The Hallmarks of Aging: Assessing accumulation of DNA lesions with age using single cell DNA sequencing in GESTALT

长期以来，基因组不稳定性一直被认为是衰老的主要原因。体细胞持续暴露于各种来源的DNA损伤，从活性氧到紫外线辐射到环境诱变剂。进化选择了一个复杂的基因组维护系统网络来修复每天发生在基因组中的数万种不同类型的病变，并随着时间的推移保持其完整性。研究人员认为，未修复的病变随着年龄的增长而积累，因为修复是错误的;病变的发生率高于修复系统的能力，或者在细胞分裂过程中偶尔无法正确复制基因组。这种病变的积累可能导致通过不同的仍然假设的机制，包括炎症，细胞衰老，细胞凋亡，线粒体功能障碍等老化的表型的发展。事实上，虽然有证据表明DNA突变在苍蝇和哺乳动物的各种器官和组织中积累，但从未确定人类是否发生可检测的DNA损伤积累，以及这些随机损伤的频率是否与衰老的表型表现相关。为了解决这个问题，我们计划研究在25个健康个体中收集的单个单核细胞中的基因组损伤累积，这些个体分布在很宽的年龄范围内，并将其与衰老的主要表型以及在相同个体中进行的DNA修复的全球测量（COMET测定）相关联。本研究将在正在进行的GESTALT研究中实施，这是一项在NIA临床研究单位进行的纵向研究，旨在了解衰老的生物学机制。

Genome instability has long been implicated as the main causal factor in aging. Somatic cells are continuously exposed to various sources of DNA damage, from reactive oxygen species to UV radiation to environmental mutagens. Evolution has selected a complex network of genome maintenance systems to repair the tens of thousands of different types of lesions that occurs into the genome each day and maintain its integrity over time. Investigators have suggested that unrepaired lesions accumulate with aging because repair is erroneous; the rate of lesions is above the capacity of the repair system or occasional failure to correctly replicate the genome during cell division. The accumulation of such lesions may lead to the development of the phenotypes of aging through different still hypothetical mechanisms including inflammation, cell senescence, apoptosis, mitochondrial dysfunction among others. Indeed, while there is evidence that DNA mutations accumulate in various organs and tissues in flies and mammals, it has never been established whether detectable accumulation of DNA damage occurs in humans and whether the frequency of these random lesions correlate with phenotypic manifestation of aging. To address this issue, we plan to study genome damage accumulation in single monocytes collected in 25 healthy individuals distributed over a wide age range and correlate them with the major phenotypes of aging and with a global measure of DNA repair (COMET assay) performed in the same individuals. This study will be implemented in the ongoing GESTALT study, a longitudinal study performed at the NIA clinical research unit that is aimed at understanding the biological mechanisms of aging.