Molecular Genetics of a Complement Factor H homolog

项目摘要 视网膜相关性黄斑变性（AMD）是发达国家中视力丧失的主要原因。 世界上有11%的85岁以上的成年人受到影响。仅在美国，这种疾病目前就困扰着 1000万人，医疗费用高达数十亿美元。2005年发现的Y 402 H 然而，补体因子H（CFH）变异作为一种危险因素是AMD遗传学的一个重大进展， CFH和Y 402 H的功能意义以及启动和促进 对这种疾病的了解仍然很少。CFH功能的典型模型是它与乙酰肝素结合 硫酸盐（HS）在细胞表面上通过两种不同的途径抑制补体旁路途径活性 机制等因此，AMD发病机制的流行假设是HS中的错义突变， CFH中的结合位点，包括Y 402 H，导致与细胞表面的结合缺陷， 激活视网膜中的替代补体途径。作为这种激活的结果， 炎症、细胞溶解活性和富含脂质沉积物（即玻璃疣）的积累增加 促进AMD发病。 与这一典型模型形成鲜明对比的是，PI及其同事的初步研究表明， CFH-1是C. elegans，定位于C. elegans 硫酸乙酰肝素依赖性的机械感觉神经元，其中它维持inversin/NPHP-2 在它的纤毛室里。其他数据表明，inversin/NPHP-2隔室 在人Y 402 H光感受器中受损，这表明CFH-1的这种新功能是 在人CFH中保守。基于这些数据，PI提出了一个激进的假设，即CFH是 是人类视网膜感觉神经元纤毛的基本结构成分， 在CFH功能缺失突变患者中，感光细胞纤毛促进AMD发病。的 这项建议的目的将扩大这些初步研究，并使用经典的分子和遗传 技术来剖析CFH-1定位机制和限制反转/NPHP-2功能 分布在C.机械感觉神经元纤毛。CFH-1在C. elegans 将在人类光感受器中使用源自诱导的多能细胞的视网膜类器官模型进行测试。 干细胞和死后视网膜的基因分型共同努力，拟议的工作将提供实质性的 深入了解以前未被重视的CFH功能，这些功能可能有助于形成独特的新模型 AMD的发病机制。

Project Summary Age-related macular degeneration (AMD) is the leading cause of vision loss in the developed world, affecting 11% of adults over the age of 85. In the United States alone, the disease currently afflicts 10 million individuals, with health care costs in the billions of dollars. The 2005 discovery of a Y402H variant in complement factor H (CFH) as a risk factor was a major advance in AMD genetics, however the functional significance of CFH and Y402H and the pathogenic mechanisms that initiate and promote the disease remain poorly understood. The canonical model of CFH function is that it binds to heparan sulfate (HS) on cell surfaces where it inhibits alternative complement pathway activity by two distinct mechanisms. Thus, the prevailing hypothesis for AMD pathogenesis is that missense mutations in HS binding sites in CFH, that include Y402H, result in defective binding to cell surfaces and ectopic activation of the alternate complement pathway in the retina. As a consequence of this activation, increased inflammation, cytolytic activity, and the accumulation of lipid-rich deposits (i.e. drusen) promote AMD pathogenesis. In stark contrast to this canonical model, preliminary studies by the PI and co-workers indicate that CFH-1, a CFH homolog in C. elegans, localizes on the ciliary membrane of C. elegans mechanosensory neurons in a heparan sulfate dependent manner where it maintains inversin/NPHP-2 within its eponymous cilia compartment. Additional data indicate that the inversin/NPHP-2 compartment is compromised in human Y402H photoreceptors, suggesting that this novel function for CFH-1 is conserved in human CFH. On the basis of this data, the PI proposes the radical hypothesis that CFH is an essential structural component of sensory neuron cilia in the human retina and that structural defects in photoreceptor cilia promote AMD pathogenesis in patients with CFH loss-of-function mutations. The aims of this proposal will extend these preliminary studies and use classic molecular and genetic techniques to dissect the mechanism of CFH-1 localization and function in restricting inversin/NPHP-2 distribution in C. elegans mechansensory neuron cilia. This novel model of CFH-1 function in C. elegans will be tested in human photoreceptors using a retina organoid model derived from induced pluripotent stem cells and genotyped post-mortem retina. Together, the proposed work will provide substantial insight into previously unappreciated CFH functions that are likely to contribute to a unique new model of AMD pathogenesis.