialyltransferase 8B gene (SIAT8B) is located at 15q26, a susceptibility region for both schizophrenia and bipolar disorder. The protein encoded by this gene has an important role in neural development and sialic acid synthesis on the neural cell adhesion molecule (NCAM). Previous research had indicated that the promoter region of SIAT8B is associated with schizophrenia in the Japanese population. To take this further we carried out an association study based on 643 unrelated schizophrenics and 527 unrelated healthy subjects, all Han Chinese, recruited from Shanghai. Although our results differed from those of the Japanese research, rs3759915, also located in the promoter region of SIAT8B, showed nominally significant association with schizophrenia (P = 0.0036). Moreover, haplotypes constructed from rs3759915 and another two SNPs reported in the Japanese study (rs3759914 and rs3759916, also located in promoter region of SIAT8B) which located in the same LD block were significantly associated with schizophrenia (global P = 0.0000050). Our findings indicate that SIAT8B may be a candidate susceptibility gene for schizophrenia in the Chinese Han population and may also provide further support for the potential importance of polysaccharide-synthesizing genes in the etiology of schizophrenia.     

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。     

Dopamine D3 receptor (DRD3) gene polymorphism is associated with the intensity of eye movement disturbances in schizophrenic patients and healthy subjects.

Altered dopamine neurotransmission and eye movement disturbances have been implicated in the pathogenic process of schizophrenia. So far, molecular genetic studies have shown little association between schizophrenia and polymorphism of any dopamine receptor or transporter genes except for some findings concerning D3 receptor (DRD3) gene. Eye movement disturbances occur in a majority of patients with schizophrenia and in a proportion of their first-degree relatives and they have been suggested as a phenotypic marker in genetic studies of this illness. Here we report an association between the Ser9Gly polymorphism of the DRD3 gene and the intensity of eye movement disturbances (fixation and smooth pursuit) observed in 119 schizophrenic patients and in 94 unrelated healthy control subjects. In schizophrenic patients, the mean intensity of both kinds of eye movement disturbances was highest in individuals with the Ser-Ser genotype, significantly lower in Ser-Gly and lowest in the Gly-Gly genotype. The Ser-Ser genotype was more prevalent in patients with a higher intensity of both fixation (58.1 vs 23.9% P < 0.001) and smooth pursuit disturbances (52.3 vs 25.8%, P < 0.02) and the Ser-Gly genotype frequency was lower in patients with higher fixation disturbances (37.0 vs 60.9%, P < 0.02). In control subjects, the genotype frequency Ser-Ser was higher in subjects with any degree of eye movement disturbances compared to subjects without such disturbances both for fixation and smooth pursuit performance (81.0 vs 50.7%, P < 0.05 and 79.2 vs 50.0%, P < 0.05, respectively). In control subjects the frequency of Ser-Gly was lower in the first group, for either fixation or smooth pursuit, compared to normal performers (9.5 vs 43.8%, P < 0.01 and 8.3 vs 45.7, P < 0.005, respectively). We suggest that the DRD3 Ser9Gly polymorphism may be a contributing factor to the performance of eye movements used as a phenotypic marker of schizophrenia.     

Oxidative stress in tardive dyskinesia: Genetic association study and meta-analysis of NADPH quinine oxidoreductase 1 (NQO1) and Superoxide dismutase 2 (SOD2, MnSOD) genes

Introduction

Tardive dyskinesia (TD) is a potentially irreversible side effect of antipsychotic medication treatment that occurs in approximately 25% of chronically treated schizophrenia patients. Oxidative stress has been one of the proposed mechanisms influencing TD risk. Pae et al. (2004) originally reported a significant association between TD and the NADPH quinine oxidoreductase 1 (NQO1) gene Pro187Ser (C609T, rs1800566) polymorphism in Korean schizophrenia patients; however, subsequent studies have not consistently replicated these findings. Similarly, Hori et al. (2000) reported an association between TD and the Manganese superoxide dismutase SOD2 (MnSOD) gene Ala9Val (rs4880) polymorphism in a Japanese sample, but most research groups failed to replicate their positive findings.

Aims

We investigated the role of the NQO1 polymorphism Pro187Ser and SOD2 (Ala9Val) in a group of well-characterized schizophrenia patients (N = 223) assessed for TD. We also performed a meta-analysis of all the previously published TD studies, including data from our sample, on these polymorphisms, Pro187Ser (N = 5 studies) and Ala9Val (N = 9 studies).

Results

We did not observe a significant association of the Pro187Ser or Ala9Val polymorphism with TD occurrence or AIMS scores in our Caucasian and African American samples when analyzed independently. Meta-analysis did not reveal a significant association of the Pro187Ser/Ala9Val alleles or genotypes with TD occurrence.

Conclusions

Neither the NQO1 Pro187Ser nor the SOD2 Ala9Val appear to play a major role in TD risk, although additional polymorphisms should be tested before the role of NQO1 and SOD2 in TD can be completely excluded.     

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.     

Catechol-O-methyltransferase gene Val/Met functional polymorphism and risk of schizophrenia: a large-scale association study plus meta-analysis.

BACKGROUND: A common functional polymorphism (Val/Met) in the catechol-O-methyltransferase gene (COMT) that markedly affects enzyme activity has been shown to affect executive cognition and the physiology of the prefrontal cortex in humans. It is hypothesized that the high activity Val allele slightly increases risk for schizophrenia through its effect on dopamine-mediated prefrontal information processing. METHODS: We compared the allele/genotype frequencies of the Val/Met polymorphism in a large independent patient-control sample (862 patient and 928 healthy control subjects) from Han Chinese population, and an update meta-analysis was performed to assess the collective evidence across individual studies. RESULTS: No statistically significant differences were found in allele or genotype frequencies between patient and normal control subjects, although a nonsignificant overrepresentation of the Val allele in schizophrenia patients (odds ratio [OR] = 1.09, 95% confidence interval [CI] = .94-1.26) was suggested. Comparatively, the meta-analysis of all published population-based association studies showed statistically significant evidence for heterogeneity among the group of studies. Stratification of the studies by ethnicity of the samples yielded no significant evidence for an association with the Val allele in Asian population (OR = .96, 95% CI = .85-1.09), nor in European population (OR = 1.06, 95% CI = .95-1.19). CONCLUSIONS: Our data provide minimal evidence that the Val allele is a susceptibility factor for schizophrenia in either European or Asian populations.     

Family-based association studies of CAPON and schizophrenia in the Chinese Han population

Although there is evidence pointing to CAPON as a susceptible gene for schizophrenia, the results of independent association studies have so far been inconsistent. A recent case-control study by Zheng et al. supported CAPON as a susceptible site for the disease in the Chinese Han population. In their study both the single polymorphism (rs348624) and individual haplotypes showed significant association with schizophrenia. Our study further investigates this relationship this time using a family-based association. We selected 5 SNPs including rs348624 and performed a Transmission Disequilibrium Test (TDT) in 319 Chinese Han trios. Our results identified no single marker nor haplotype associated with schizophrenia, which did not suggest that CAPON was a susceptible site in the Chinese Han population, or it appeared unlikely that the CAPON played a major role in the aetiology of schizophrenia. Since there is consistent evidence pointing to 1q21-22 as a positional candidate region for schizophrenia, we suggest that further research should focus on other genes located in this region.