The role of somatic mutation in neurodegenerative disease

该项目的目标是利用单细胞分析，了解体细胞突变在神经退行性变中的作用，特别是在神经退行性疾病阿尔茨海默病和共济失调毛细血管扩张症中。阿尔茨海默病是一种进行性神经退行性疾病，导致记忆和其他认知功能丧失；共济失调毛细血管扩张症是另一种神经退行性疾病，在DNA双链断裂(DSB)修复方面存在遗传缺陷。体细胞突变在癌症中得到了最广泛的研究，但它们也会导致神经发育障碍，如癫痫和半巨脑。以前的研究已经在一些神经退行性疾病中发现了因果相关基因的体细胞马赛克突变，例如阿尔茨海默病中的早老素-1。包括我们的工作在内的其他研究表明，毛细血管扩张性共济失调缺乏适当的DSB修复可能会导致体细胞突变的增加，包括重复DNA中的突变，并导致神经细胞死亡。我们最近的单神经元基因组研究表明，即使在神经学上正常的人类大脑也是一个人一生中发生的体细胞突变的拼凑，而活跃的转录可能在罕见的体细胞突变的产生中发挥作用。因此，我们假设，少数神经元发育迟缓甚至有丝分裂后突变可能在阿尔茨海默病的突触功能丧失和细胞丢失中发挥作用。为了克服当前批量细胞分析中对低频变异的有限检测灵敏度，我们将使用单细胞基因组学来测试我们的假设，使用新的计算工具来规避当前单细胞测序协议中必需的基因组扩增过程引入的数据中的噪声。在目标1中，我们建议开发强大的分析方法来减轻基因组扩增偏差在检测多种形式的体细胞突变中的影响，包括重复突变(端粒和反转录转座子等串联重复)。在目标2中，我们将使用单神经元全基因组测序来分析阿尔茨海默病和共济失调毛细血管扩张症患者死后脑中的体细胞突变。

The goal of this project is to understand the role of somatic mutations in neurodegeneration, specifically in neurodegenerative disorders Alzheimer’s Disease and Ataxia Telangiectasia, using single-cell analysis. Alzheimer’s Disease is a progressive neurodegenerative disorder leading to the loss of memory and other cognitive functions; Ataxia Telangiectasia is another neurodegenerative disorder with inherited defects in DNA double strand break (DSB) repair. Somatic mutations have been studied most extensively in cancer, but they also cause neurodevelopmental disorders such as epilepsy and hemimegalencephaly. Previous studies have found somatic mosaic mutations in causally implicated genes in some neurodegenerative diseases, such as presenilin-1 in Alzheimer’s Disease. Other studies, including our work, have suggested that the lack of proper DSB repair in Ataxia Telangiectasia may allow increased accumulation of somatic mutations, including those in repetitive DNA, and lead to neuronal cell death. Our recent single-neuron genomic studies showed that even neurologically normal human brains are a patchwork of somatic mutations that occur throughout one’s life, and that active transcription may play a role in generation of rare somatic mutations. We therefore hypothesize that late-development or even post-mitotic mutations in a small number of neurons may have a functional role in the loss of synaptic function and cell loss in Alzheimer’s Disease. To overcome the limited detection sensibility for low frequency variants in current bulk-cell analysis, we will employ single-cell genomics to test our hypothesis, using novel computational tools to circumvent the noise in the data introduced by the genome amplification process necessary in current single-cell sequencing protocols. In Aim 1, we propose to develop robust analytical methods to mitigate the impact of genome amplification bias in detecting multiple forms of somatic mutations, including repeat aberrations (tandem repeats such as telomere and retrotransposons). In Aim 2, we will analyze somatic mutations in post-mortem brains of patients with Alzheimer’s Disease and Ataxia Telangiectasia using single-neuron whole genome sequencing.