Altered reverse transcriptase-dependent gene diversification mechanisms in Alzheimer's disease brains

项目总结/摘要 我们已经确定了体细胞基因重组（SGR）在人脑神经元，特别是相关的 散发性阿尔茨海默病（SAD）（Nature 563，639-645（2018））。这一发现代表了一种新的， 基因组嵌合的功能重要方面（eLife;4：e05116（2015）），其具有真正的治疗效果， 新发现的分子靶点。事实上，我们发现SGR，作用于AD基因， 淀粉样前体蛋白（APP）产生数千种不同形式的APP，其中一些富含淀粉样前体蛋白。 或AD独有的。迄今为止分析的与AD相关的APP基因变异包括拷贝数 变异（CNVs）和至少11个单核苷酸变异（SNVs），这些变异以前被报道为 在家族性AD中致病，但在SAD中出现体细胞和嵌合体;这些变异在 未患病的神经元。SGR利用逆转录酶（RT）对转录RNA的活性， 通过DNA链断裂和APP基因转录，产生反向插入的双链DNA 插入基因组中形成基因组cDNA（genocDNAs）。这些公布的数据有助于科学 目前的建议将建立的基础上，测试的假设，改变SGR，涉及脑- 特异性逆转录酶，在功能上有助于AD并影响多个基因，提供了新的靶点 用于AD治疗。来自经验证的AD供体的IRB批准和去识别的尸检脑样本， 性别将与非疾病对照进行比较，而IACUC批准的动物实验将模拟SGR 及其AD相关终点。五年内将实现三个目标。目标1将定义分子 APP基因cDNA多样性的神经生物学研究，并鉴定在AD脑中增强的新SGR基因。目标2将 确定SGR基因在AD脑和模型系统中的表达和功能。目标3将确定基因 负责正常和AD脑内的RT SGR活性。这一建议将为AD开辟新的前景 通过新的SGR机制，并将确定新的治疗AD的治疗靶点。

PROJECT SUMMARY/ABSTRACT We have identified somatic gene recombination (SGR) in neurons of the human brain, with particular relevance to sporadic Alzheimer’s disease (SAD) (Nature 563, 639-645 (2018)). This discovery represents a new and functionally significant aspect of genomic mosaicism (eLife;4:e05116 (2015)) that has genuine therapeutic potential through newly identified molecular targets. Indeed, we found that SGR, acting on the AD gene for Amyloid Precursor Protein (APP), produces thousands of distinct forms of APP, some of which are enriched in or unique to AD. The APP gene variations related to AD that were analyzed thus far include copy number variations (CNVs) and at least 11 single-nucleotide variations (SNVs) that were previously reported as pathogenic in familial AD, yet that arose somatically and mosaically in SAD; these variations were absent from non-diseased neurons. SGR utilizes reverse transcriptase (RT) activity on transcribed RNAs that, combined with DNA strand-breaks and APP gene transcription, produce double-stranded DNA that is retro-inserted back into the genome to form “genomic cDNAs” (gencDNAs). These published data contribute to the scientific foundation on which the current proposal will build, to test the hypothesis that altered SGR, involving brain- specific reverse transcriptases, functionally contributes to AD and affects multiple genes, providing novel targets for AD therapies. Postmortem IRB-approved and de-identified brain samples from validated AD donors of both sexes will be compared to non-diseased controls, while IACUC-approved animal experiments will model SGR and its AD-relevant endpoints. Three Aims will be pursued over 5 years. Aim 1 will define the molecular neurobiology of APP gencDNA diversity and identify new SGR genes enhanced in AD brains. Aim 2 will determine expression and function of SGR genes in AD brain and model systems. Aim 3 will identify genes responsible for RT SGR activity within normal and AD brains. This proposal will thus open new vistas into AD via novel SGR mechanisms and will identify new therapeutic targets for the treatment of AD.