The role of APOE locus genes regulation in Alzheimer's disease

描述（由申请人提供）： 阿尔茨海默病（AD）是老年人痴呆症的最常见原因。据估计，到2010年，510万65岁或65岁以上的美国人将发展为AD，并且患有AD的人数将继续显著增加，因为老龄化人口预计在未来25年内将翻一番。退伍军人事务部（VA）医疗保健系统服务于大量老龄化人口，并且由于老龄化与AD风险增加相关，因此处于AD风险的老龄化退伍军人的预计数量正在以惊人的速度增加;因此，非常需要治疗或预防AD的补救措施。 到目前为止，晚发性阿尔茨海默病（LOAD）唯一明确的易感因素是载脂蛋白E基因（APOE）。与该疾病密切相关的APOE e4等位基因以剂量依赖性方式影响LOAD状态和发病年龄。然而，单独的e4不是引起LOAD所必需的或足够的。因此，人们推测，其他遗传、表观遗传或环境因素是复合APOE e4效应以发展LOAD所必需的。 包括我们自己的工作在内的几条证据表明，在APOE基因座中存在多种影响LOAD风险的遗传因子，并且e4可能在APOE基因座基因的转录调节中具有生物学功能。拟议的研究将探索遗传和生物学证据，以证明APOE e4具有增强子/沉默子活性。这种活性可以改变APOE基因座中多个基因的表达谱，并且与LOAD风险在功能上相关。我们的短期目标是确定e4相关的APOE基因座基因调控在LOAD中的作用。我们的长期目标是精确定义APOE区域的LOAD致病机制，从而改进LOAD的预测、预防和干预策略。 我们的假设是，载脂蛋白E e4有很强的转录调控作用，并认为e4在LOAD中的不利影响可能不仅与apoE蛋白结构和功能的改变有关，而且与apoE基因座基因表达的变化有关。拟议的实验是专门针对测试这一假设。 我们的研究的具体目标将调查这一整体范式的组成部分。目的1探讨APOE e2/e3/ e4等位基因在APOE及其邻近基因转录调节中的作用。我们将使用荧光素酶报告基因构建体和测定来研究人类细胞系中的转录活性。目的2将构建APOE核心区的染色体相位分离单倍型，确定LOAD的高风险或低风险单倍型，并确定关键的LOAD相关遗传变异。这些单倍型将促进LOAD风险与目标1中鉴定的转录活性的单倍型-表型相关性。目的3在细胞模型和AD/对照死后脑组织中验证APOE基因单倍型对基因调控的影响。 公共卫生相关性： 阿尔茨海默病（AD）困扰着超过500万的美国老年人，随着老年人在人口中的比例增加，这种流行病的患病率预计在未来几十年将急剧增加。退伍军人事务部的医疗保健系统为大量老龄化人口提供服务，预计有AD或某种形式痴呆风险的老年退伍军人人数正在急剧增加。因此，非常需要治疗或预防神经退行性疾病如AD的补救措施。目前，我们既没有预防也没有治愈AD，目前的治疗方法充其量只能适度帮助稳定临床症状。只有通过集中的研究努力，我们才能开发出更有效的方法来治疗并最终预防AD。本申请中提出的研究可能有助于进一步阐明各种遗传变异影响AD风险的机制，也可能为AD和其他常见神经退行性疾病的治疗干预提供线索。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most common cause of dementia among the elderly. It is estimated that 5.1 million Americans aged 65 or older will develop AD by the year 2010, and the number of people with AD will continue to increase significantly, as the aging population is expected to double over the next 25 years. The Veterans Affairs (VA) health care system serves a large aging population, and because aging is associated with an increased risk of AD, the projected number of aging Veterans at risk for AD is increasing at a dramatic pace; thus, there is a great need for remedies that treat or prevent AD. To date, the only well established susceptibility factor for late-onset Alzheimer's disease (LOAD) is the apolipoprotein E gene (APOE). APOE e4 allele, which is strongly associated with the disease, affects LOAD status and age-at-onset in a dose-dependent manner. However, e4 alone is not necessary or sufficient to cause LOAD. It has therefore been postulated that other genetic, epigenetic, or environmental factors are necessary to compound the APOE e4 effect to develop LOAD. Several lines of evidence, including our own work, suggests the presence of multiple LOAD risk- influencing genetic factors in the APOE locus, and e4 may have a biological function in transcriptional regulation of APOE-locus genes. The proposed studies will explore genetic and biological evidence to demonstrate that APOE e4 has enhancer/silencer activity. This activity can alter the expression profiles of multiple genes in the APOE locus and is functionally relevant for the risk of LOAD. Our short-term goal is to determine the role of e4-related APOE-locus gene regulation in LOAD. Our long-term goal is to precisely define LOAD-causative mechanisms in the APOE region, thereby yielding improved prediction, prevention, and intervention strategies for LOAD. Our hypothesis is that APOE e4 has a strong effect in transcriptional regulation, and that the adverse effects of the e4 in LOAD may be related not only to alterations in apoE protein structure and function but also to changes in the expression of APOE-locus genes. The proposed experiments are specifically aimed at testing this hypothesis. The specific aims of our study will investigate the components of this overall paradigm. Aim 1 will investigate the role of APOE e2/e3/ e4 alleles in the transcriptional regulation of APOE and its adjacent genes. We will use the luciferase reporter gene constructs and assays to study the transcriptional activities in human cell lines. Aim 2 will construct the chromosome-phase-separated haplotypes of the APOE core region, determine the higher- or the lower-risk haplotypes of LOAD, and identify critical LOAD-associated genetic variants. These haplotypes will facilitate haplotype-phenotype correlations of LOAD risk with the transcriptional activities identified in Aim 1. Aim 3 will validate haplotype effects of APOE locus on genes regulation in cellular models and in AD/control postmortem brain. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) afflict over 5 million older Americans, this epidemic prevalence is projected to increase dramatically in the coming decades as the proportion of elderly in the population increases. The Veterans Affairs health care system serves a large aging population, the projected number of aging Veterans at risk for AD or some form of dementia is increasing at a dramatic pace. Therefore, there is great need for remedies to treat or prevent neurodegenerative disorders like AD. At present we have neither prevention nor cure for AD, and present treatment approaches are, at best, modestly helpful in stabilizing clinical symptoms. Only through a concentrated research effort can we develop more effective approaches to treating and ultimately preventing AD. The studies proposed in this application may help to further elucidate the mechanisms by which various genetic variations affect risk of AD, and may also provide clues for therapeutic intervention in AD and other common neurodegenerative disorders.