Family-based association study of 76 candidate genes in bipolar disorder: BDNF is a potential risk locus. Brain-derived neutrophic factor

Identification of the genetic bases for bipolar disorder remains a challenge for the understanding of this disease. Association between 76 candidate genes and bipolar disorder was tested by genotyping 90 single-nucleotide polymorphisms (SNPs) in these genes in 136 parent-proband trios. In this preliminary analysis, SNPs in two genes, brain-derived neurotrophic factor (BDNF) and the alpha subunit of the voltage-dependent calcium channel were associated with bipolar disorder at the P<0.05 level. In view of the large number of hypotheses tested, the two nominally positive associations were then tested in independent populations of bipolar patients and only BDNF remains a potential risk gene. In the replication samples, excess transmission of the valine allele of amino acid 66 of BDNF was observed in the direction of the original result in an additional sample of 334 parent-proband trios (T/U=108/87, P=0.066). Resequencing of 29 kb surrounding the BDNF gene identified 44 additional SNPs. Genotyping eight common SNPs identified three additional markers transmitted to bipolar probands at the P < 0.05 level. Strong LD was observed across this region and all adjacent pairwise haplotypes showed excess transmission to the bipolar proband. Analysis of these haplotypes using TRANSMIT revealed a global P value of 0.03. A single haplotype was identified that is shared by both the original dataset and the replication sample that is uniquely marked by both the rare A allele of the original SNP and a novel allele 11.5 kb 3'. Therefore, this study of 76 candidate genes has identified BDNF as a potential risk allele that will require additional study to confirm.     

A quantitative association study between schizotypal traits and COMT, PRODH and BDNF genes in a healthy Chinese population

Previous studies have suggested that catechol-O-methyltransferase (COMT), proline dehydrogenase (PRODH), and brain-derived neurotrophic factor (BDNF) genes are possible susceptibility genes for schizophrenia. We hypothesized that these genes are also associated with schizotypal traits, which are heritable and related to schizophrenia. We genotyped five single nucleotide polymorphism (SNPs) from the COMT, PRODH and BDNF genes, and performed a series of association analyses between alleles, genotypes or haplotypes, and quantitative schizotypal trait scores derived from the Schizotypal Personality Questionnaire (SPQ), in 465 Chinese healthy subjects. We found that 'years of education' was a major influence on seven out of nine schizotypal components, three schizotypal factors and the total SPQ scores. Molecular genetic analysis of COMT, PRODH and BDNF genes showed no significant effects of any variants on schizotypal components or factors of SPQ after correction for multiple testing, although there were weak association between COMT Val158Met (rs4680G/A) and the odd speech subscale (allele-wise, P=0.04; genotype-wise, P=0.049), between COMT Val158Met (rs4680G/A) and the suspiciousness subscale (genotype-wise, P=0.024), and between BDNF Val66Met and the Factor 2 interpersonal measure (genotype-wise, P=0.027) before correction. Furthermore, we found SNP Val158Met (rs4680) of the COMT gene significantly influenced the scores of some of schizotypal traits including total SPQ score, the disorganization factor and the constricted affect subscale in male subjects only. However, the effect was in the opposite direction of an earlier association with the SPQ reported by Avramopoulos et al. [Avramopoulos, D., Stefanis, N.C., Hantoumi, I., Smyrnis, N., Evdokimidis, I., Stefanis, C.N., 2002. Higher scores of self reported schizotypy in healthy young males carrying the COMT high activity allele. Molecular Psychiatry 7, 706-711]. We conclude that SNP Val158Met (rs4680) in the COMT gene may be associated with some schizotypal traits in male subjects, but our results are not conclusive.     

Family-based association study of serotonergic candidate genes and attention-deficit/hyperactivity disorder in a German sample

Summary Alterations in the serotonergic pathway have been implicated in the pathogenesis of attention-deficit/hyperactivity disorder (ADHD). The aim of this study was to investigate seven genetic variants in three genes (serotonin transporter (5-HTT), serotonin receptor 1B (5-HTR1B) and serotonin receptor 2A (5-HTR2A)), which have previously been shown to be associated with ADHD. The polymorphisms under investigation were the 5-HTTLPR, the VNTR in intron 2 and the 3′UTR SNP in 5-HTT, the 5-HTR1B variations 861G>C and 102T>C, and the 5-HTR2A variations His452Tyr and 1438G>A. We genotyped these variants in a sample of 102 families with 229 children with ADHD according to DSM-IV criteria. Among the affected children, 69% fulfilled criteria for the combined type, 27% for the predominantly inattentive type, and 4% for the predominantly hyperactive-impulsive type. Associations were tested by the pedigree transmission disequilibrium test (PDT). All investigated polymorphisms in serotonergic candidate genes showed no association to ADHD in our sample. Earlier studies of these polymorphisms had also shown inconsistent results, with some studies reporting significant associations and others demonstrating no association. This discordance between studies may reflect variation in patient ascertainment criteria, genetic heterogeneity, too low statistical power for the expected effects or false positive results in the initial reports. We cannot rule out the possibility that other variations in the investigated genes contribute to the etiology of ADHD.     

Family-based association studies of bipolar disorder with candidate genes involved in dopamine neurotransmission: DBH, DAT1, COMT, DRD2, DRD3 and DRD5

The dopaminergic system has been implicated in the aetiology of mood disorders. We conducted family-based association studies for polymorphisms at three genes involved in the metabolism of dopamine: dopamine transporter (DAT1), dopamine-beta-hydroxylase (DBH) and catechol-O-methyl transferase (COMT); and three dopamine receptors: DRD2, DRD3 and DRD5. We used a sample of 122 parent-offspring trios of British Caucasian origin where the proband had bipolar disorder I (BPI), and analysed the results with the transmission/disequilibrium test (TDT) which is robust to hidden population stratification. No statistically significant differences were found between transmitted and not transmitted alleles for any of the polymorphisms studied.     

Family-based association of FKBP5 in bipolar disorder

The FKBP5 gene product forms part of a complex with the glucocorticoid receptor and can modulate cortisol-binding affinity. Variations in the gene have been associated with increased recurrence of depression and with rapid response to antidepressant treatment. We sought to determine whether common FKBP5 variants confer risk for bipolar disorder. We genotyped seven tag single-nucleotide polymorphisms (SNPs) in FKBP5, plus two SNPs previously associated with illness, in 317 families with 554 bipolar offspring, derived primarily from two studies. Single marker and haplotypic analyses were carried out with FBAT and EATDT employing the standard bipolar phenotype. Association analyses were also conducted using 11 disease-related variables as covariates. Under an additive genetic model, rs4713902 showed significant overtransmission of the major allele (P=0.0001), which was consistent across the two sample sets (P=0.004 and 0.006). rs7757037 showed evidence of association that was strongest under the dominant model (P=0.001). This result was consistent across the two datasets (P=0.017 and 0.019). The dominant model yielded modest evidence for association (P<0.05) for three additional markers. Covariate-based analyses suggested that genetic variation within FKBP5 may influence attempted suicide and number of depressive episodes in bipolar subjects. Our results are consistent with the well-established relationship between the hypothalamic-pituitary-adrenal (HPA) axis, which mediates the stress response through regulation of cortisol, and mood disorders. Ongoing whole-genome association studies in bipolar disorder and major depression should further clarify the role of FKBP5 and other HPA genes in these illnesses.     

Meta-analysis of the association of serotonin transporter gene polymorphism with obsessive-compulsive disorder

Evidence has supported a role for serotonin system dysfunction in the pathogenesis of the obsessive-compulsive disorder (OCD). Many studies examined the association between OCD and a functional polymorphism of the serotonin transporter gene promoter (5-HTTLPR) but yielded inconsistent results. Current study aimed to determine conclusively whether there is an association by using a meta-analytic method. Over 3000 subjects from 13 independent case-control association studies were included in the analysis. By using random effects model, data from these studies were pooled to compare the genotypes and allelic distribution of the 5-HTTLPR polymorphism between OCD patients and control subjects. In the analysis, OCD was found to be associated with the SS homozygous genotype (OR=1.21, p=0.04), but was inversely associated with the LS heterozygous genotype (OR=0.79, p=0.03). No association with the LL homozygous genotype or the allelic distribution was found. These results suggest that variations of the serotonin transporter gene influence the risk of OCD, but their functional roles in the pathogenesis of OCD need to be elucidated.     

Family-based association studies support a sexually dimorphic effect of COMT and MAOA on genetic susceptibility to obsessive-compulsive disorder.

BACKGROUND: Obsessive-compulsive disorder (OCD) is a common and severe psychiatric illness that affects 1-3% of the population and presents a well-established co-morbidity with major depressive disorder (MDD). Twin and family studies have suggested a genetic component in the etiology of OCD, although the mode of inheritance is unknown. Pharmacotherapy of the disease implicates both serotonergic and dopaminergic pathways. Previously, guided by the 22q11 microdeletion-related psychiatric phenotype, we provided evidence for a sexually dimorphic association between OCD and the gene for catechol-O-methyltransferase (COMT). In this report, we use 110 nuclear OCD families to analyze the inheritance of variants of COMT and monoamine oxidase-A (MAOA), another gene modulating monoamine metabolism. METHODS: A sample of 110 nuclear OCD families was collected, and lifetime diagnoses were ascertained using the Diagnostic Interview for Genetic Studies (DIGS). DNA was genotyped for functional variants of the COMT and MAO genes, and allele inheritance was examined using the Transmission Disequilibrium Test (TDT) and Haplotype-based Haplotype Relative Risk (HHRR) test. RESULTS: We provide evidence supporting the previously reported sexually dimorphic association between low COMT enzymatic activity and OCD. We also provide evidence for a similar sexually dimorphic association between OCD and an allele of the MAOA gene, previously linked to high MAO-A enzymatic activity. In agreement with the well-established action of MAO-A inhibitors as antidepressants, this association is particularly marked among male OCD probands with co-morbid MDD, who represent more than 50% of our male OCD sample. CONCLUSIONS: Our analysis indicates that variants of two genes modulating monoamine metabolism contribute significantly to OCD susceptibility. Most importantly, an unexpected sexually dimorphic pattern of genetic susceptibility to OCD is revealed and suggests the possibility that profound gender differences in genetic predisposition may exist not only for other OCD susceptibility genes, but for an array of other psychiatric disorders as well.     

5-羟色胺转运体启动子区基因多态性与强迫症的关联分析

目的:探索汉族人群中的5-羟色胺转运体启动子区(5-HTTLPR)基因多态性与强迫症的发病关系.方法:对强迫症患者(强迫症组)和正常对照者(对照组)分别采用聚合酶链反应扩增片断长度多态技术测定基因型.结果:强迫症组与对照组5-HTTLPR的基因型频率无显著性差异;两组的等位基因频率有显著性差异.L等位基因与强迫症呈正关联(OR=1.929,P＜0.05).结论:5-HTTLPR基因多态性的L等位基因与强迫症相关联,是强迫症的危险因子.     

情感性精神障碍与5-羟色胺转运体基因的连锁不平衡研究

目的探讨情感性精神障碍与5-羟色胺转运体(5-HTT)基因之间的分子遗传学联系：方法以中国汉族人群中的72个情感性精神障碍核心家系(双相情感性精神障碍56例，重性抑郁症34例)作为研究对象，采用自编家系调查表、美国精神障碍诊断与统计手册第4版诊断标准并结合心理测评工具，应用聚合酶链反应(PCR)和限制性片段长度多态性分析方法，检测其5-HTT基因启动子区(5-HTTLPR)、第2内含子[数目可变的顺向重复(VNTR)]和3’端非编码区(3’UTRG／T)基因多态性，并进行连锁不平衡(TDT)分析。结果5-HTT基因中的VNTR与3’UTRG／T2个位点组合单体型与情感性精神障碍存在关联(TDT-x^2=4．08，经Monte Carlo逼真法1000次重复校正后的经验P值=0．04)，其他各位点5-HTTLPR、VNTR、3’UTRG／T等位基因与情感障碍未发现存在连锁不平衡，其他位点组合的单体型分析也未发现存在连锁不平衡。结论5-HTT基因在情感性精神障碍的遗传病因中可能起着一定作用。     

5-羟色胺转运体基因启动子区域多态性与汉族强迫症的关联分析

目的探讨5-羟色胺转运体（Serotonin transporter,5-HTT）基因SLC6A4（solute car-rier family6,member4）启动子区域上44个碱基对插入/缺失多态性与汉族强迫症的关系,研究强迫症病理生理机制。方法将符合《疾病及有关健康问题的国际分类》（第10版,ICD-10）诊断标准的23例强迫症患者,及其父母纳入研究。用PCR法检测判定各自的基因型,用传递不平衡检测（transmission disequilibriumtest,TDT）及单体型相对风险检测（haplotype-based haplotype relative risk,HHRR）测其等位基因的传递是否平衡。结果在所收23个核心家系中,共有24个父母为杂和基因型,在24个杂合子父母中,13个传递了‘l’等位基因,11个传递了‘s’等位基因,未发现有传递不平衡存在（χ^2 DT=0.167,P〉0.05;χ^2HRR=0.820,P〉0.05）。结论5-羟色胺转运体基因启动子区域多态性与中国汉族强迫症可能不存在关联。     

广泛性焦虑障碍与5-羟色胺转运体基因多态性的相关研究

目的　探讨广泛性焦虑障碍与 5 羟色胺转运体 (5 HTT)基因启动子区和内含子 2区两种多态性的相关性。方法　运用聚合酶链反应技术检测 4 7例广泛性焦虑障碍患者 (患者组 )和 90名健康对照者 (对照组 )两种基因多态性的分布频率。结果　患者组启动子区多态性 (5 HTTLPR)的short/short(SS)基因型和short(S)等位基因频率分别为 72 %和 83% ,对照组SS基因型和S等位基因频率分别为 4 9%和 71% ,两组间的差异有显著性 (P <0 0 5 )。内含子 2区数目可变的顺向重复多态性各基因型 (12 / 12 ,12 / 10 ,10 / 10 )频率在患者组中分别为 72 % ,2 6 % ,2 % ,在对照组中分别为 78% ,2 1% ,1% ,两组间的差异无显著性 (P >0 0 5 ) ;等位基因频率比较的差异亦无显著性 (P >0 0 5 )。结论　 5 HTTLPR的SS基因型可能是广泛性焦虑障碍的易感基因之一。     

5-羟色胺转运体基因和单胺氧化酶A基因多态性与汉族男性反社会人格障碍患者的关联分析

目的 探讨5-羟色胺转运体基因(5-HTT)第2内含子的一个可变数串联重复序列(Stin2.VNTR)和单胺氧化酶A(MAOA)基因14外显子上的一种限制性片段长度多态性(EcoRV-RFLP)与汉族男性反社会人格障碍(APD),尤其是具有高度冲动性APD的遗传易感性的关系.方法 (1)APD组:对南京地区某监狱男性服刑人员进行人格诊断问卷(PDQ-4+)调查,在PDQ得分为阳性的可疑人群中由临床医师以美国精神障碍诊断与统计手册第4版(DSM-Ⅳ)关于APD诊断标准进一步确诊,入组118例;全部进行Barratt冲动量表(BIS-11)评分,以冲动总分中位值为界,划分为高冲动APD组和低冲动APD组.(2)监狱对照组:经PDQ排除人格障碍的250名服刑人员作为监狱内对照.(3)正常对照组:同时期医院健康体检者300名设为正常对照.取所有人员血液标本提取DNA,应用聚合酶链反应(PCR)和限制性片段长度多态性方法,对等位基因频率和基因型频率进行对比分析.结果 (1)APD组与正常对照组比较,5-HTT-VNTR基因型多态、MAOA-EcoRV-RFLP多态差异无统计学意义(x2=2.819,P=0.244;x2=2.347,P=0.126).(2)高冲动APD组与正常对照组比较,5-HTT-VNTR基因型多态差异有统计学意义(x2=7.422,P=0.024),MAOA-EcoRV-RFLP的等位基因频率有统计学意义(x2=5.478,P=0.019).(3)2个位点的联合分析中,APD组和高冲动APD组分别与对照组比较,12/12/-多倍体型的差异均有统计学意义(x2=7.164,P=0.007;x2=9.590,P=0.002);12/10/+仅在高冲动APD组与正常对照组间差异有统计学意义(x2=5.378,P=0.020).结论 5-HTT基因第2内含子VNTR多态、MAOA基因EcoRV-RFLP多态与具有高冲动的APD关联,12/12/-多倍体型与中国汉族男性APD发病风险可能有关.     

Obsessive-compulsive disorder, factor-analyzed symptom dimensions and serotonin transporter polymorphism

Recently, on the basis of the effects of serotonin (5-HT) reuptake inhibitors in obsessive-compulsive disorder (OCD) treatment, several candidate genes related to 5-HT regulation have been hypothesized to play an important role in the development of OCD. One of them is 5-HT transporter gene. Therefore, the aims of this study were to investigate the associations between 5-HT transporter polymorphism and OCD. One hundred and twenty-four OCD patients and 171 normal controls participated in this study. Genomic DNA was extracted from their blood. Comparison of the genotypes and allele frequencies of the SERTPR polymorphism between the OCD group and the control group was made. Using principal component analysis, we derived four factors from thirteen main contents of the Y-BOCS checklist and investigated the association between these four factors and the SERTPR polymorphism. In this case-control study, we could not find any associations between the SERTPR polymorphism and the development of OCD. In the OCD group, patients with the L genotype had higher scores for the religious/somatic factor than with the S genotype. In conclusion, the SERTPR polymorphism does not affect the development of OCD. But SERTPR polymorphisms affect certain factors of OC symptoms. Moreover, the factor analytic approach used in the present study has identified meaningful symptom dimensions to help guide future research.     

Family-based association study of Epsin 4 and Schizophrenia

Recently, Pimm et al. identified Epsin 4 on chromosome 5q33 as a susceptibility gene for schizophrenia in the British population, based on linkage and association evidence. In Pimm's case-control study, both the single polymorphisms and the individual haplotypes at the 5' end of the gene showed genetic association with schizophrenia. Here, we report the first study evaluating the relevance of Epsin 4 and schizophrenia outside the British population. Markers showing positive results in the original work as well as two additional polymorphisms were genotyped in 308 Han Chinese family trios. Transmission disequilibrium analysis was used to test for association of single-locus markers and multi-locus haplotypes with schizophrenia. Although no individual marker was significant at the P=0.05 level, the haplotypes detected in our samples, different from those previously reported, showed strong evidence of association (most significant global P=0.0021). Our results indicate the presence of a locus near the 5' end of Epsin 4 conferring susceptibility to the disease and provide further support for Epsin 4 as an important potential contributor to genetic risk in schizophrenia.     

Controlled study of encopresis and enuresis in children with a prepubertal and early adolescent bipolar-I disorder phenotype

OBJECTIVE: To examine the prevalence of encopresis/enuresis, relationship between maternal hostility and encopresis, parent-child concordance of reporting encopresis/enuresis, and familial aggregation of enuresis in subjects with a prepubertal and early adolescent bipolar-I disorder phenotype (PEA-BP), attention-deficit/hyperactivity disorder (ADHD), and healthy controls (HC). METHOD: There were 268 consecutively ascertained subjects (93 PEA-BP, 81 ADHD, and 94 HC). PEA-BP was defined as DSM-IV BP-I (manic or mixed phase) with elation and/or grandiosity. The WASH-U-KSADS and Psychosocial Schedule for School-Age Children-Revised were administered to parents about their children and separately to children about themselves. RESULTS: Encopresis was more prevalent in PEA-BP versus HC subjects (15.1% versus 3.2%, chi2 = 6.4, p = .012). Enuresis was more common in PEA-BP versus HC (21.5% versus 6.4%, chi2 = 7.8, p = .005) and ADHD versus HC (22.2% versus 6.4%, chi2 = 6.1, p = .014) subjects. All enuresis onset in subjects not receiving lithium. Most encopresis (81.8%) and enuresis (75.0%) onset before mania. Familial aggregation of enuresis was more frequent in enuretics than nonenuretics (47.7% versus 5.4%, chi2 = 41.2, p < .0001). Maternal hostility was more prevalent in encopretic versus nonencopretic subjects (91.7% versus 55.6%, chi2 = 8.3, p = .004). Parent-child concordance on reporting encopresis and enuresis was poor to fair. CONCLUSIONS: Children with PEA-BP need to be evaluated for encopresis, enuresis, and mother-child relationships.