Human induced pluripotent stem cell modeling of genetic risk factors for Alzheimer's disease

项目摘要 阿尔茨海默病（AD）现在是一个全球性的健康危机，仅在美国就有AD相关的费用 预计到2050年将超过1万亿美元。由于人口日益老龄化和缺乏有效的治疗方法， 我们迫切需要提高对这种疾病的病因和发病机制的认识。 有趣的是，虽然>95%的AD病例是散发性的（sAD），因此没有已知的原因，但sAD显示出高的发病率。 （~60-80%）的遗传率，全基因组关联研究（GWAS）已经确定了>20个基因组位点， 影响sAD风险，强烈暗示sAD发病机制中的遗传风险因素。若干条证据 提示许多GWAS风险基因座通过对基因表达细胞类型特异性作用影响疾病风险。 然而，在1）解释非编码基因组的功能（其中>90%的疾病- 相关的风险变体）和2）产生生理相关的人脑细胞类型， 模型人脑疾病阻碍了这些基因座的机制研究的进展。为了 为了解决这些问题，该提案将联合收割机最先进的功能基因组学方法与人类基因组学方法相结合。 诱导多能干细胞（hiPSC）技术，以确定sAD遗传风险基因座在sAD中的作用 发病机制基因匹配的脑源性和hiPSC源性的表观基因组学和转录组学分析 神经元、星形胶质细胞、少突胶质细胞和小胶质细胞将鉴定活性基因、顺式调节元件， 增强子/启动子相互作用在每种细胞类型中，没有个体间变异的混杂变量， 并将促进sAD风险位点的优先化和功能解剖。在三个优先位点，表观基因组 将进行基因编辑和精确的基因组编辑，以确定致病sAD风险变体及其靶点。 基因.然后将使用等基因hiPSC系来研究这些变体对已知sAD的影响。 相关细胞表型，包括淀粉样蛋白β和tau水平和病理学，淀粉样蛋白β纤维诱导的毒性， 神经元兴奋性毒性，星形胶质细胞和小胶质细胞对淀粉样β纤维的吞噬作用，以及胶质依赖性 对神经元活力的影响。最后，将进行基因集富集分析以鉴定细胞 以无偏见的方式破坏sAD因果风险变异的途径，这将为未来的研究提供信息。 实验，并可能确定潜在的治疗目标。总之，本提案将从功能上剖析 sAD风险位点的潜在机制，以确定新的sAD相关基因和途径， 下游治疗开发。

Project Summary Alzheimer’s disease (AD) is now a global health crisis, with AD-associated costs in the U.S. alone expected to exceed $1 trillion by 2050. Due to the growing aging population and lack of effective treatments, there is an urgent need to improve our understanding of the causes and pathogenesis of the disease. Interestingly, while >95% of AD cases are sporadic (sAD) and thus have no known cause, sAD displays high (~60-80%) heritability, and genome-wide association studies (GWAS) have identified >20 genomic loci that affect sAD risk, strongly implicating genetic risk factors in sAD pathogenesis. Several lines of evidence suggest that many GWAS risk loci affect disease risk through cell type-specific effects on gene expression. However, difficulties in 1) interpreting the functions of the non-coding genome (in which >90% of disease- associated risk variants reside) and 2) generating physiologically-relevant human brain cell types with which to model human brain disease have impeded progress in the mechanistic interrogation of these loci. In order to address these issues, this proposal will combine state-of-the-art functional genomics approaches with human induced pluripotent stem cell (hiPSC) technology in order to determine the role of sAD genetic risk loci in sAD pathogenesis. Epigenomic and transcriptomic profiling of genetically-matched brain- and hiPSC-derived neurons, astrocytes, oligodendrocytes and microglia will identify the active genes, cis-regulatory elements, and enhancer/promoter interactions in each cell type, without the confounding variable of inter-individual variation, and will facilitate the prioritization and functional dissection of sAD risk loci. At three prioritized loci, epigenome editing and precise genome editing will be performed to determine the causal sAD risk variants and their target genes. Isogenic hiPSC lines will then be used to investigate the effects of these variants on known sAD- relevant cellular phenotypes, including amyloid β and tau levels and pathology, amyloid β fibril-induced toxicity, neuronal excitotoxicity, phagocytosis of amyloid β fibrils by astrocytes and microglia, and glial-dependent effects on neuronal viability. Finally, gene set enrichment analyses will be performed to identify cellular pathways that are disrupted sAD causal risk variants in an unbiased manner, which will inform future experiments and may identify potential therapeutic targets. In summary, this proposal will functionally dissect the mechanisms underlying sAD risk loci in order to identify novel sAD-related genes and pathways for downstream therapeutic development.