Functional Studies of VHL by Conditional Gene Targeting

描述（由申请人提供）： von Hippel-Lindau基因（VHL）突变的患者发生多形性家族性肿瘤综合征，其特征为发生具有不同生物学行为的高度血管化肿瘤，如CNS血管母细胞瘤和透明细胞肾细胞癌（RCC），这些肿瘤通常在肾囊肿之前发生。近年来研究发现VHL蛋白（pVHL）可调节缺氧诱导因子（HIF）的稳定性。然而，并不是这种疾病的所有方面，如RCC的恶性表型，都可以很容易地用这种相互作用来解释。VHL小鼠模型将为鉴定对VHL表型的发病机制至关重要的分子因子提供强有力的工具。然而，这样一个模型的发展受到阻碍的事实，即传统的VHL基因敲除小鼠在妊娠中期死于胎盘衰竭，这最初排除了该基因在成人的功能分析。为了克服胚胎致死性的这个问题，主要研究者已经产生了允许通过Cre/loxP介导的重组在成人中组织特异性缺失Vhl的小鼠。已经产生了几种条件性小鼠突变体。例如，肝脏中Vhl的失活导致肝细胞中中性脂质的积累、内皮细胞的增殖以及红细胞增多，所有这些都与pVHL在HIF调节中的作用一致。目前尚不清楚在条件性VHL基因敲除小鼠中观察到的表型是否可以完全归因于HIF-1依赖性靶基因的上调，以及是否存在不受HIF调控的pVHL控制的分子途径。这里提出的研究将解决这些问题，并旨在通过产生几个组织特异性条件小鼠突变体，是在VHL和HIF-1双缺陷的VHL表型定义的关键分子介质。利用基因芯片技术对这些突变体进行分子生物学分析，可能为研究肾小管细胞生长和凋亡的调控机制提供重要的线索。拟议的调查代表了最初在申请人的K 08中描述的研究的延续和扩展，并基于在此资助下生成的数据。它们将在Volker H博士的实验室进行。他是宾夕法尼亚大学肾脏分部的医学助理教授。医学教授Michael Madaio博士将担任Haase博士的导师。

DESCRIPTION (provided by applicant): Patients with mutations in the von Hippel-Lindau gene (VHL) develop a pleomorphic familial tumor syndrome that is characterized by the development of highly vascularized tumors with different biological behaviors such as CNS hemangioblastomas and clear cell renal cell cancers (RCC) which are often preceded by renal cysts. Recently the VHL protein (pVHL) has been found to regulate the stability of hypoxia-inducible-factor (HIF). However not all aspects of this disease, such as the malignant phenotype of RCCs, can be easily explained by this interaction. A VHL mouse model would provide a powerful tool for the identification of molecular factors that are critical for the pathogenesis of the VHL phenotype. However, the development of such a model was hampered by the fact that conventional VHL knockout mice died during midgestation from placental failure, which initially precluded a functional analysis of this gene in the adult. In order to overcome this problem with embryonic lethality, the Principal Investigator has generated mice that allow tissue-specific deletions of Vhl in the adult through Cre/loxP-mediated recombination. Several conditional mouse mutants have been generated. Inactivation of Vhl in the liver for example leads to the accumulation of neutral lipids in hepatocytes, proliferation of endothelial cells, as well as erythrocytosis, all of which is consistent with pVHL's role in the regulation of HIF. At the moment it remains unclear whether the phenotypes that were observed in conditional VHL knockout mice can be solely attributed to the up-regulation of HIF-1 dependent target genes and whether pVHL controlled molecular pathways exist that are not regulated by HIF. The studies proposed here will address these questions and aim at defining the critical molecular mediators of the VHL phenotype by generating several tissue-specific conditional mouse mutants that are double deficient in Vhl and Hif-1. The molecular analysis of these mutants with microarrays might provide important insights into the regulation of growth and apoptosis of renal tubule cells. The proposed investigations represent a continuation and expansion of research that was initially described in the applicant's K08 and is based on data that were generated under this grant. They will be carried out in the laboratory of Dr. Volker H. Haase, who is an Assistant Professor of Medicine in the University of Pennsylvania's Renal Division. Dr. Michael Madaio, Professor of Medicine, will function as Dr. Haase's mentor for this grant.