Genetic control of hepatic fibrogenesis

描述（由申请人提供）：酒精性和非酒精性脂肪性肝病（NAFLD）是一种慢性肝脏疾病，其中肝脏从脂肪蓄积和脂肪性肝炎（NASH）逐渐转变为纤维化和肝硬化。尽管人们对这一转变产生了极大的兴趣，并进行了大量的研究，但其调控机制在很大程度上仍未得到解决。我们的具体假设是，在协作杂交重组近交8路互交菌株中产生的遗传变异性将允许识别调节肝纤维化的遗传因素。换句话说，我们假设纤维化易感性是由称为“数量性状基因座”（QTL）的基因内遗传变异的综合效应引起的。为了解决这一重要假设，新开发的协作交叉菌株将用于建立与四氯化碳诱导的纤维化相关的表型。使用协作杂交菌株的基本原理是在近100个亚株中捕获超过95%的遗传变异性，并建立超过100，000个遗传重组点，使表型的超精细QTL定位更加精确和重要。此外，由于亲本多态性均匀地分散在整个协作杂交系中，因此预期菌株中的表型反应均匀且连续分布。因此，这种连锁方法比使用单基因转基因、敲除菌株或甚至重组近交菌株的传统方法上级得多，并且与人类生物学更相关。主要目的是鉴定纤维化易感菌株，表征所有菌株中的几种纤维化基准表型，鉴定与纤维化表型相关的QTL，并在乙醇暴露的慢性模型中利用易感菌株。为突出这些目标，现概述以下目标。具体目标1的目标是确定纤维化易感菌株，并在120株协作杂交菌株中表征与纤维化相关的表型性状。然后，在特定目标2中，我们将根据CC基因型将与肝纤维化相关的数量性状遗传定位到QTL。最后，在具体目标3中，我们将在乙醇暴露的慢性模型中利用上文鉴定的纤维化倾向菌株来确定这些菌株中乙醇诱导的纤维化易感性。这些研究将是正在进行的研究的跳板，这些研究将允许识别和评估参与肝脂肪积累在向肝纤维化转变中的作用的候选基因，途径和系统，这是一个与代谢综合征，肥胖，糖尿病甚至心血管疾病的演变特别相关的领域。 公共卫生相关性：慢性肝病是从脂肪肝到脂肪性肝炎到纤维化再到肝硬化的一系列病理过程。控制向纤维化转变的机制还不清楚。我们将使用一种新的遗传定义的小鼠种群，该种群来自称为协作杂交的常见近交系的8向互交，以解决肝纤维化机制背后的复杂遗传因素。这项研究的结果是鉴定了新的纤维化易感小鼠品系，这将是一个有价值的研究工具，而且还鉴定了与纤维化相关的遗传标记（数量性状基因座）。

DESCRIPTION (provided by applicant): Alcoholic and non-alcoholic fatty liver disease (NAFLD) are chronic liver disorders in which the liver progressively transitions from fatty accumulation and steatohepatitis (NASH) to fibrosis and cirrhosis. The mechanisms regulating this transition, despite significant interest and research efforts, are still largely unresolved. Our specific hypothesis is that the genetic variability created in the Collaborative Cross recombinant inbred 8-way intercross strains will allow the genetic factors regulating hepatic fibrogenesis to be identified. In other words, we hypothesize that fibrosis susceptibility results from the combined effects of genetic variations within genes termed "quantitative trait loci" (QTL). To address this important hypothesis, the newly developed Collaborative Cross strains will be used to establish phenotypes associated with fibrosis induced by carbon tetrachloride. The rationale for the use of the Collaborative Cross strains is that within nearly 100 substrains over 95% of genetic variability is captured and over 100,000 genetic recombination points are established, making ultra-fine QTL mapping of a phenotype more precise and significant. Also, because parental polymorphisms are uniformly dispersed throughout the Collaborative Cross lines, a uniform and continuous distribution of phenotypic responses is anticipated in the strains. Thus, this approach of linkage is far more superior and much more relevant to human biology than the traditional approaches using single-gene transgenic, knock-out strains or even recombinant inbred strains. The key objectives are to identify fibrosis-susceptible strains, characterize several fibrosis benchmark phenotypes across all strains, identify QTLs associated with the fibrosis phenotypes and exploit susceptible strains in a chronic model of ethanol exposure. The following aims are outlined to highlight these objectives. The goal of Specific Aim 1 is to identify fibrosis-susceptible strains and characterize phenotypic traits associated with fibrogenesis across 120 strains of the Collaborative Cross. Then, in Specific Aim2, we will genetically map quantitative traits associated with liver fibrogenesis to QTLs based on the CC genotypes. Finally, in Specific Aim 3, we will utilize fibrosis-prone strains identified above in a chronic model of ethanol exposure to determine ethanol-induced fibrosis susceptibility in these strains. These studies will be the springboard of ongoing studies which will allow for the identification and evaluation of candidate genes, pathways, and systems involved in the role of hepatic fat accumulation in the transition to liver fibrosis, an area with particular relevance to the evolution of metabolic syndrome, obesity, diabetes, and even cardiovascular disease. PUBLIC HEALTH RELEVANCE: Project Narrative Chronic liver disease is a continuum of pathologies starting with fatty liver disease to steatohepatitis to fibrosis to cirrhosis. The mechanisms governing the transition to fibrosis are not well understood. We will use a novel genetically-defined mouse population derived from an 8-way intercross of common inbred strains called the Collaborative Cross in order to address the complex genetic factors that underlie the mechanisms of liver fibrosis. The outcome of this study is the identification of novel fibrosis-susceptible strains of mice that will be a valuable research tool but also the identification of genetic markers (quantitative trait loci) that are associated with fibrosis.