The Role of Mia2 in Lipoprotein Biogenesis

描述(申请人提供)：血浆胆固醇和甘油三酯与动脉粥样硬化有因果关系，动脉粥样硬化是心脏病的先兆，是工业化世界的头号杀手。因此，全面了解胆固醇和甘油三酯的代谢以及血液中携带胆固醇和甘油三酯的脂蛋白，对于对抗这种疾病和完成NIH和NHLBI的使命至关重要。一项正向遗传筛查发现了一个胆固醇水平非常低(约为正常水平的25%)的小鼠家族。对突变小鼠不同大小的血浆的分析显示，两种主要的小鼠脂蛋白(高密度脂蛋白和极低密度脂蛋白)的胆固醇和甘油三酯含量降低。导致这种低胆固醇表型的基因已经被确认为MIA2。它是脂蛋白新陈代谢的新参与者，显然 通过显著减少它们从肝脏和/或肠道的分泌而起作用。这个小鼠模型将被用来进一步了解脂蛋白的产生。这项提议旨在回答一些关于行动机制的非常基本的问题。利用突变动物的原代肝细胞和已建立的组织培养细胞系，将研究被这种突变干扰的脂蛋白产生的准确步骤。其次，将使用新产生的工具来探索这种新基因在整个动物中的作用，包括转基因小鼠系和重组腺病毒，重组腺病毒是一种在各种细胞系和组织以及活体小鼠中表达外源基因的非常通用的方法。然后，这些工具将被用于几项实验，包括在体外和体内拯救突变表型。挽救是重要的，因为它毫无疑问地证明了我们已经确定了导致表型的突变基因。然后，将研究被拯救的小鼠和细胞中的脂蛋白代谢，以全面探索这一新的脂蛋白产生途径。

DESCRIPTION (provided by applicant): Plasma cholesterol and triglyceride are causally related to atherosclerosis, a precursor to heart disease, which is the leading killer in the industrialized world. A complete understanding of cholesterol and triglyceride metabolism and the lipoproteins that carry them in the blood is therefore essential to combat this disease and fulfill the mission of the NIH and NHLBI. A forward genetic screen has identified a family of mice with very low (~25% of normal) cholesterol levels. Analysis of size- fractionated plasma from mutant mice revealed a reduction in the cholesterol and triglyceride content of the two major mouse lipoproteins (HDL and VLDL). The gene responsible for this low cholesterol phenotype has been identified as Mia2. It is a novel player in the metabolism of lipoproteins that apparently works by dramatically reducing their secretion from the liver and/or intestine. This mouse model will be exploited to further the basic understanding of lipoprotein production. This proposal aims to answer some very basic questions as to mechanism of action. Using primary hepatocytes of mutant animals and established tissue culture cell lines, the precise step in the production of lipoproteins that is perturbed by this mutation will be investigated. Secondly, the action of this novel gene in the whole animal will be explored using newly generated tools, including a transgenic mouse line and recombinant adenovirus, which is a very versatile means of expressing foreign genes in a variety of cell lines and tissues and in live mice. These tools will then be used for several experiments, including rescue of the mutant phenotype in vitro and in vivo. Rescue is important in that it proves beyond any doubt that we have identified the mutant gene responsible for the phenotype. Lipoprotein metabolism in rescued mice and cells will then be studied for a full exploration of this novel pathway in lipoprotein production.