The role of transcription factor 4 repeat expansion in Fuchs endothelial corneal dystrophy

 描述(申请人提供)：这是一个多PI R21应用程序，用于测试三核苷酸重复(TNR)扩展在Fuchs内皮性角膜营养不良(FECD)发病机制中起作用的假设，FECD是一种常见的常染色体显性遗传晚发型眼病。在美国，由FECD引起的角膜水肿是角膜移植最常见的适应症。目前还没有已知的阻止疾病进展的药物，其发病机制也不是很清楚。我们之前的工作已经发现，转录因子4(TCF4)基因中的TGC TNR扩增是该病最强有力的生物标志物，在约80%的病例和3%的对照中存在。我们现在有初步数据表明，来自TCF4重复扩增的转录本在FECD患者的角膜内皮细胞中形成了RNA灶。这一发现类似于强直性肌营养不良1型(DM1)，在DM1中，蛋白激酶基因3‘非翻译区的相同三核苷酸扩展导致转录重复序列聚集到特征核RNA焦点，从而隔离关键剪接因子类肌盲1(MBNL1)。在DM1中，有效MBNL1水平的降低改变了许多转录本的mRNA剪接模式，有助于疾病的临床表现谱。我们建议检验这样一种假设，即TCF4中CTG重复序列的扩展类似地改变了FECD患者角膜内皮的剪接模式。次要目标将包括分析TCF4重复扩增对基因表达谱的影响，以及角膜内皮细胞基因组结构的这种广泛变化与FECD疾病进展之间的关系。我们的统一假设是FECD是一种TNR扩张性疾病。从机制上讲，我们假设这种疾病是由TNR扩张对角膜内皮(CE)基因表达的定性和定量影响所致。为了解决这个问题，我们将分析疾病和正常人CE中的mRNA表达模式，以确定FECD患者的基因表达模式是如何改变的。相关性初步实验表明，FECD是迄今为止描述的最常见的TNR扩张性疾病。如果拟议的实验支持这一假说，它将提供对致病机制的洞察，并提出治疗FECD的新方法。没有可信的方法来逆转TNR的扩张，所以我们对新疗法的希望取决于详细说明FECD发病的分子基础。我们希望最终确定治疗目标，以减缓疾病进展并减少对角膜移植的需求。

 DESCRIPTION (provided by applicant): This is a multiple PI R21 application to test the hypothesis that trinucleotide repeat (TNR) expansion plays a role in the pathogenesis of Fuchs endothelial corneal dystrophy (FECD), a common, autosomal dominant, late-onset eye disease. Corneal edema due to FECD is the most common indication for corneal transplantation in the United States. There are no known medical therapies to halt disease progression, and the pathogenesis is not well understood. Our previous work has identified a TGC TNR expansion in the transcription factor 4 (TCF4) gene as the most robust biomarker for the disease, being present in ~80% of cases and in 3% of controls. We now have preliminary data suggesting that transcripts from the TCF4 repeat expansion form RNA foci in corneal endothelial cells from FECD patients. This finding is analogous to myotonic dystrophy, type 1 (DM1) in which an identical trinucleotide expansion in the 3' untranslated region of a protein kinase gene leads to aggregation of the transcribed repeat sequence into characteristic nuclear RNA foci, which sequester the critical splicing factor muscleblind-like 1 (MBNL1). In DM1 the reduction in effective MBNL1 levels alters the patterns of mRNA splicing of numerous transcripts, contributing to the spectrum of clinical findings in the disease. We propose to test the hypothesis that expansion of CTG repeats in TCF4 similarly alters splicing patterns in the corneal endothelium from FECD patients. Secondary objectives will include analysis of the effect of TCF4 repeat expansion on gene expression profiles and the relationship between such widespread changes in the genomic architecture of corneal endothelial cells and disease progression in FECD. Our unifying hypothesis is that FECD is a TNR expansion disease. Mechanistically, we hypothesize that the disease results from both qualitative and quantitative effects of TNR expansion on gene expression in the corneal endothelium (CE). To address this issue, we will analyze mRNA expression patterns in diseased and normal human CE to determine how gene expression patterns are altered in FECD patients. Relevance Preliminary experiments suggest the hypothesis that FECD is the most common TNR expansion disease described to date. If the proposed experiments support this hypothesis, it will provide insight int pathogenic mechanisms and suggest novel approaches for treating FECD. There is no plausible way to reverse TNR expansion, so our hope for novel therapies depends upon detailing the molecular basis of FECD pathogenesis. We hope to eventually identify therapeutic targets to mitigate disease progression and reduce the need for corneal transplants.