Genetic control of hepatic fibrogenesis

描述(申请人提供)：酒精性和非酒精性脂肪性肝病(NAFLD)是指肝脏从脂肪堆积和脂肪性肝炎(NASH)逐渐过渡到纤维化和肝硬变的慢性肝病。尽管有很大的兴趣和研究努力，但规范这一过渡的机制在很大程度上仍然没有解决。我们的具体假设是，在协作杂交重组近交系8向杂交品系中产生的遗传变异性将使调控肝纤维化的遗传因素得以识别。换句话说，我们假设纤维化易感性是被称为“数量性状基因座”(QTL)的基因内遗传变异的综合作用的结果。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。使用协同交叉品系的基本原理是，在近100个亚系中，超过95%的遗传变异被捕获，并建立了超过100,000个遗传重组点，使得对表型的超精细QTL定位更加准确和重要。此外，由于亲本的多态分布均匀地分布在合作交叉系中，预期在品系中会有均匀和连续的表型反应分布。因此，这种连锁方法比使用单基因转基因、敲除品系甚至重组近交系的传统方法更优越，与人类生物学更相关。主要目标是识别纤维化易感菌株，表征所有菌株中的几种纤维化基准表型，识别与纤维化表型相关的QTL，并在慢性酒精暴露模型中利用易感菌株。为突出这些目标，概述了以下目标。具体目标1的目标是在合作杂交的120个菌株中识别纤维化易感菌株，并表征与纤维化形成相关的表型特征。然后，在特定的AIM2中，我们将基于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，在特定的目标3中，我们将利用在酒精暴露的慢性模型中确定的上述容易纤维化的菌株来确定这些菌株对酒精诱导的纤维化的易感性。这些研究将成为正在进行的研究的跳板，这些研究将允许识别和评估候选基因、途径和系统，这些基因、途径和系统参与了肝脏脂肪积聚在向肝纤维化转变过程中的作用，这一领域与代谢综合征、肥胖、糖尿病甚至心血管疾病的演变特别相关。 公共卫生相关性：项目叙述慢性肝病是从脂肪性肝病到脂肪性肝炎再到纤维化再到肝硬变的一系列病理过程。向纤维化过渡的机制还不是很清楚。我们将使用一种新的基因定义的小鼠群体，该群体来自于常见近交系的8向杂交，称为合作杂交，以解决导致肝纤维化机制的复杂遗传因素。这项研究的结果是鉴定了新的纤维化易感品系，这将是一种有价值的研究工具，同时也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.