双相Ⅱ型障碍伴冲动攻击行为患者的全基因组DNA 甲基化修饰研究

目的 探讨双相Ⅱ型障碍伴冲动攻击行为患者的全基因组DNA 甲基化修饰情况。 方法 纳入5 例有冲动攻击行为的双相Ⅱ型障碍患者（攻击组）及5 例无冲动攻击行为的双相Ⅱ型障碍 患者（非攻击组）,采用Illumina 公司的人类450K 甲基化芯片技术对10 例患者的全血进行甲基化水平的 分析。利用R 软件对原始数据进行预处理并筛选出样本分组间的差异甲基化位点采用GCBI 在线分 析软件对差异候选基因进行功能富集分析。结果 （1）攻击组与非攻击组样本比较甲基化水平有差异。 （2）攻击组与非攻击组样本差异甲基化位点在染色体上的分布有差异。（3）按基因注释分类和CpG 岛注 释分类筛选攻击组与非攻击组样本间的差异甲基化区域,差异甲基化区域在11个注释区域内均有分布。 （4）GO 分析结果显示,差异甲基化位点参与信号传递等功能。Pathway 分析中,主要参与多巴胺能神经 突触信号通路、趋化因子信号通路。结论 有无冲动攻击行为的双相Ⅱ型障碍患者的全基因组DNA 甲 基化水平及差异甲基化DNA 在染色体上的分布均有差异,差异甲基化位点主要参与信号传递等。     

儿童青少年双相抑郁伴攻击行为患者全基因组 DNA甲基化修饰研究

目的 研究儿童青少年双相抑郁伴攻击行为患者全基因组DNA 甲基化情况。方法 选 取2019 年9 月至2021 年1 月在新疆维吾尔自治区人民医院临床心理科就诊的45 例儿童青少年双相障 碍抑郁患者，按照有、无攻击行为分为攻击组（16 例）与无攻击组（29 例）。纳入5 例有攻击行为的儿童 青少年双相障碍抑郁患者（攻击组）及5 例无攻击行为的儿童青少年双相障碍抑郁患者（无攻击组），应 用Illumina 公司的850K 甲基化芯片（Illumina Infinium HumanMethylation EPIC BeadChip，850K array）对 10 例患者外周血中的DNA 进行甲基化分析，使用Genome Studio 软件分析原始数据并筛选出两组间的 差异甲基化位点，使用DAVID 在线数据库对甲基化差异基因进行功能富集分析，并选出2 个基因，使 用焦磷酸测序对攻击组患者、无攻击组患者的外周静脉血样本进行验证。结果 攻击组与非攻击组 样本间存在差异高甲基化位点172 个，包含高甲基化基因87 个；其中差异低甲基化位点148 个，包含低 甲基化基因74 个。差异甲基化位点存在于每条染色体上，主要分布于5''胞嘧啶-磷酸-鸟嘌呤-3''岛 （CpG）的其他区域。有攻击组甲基化β 值峰值在0.63 左右，无攻击组甲基化β 值峰值分别在0.40、0.85 左右。Gene Ontology 分析结果显示，差异甲基化基因参与轴突导向等生物学功能。Pathway 分析中， 存在于粘蛋白型O-聚糖生物合成通路。焦磷酸测序验证中，DPYSL2 基因在两组的甲基化率分别是 （27.438±17.874）%、（27.345±18.832）%，差异无统计学意义（P=0.987）。ABI3BP 基因在两组的甲基化率 分别是（84.188±25.761）%、（78.586±23.567）%，差异无统计学意义（P=0.113）。结论 攻击组与非攻击组 样本间存在差异甲基化位点及基因，这些差异甲基化位点及基因为明确儿童青少年双相抑郁患者攻击行 为的发生原因提供了基础。     

GABRB2基因启动子区DNA甲基化与精神分裂症及其治疗的关系

目的探讨γ-氨基丁酸A型受体β2亚基(gamma-aminobutyric acid type A receptor beta2 subunit,GABRB2)基因启动子区DNA甲基化水平与精神分裂症及其药物治疗的关系。方法纳入精神分裂症患者53例和正常对照53名,采用Mass ARRY Epi TYPER DNA甲基化分析技术检测所有受试者外周血GABRB2基因启动子区DNA甲基化水平。患者组中12例在药物治疗8周后再次检测该基因启动子区DNA甲基化水平。结果患者组与对照组外周血GABRB2基因启动子区总甲基化和各Cp G位点的甲基化水平组间差异无统计学意义(P0.05)。经性别分层分析,患者组男性Cp G_28位点的甲基化水平较对照组男性降低[(0.215±0.084)vs.(0.264±0.103),P0.05]。治疗后患者组外周血GABRB2基因启动子区总DNA甲基化水平较治疗前降低[(0.088±0.037)vs.(0.121±0.063),P0.01],治疗前后各Cp G位点甲基化水平差异无统计学意义(P0.05)。结论抗精神病药物治疗可降低精神分裂症患者外周血中GABRB2基因启动子区DNA甲基化水平,提示基因启动子区DNA甲基化可能参与抗精神病药物治疗的作用机制。     

双相情感障碍患者自杀意念与基因甲基化相关性的研究进展

双相情感障碍是高致残性的重型精神障碍，具有很高的自杀率。近几年，多项研究显示 基因甲基化与双相情感障碍患者自杀意念相关。现对近年来有关双相情感障碍患者自杀意念与基因甲 基化相关性的研究进行归纳总结     

儿童青少年注意缺陷多动障碍外周血全基因组DNA甲基化研究

目的 应用甲基化芯片技术对注意缺陷多动障碍（ADHD）患儿DNA甲基化特征进行研究, 探讨 DNA 甲基化在 ADHD 发病机制中的作用。方法 于 2018 年 10 月至 2019 年 5 月选取在首都医科大 学附属北京安定医院门诊确诊的 8 例 8～16 岁的儿童青少年 ADHD 患儿作为 ADHD 组;招募 8 名年龄、 性别与 ADHD 组匹配的健康儿童青少年作为对照组。采用 Illumina Infinium Methylation EPIC Bead Chip 芯片（850K 芯片）技术对受试者进行全基因组 DNA 甲基化检测,分析和筛选差异甲基化位点。采用 gene ontology（GO）富集分析和 pathway 分析对筛选基因进行功能分类和通路分析。结果 与对照组比较, ADHD 组共有 2 068 个 CpG 位点甲基化水平发生改变,差异有统计学意义（P＜ 0.05）。其中有 842 个高 甲基化位点,1 226 个低甲基化位点,对应 468 个高甲基化基因如 GPR88、ARHGEF10 等,对应 705 个低 甲基化基因如 SKI、PMP2、PRR12、EBF3、BRSK2 等。GO 富集分析显示,差异甲基化基因参与生物学过 程富集于系统发育、神经系统发育以及细胞黏附等。pathway 分析显示,差异甲基化基因与钙黏蛋白信 号通路、神经元系统、Wnt 信号通路、谷氨酸能突触等信号通路相关。结论 DNA 甲基化的异常参与了 ADHD 的发生发展,检测出的差异甲基化基因可能成为 ADHD 的生物标志物或预测因子,差异甲基化基 因相关的信号通路可能与 ADHD 的发病机制相关。     

有自杀意念的儿童青少年双相障碍抑郁发作患者SLC6A4 基因甲基化研究

目的 探讨儿童青少年双相障碍（PBD）抑郁发作患者自杀意念与SLC6A4基因甲基化 的关系。方法 选取 2020 年 12 月至 2022 年 12 月于新疆维吾尔自治区人民医院临床心理科住院的 43 例 PBD 抑郁发作患者为研究对象。采用自杀意念自评量表（SIOSS）评估患者的自杀意念，将总分≥ 12 分且掩饰因子得分＜ 4 分的患者纳入有自杀意念组（n=29），将总分＜ 12 分的患者纳入无自杀意念组 （n=14）。采用 Methprimer 软件对SLC6A4基因启动子区进行甲基化岛预测和甲基化引物设计，将提取好 的DNA经亚硫酸盐转化后进行PCR扩增和焦磷酸盐测序，确定甲基化的CpG位点和甲基化率。比较两组 患者SLC6A4基因不同位点甲基化的差异，采用 Spearman 相关分析基因甲基化与自杀意念的相关性。 结果 基因甲基化检测结果显示，两组患者SLC6A4基因甲基化的位点包括 CpG1、CpG2.3、CpG4、 CpG5.6位点。有自杀意念组与无自杀意念组患者CpG1、CpG2.3、CpG4位点的基因甲基化率比较［48.28% （14/29）比 8/14、96.55%（28/29）比 14/14、20.69%（6/29）比 6/14］，差异无统计学意义（χ2 =0.297、0.494、2.306； P＞ 0.05）。有自杀意念组患者的 CpG5.6 位点基因甲基化率高于无自杀意念组［68.97%（20/29）比 5/14］， 差异有统计学意义（χ2 =4.289，P＜ 0.05）。相关分析结果显示，PBD 抑郁发作患者的 SIOSS 得分与 SLC6A4基因甲基化CpG1位点、CpG2.3位点、CpG4位点不存在相关性（r=-0.244、-0.210、-0.281；P＞0.05）； 与甲基化 CpG5.6 位点呈正相关（r=0.312，P＜ 0.05）。结论 PBD 抑郁发作患者的自杀意念与SLC6A4基 因甲基化 CpG5.6 位点有关，为明确其自杀意念的发生原因提供了基础。     

外周血全基因组DNA甲基化水平与高脂血症发病风险的相关性分析

目的 探讨外周血全基因组DNA甲基化水平与高脂血症发病风险的相关性。方法 选取2019年1月-2021年1月医院门诊患者282例为研究对象,其中高脂血症患者162例(研究组),非高脂血症患者120例(对照组); 采集所有患者晨起空腹外周静脉血,采用高效液相色谱-串联质谱(Liquid chromatography-tandem mass spectrometry,LC-MS/MS)测定2组外周血全基因组DNA甲基化水平; 收集所有患者的相关资料,采用单因素分析影响高脂血症发病的可能相关因素; 采用Logistic多元回归分析影响高脂血症发病的相关因素; 采用Spearman相关性方法分析高脂血症患者外周血全基因组DNA甲基化水平与影响高脂血症发病因素之间的关系,并绘制受试者工作特征曲线(Receiver operating characteristic curve,ROC)分析外周血全基因组DNA甲基化水平对高脂血症的诊断价值。结果 研究组外周血全基因组DNA甲基化水平高于对照组(P<0.05)。研究组BMI≥23 kg/m²、高热量饮食占比高于对照组; 血清总胆固醇(Total cholesterol,TC)、甘油三酯(Triglyceride,TG)、低密度脂蛋白(Low density lipoprotein,LDL)水平均高于对照组; 高密度脂蛋白(High density lipoprotein,HDL)、总胆红素(Total bilirubin,TBIL)水平均低于对照组(P<0.05)。外周血全基因组DNA甲基化水平、TC,TG,HDL,TBIL均是影响高脂血症发病的相关因素(P<0.05)。Spearman相关性分析显示,外周血全基因组DNA甲基化水平与TC,TG水平呈正相关(r=0.321,0.334,P<0.05); 外周血全基因组DNA甲基化水平与HDL,TBIL水平呈负相关(r=-0.352,-0.341,P<0.05)。外周血全基因组DNA甲基化水平诊断高脂血症的最佳截断点为9.51%,ROC曲线下面积(AUC)为0.695,灵敏度为87.04%,特异度为81.67%。结论 高脂血症患者外周血全基因组DNA甲基化水平较高,是影响高脂血症发病的相关因素,与高脂血症发病风险有关,对于高脂血症具有良好诊断价值。     

山东省双相情感障碍6号染色体基因扫描研究

目的 对双相情感障碍患者及正常对照者的6号染色体进行扫描,查找双相情感障碍的关联位点,进而定位易感基因.方法 在6号染色体上间隔10 cM(厘摩)遗传距离选择了20个微卫星遗传标记,对104例发病年龄≤20岁的双相情感障碍患者与1000例正常对照者组成的DNA混合样本分别进行了扫描.采用CLUMP软件进行统计学分析,逐一比较患者组与对照组等位基因频率的差异.结果 在D6S262位点发现患者组与对照组的等位基因频率差异有显著性意义(P<0.05).结论 山东省双相情感障碍患者与6号染色体上D6S262位点关联,基因突变或甲基化调控等致病因子可能位于其附近.     

ANXA7基因异常甲基化与神经胶质瘤发生相关性的研究

目的 研究ANXA7基因异常甲基化与神经胶质瘤发生的相关性.方法 采用硫化测序PCR(BS-PCR)引物以及DNA甲基化特异性PCR(MS-PCR)引物检测ANXA7基因在人脑神经胶质组织及正常脑组织中的表达差异,随后经PCR扩增进行电泳以及测序分析.结果 5例健康标本及5例神经胶质瘤患者标本DNA经硫化且BS-PCR测序分析,其健康标本甲基化率分别为1.5％、1％、1％、1.5％、1％,神经胶质瘤患者甲基化率分别为92％、78.5％、86％、56％、90％;MS-PCR分析结果显示:ANXA7基因在24例正常脑组织中呈完全非甲基化状态,在60例神经胶质瘤患者中其甲基化阳性率为46.67％(p=0.000);高级别神经胶质瘤患者甲基化阳性率(56.67％)高于低级别组(26.67％)(P=0.018).结论 ANXA7基因异常甲基化可能参与神经胶质瘤的发生发展.     

神经胶质瘤Wnt信号通路抑制基因高甲基化改变及其意义

目的研究表明神经胶质瘤中存在Wnt信号通路的异常活化。本研究探讨神经胶质瘤中Wnt信号通路抑制基因启动子区甲基化的改变以及去甲基化药物对其影响。方法对53例恶性胶质瘤组织样本和人胶质瘤细胞系U251、A172检测5个Wnt通路胞外抑制基因:SFRP1、SFRP2、SRFP5、DKK1和WIF1启动子区甲基化状况。去甲基化药物处理胶质瘤细胞后,检测上述5个基因表达水平;采用MTT法和软琼脂细胞集落实验检测胶质瘤细胞生长行为。结果神经胶质瘤组织和细胞系中上述五个基因启动子区存在明显高甲基化修饰。去甲基化药物处理胶质瘤细胞后,RT-PCR分析显示SFRP1、SFRP2、SFRP5和WIF1的表达明显增加,DKK1表达无明显变化;Wnt/β-catenin靶基因CCND1表达明显降低(P0.05);靶基因LRP6表达显著增加(P0.01)。MTT实验和软琼脂细胞集落实验显示去甲基化药物可明显抑制胶质瘤细胞增殖。结论在胶质瘤中Wnt信号通路胞外抑制基因的表达受甲基化调控,去甲基化药物可通过逆转基因的甲基化抑制神经胶质瘤细胞增殖,这为将来去甲基化药物用于恶性胶质瘤治疗提供研究依据。     

Aberrant DNA methylation associated with bipolar disorder identified from discordant monozygotic twins

To search DNA methylation difference between monozygotic twins discordant for bipolar disorder, we applied a comprehensive genome scan method, methylation-sensitive representational difference analysis (MS-RDA) to lymphoblastoid cells derived from the twins. MS-RDA isolated 10 DNA fragments derived from 5' region of known genes/ESTs. Among these 10 regions, four regions showed DNA methylation differences between bipolar twin and control co-twin confirmed by bisulfite sequencing. We performed a case-control study of DNA methylation status of these four regions by pyrosequencing. Two regions, upstream regions of spermine synthase (SMS) and peptidylprolyl isomerase E-like (PPIEL) (CN265253), showed aberrant DNA methylation status in bipolar disorder. SMS, a gene on X chromosome, showed significantly higher DNA methylation level in female patients with bipolar disorder compared with control females. However, there was no difference of mRNA expression. In PPIEL, DNA methylation level was significantly lower in patients with bipolar II disorder than in controls. The expression level of PPIEL was significantly higher in bipolar II disorder than in controls. We found strong inverse correlation between gene expression and DNA methylation levels of PPIEL. These results suggest that altered DNA methylation statuses of PPIEL might have some significance in pathophysiology of bipolar disorder..     

酒精依赖甲基化敏感基因筛选

目的 探讨候选基因甲基化状态和酒精依赖之间的关联,初步了解表观遗传在酒精依赖病理机制中的作用和意义.方法 运用全基因组甲基化芯片,对63例酒精依赖者(酒精依赖组)及65名年龄、文化程度、地域相匹配的健康对照者(对照组)进行检测和分析.结果 2组基因乙醇脱氢酶1A(ADH1A)、乙醛脱氢酶3B2(ALDH3B2)、5-羟...     

Catechol o-methyltransferase, serotonin transporter, and tryptophan hydroxylase gene polymorphisms in bipolar disorder patients with and without comorbid panic disorder.

OBJECTIVE: Genetic epidemiologic and clinical data suggest that comorbid panic disorder may define a subtype of bipolar disorder. Comorbid panic disorder might thereby influence the strength of association between bipolar disorder and genes that have been implicated in bipolar disorder on the basis of their function in monoamine neurotransmission and previously reported linkage results. Polymorphic markers at catechol O-methyltransferase (COMT), serotonin transporter (5-HTT), and tryptophan hydroxylase (TPH) genes were analyzed in a case-control association study of bipolar disorder patients with or without lifetime panic disorder. METHOD: Unrelated subjects of Italian descent meeting DSM-III-R criteria for lifetime bipolar disorder (N=111), with (N=49) or without (N=62) comorbid lifetime panic disorder, were compared to 127 healthy subjects. DNA was extracted from blood leukocytes. The frequencies of COMT Val158Met, 5-HTTLPR, and TPH IVS7+218C>A polymorphisms were determined. Genotype and allele frequency comparisons between affected (bipolar disorder, bipolar disorder without panic disorder, or bipolar disorder with panic disorder) and unaffected individuals were carried out with chi-square tests or Fisher's exact tests. RESULTS: Relative to the comparison subjects, subjects with bipolar disorder without panic disorder, but not those with comorbid bipolar disorder and panic disorder, showed significantly higher frequencies of the COMT Met158 and the short 5-HTTLPR alleles and genotypes. The differences in the frequencies of the TPH IVS7+218A alleles and genotypes approached statistical significance. CONCLUSIONS: The findings support the hypothesis that comorbid panic disorder identifies a genetic subtype of bipolar disorder and suggest a role for COMT and 5-HTT in vulnerability to these disorders.     

DNA methylation of the serotonin transporter gene (SLC6A4) is associated with brain function involved in processing emotional stimuli

Background

The aim of the present study was to investigate the association of fMRI blood oxygen–level dependent (BOLD) reactivity with the level of epigenetic methylation of SLC6A4 in blood DNA from a sample of healthy participants and patients with major depressive disorder (MDD).

Methods

We investigated patients with MDD and healthy controls using fMRI and an emotional attention-shifting task. We assessed site-specific DNA methylation of a previously characterized SLC6A4 region in peripheral blood DNA using pyrosequencing.

Results

Our study involved 25 patients with MDD and 35 healthy controls. Activation in the anterior insula elicited by negative emotional content was significantly positively associated with the degree of SLC6A4 methylation. Significantly negative associations were observed between activation in the posterior insula and the degree of SLC6A4 methylation when judging the geometry of pictures after seeing negative in contrast to positive emotional stimuli. Healthy controls with a high degree of SLC6A4 methylation depicted significantly more activity elicited by positive stimuli in limbic regions and more activity elicited by negative stimuli in limbic as well as cognitive control regions than those with a low degree of SLC6A4 methylation.

Limitations

It is impossible to measure methylation directly in the brain and thus we assessed peripheral methylation of SLC6A4. Since the association was cross-sectional, no conclusion about cause and effect can be drawn.

Conclusion

Our study provides further support to the hypothesis that particular DNA methylation states that are associated with brain function during emotion processing are detectable in the periphery.     

Differences in cerebellar blood volume in schizophrenia and bipolar disorder

Brain morphometry has been studied extensively in schizophrenic patients, and among the cortical differences identified two consistent findings are decreased cerebellar vermal volume and increased volume of the fourth ventricle; although contradictory findings are reported as well. Recent cognitive activation studies utilizing PET, SPECT and fMRI have identified both decreased and increased activation in the cerebellum of schizophrenic patients compared with healthy controls. This study used DSC fMRI to map cerebellar blood volume in patients with schizophrenia or bipolar disorder and healthy controls. For all cerebellar regions analyzed, schizophrenic patients had the highest cerebellar blood volume, while bipolars had the lowest blood volume. Morphometric measurements were completed and indicated that the ratio of vermis to whole CBL tissue volume was 24% less for the schizophrenic population than controls, whereas the subjects with bipolar disorder had a ratio that was non-significantly smaller than controls by 19%. Comparison of morphometric data with blood volume data did not reveal any statistically significant correlations among the study groups.     

A multi-tissue analysis identifies HLA complex group 9 gene methylation differences in bipolar disorder

Epigenetic studies of DNA and histone modifications represent a new and important activity in molecular investigations of human disease. Our previous epigenome-wide scan identified numerous DNA methylation differences in post-mortem brain samples from individuals affected with major psychosis. In this article, we present the results of fine mapping DNA methylation differences at the human leukocyte antigen (HLA) complex group 9 gene (HCG9) in bipolar disorder (BPD). Sodium bisulfite conversion coupled with pyrosequencing was used to interrogate 28 CpGs spanning ～700 bp region of HCG9 in 1402 DNA samples from post-mortem brains, peripheral blood cells and germline (sperm) of bipolar disease patients and controls. The analysis of nearly 40?000 CpGs revealed complex relationships between DNA methylation and age, medication as well as DNA sequence variation (rs1128306). Two brain tissue cohorts exhibited lower DNA methylation in bipolar disease patients compared with controls at an extended HCG9 region (P=0.026). Logistic regression modeling of BPD as a function of rs1128306 genotype, age and DNA methylation uncovered an independent effect of DNA methylation in white blood cells (odds ratio (OR)=1.08, P=0.0077) and the overall sample (OR=1.24, P=0.0011). Receiver operating characteristic curve A prime statistics estimated a 69-72% probability of correct BPD prediction from a case vs control pool. Finally, sperm DNA demonstrated a significant association (P=0.018) with BPD at one of the regions demonstrating epigenetic changes in the post-mortem brain and peripheral blood samples. The consistent multi-tissue epigenetic differences at HCG9 argue for a causal association with BPD.     

Association and linkage studies of candidate genes involved in GABAergic neurotransmission in lithium-responsive bipolar disorder

OBJECTIVE: To test for genetic linkage and association with GABAergic candidate genes in lithium-responsive bipolar disorder. DESIGN: Polymorphisms located in genes that code for GABRA3, GABRA5 and GABRB3 subunits of the GABAA receptor were investigated using association and linkage strategies. PARTICIPANTS: A total of 138 patients with bipolar 1 disorder with a clear response to lithium prophylaxis, selected from specialized lithium clinics in Canada and Europe that are part of the International Group for the Study of Lithium-Treated Patients, and 108 psychiatrically healthy controls. Families of 24 probands were suitable for linkage analysis. OUTCOME MEASURES: The association between the candidate genes and patients with bipolar disorder versus that of controls and genetic linkage within families. RESULTS: There was no significant association or linkage found between lithium-responsive bipolar disorder and the GABAergic candidate genes investigated. CONCLUSIONS: This study does not support a major role for the GABAergic candidate genes tested in lithium-responsive bipolar disorder.     

Association studies of candidate genes in bipolar disorders

The aim of the investigation was to test genes for predisposition to bipolar affective disorder. Therefore, we studied candidate genes in a sample of unrelated patients (n = 102) and healthy controls (n = 79) of Austrian origin, searching for a possible association between polymorphic DNA markers of 5 candidate genes (serotonin transporter, 5-HTT; serotonin 2a receptor, 5-HT2a; dopamine D2 receptor, DRD2; dopamine D3 receptor, DRD3; dopamine transporter, DAT1) and bipolar disorder. There was an association between allelic and genotypic frequencies of 5-HTT and affection status (p = 0.014 and p = 0.017, respectively). However, after correction for multiple comparisons (Bonferroni), these results did not remain significant. Nevertheless, the findings might suggest that alterations in the structure of 5-HTT are involved in the pathogenesis of bipolar disorder, which could have major implications in treatment. No association between 5-HT2a, DRD2, DRD3, DAT1 and bipolar disorder was found.     

The DRD2 gene and the risk for alcohol dependence in bipolar patients.

The high co-morbidity between bipolar disorder and alcohol dependence may have different explanations, one of them being the existence of common genetic factors for the two disorders. Several candidate genes may be involved but the genes acting in the dopaminergic pathway may be more specifically involved. We have thus tested the role of the gene encoding the D2 dopamine receptor (TaqI A1 allele) in the potentially shared vulnerability to alcohol dependence and bipolar disorder. One hundred and twenty-two French (for at least two generations) patients were recruited on the basis of hospital or outpatient files and were interviewed with the DIGS. The A1 allele frequencies were compared between four groups, namely, with bipolar patients and co-morbid alcohol dependence (N = 21), with bipolar patients without alcohol morbidity (N = 31), with alcohol dependence without mood disorder (N = 35) and unaffected controls (N = 35). The Hardy Weinberg equilibrium for the DRD2 Taq1 A1 genotypes was respected for the sample as a whole, and for each subsample. We observed that 42.9% of control subjects have at least one A1 allele, a frequency which is not significantly different from the one observed in the affected sample as a whole (39.1%), neither from patients with alcohol dependence (37.1%), patients with bipolar disorder (48.4%) nor patients with alcohol dependence and bipolar disorder (28.6%). The regression analysis based on the three variables (bipolar disorder, alcohol dependence and interaction between these two disorders) does not explain the presence of the A1 allele of the DRD2 gene. We thus found no evidence for a significant role of the A1 allele of the D2 dopamine receptor gene in the specific association between bipolar disorder and alcohol dependence in our sample.