HTRA1 and Age-Related Macular Degeneration

描述（由申请人提供）： 视网膜相关性黄斑变性（AMD）是美国老年人视力损害的最常见原因。我们以前已经确定了HTRA 1/ARMS 2染色体区域的遗传变异与AMD的主要易感性相关。这种疾病基因型导致高温需要因子A1（HTRA 1）的表达增加。在我们之前的资助期间，我们系统地扫描了所有与AMD相关的单核苷酸多态性（SNP），并研究了它们对HTRA 1和ARMS 2表达的调节。我们的功能研究揭示HTRA 1基因敲除（htra 1-/-）小鼠中HTRA 1的缺失导致视网膜血管发育减少和血管内皮生长因子（VEGF）基因表达显著下调。相反，我们发现RPE中HTRA 1的表达增加导致Bruch膜病理学和VEGF表达升高。我们进一步揭示了HTRA 1对VEGF的上调与TGF-β家族成员生长分化因子6（GDF 6）的下调呈负相关。本提案的长期目标是表征HTRA 1的正常功能，阐明HTRA 1导致AMD风险增加的分子机制，并开发潜在的治疗方法。我们的中心假设是HTRA 1通过调节血管发育、血管生成、TGF-β信号传导和细胞外基质模型而导致AMD风险。在这一假设的指导下，我们建议实现以下具体目标。 具体目标1：HTRA 1的单克隆抗体的产生，并通过组织特异性递送到RPE细胞中来研究其治疗潜力。HTRA 1表达增加可导致PCV和视网膜色素上皮萎缩和感光细胞变性。我们将产生特异性结合HTRA 1的单克隆抗体。选择的对HTRA 1具有高亲和力的抗体菌株将被转化为单链形式（scFv），其将被进一步“进化”以使用最先进的新型蛋白质体外进化技术使结合特异性和亲和力最大化。我们将使用基因治疗策略将这种优化的HTRA 1抗体递送到RPE中，并在HTRA 1转基因小鼠和激光CNV模型中测试其对抑制的作用。 具体目的2：探讨TGF-β信号通路在视网膜发育和病理中的作用。我们发现GDF 6与AMD显著相关，并证明GDF 6 AMD风险等位基因与GDF 6表达降低和HTRA 1表达增加相关。我们还发现，TGF-β受体1（TGF-β R1）与AMD有关。我们将产生在视网膜或RPE中缺失GDF 6和TGF-β R1的条件性敲除小鼠，以研究TGF-β信号通路在视网膜发育和致病变化中的作用，包括检眼镜检查、组织学、ERG和表达谱、免疫组织化学和脉络膜新生血管（CNV）形成。 公共卫生相关性： AMD是一种具有经济和社会影响的重大公共卫生负担。对AMD风险有实质性影响的基因的鉴定和功能研究可能定义参与其发病机制的关键分子途径。我们提出的实验将产生与早期和晚期AMD的发病机制相关的新的机制见解，这可能导致针对根本原因的治疗和症状前诊断，以允许用这些治疗进行早期干预。

DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is the most common cause of visual impairment of the elderly in the United States. We have previously identified a genetic variant in the chromosome region of HTRA1/ARMS2 was associated with major susceptibility to AMD. This disease genotype results in increased expression of high temperature requirement factor A1 (HTRA1). In our previous funding period, we systematically scanned all single nucleotide polymorphisms (SNPs) related to AMD and investigated their regulation of expression of HTRA1 and ARMS2. Our functional study reveals loss of HTRA1 leads to decreased retinal vascular development and significant down-regulation of vascular endothelial growth factor (VEGF) gene expression in HTRA1 knockout (htra1-/-) mice. Conversely, we show Increased expression of HTRA1 in RPE leads to Bruch's membrane pathology and elevated VEGF expression. We further revealed that the up-regulation of VEGF by HTRA1 is inversely correlated to the down-regulation of a member of the TGF-b family, the growth differentiation factor 6 (GDF6). The long term objectives of this proposal are to characterize the normal function of HTRA1, elucidate molecular mechanism by which HTRA1 contributes increased risk of AMD, and development potential therapies. Our central hypothesis is that HTRA1 contributes to AMD risk by regulation of vascular development, angiogenesis, TGF-b signaling, and extracellular matrix modeling. Guided by this hypothesis, we propose to conduct the following specific aims. Specific Aim 1: Generation of monoclonal antibodies to HTRA1 and investigating their therapeutic potential by tissue specific delivery into the RPE cells. Increased HTRA1 expression induced PCV and retinal pigment epithelium atrophy and photoreceptor degeneration. We will generate monoclonal antibodies specifically bind to HTRA1. The selected antibody strains with the high affinity to HTRA1 will be converted into a single chain format (scFv), which will be further "evolved" to maximize binding specificity and affinity using a state-of-the-art novel protein in vitro evolution technology. We will use a gene therapy strategy to deliver such optimized HTRA1 antibodies into RPE and test its effect on inhibition in HTRA1 transgenic mice and a laser-CNV model. Specific Aim 2: To determine the role of TGF-b signal pathway in retinal development and pathology. We show that GDF6 significantly associated with AMD and demonstrated that the GDF6 AMD risk allele is associated with decreased expression of the GDF6 and increased expression of HTRA1. We also showed that TGF-b receptor 1 (TGF-b R1) is associated with AMD. We will generate conditional knockout mice which delete GDF6 and TGF-b R1 in either retina or RPE to examine the role of TGF-b signal pathway in retinal development and pathogenic changes, including ophthalmoscopy, histology, ERG, and expression profile, immunohistochemistry and choroidal neovascularization (CNV) formation. PUBLIC HEALTH RELEVANCE: AMD represents a major public health burden with economical and social impacts. Identification and functional studies of genes that have substantial impact on the risk of AMD may define key molecular pathways involved in its pathogenesis. The experiments we propose will yield novel mechanistic insight relevant to the pathogenesis of both early and late AMD, which may lead to therapies directed at the underlying cause and pre-symptomatic diagnostics to allow for earlier intervention with those therapies.