Regulation of ApoB Secretion in Inbred Mouse Strains

近交系小鼠品系中 ApoB 分泌的调节

• 批准号: 6983344
• 负责人: LI-SHIN HUANG
• 金额: $ 36.23万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6983344
• 关键词: Regulation; ApoB; Secretion; Inbred; Mouse

DESCRIPTION (provided by applicant): Elevated plasma levels of apolipoprotein B (apo B) and low density lipoprotein (LDL) are associated with a higher risk for atherosclerotic coronary heart disease (CHD), a leading cause of mortality in the industrialized world. Elevated plasma apo B levels and overproduction of apo B are also major characteristics of familial combined hyperlipidemia (FCHL), a prevalent disorder in the general population. The genetic basis of this prevalent disease is heterogeneous and unknown. Genes that regulate plasma apo B levels are logical candidates for genes which contribute to the FCHL phenotype. Apo B is required for the secretion of very low density lipoproteins (VLDL) from the liver and is the mandatory protein constituent of both plasma VLDL and LDL. Plasma apo B levels are controlled, in part, by secretion rates of apo B-containing lipoprotein particles. Using the human apo B transgenic mouse model (HuBTg), we have shown that HuBTg mice of C57BL/6 (B6) and 129/Sv (129) background differ in their plasma apo B levels mainly due to hepatic apo B secretion rates via post-transcriptional regulation. Further genetic studies of two mouse strains identified two novel quantitative trait loci (QTL) on chromosomes 6 and 4 which have major effects on plasma apo B levels. These genes are designated Apo B regulatory genes (Abrg). Our fine-mapping analyses have localized the Abrgl to an interval of approximately 2.9 Mb on chromosome 6 and the Abrg2 to a 12-cM interval on chromosome 4. The goals of the current proposal are to identify and characterize the Abrgl gene on chromosome 6. The specific aims are: 1. Positional cloning of the Abrgl on chromosome 6 that regulates plasma apo B levels. Several parallel approaches will be taken to identify candidate genes for the Abrgl. These approaches include RT-PCR, quantitative real-time PCR assays, and DNA sequencing analysis. Studies will also be designed to determine the effects of allelic variations of expression variants on transcription. 2. Characterization of the Abrg genes in congenic mice and functional studies of the Abrgl candidate genes. We will perform functional tests on candidate variant genes, including the Copsla gene (an expression variant), by over expression studies in vitro and in vivo. The best candidate for the Abrgl gene, either Cops7a or another gene to be identified, will then be verified via knock-in and/or knock-out gene-targeting techniques. Studies will be designed to characterize the functional roles of the Abrgl gene. Overall, the gene identified will be a novel regulator affecting the pathways involved in the assembly and secretion of apo B containing lipoproteins. As a regulator of apo B secretion rates, this novel gene will be a strong candidate for one of the genes causative for overproduction of apo B in subsets of FCHL patients. It will also be a potential target for drug discovery and pharmacological intervention in hyperlipidemic patients in the general population.

描述（由申请人提供）：载脂蛋白 B (apo B) 和低密度脂蛋白 (LDL) 血浆水平升高与动脉粥样硬化性冠心病 (CHD) 风险较高相关，而动脉粥样硬化性冠心病 (CHD) 是工业化国家死亡的主要原因。血浆载脂蛋白 B 水平升高和载脂蛋白 B 生成过多也是家族性混合性高脂血症 (FCHL) 的主要特征，FCHL 是普通人群中的一种常见疾病。这种流行疾病的遗传基础是异质且未知的。调节血浆载脂蛋白 B 水平的基因是促成 FCHL 表型的基因的逻辑候选者。 Apo B 是肝脏分泌极低密度脂蛋白 (VLDL) 所必需的，并且是血浆 VLDL 和 LDL 的必需蛋白质成分。血浆载脂蛋白 B 水平部分受含载脂蛋白 B 的脂蛋白颗粒的分泌速率控制。使用人载脂蛋白 B 转基因小鼠模型 (HuBTg)，我们发现 C57BL/6 (B6) 和 129/Sv (129) 背景的 HuBTg 小鼠血浆载脂蛋白 B 水平存在差异，这主要是由于肝脏载脂蛋白 B 分泌率不同。 -转录调控。对两种小鼠品系的进一步遗传学研究发现，第 6 号和第 4 号染色体上有两个新的数量性状基因座 (QTL)，它们对血浆载脂蛋白 B 水平具有重大影响。这些基因被指定为 Apo B 调节基因 (Abrg)。我们的精细作图分析已将 Abrgl 定位到 6 号染色体上约 2.9 Mb 的区间，将 Abrg2 定位到 4 号染色体上 12 cM 的区间。当前提案的目标是识别和表征 6 号染色体上的 Abrgl 基因。具体目标是： 1. 对 6 号染色体上调节血浆 apo B 水平的 Abrgl 进行定位克隆。将采取几种并行方法来鉴定 Abrgl 的候选基因。这些方法包括 RT-PCR、定量实时 PCR 测定和 DNA 测序分析。研究还将旨在确定表达变体的等位基因变异对转录的影响。 2.同系小鼠Abrg基因的表征和Abrgl候选基因的功能研究。我们将通过体外和体内的过度表达研究，对候选变异基因（包括 Copsla 基因（一种表达变异））进行功能测试。 Abrgl 基因的最佳候选者，无论是 Cops7a 还是其他待鉴定的基因，都将通过敲入和/或敲除基因靶向技术进行验证。研究将旨在表征 Abrgl 基因的功能作用。总体而言，所鉴定的基因将是一种新型调节因子，影响含载脂蛋白 B 的组装和分泌所涉及的途径。作为 apo B 分泌率的调节因子，这种新基因将是导致 FCHL 患者亚群中 apo B 过量产生的基因之一的有力候选者。它也将成为普通人群高脂血症患者药物发现和药理干预的潜在靶点。