Characterization of a Lysosomal Acid Lipase Variant Associated with Coronary Disease

 描述（由申请方提供）：在大规模全基因组关联研究中，溶酶体酸性脂肪酶（利帕）基因座的两种紧密连锁的常见内含子变体（存在于近三分之一的人群中）已显示可使冠状动脉疾病（CAD）风险增加13-17%。利帕介导胆固醇酯的水解，具有罕见功能丧失突变的患者发展为高胆固醇血症和CAD。然而，这些常见的利帕变体是内含子的，与脂质异常无关，并导致单核细胞中利帕转录物增加，这一系列发现阻碍了进一步的机制理解。我们已经发现了一个以前未被识别的编码变异与内含子变异密切相关，这与CAD风险同样相关。我们假设，编码变异，与潜在的后果，利帕酶的活性和细胞胆固醇稳态，是罪魁祸首与心血管疾病。将通过评估编码变体对从患有和不患有已知CAD的患者队列中分离的循环单核细胞中的利帕mRNA、蛋白质和酶活性水平的影响来评价该概念。为了明确涉及编码变体，将研究在不存在混杂内含子变体的情况下含有编码变体的诱导多能干细胞衍生的单核细胞/巨噬细胞。该模型将允许确定分离的编码变体是否改变利帕mRNA、蛋白质和酶活性。进一步的机制表征将包括对CAD发病机制中涉及的关键脂质代谢表型的影响，包括胆固醇流出、脂质摄取和泡沫细胞形成。最后，鉴于编码变体位于利帕的信号肽区域，其对利帕运输、成熟和分泌的影响将被评估为功能障碍的潜在机制。总之，这一高度转化的实验组将提供第一个机制的见解，以一个重要的遗传风险等位基因与CAD。

 DESCRIPTION (provided by applicant): Two tightly linked common intronic variants of the Lysosomal Acid Lipase (LIPA) locus, present in nearly one- third of the population, have been shown to increase the risk of coronary artery disease (CAD) by 13-17% in large-scale genome-wide association studies. LIPA mediates the hydrolysis of cholesteryl esters and patients with rare loss-of-function mutations develop hypercholesterolemia and CAD. However, these common LIPA variants are intronic, not associated with lipid abnormalities, and result in increased LIPA transcripts in monocytes, a constellation of findings that has prevented further mechanistic understanding. We have discovered a previously unrecognized coding variant in close linkage with the intronic variants that is equally associated with CAD risk. We hypothesize that the coding variant, with potential consequences to LIPA enzyme activity and cellular cholesterol homeostasis, is the culprit link with cardiovascular disease. This concept will be evaluated by assessing the effect of the coding variant on levels of LIPA mRNA, protein, and enzyme activity in circulating monocytes isolated from cohorts of patients with and without known CAD. In order to definitely implicate the coding variant, induced pluripotent stem cell derived monocytes/macrophages harboring the coding variant in the absence of the confounding intronic variants will be studied. This model will allow determination of whether the coding variant in isolation alters LIPA mRNA, protein, and enzyme activity. Further mechanistic characterization will include effects on crucial lipid metabolic phenotypes implicated in CAD pathogenesis including cholesterol efflux, lipid uptake, and foam cell formation. Finally, given that the coding variant lies in the signal peptide region of LIPA, its impact on LIPA trafficking, maturation, and secretion will be assessed as potential mechanisms for dysfunction. Taken together, this highly translational set of experiments will provide the first mechanistic insight ito an important genetic risk allele associated with CAD.