Cloning/Gene/Posterior Polymorphous corneal dystrophy

描述(申请人提供)：后部多形性角膜营养不良(PPCD、PPMD、PPD；OMIM#122000)是一种主要的遗传性角膜内皮疾病，与广泛的临床特征和病程有关，从良性到深度视力丧失，从角膜肿胀到伴有或不伴有青光眼，大约15%的患者会发生这种疾病。利用标记D20S45，将PPCD定位在染色体20p11-q11上，在theta=0.0处观察到的最大LOD分数为5.54。对一个大家族中21名患者中的4名患者的重组事件分析显示，PPCD基因位于标记D20S98和D20S108之间的30 cM区域。这项建议的目的是确定和表征与PPCD有关的基因(S)。具体工作如下：1.更好地确定PPCD的最小候选基因组区域。在先前确定的和其他新的家系中进行连锁分析，以继续精细绘制疾病基因座图，缩小候选区域，从而缩小PPCD候选基因的数量。检查20号染色体候选基因区域缺失的患者是否具有PPCD的临床特征，从而排除疾病间隔中受影响部分的候选基因。2.选择候选基因并确定其优先顺序。确定哪些基因在成人角膜内皮细胞中表达。基因芯片分析(正常角膜内皮细胞、PPCD角膜内皮细胞)。基因表达序列分析(SAGE)。确定在角膜内皮细胞中发现的哪些表达基因映射到候选基因区域(定位法)。分析映射到定义的候选区间的基因的功能，选择那些当突变时可能导致PPCD临床和组织病理异常的基因(功能方法)。3.进行候选基因筛选。识别候选基因中的序列变异。确定已识别的序列变体是多态还是突变。PPCD的遗传学基础的发现将提供一种明确的手段，将其与其他临床特征重叠的疾病区分开来，并识别青光眼视力丧失的高危人群，以及更好地了解青光眼的发生机制。此外，对该基因的操作可能允许研究人员在体内或体外诱导受控的角膜内皮细胞增殖，为角膜内皮细胞数量不足的患者提供一种替代角膜移植的方法，以保持角膜的透明度，这是全球最常见的角膜移植适应症之一。

DESCRIPTION (provided by applicant): Posterior polymorphous corneal dystrophy (PPCD, PPMD, PPD; OMIM # 122000) is a dominantly inherited disorder of the corneal endothelium that is associated with a wide spectrum of clinical features and courses ranging from benign to profound visual loss from corneal swelling with or without associated glaucoma, which develops in approximately 15% of patients. PPCD has been mapped to chromosome 20p11-q11 with a maximum observed LOD score of 5.54 at theta = 0.0 with marker D20S45. Analysis of recombination events in 4 of the 21 affected patients in a single large family revealed that the PPCD gene is located in the 30 cM region between markers D20S98 and D20S108. The objective of this proposal is to identify and characterize the gene(s) responsible for PPCD. This will be accomplished as follows: 1. Better define the minimal candidate genomic region for PPCD. Perform linkage analysis in previously identified and additional new families to continue to fine map the disease locus, narrowing the candidate region, and therefore the number of candidate genes for PPCD. Examine patients with deletions in the candidate gene region of chromosome 20 for clinical features of PPCD, thereby ruling in or out candidate genes in the affected portion of the disease interval. 2. Select and prioritize candidate genes. Determine which genes are expressed in the adult human corneal endothelium. Microarray analyses (normal corneal endothelium, corneal endothelium in PPCD). Serial analysis of gene expression (SAGE). Determine which of the genes found to be expressed in the corneal endothelium map to the candidate gene region (positional approach). Analyze the function of the genes that map to the defined candidate interval, selecting those that may, when mutated, result in the clinical and histopathologic abnormalities seen in PPCD (functional approach). 3. Perform candidate gene screening. Identify sequence variants in the candidate genes. Determine whether identified sequence variants are polymorphisms or mutations. Discovery of the genetic basis of PPCD will provide a definitive means to distinguish it from other conditions with overlapping clinical features and to identify those at increased risk for vision loss from glaucoma as well as provide a greater understanding of the mechanisms of glaucoma development. Additionally, manipulation of this gene may allow researchers to induce the controlled proliferation of corneal endothelial cells in vivo or in vitro, providing an alternative to corneal transplantation for patients with an insufficient number of corneal endothelial cells to maintain corneal clarity, one of the most common indications for corneal transplantation worldwide.