Genetics of Nicotine Dependence

描述(由申请人提供)：吸烟是北美和欧洲最大的可预防的发病率和死亡率来源。双胞胎和领养研究表明，尼古丁依赖(ND)的大部分风险是遗传的。对来自欧洲的约7500名个体进行了每日卷烟数量性状的全基因组关联(WGA)研究。用Affymetrix 500K芯片进行基因分型。α3烟碱受体亚单位基因的单核苷酸多态与慢性阻塞性肺疾病作为数量性状相关(p=0.00007)。采用病例对照模式(吸烟者25例，对照组5例)，对第二个欧洲人群中约6200名对照和约1740名病例进行了CPD分析，基因分型为~6000个SNPs。在这第二个群体中，CHRNA3SNP与慢性阻塞性肺疾病密切相关(p=0.0000026，优势比1.3，95%可信区间1.17~1.48)。这些结果类似于Saccon等人(2007年)进行的新城疫病例对照研究，他们报告了几个CHRNA3 SNP之间的关联(0.0003&lt；p&lt；0.01)。这些SNPs的所有已识别的危险等位基因(N=7)都位于单一的常见单倍型上，在欧亚血统人群中的等位基因频率约为38%。由于CHRNA3和相邻的CHRNA5基因之间存在很强的连锁不平衡，额外的基因分型不太可能识别原因变异。这项建议描述了CHRNA3和CHRNA5基因的功能研究。对约200名ND患者的CHRNA3和CHRNA5进行重新测序，以确定可能易患ND的罕见功能变异。这些罕见的功能变异将在全部起源于欧洲的~1500名ND个体和~1500名对照人群中进行连锁不平衡检查，以确定它们是否可能易患ND。CHRNA3和CHRNA5的mRNA和蛋白将在死后的人脑中进行评估，这些人来自具有可能的风险和保护性单倍型的个体。来自风险和保护性单倍型的CHRNA3和CHRNA5启动子序列将在组织培养中进行转录效率评估。将评估CHRNA5中存在风险单倍型的错义编码SNP的结合亲和力和离子电导的变化。这些结果应该确定CHRNA3和CHRNA5基因中的启动子和转录的SNPs的功能效应。这项研究应该确定增加ND风险的CHRNA3和/或CHRNA5基因序列的后果，并应该促进治疗ND的新药开发。 与公共健康相关：这项研究建议研究产生尼古丁大脑结合蛋白的基因的DNA变异。这些结合蛋白与尼古丁成瘾的形成有关。了解这些DNA变异的功能后果将为开发治疗尼古丁成瘾的新药提供方向。

DESCRIPTION (provided by applicant): Cigarette smoking is the single largest preventable source of morbidity and mortality in North America and Europe. Twin and adoption studies indicate that a majority of risk for nicotine dependence (ND) is genetic. A genome-wide association (WGA) study of cigarettes per day (CPD), as a quantitative trait, was conducted with ~ 7500 individuals of European origin. Genotyping was done with Affymetrix 500K chips. A SNP in the alpha 3 nicotinic receptor subunit gene (CHRNA3) was associated with CPD as a quantitative trait (p = 0.00007). Analyses of CPD in a case-control mode (cases defined as smoking > 25 CPD versus controls < 5 CPD), was done in a second European-origin population of ~ 6200 controls and ~ 1740 cases, genotyped at ~ 6000 SNPs. In this second population, a CHRNA3 SNP was strongly associated with CPD (p = 0.0000026, odds ratio 1.30, 95% CI 1.17-1.48). These results are similar to a case-control study of ND by Saccone et al (2007), who reported association of several CHRNA3 SNPs (0.0003< p < 0.01). All the identified risk alleles (N = 7) at these SNPs lie on a single common haplotype, with ~ 38% allele frequency in persons of Euorpean origin. Because of strong linkage disequilibrium across the CHRNA3 and the adjacent CHRNA5 gene, additional genotyping is unlikely to identify causal variations. This proposal describes functional studies of CHRNA3 and CHRNA5 genes. Re-sequencing of CHRNA3 and CHRNA5 in ~ 200 ND persons will be employed to identify rare functional variants which might predispose to ND. These rare functional variants will be examined for linkage disequilibrium in a population of ~ 1500 ND individuals and ~ 1500 controls, all of European origin, to determine whether they might predispose to ND. CHRNA3 and CHRNA5 mRNA and protein will be assessed in post mortem human brain from individuals with the putative risk and protective haplotypes. CHRNA3 and CHRNA5 promoters sequences, from the risk and protective haplotypes, will be assessed in tissue culture for transcriptional efficiency. A mis-sense coding SNP in CHRNA5, which lies on the risk haplotype, will be assessed for change in binding affinties and ionic conductance. These results should identify the functional effects of promoter and transcribed SNPs in CHRNA3 and CHRNA5 genes. This study should identify the consequences of CHRNA3 and/or CHRNA5 gene sequences which increase risk for ND and should facilitate new drug development for treatment of ND. PUBLIC HEALTH RELEVANCE: This research proposes to study DNA variations in genes which produce brain binding proteins for nicotine. These binding proteins are involved in the development of nicotine addiction. Understanding the function consequences of these DNA variations will provide direction in developing new medications for nicotine addiction.