Age-Related Macular Degeneration: Genetic Variations and Animal Model

年龄相关性黄斑变性（AMD）在全球老年人中引起不可逆的中央视力丧失。各种研究表明AMD有显著的遗传成分。目前的证据支持基因变异导致患病倾向的假设。2003年，我们启动了这个项目，招募了晚期AMD患者和年龄匹配的正常视网膜对照个体。迄今为止，已有482人入选，并收集了107例AMD组织病理学病例。我们继续分析来自澳大利亚蓝山眼科研究的835份DNA样本和来自美国AREDS项目的534份DNA样本，因为一些DNA样本已经用完了。我们比较了AMD和对照组之间候选基因内单核苷酸多态性（snp）的等位基因频率，然后通过体外和/或体内实验对这些snp进行了功能研究。通过这种方法，我们已经确定了AMD的遗传危险因素以及这些基因变异在疾病发病机制中的可能作用。基于上述方法获得的信息，2007年，我们产生了一种基因工程动物（DKO rd8背景小鼠的Ccl2/Cx3cr1双重缺陷）作为AMD模型。

Age-related macular degeneration (AMD) causes irreversible central visual loss in the aged population worldwide. Various studies suggest that AMD has a significant genetic component. Current evidence supports the hypothesis that gene variation creates a predisposition to the disease. In 2003, we initiated this project by recruiting advanced AMD patients and age-matched control individuals with normal retinas. Up to date, 482 individuals have been enrolled and 107 histopathological cases with AMD have been collected. We continue to analyze parts of 835 DNA samples from the Blue Mountain Eye Study in Australia and 534 DNA samples from the AREDS project in USA because some DNA samples had been ran out. We have compared the allelic frequencies of single nucleotide polymorphisms (SNPs) within candidate genes between AMD and control subjects, followed by functional studies of these SNPs by in vitro and/or in vivo experiments. Through this approach, we have identified genetic risk factors of AMD and the possible roles of these gene variations in the pathogenesis of the disease. Based on the information obtained from the above approaches, a genetically engineered animal (Ccl2/Cx3cr1 double deficiencies on rd8 background mice, DKO rd8) was generated to act as an AMD model in 2007. In FY2013, (1) we published the merits of using the DKO rd8 mouse model as a platform to screen therapeutic compounds for AMD treatment (Chu, et al. Bioengineered 5:13-15, 2013; Zhang, et al. Synapse 67:515-531, 2013; Wang, et al. Apoptosis 17:1144-1155, 2012); (2) we continue working with collaborators to use our DKO rd8 model to study disease pathogenesis and therapeutic options of AMD, by evaluating the roles of PDGF-CC (collaboration with Dr. Xuri Li), PEDF (collaboration with Dr. S. Patricia Becerra), TSG-6 (collaboration with Dr. Darwin Prockop: J Neuroinflamm e959, 2012) and AREDS II formula (Ramakumar, et al. J Nutr 143:1129-1135, 2013). The role of AREDS II formula has been published; (3) we initiated a study of antibody therapy to block WNT pathway in the retinal tissue of the DKO rd8 mice (collaboration with Dr. Wen-xin Ma); (4) we provided DKO rd8 retina for studying the microRNAs role in AMD (collaboration with Dr. Shusheng Wang); (5) we reported the pharmacogenomics study (collaboration with Drs. Catherine Meyerle, Richard Rosen and Shree Kurup) on the efficacy of anti-VEGF therapy on AMD and patients genotypes (Wang, et al. Mol Vis 18:2578-2585, 2012); (6) A large scale SNP association study on the role of TIMPs in AMD was published. A similar study on the role of DNA repair gene RAD51B in AMD is completed and the paper is in Eur Hum Genet (2013 Feb 20. doi: 10.1038/ejhg.2013.14); (7). some subjects recruited in this protocol were screened for their AMD related genotypes and will be used in the iPS project in collaboration with Drs. Sheldon Miller and Kapil Bharti; (8) we used a systems biology subtyping of AMD on the basis of gene expression (Abu-Asab, et al. J Ophthalmology 2013, in press) and reviewed how to distinguish AMD from aging (Ardeljan, Prog Retin Eye Res. 2013 Aug 9. doi:pii: S1350-9462(13)00045-1 Epub ahead of print); (9) in this period, we published a total of 13 relevant original or review papers including the novel findings of hypomethylation of the IL17RC promoter in AMD (collaboration with Dr. Lai Wei & Robert Nussenblatt: Cell Report 2:1151-1158, 2012) and the 7 new loci associated with AMD (collaboration with Dr. Anand Swaroop and the AMD Gene Consortium: Nat Genet 45:433-439, 2013).