Genetics of Renal End Organ Damage in Hypertension

摘要：在美国，终末期肾脏疾病的发病率正以惊人的速度增长，其中高血压和糖尿病是主要原因。目前，有2560万人处于肾脏疾病的早期阶段（1 - 3期），虽然严格控制血压和血糖水平可能会减缓，但并不能阻止这些患者肾功能的进行性下降。因此，了解高血压肾病的遗传基础具有重要意义。在确定家族性肾病（肾病综合征）的遗传原因方面取得了重大进展。然而，没有发现遗传变异与常见形式的肾脏疾病有因果关系。我们的目标是更好地了解在达尔盐敏感(S)大鼠中观察到的高血压性肾脏疾病的遗传基础，它表现出明显的蛋白尿和局灶节段性肾小球硬化（FSGS）。对来自美国的人群进行了蛋白尿和肾损伤的初步遗传分析。研究确定了10个与肾损伤（通过蛋白尿测量）和/或功能相关的基因组区域。在2号染色体上发育的基因菌株表现出明显减少的蛋白尿和FSGS。该提案将评估位于大鼠2号染色体小区域的遗传变异在s大鼠观察到的进行性FSGS和蛋白尿中起重要作用的假设。根据同源菌株分析，致病位点已缩小到<1.2 mb，包含27个基因。然而，跨物种比较、基于近交的SNP分析、综合编码序列和基因表达分析已经令人信服地确定了4个基因，值得进一步研究。本研究的目的是：(1)进行血压和肾脏血流动力学的时间研究，包括肾血流、肾小球毛细血管压力和肾小球通透性；(2)对大鼠2号染色体上狭窄区域的基因进行全面的基因表达、western blot分析、测序和单倍型分析；(3)利用基于细胞和全动物的方法评估已鉴定的等位变异的功能意义。综上所述，本提案将在高血压肾病Dahl s模型中识别和优先考虑与蛋白尿和FSGS相关的基因，并为功能研究、基因验证以及最终在人类人群中进行研究提供基础。高血压是终末期肾病（ESRD）的主要诱因。从1991年到2004年，接受透析或移植治疗的ESRD患者数量增加了一倍多，从209,000人增加到472,000人。在未来20年，预计ESRD患者数量将增加到200多万。此外，经济影响是巨大的，给医疗保险系统（花费201亿美元，占医疗保险总支出的7%）和私营保险部门（估计为121亿美元）带来负担。不幸的现实是，治疗选择是有限的，只能减缓疾病的进展。这项工作的重点是鉴定使达尔盐敏感(S)大鼠易患高血压肾病的基因。先前使用S大鼠进行的遗传分析确定了与肾脏疾病相关的几个染色体区域。特别是，我们发现大鼠2号染色体上的一个区域在S大鼠肾损伤中起着重要作用。在多项研究中，人类染色体1q21上的同源区域也与肾脏疾病有关。这是鉴定大鼠基因的重要性的基础，因为这些发现可能很容易应用于人类肾脏疾病。总之，这项提议的目标是利用人类疾病的啮齿动物模型和先进的遗传技术来加速识别与肾脏疾病有关的基因。从这项研究中获得的知识的应用将有助于更好地理解这种疾病的发生方式和原因，并最终在肾衰竭发生之前提供更早、更有效的治疗方法。

DESCRIPTION (provided by applicant): Abstract There is an alarming increase in the incidence of end-stage renal disease in the Unites States, with hypertension and diabetes being the major cause. Currently, 25.6 million people are in the early phase of kidney disease (stage 1 to 3) and while strict control of blood pressure and glucose levels may slow, it will not prevent the progressive decline of renal function in these patients. Therefore, understanding the genetic basis of hypertension-induced renal disease is of considerable interest. Significant progress has been made to identify the genetic causes of familial forms of renal disease (nephrotic syndrome). However, no genetic variants have been found to be causally linked to common forms of renal disease. It is our goal to develop a better understanding of the genetic basis of hypertension-induced renal disease observed in the Dahl salt- sensitive (S) rat, which exhibits significant proteinuria and focal segmental glomerulosclerosis (FSGS). An initial genetic analysis for proteinuria and renal injury was performed using a population derived from the S. The study identified ten genomic regions linked to renal damage (measured by proteinuria) and/or function. A congenic strain developed on chromosome 2 exhibited significantly less proteinuria and FSGS. This proposal will evaluate the hypothesis that genetic variant(s) located to a small region on rat chromosome 2 play a significant role in the progressive FSGS and proteinuria observed in the S rat. Based on congenic strain analysis, the causative locus has been narrowed to <1.2 Mbs containing 27 genes. However, cross-species comparative, inbred-based SNP analysis, comprehensive coding sequence and gene expression analysis has convincingly identified 4 genes for further study. The aims of the proposed study are: (1) to perform temporal studies of blood pressure and renal hemodynamics, including renal blood flow, glomerular capillary pressure, and glomerular permeability in the S and small congenic strain; (2) to perform comprehensive gene expression, western blot analysis, sequencing, and haplotype analysis for genes narrowed to the small region on rat chromosome 2; and (3) to evaluate the functional significance of identified allelic variants using cell- based and whole-animal approaches. In summary, this proposal will identify and prioritize gene(s) linked to proteinuria and FSGS in the Dahl S model of hypertension-induced renal disease and provide a basis for functional studies, gene validation, and eventually study in human-based populations. PUBLIC HEALTH RELEVANCE: Project Narrative High blood pressure is major contributor to end-stage renal disease (ESRD). The number of ESRD patients treated by either dialysis or transplantation has more than doubled in the period from 1991 to 2004 from 209,000 to 472,000. In the next 20 years, the numbers of ESRD patients are expected to increase to over 2 million. Additionally, the economic impact is substantial, burdening the Medicare system (costing $20.1 billion or 7% percent of total Medicare expenditures), and the private insurance sector (estimated at $12.1 billion). The unfortunate reality is that treatment options are limited and only slow the progression of the disease. The focus of the proposed work is to identify genes that predispose the Dahl salt-sensitive (S) rat to develop hypertension-induced kidney disease. Previous genetic analysis using the S rat identified several chromosomal regions linked to kidney disease. In particular, a region on rat chromosome 2 was found to play a significant role in the kidney injury observed in the S rat. The homologous region on human chromosome 1q21 has also been linked to kidney disease in multiple studies. This underlies the importance in identifying the gene in the rat because the findings may be readily applied to human kidney disease. In summary, it is the goal of this proposal to utilize a rodent model of human disease and advanced genetic techniques to expedite the identification of a gene involved in kidney disease. The application of knowledge gained from this research will contribute to a better understanding of the how and why of the disease and ultimately provide earlier and more effective treatments of the disease before kidney failure is reached.