A Forgotten Connection: Retrotransposon contribution to Alzheimer's Disease

现有R01的一个目标是开发高通量方法，称为 SCORE，用于检测人类DNA中多态性L1s（pL1s）反转录转座子。我们现有 R01不包括任何涉及阿尔茨海默病（AD）患者分析的研究。 基因组然而，这种分析将在本R01的范围内，因为pL1及其 DNA损伤是受资助的R01和拟议的行政 补充.这项研究对AD很重要，因为AD患者的大脑 与年龄匹配的对照组相比，DNA断裂水平增加，有证据支持 这种损伤导致AD临床前阶段的神经元损失， 尚未形成。因此，鉴定神经元损失的额外机制 将显著提高我们对AD病因学的认识和治疗进展 发展有几种分子机制可以防止L1相关的损伤。其中一 是TRIM28介导的通过L1启动子的表观遗传沉默抑制L1表达。 虽然TRIM28在整个大脑的神经元中表达，但L1损伤发生在神经元中。 海马体和大脑皮层，这也是AD患者受影响的区域。我们 初步研究结果表明，TRIM 28与其抑制L1转录的作用无关， 与L1蛋白相互作用并刺激L1反转录转座。 我们假设AD患者的基因组比正常人的基因组有更多的pL1， 受试者，这可能导致与L1相关的神经元损失增加 DNA损伤，特别是当与TRIM28的失调相结合时。我们将测试我们的假设 通过两个具体目标。Aim 1将进行病例对照研究，以确定 AD患者（病例）和年龄匹配的无认知功能的受试者基因组中的pL1 控制（Control）。这一目标将决定pL1的数量和/或组成是否与细胞的生长有关。 与AD有关。目的2：确定TRIM28与L1 ORF 2p相互作用的机制 蛋白及其对L1整合和DSB形成的影响。这一目标将决定 TRIM28在L1扩增循环和TRIM28相关的细胞凋亡机制中起双重作用。 刺激L1反转录。这些目标的综合积极成果将证明 大规模研究测试基因组L1含量在识别个体风险中的效用， 发展AD和/或其他年龄相关性痴呆。

One goal of the existing R01 is the development of a high throughput method, called SCORE, for detection of polymorphic L1s (pL1s) retrotransposons in human DNA. Our existing R01 does not include any studies involving analysis of Alzheimer's Disease (AD) patents' genomes. However, such analysis would be within the scope of this R01 because pL1s and their DNA damage are a common theme of both the funded R01 and the proposed Administrative Supplement. The proposed research is important to AD because brains of AD patients have increased levels of DNA breaks compared to age-matched controls with evidence supporting that this damage leads to neuronal loss at the pre-clinical stage of AD when plaques and tangles have not yet been formed. Thus, identification of an additional mechanism(s) underlying neuronal loss will significantly improve our understanding of AD etiology and progress in treatment development. Several molecular mechanisms guard against L1-associated damage. One of them is a TRIM28-mediated suppression of L1 expression by epigenetic silencing of L1 promoters. Although TRIM28 is expressed in neurons throughout the brain, L1 damage occurs in hippocampus and cerebral cortex, which are the areas that are also affected in AD patients. Our preliminary findings show that, independent of its role in suppression of L1 transcription, TRIM28 interacts with L1 proteins and stimulates L1 retrotransposition. We hypothesize that genomes of AD patients have more pL1s than genomes of normal subjects, which can contribute to the neuronal loss associated with an increase in L1-associated DNA damage, especially when combined with deregulation of TRIM28. We will test our hypothesis through two specific aims. Aim 1 will perform a case-control study to determine the number of pL1s in the genomes of AD patients (case) and age-matched subjects without cognitive impairment (control). This aim will determine whether the number and/or composition of pL1s is associated with AD. Aim 2 will determine the mechanism of TRIM28 interaction with L1 ORF2p protein and its effect on L1 integration and DSB-formation. This aim will determine whether TRIM28 plays a dual role in the L1 amplification cycle and the mechanism of TRIM28-associated stimulation of L1 retrotransposition. Combined positive outcomes of these aims would justify large-scale studies testing the utility of genomic L1 content in identifying individual risk of developing AD and/or other age-related dementias.