RNA Targets of the Wilm's Tumor Protein in the Kidney

描述（由申请人提供）：肾母细胞瘤基因（WT 1）的产物是肾脏发育以及维持正常肾小球结构和功能所必需的。在成人肾脏中，WT 1表达仅限于足细胞，WT 1蛋白对正常足细胞功能的重要性通过导致两种肾小球疾病Denys-Drash和Frasier综合征的WT 1蛋白突变而突出。由于编码足细胞特异性蛋白质的其他基因突变也会导致肾小球疾病，因此最近的许多工作都集中在足细胞中维持狭缝隔膜正确形成和功能的分子途径上。WT 1的两种剪接变体导致在第三和第四锌指之间含有[WT 1（+KTS）]或排除[WT 1（-KTS）]三个氨基酸的蛋白质似乎在表达细胞的细胞核中具有不同的功能。WT 1（-KTS）蛋白以高亲和力结合DNA序列并作为转录调节因子发挥作用，而WT 1（+KTS）似乎作为具有转录后功能的RNA结合蛋白发挥作用。由于突变或通过在小鼠中定向敲除该变体而导致+KTS变体的缺失分别导致人类的Frasier综合征或小鼠的肾小球硬化。因此，+ KTS变体是维持正常足细胞生理学所特别需要的。这些研究是针对这样的假设，即WT 1（+KTS）影响足细胞基因的转录后处理，通过直接相互作用与他们的转录在核中。然而，在足细胞中被WT 1（+KTS）结合的RNA仍然不确定，因此这种蛋白质亚型影响足细胞功能的机制仍然未知。我们打算通过以下具体目标来追求这些特异性RNA靶标的身份：1）使用体外选择来鉴定被WT 1（+ KTS）以高亲和力结合的保守序列。为了鉴定以高亲和力结合WT 1（+KTS）的特异性RNA共有序列，我们将使用通过系统富集的配体系统进化（SELEX）方法。2)使用免疫共沉淀试验鉴定分化足细胞中与WT 1（+ KTS）相关的体内RNA靶标。我们将通过特异性核糖核蛋白（RNP）复合物的免疫沉淀（IP）直接在培养的足细胞中追踪相关RNA转录物。微阵列将用于鉴定与WTI（+KTS）特异性共IP的特异性RNA。

DESCRIPTION (provided by applicant): Products of the Wilm's tumor gene (WT1) are required for both the development of the kidney as well as maintenance of normal glomerular structure and function. In the adult kidney, WT1 expression is confined to the podocyte and the importance of WT1 protein for normal podocyte function is highlighted by the mutations in the WT1 protein that result in two glomerular diseases, Denys-Drash and Frasier syndromes. Because mutations in other genes encoding podocyte specific proteins also result in glomerular diseases, much recent work has focused on molecular pathways in podocytes that maintain proper formation and function of the slit diaphragm. Two splice variants of WT1 that result in proteins that contain [WT1(+KTS)] or exclude [WT1(-KTS)] three amino acids between the third and fourth zinc fingers appear to have distinct functions in the nucleus of expressing cells. The WT1(-KTS) protein binds DNA sequences with high affinity and functions as a transcriptional regulator, whereas WT1 (+KTS) appears to function as an RNA binding protein with post-transcriptional functions. Loss of the +KTS variant due to mutation or by directed knockout in mice of this variant results in Frasier syndrome in humans or glomerular sclerosis in mice, respectively. Thus, the + KTS variant specifically is required for maintenance of normal podocyte physiology. These studies are directed towards the hypothesis that WT1 (+KTS) affects post-transcriptional processing of podocyte genes through direct interactions with their transcripts in the nucleus. However, RNAs that are bound by WT1 (+KTS) in podocytes remain undefined and thus the mechanism by which this protein isoform influences podocyte function remains unknown. We intend to pursue the identity of these specific RNA targets through the following specific aims: 1) Identify conserved sequences that are bound with high affinity by WT1(+ KTS) using in vitro selection. In order to identify specific RNA consensus sequences that bind to WT1(+KTS) with high affinity we will use the method of Systematic Evolution of Ligands by Systematic Enrichment (SELEX). 2) Identify in vivo RNA targets associated with WT1 (+ KTS) in differentiated podocytes using co-immunoprecipitation assays. We will pursue relevant RNA transcripts directly in cultured podocytes by immunoprecipitation (IP) of specific ribonucleoprotein (RNP) complexes. Microarrays will be used to identity of specific RNAs that specifically co-IP with WTI(+KTS).