Role of clonal somatic mutations in microglia activation and Alzheimer’s disease

项目总结/摘要 阿尔茨海默病（AD）和其他神经退行性疾病的特征在于与年龄相关的 发作和进行性神经元损失。神经炎症是大脑先天免疫系统的激活， 已知与神经变性的发生和发展密切相关。作为主要的免疫系统 细胞在大脑中，激活的小胶质细胞最近已被报道，以促进神经元死亡，在AD 发病机制，但年龄和遗传风险相互作用的机制在很大程度上仍然未知。体细胞 在人体的发育和衰老过程中，突变在各种细胞类型中积累。 某些细胞群体的克隆扩增，由调节细胞增殖的基因中的体细胞突变驱动， 长期以来，随着年龄的增长，癌症的风险增加，但直到最近才被认为与癌症有关。 越来越多的非癌症神经系统疾病。值得注意的是，小胶质细胞谱系中的体细胞BRAF突变具有以下作用： 与组织细胞增多症相关的神经退行性疾病有关。我们对两个AD的初步结果 队列和两种测序技术一致地显示AD中过量的克隆体细胞突变 大脑，特别是小胶质细胞的增殖相关基因。 这项新研究旨在检查体细胞突变的积累是否会导致与年龄相关的疾病 通过激活小胶质细胞的克隆扩增增加AD风险，随后诱导神经炎症 和AD大脑中的神经元损失。本研究的第一个目的是通过重新分析 来自大型AD队列的现有批量和单细胞RNA-seq数据集，并比较转录组范围 AD患者和年龄匹配的不同脑区之间的体细胞突变负担和分布 对照在研究的第二个目的中，分子条形码超深度面板测序将应用于 在调节细胞周期和增殖的基因中筛选克隆体细胞突变， AD和控制大脑，这将使我们能够探索频繁突变的基因或途径， AD发病过程中载体细胞的克隆性扩增。研究的第三个目标将侧重于 突变体分数和潜在致病性体细胞突变在不同细胞类型中的功能影响， AD大脑，特别是小胶质细胞，通过结合单细胞RNA-seq和PRDD-seq，我们开发的方法 用于对来自相同单细胞的体细胞突变和细胞类型信息进行并行分析。的成果 这项研究将揭示体细胞突变对AD风险增加的贡献，并强调克隆突变。 增殖相关基因体细胞突变引发的小胶质细胞扩增是一种潜在机制 AD发病机制

Project Summary/Abstract Alzheimer’s disease (AD) and other neurodegenerative diseases are characterized by age-related onset and progressive neuronal loss. Neuroinflammation, the activation of the brain's innate immune system, is known to be critically involved in the initiation and development of neurodegeneration. As the primary immune cells in the brain, activated microglia have been recently reported to promote neuronal death during AD pathogenesis, yet the mechanisms by which age and genetic risk interact remain largely unknown. Somatic mutations accumulate in various cell types during the development and aging process of the human body. Clonal expansion of certain cell populations, driven by somatic mutations in genes regulating cell proliferation, has long been associated with an increased risk of cancer with age, but has only recently been linked to a growing list of non-cancer neurological diseases. Notably, somatic BRAF mutation in the microglial lineage has been implicated in histiocytosis-associated neurodegenerative conditions. Our preliminary results from two AD cohorts and with two sequencing technologies consistently show an excess of clonal somatic mutations in AD brains, particularly in proliferation-related genes of microglia. This new study aims to examine if the accumulation of somatic mutations contributes to an age-related increase of AD risk by activating clonal expansion of microglia, which subsequently induces neuroinflammation and neuronal loss in AD brains. The first Aim of the study is to identify somatic mutations by re-analysis of the existing bulk and single-cell RNA-seq datasets from large AD cohorts, and compare the transcriptome-wide burden and distribution of somatic mutation between different brain regions of AD patients and age-matched controls. In the second Aim of the study, molecule-barcoded ultra-deep panel sequencing will be applied to screen for clonal somatic mutations more sensitively among genes that regulate cell cycle and proliferation in AD and control brains, which will enable us to explore frequently mutated genes or pathways that may drive the clonal expansion of carrier cells during AD pathogenesis. The third Aim of the study will focus on the mutant fraction and functional impact of potentially pathogenic somatic mutations across different cell types in AD brains, especially for microglia, by combining single-cell RNA-seq and PRDD-seq, a method we developed for parallel analysis of somatic mutation and cell-type information from the same single-cells. The results of our study will shed new light on the contribution of somatic mutation to increased AD risk, and highlight the clonal expansion of microglia triggered by somatic mutations in proliferation-related genes as a potential mechanism of AD pathogenesis.