Mechanisms of Environmental and Nuclear and Mitochondrial Mutagenesis

描述（由申请人提供）：线粒体是功能多样的细胞器，在许多细胞过程（包括氧化磷酸化和细胞凋亡）中发挥核心作用。衰老的线粒体理论假设，线粒体DNA（mtDNA）突变在多个组织中的终身积累导致线粒体衰竭、下游过程如细胞凋亡和组织功能的进行性衰退（即，衰老和疾病）。此外，线粒体DNA突变被怀疑有助于许多与年龄相关的疾病的病因学，包括帕金森病，肌肉萎缩和癌症的转移潜力。由于真核细胞含有数百个mtDNA拷贝，因此在组织功能障碍和临床症状变得明显之前，必须存在最小临界数量的突变mtDNA。然而，我们并不完全了解这些致病性突变群体的扩增和固定的机制。有证据表明，这些突变在正常细胞和组织中以极低的频率作为随机突变预先存在。我们的工作假设是，随机mtDNA突变的诱导和积累助长了致病突变群体、衰老和与年龄相关的疾病。因此，特别是环境诱变剂可能通过破坏线粒体DNA和增加线粒体突变积累的速率，在衰老和疾病的起源和发病率中发挥重要作用。本提案的目的是确定与DNA损伤剂和疾病相关的体细胞mtDNA诱变的分子机制，其指导目标如下：（1）检验人类随机mtDNA突变频率随年龄增长而增加的假设，（2）确定环境毒素是否会增加线粒体突变积累的速度，（3）评估随机mtDNA突变是否先于并驱动人类细胞中的致病突变群体，以及（4）减少人类细胞中的mtDNA突变。我们的具体目标是可行的，因为我们在敏感地测量线粒体突变的能力方面取得了巨大的进步，而且考虑到线粒体在衰老和癌症中的关键作用，这一点很重要。对加速mtDNA突变的环境因素的机械理解有助于识别预防和/或减缓年龄相关性衰弱和疾病的风险因素和方法。 最终，实现我们提出的目标将有助于揭示线粒体诱变在人类衰老中的作用，并可能有助于改善与年龄相关的疾病，延长健康和活跃的生命年数。 公共卫生相关性：线粒体突变被怀疑与许多年龄相关疾病的病因有关，包括帕金森病、肌肉萎缩和癌症的转移潜力。然而，我们并不完全了解线粒体突变产生的机制。最终，实现我们提出的目标，阐明线粒体突变，将有助于改善与年龄相关的疾病，并延长健康的活跃寿命。

DESCRIPTION (provided by applicant): Mitochondria are functionally diverse organelles with a central role in many cellular processes, including oxidative phosphorylation and apoptosis. The mitochondrial theory of aging postulates that the lifelong accumulation of mitochondrial DNA (mtDNA) mutations in multiple tissues leads to mitochondrial failure, downstream processes such as apoptosis, and the progressive decline of tissue function (i.e., aging and disease). Moreover, mtDNA mutations are suspected to contribute to the etiology of a number of age-related disorders, including Parkinson's disease, muscle-wasting, and the metastatic potential of cancers. As eukaryotic cells contain many hundreds copies of mtDNA, it stands to reason that a minimum critical number of mutant mtDNAs must be present before tissue dysfunction and clinical signs become apparent. Yet, we do not fully understand the mechanisms underlying the amplification and fixation of these pathogenic mutant populations. There is evidence that these mutations pre-exist at extremely low frequency as random mutations in normal cells and tissues. Our working hypothesis is that the induction and accumulation of random mtDNA mutations fuels pathogenic mutant populations, aging, and age-related disease. Thus, environmental mutagens in particular may play a substantial role in the origin and incidence of aging and disease by damaging mtDNA and increasing the rate at which mitochondrial mutations accumulate. The goal of this proposal is to determine the molecular mechanisms of somatic mtDNA mutagenesis associated with DNA damaging agents and disease, under the direction of the following Aims: (1) test the hypothesis that the frequency of random mtDNA mutations increases with age in humans, (2) determine whether an environmental toxin can increase the rate at which mitochondrial mutations accumulate, (3) evaluate whether random mtDNA mutations precede and drive pathogenic mutant populations in human cells, and (4) reduce mtDNA mutations in human cells. Our Specific Aims are feasible, because of our dramatic advance in our ability to sensitively measure mitochondrial mutations, and important, given the critical role of mitochondria in aging and cancer. A mechanistic understanding of the environmental factors that accelerate mtDNA mutation should aid in the identification of risk factors and methods that prevent and/or slow age-related debilitation and disease. Ultimately, fulfillment of our proposed aims will help unravel the role of mitochondrial mutagenesis in human aging and potentially aid in the amelioration of age-related disease, extending the number of healthy and active years of life. PUBLIC HEALTH RELEVANCE: Mitochondrial mutations are suspected to contribute to the etiology of a number of age-related disorders, including Parkinson's disease, muscle-wasting, and the metastatic potential of cancers. Yet, we do not fully understand the mechanisms underlying the generation of mitochondrial mutations. Ultimately, fulfillment of our proposed aims, to elucidate mitochondrial mutagenesis, will aid in the amelioration of age-related disease, and extend the number of healthy active years of life.