The Role of Mia2 in Lipoprotein Biogenesis

描述（由申请人提供）：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前兆，是工业化国家的主要杀手。因此，全面了解胆固醇和甘油三酯代谢以及血液中携带它们的脂蛋白对于对抗这种疾病并完成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。对来自突变小鼠的大小分级血浆的分析揭示了两种主要小鼠脂蛋白（HDL和VLDL）的胆固醇和甘油三酯含量的降低。负责这种低胆固醇表型的基因已被鉴定为Mia 2。它是脂蛋白代谢的一个新的参与者， 通过显著减少它们从肝脏和/或肠道的分泌来起作用。该小鼠模型将被用于进一步了解脂蛋白的产生。本建议旨在回答有关作用机制的一些非常基本的问题。使用突变动物的原代肝细胞和已建立的组织培养细胞系，将研究受该突变干扰的脂蛋白生产的精确步骤。其次，将使用新产生的工具，包括转基因小鼠系和重组腺病毒，这是一种非常通用的手段，表达外源基因在各种细胞系和组织，并在活的小鼠中，探索这种新的基因在整个动物的行动。然后，这些工具将用于几个实验，包括体外和体内突变表型的拯救。拯救是重要的，因为它毫无疑问地证明了我们已经确定了负责表型的突变基因。然后将研究获救小鼠和细胞中的脂蛋白代谢，以充分探索脂蛋白产生的这种新途径。

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.