Genetic Determinants of COMT Expression

描述(申请人提供)：儿茶酚-O-甲基转移酶，COMT，代谢内源性儿茶酚底物，因此在包括神经传递在内的各种过程中都很重要。儿茶酚水平的失调与神经行为障碍有关。大量的基因关联研究表明，COMT与精神分裂症和恐慌症等脑部疾病有关。这些等位基因关联中的许多都涉及到改变酶活性的功能性COMT DNA。这些关联结果通常是相互矛盾的，并涉及COMT基因座或其附近的另一个或多个变异体。此外，已经观察到使用这种功能性COMT变异体的等位基因特异性mRNA的表达。这项建议概述了一项可行性研究，以表征个体的DNA序列和表达变异，以努力了解序列变异对COMT在疾病人群中表达的潜在影响。我们推测儿茶酚-O-甲基转移酶基因区域的DNA变异导致了COMT基因表达的变异。为了验证这一假设，我们将使用来自犹他州30个高加索CEPH三人组的淋巴母细胞系，这个群体已经由HapMap Consortium进行了基因分型，以表征人类群体的遗传多样性。有了这个群体，我们将使用定量逆转录-聚合酶链式反应来表征细胞系COMT mRNA的表达。对于转录本中存在DNA变异杂合子的受试者，我们将使用单碱基延伸方法来测量等位基因特异性的mRNA表达。然后，我们将检验COMT中的基因和mRNA表达变化之间的相关性。我们将在COMT基因座内和COMT上游约340kb的区域对我们的样本进行常见单核苷酸多态(SNPs)的基因分型，并在HapMap项目期间使用已经在同一样本中对该相同区域的约100个SNP进行基因分型的基因类型。单标记和多标记单倍型将被用来检验与mRNA表达变异的相关性。最后，我们将通过评估用雌激素处理细胞系后COMT的表达，然后测量与SNP基因型的关联，包括预测的雌激素反应元件的变异，来观察雌激素对COMT活性的调节作用。与COMT表达差异相关的遗传多态可用于识别预测COMT功能差异的顺式作用调控元件。这项体外工作可能有助于理解COMT对疾病易感性的遗传贡献，特别是关于COMT基因的顺式调节。

DESCRIPTION (provided by applicant): Catechol-O-methyltransferase, COMT, metabolizes endogenous catechol substrates, and thus is important in a variety of processes, including neurotransmission. Dysregulation of catechol levels is implicated in neurobehavioral disorders. Numerous genetic association studies suggest the involvement of COMT in brain diseases like schizophrenia and panic disorder. Many of these allelic associations involve a functional COMT DNA that alters enzymatic activity. These association results are often contradictory and implicate another variant or variants at or near the COMT locus. Additionally, allele-specific mRNA expression using this functional COMT variant has been observed. This proposal outlines a feasibility study to characterize the DNA sequence and expression variation in individuals in an effort to understand the potential impact of sequence variation on COMT expression in a disease population. We hypothesize that DNA variation in the catechol-O-methlytransferase gene region contributes to variability in COMT mRNA expression. In order to test this hypothesis, we will use lymphoblastoid cell lines from 30 Caucasian CEPH trios from Utah, a population that has been genotyped by the HapMap Consortium in order to characterize genetic diversity in the human population. With this population, we will characterize cell line COMT mRNA expression using quantitative reverse transcription-polymerase chain reaction. For subjects heterozygous for DNA variants present in transcripts, we will measure allele-specific mRNA expression using a single base extension method. We will then test the correlation between genotype and mRNA expression variation in COMT. We will genotype our sample for common single nucleotide polymorphisms (SNPs) within the COMT locus and across a region approximately 340kb upstream of COMT, as well as use genotypes from ~100 SNPs already genotyped in this same sample in this same region during the HapMap project. Single markers and multiple-marker haplotypes will be used to test for correlation with variation in mRNA expression. Finally, we will exploit observations of the regulatory role that estrogen plays in COMT activity by assessing COMT expression after treating cell lines with estrogen, and then measuring association to SNP genotypes, including variants in predicted estrogen response elements. Genetic polymorphisms correlated with differences in COMT expression can be used to identify cis- acting regulatory elements for predicting COMT functional differences. This in vitro work may be useful for the understanding of the genetic contribution of COMT to disease susceptibility, particularly with regard to the cis regulation of the COMT locus.