Dissecting the genetics of the Metabolic Syndrome on Chromosome 17 of the LH rat

描述（申请人提供）：肥胖、血脂异常、胰岛素抵抗和高血压等疾病的集合被称为代谢综合征，是心血管疾病的主要危险因素。其发病率继续上升，部分原因是肥胖症的流行增加。里昂高血压（LH）大鼠是一个强大的近交系模型，用于解剖人类代谢综合征的遗传贡献，具有高体重、高胆固醇、高甘油三酯和高胰岛素/葡萄糖比，以及盐敏感性高血压。有趣的是，同时从相同SD菌落中选择的里昂血压正常（LN）对照菌株与LH在遗传上非常相似（85%），但表型非常不同。在LH × LN互交的遗传连锁作图中，在大鼠染色体（RNO）17上确定了3个数量性状位点（QTL）簇，用于LH大鼠代谢综合征的多种特征，并在RNO 17、2和13上确定了3个血压QTL。我们假设LH染色体17具有对代谢综合征的所有主要性状有贡献的基因，并且RNO 17上的QTL之间以及RNO 17、2和13之间存在QTL相互作用。为了确定这些基因中的至少一个，我们提出了一个组合的传统位置克隆，在硅片映射，QTL（表型和基因表达）定位，以确定致病基因和途径，导致代谢综合征。我们将：1：在LH和LN株系中定位RNO 17的QTL区域。LH和LN菌株的紧密遗传同一性允许快速产生和表征同源LH-17 LN菌株和同源亚株。这些菌株将用于缩小QTL区域，并确定哪些表型是由于多个QTL、相互作用的QTL或QTL内单个基因的多效性效应。2：研究反式作用和顺式作用单倍型对代谢综合征潜在性状的相互作用。我们将在LH和LN之间进行F2互交，以确定RNO 17，2和13上的QTL与引起我们在LH中观察到的表型的调控网络之间的相互作用。后代将通过表型分型、SNP基因分型和基因表达谱分析进行综合研究，以进行表型（p）QTL和表达（e）QTL作图。3：通过SNP精细定位和同类大鼠实验验证，细化RNO 17上的QTL。对于每个候选区域，我们将通过额外的SNP分型来精细绘制单倍型，以缩小并定义最小QTL间隔。将在这些最小区域中确定所有遗传变异，以鉴定候选基因和序列变体。这些区域将在同类中得到实验验证。4：通过大鼠转基因拯救的非功能性变体。对于在上述目的中鉴定的具有功能序列变体证据的最强候选者，我们将开发转基因大鼠，将LN等位基因引入LH大鼠或将LH等位基因引入LH-17 LN。

DESCRIPTION (provided by applicant): The collection of maladies including obesity, dyslipidemia, insulin resistance and hypertension is referred to as the metabolic syndrome and is a major risk factor for cardiovascular disease. Its incidence continues to rise, in part as a result of the epidemic increase in obesity. The Lyon Hypertensive (LH) rat is a powerful inbred model for dissecting the genetic contributions of the human metabolic syndrome, with high body weight, cholesterol, triglycerides, and insulin/glucose ratios, and salt-sensitive hypertension. Interestingly, the Lyon normotensive (LN) control strain, concurrently selected from the same SD colony, is genetically quite similar (85%) to the LH, but phenotypically very distinct. Genetic linkage mapping in an LH x LN intercross identified 3 clusters of Quantitative Traits Loci (QTL) on rat chromosome (RNO) 17 for multiple features of the metabolic syndrome in the LH rat and 3 QTL for blood pressure on RNO17, 2, and 13. We hypothesize that the LH chromosome 17 has genes contributing to all major traits of the metabolic syndrome, and that there are QTL interactions between QTL on RNO 17 and between RNO 17, 2, and 13. To identify at least one of these genes, we propose a combined traditional positional cloning, in silico mapping, and QTL (phenotype and gene expression) mapping to identify causal genes and pathways leading to the metabolic syndrome. We will: 1: Validate the QTL regions for RNO17 in the LH and LN strains. The close genetic identity of the LH and LN strains allows for rapid generation and characterization of a consomic LH-17LN strain and congenic substrains. These strains will be used to narrow the QTL regions and to determine which phenotypes are due to multiple QTL, interacting QTL, or pleiotropic effects of a single gene within a QTL. 2: Investigate interactions between trans-acting and cis-acting haplotypes on traits underlying the metabolic syndrome. We will perform an F2 intercross between LH and LN to determine the interactions between QTL on RNO17, 2, and 13, and regulatory networks causing the phenotypes we observe in the LH. The offspring will be comprehensively studied by phenotyping, SNP genotyping, and gene expression profiling for combined phenotype (p) QTL and expression (e) QTL mapping. 3: Refine the QTL on RNO17 through SNP fine-mapping and experimental validation in congenic rats. For each candidate region, we will fine-map the haplotypes by additional SNP typing to narrow and define minimal QTL intervals. All genetic variation will be determined in these minimal regions to identify candidate genes and sequence variants. These regions will be experimentally validated in the congenics. 4: Validate functional variants through rat transgenic rescue. For the strongest candidate with evidence of functional sequence variants identified in the above aims, we will develop a transgenic rat, either introducing the LN allele into the LH rat or the LH allele into the LH-17LN.