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

基因组不稳定一直被认为是导致衰老的主要因素。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再到环境诱变剂。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成千上万种不同类型的损伤，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；病变的速率高于修复系统的能力，或者偶尔在细胞分裂期间不能正确复制基因组。这些病变的积累可能通过不同的仍在假设的机制，包括炎症、细胞衰老、细胞凋亡、线粒体功能障碍等，导致衰老表型的发展。事实上，虽然有证据表明DNA突变在果蝇和哺乳动物的各种器官和组织中积累，但从未确定可检测到的DNA损伤积累是否会发生在人类身上，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个年龄范围广泛的健康个体中收集的单个单核细胞的基因组损伤积累，并将它们与衰老的主要表型和在同一个体中进行的DNA修复的全球测量（COMET测定）相关联。这项研究将在正在进行的完形研究中实施，完形研究是NIA临床研究单位进行的一项纵向研究，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.