Polymorphisms in Regulatory Regions of Addiction Genes

描述（由申请人提供）： 药物成瘾是一种复杂的疾病，被认为涉及环境因素与多种遗传因素的相互作用。几个基因的遗传变异组合可能会协同增加个体对成瘾的易感性。候选基因是那些编码药物代谢酶和转运蛋白、神经递质受体、信号蛋白和影响神经生物学功能（如突触重塑和记忆）的蛋白质的基因。改变蛋白质结构的多态性已被广泛研究，但影响基因表达和mRNA加工的顺式作用变异可能更为普遍。因此，顺式调节多态性可能解释了个体之间的差异及其对成瘾的易感性。然而，已经证明很难在一个大的基因组中检测到这样的顺式调节变体。在这里，介绍了一种新的方法来广泛筛选影响基因表达和mRNA加工的多态性，利用候选基因转录区的单核苷酸多态性（SNP）。通过精确测量杂合携带者基因组DNA和mRNA中两个SNP等位基因的比率，检测mRNA水平的变化，将一个等位基因与通过尸检从多个个体获得的相关靶组织中的另一个等位基因进行比较。通过单倍型和关联分析扫描在mRNA水平上显示显著等位基因差异的基因的功能多态性。本研究的具体目的是：1）鉴定具有位于转录区域中的合适标记SNP的候选基因，所述转录区域在相关靶组织中表现出等位基因特异性mRNA差异（例如，脑区域、肝脏）。2)分离与差异等位基因表达相关的单倍型块。3)发现与差异等位基因表达相关的功能性遗传病变。这些结果将使我们能够分配顺式调节多态性的功能意义，作为药物成瘾的临床关联研究的指导。

DESCRIPTION (provided by applicant): Drug addiction is a complex disorder thought to involve the interaction of environmental factors with multiple genetic factors. Combinations of genetic variations in several genes likely cooperate to increase the susceptibility of an individual to addiction. Candidate genes are those encoding drug metabolizing enzymes and transporters, neurotransmitter receptors, signaling proteins, and proteins affecting neurobiological functions, such as synaptic remodeling and memory. Polymorphisms that alter protein structure have been studied extensively, but cis-acting variations affecting gene expression and mRNA processing are likely to be more prevalent. Therefore, cis-regulatory polymorphisms might account for much of the diversity between individuals and their susceptibility to addiction. Yet, it has proven difficult to detect such cis-regulatory variants across a large panel of genes. Here, a novel approach to screen broadly for polymorphisms that affect gene expression and mRNA processing is introduced, taking advantage of single nucleotide polymorphisms (SNPs) in the transcribed region of a candidate gene. By precisely measuring the ratios of the two SNP alleles in both genomic DNA and mRNA in heterozygous carriers, one detects variations in mRNA levels, comparing one allele against the other in a relevant target tissue obtained by autopsy from multiple individuals. Genes showing significant allelic differences in mRNA levels are scanned for functional polymorphisms by haplotype and association analysis. The specific aims of this study are to: 1) Identify candidate genes with suitable marker SNPs located in transcribed regions that exhibit allele-specific mRNA differences in relevant target tissues (e.g., brain regions, liver). 2) Isolate haplotype blocks that are associated with differential allelic expression. 3) Discover functional genetic lesions associated with differential allelic expression. The results will permit us to assign functional significance to cis-regulatory polymorphisms as a guide in clinical association studies of drug addiction.