GENETIC MODIFIERS IN ANGIOTENSIN RECEPTOR-DEFICIENCY

肾素-血管紧张素系统（RAS）是血压和体液平衡的关键调节因子。在不同的人群中，RAS对高血压发病和终末器官损伤的相对作用可能差异很大。我们假设这种变异可以通过调节RAS在健康和疾病中的功能的遗传因素来解释；这些因素可能涉及编码RAS成分的基因或RAS之外的其他基因。在我们的初步研究中，我们已经确定了基因修饰剂，可以通过靶向破坏AT1A血管紧张素受体基因（Agtr1a）来显著改变小鼠的肾脏结构。这些研究的目的是通过以下特定目的，使用该小鼠模型来定位和表征这些自然发生的RAS遗传修饰因子：特定目的#1：通过交叉和回交来确定修饰因子位点对AT1A受体缺乏肾血管表型的影响。在我们的初步研究中，我们发现近交系C57BL/6或129/J背景的AT1A受体缺乏具有严重的肾脏表型，而F1(C57BL/6 x 129) AT1A受体缺乏小鼠的肾脏是正常的。我们将对亲本株进行F1交叉和回交，并分析后代是否存在肾血管病变，以进一步表征这些遗传修饰因子。在大量动物中对这种表型的精确定义将是Specific Aim 2中提出的制图研究成功的关键。特异性目标#2：定位和鉴定AT1A受体缺陷小鼠肾血管病变的修饰位点。在仔细分析回交和交间后代的表型后，我们将获得基因组DNA，并使用亲本（C57BL/6和129）菌株之间多态性的标记进行基因组微卫星分析。基于这个全基因组扫描的结果，我们将使用连锁分析来绘制位点。然后，我们将采用系统的方法，缩小连锁间隔，尝试通过定位克隆和候选基因分析来分离修饰基因。这些研究为鉴定对RAS生理有重大修饰作用的新基因提供了潜力。实验方法的结合将为乐博士提供一个优秀的培训工具。通过这些学习，她应该能够熟练掌握一系列分子遗传技术，为她的职业生涯奠定基础。

The renin-angiotensin system (RAS) is a key regulator of blood pressure and fluid homeostasis. Within different human populations, the relative contribution of the RAS to the pathogenesis of hypertension and end- organ injury may vary widely. We hypothesize that some of this variation may be explained by genetic factors that modulate the functions of the RAS in health and disease; these factors may involve genes encoding the RAS components or other genes outside of the RAS. In our preliminary studies, we have identified genetic modifiers that dramatically alter kidney structure of mice with targeted disruption of the AT1A angiotensin receptor gene (Agtr1a). The objective of these studies is to use this mouse model to localize and characterize these naturally occurring genetic modifiers of the RAS through the following specific aims: Specific Aim #1: To define the influence of modifier loci on renal vascular phenotype in AT1A receptor-deficiency using inter-crosses and back crosses. In our preliminary studies, we have found that AT1A receptor-deficiency on inbred C57BL/6 or 129/J backgrounds has a severe renal phenotype, while kidneys are normal in F1(C57BL/6 x 129) AT1A receptor-deficient mice. We will perform F1 inter-crosses along with back crosses to the parental strains and analyze the progeny for the presence or absence of renal vascular lesions to further characterize these genetic modifiers. Precise definition of this phenotype in a large number of animals will be critical to the success of the mapping studies proposed in Specific Aim 2. Specific Aim #2: Mapping and identification of the modifying loci for renal vascular lesions in AT1A receptor-deficient mice. After a careful analysis of phenotype of progeny from back crosses and intercrosses, we will obtain genomic DNA and perform genomic micro-satellite analysis using markers that are polymorphic between the parental (C57BL/6 and 129) strains. Based on the results of this genome- wide scan, we will use linkage analysis to map the loci. Then, we will use a systematic approach to narrow the linkage intervals to attempt to isolate the modifier genes by positional cloning and candidate gene analysis. These studies provide the potential for identifying novel genes that have significant modifying effects on the physiology of the RAS. The combination of experimental methods that will be utilized provides an outstanding training vehicle for Dr. Le. Through the course of these studies, she should become fluent in a range of molecular genetic techniques that should provide a foundation for her career.