Mutational and evolutionary impact of mitochondrial dysfunction

描述（由申请人提供）： 拟议研究项目的主要目标是提供有关线粒体功能障碍导致的活性氧（ROS）突变和进化后果的知识。ROS是多种人类疾病和衰老过程中的核心参与者，但也在对抗寄生虫的先天免疫中发挥重要的保护作用。主要目的将使用模式线虫秀丽隐杆线虫及其姊妹种C.布里格塞第一个具体目标是确定ROS对全基因组种系突变过程的影响。这一目标将通过首先从C.与野生型相比，秀丽隐杆线虫遗传突变体经历更高或更低水平的活性氧，以及来自C. Briggsae菌株由于天然存在的线粒体基因组缺失的变异而经历不同水平的ROS。将使用Solexa高通量DNA测序技术全面分析所得MA系的核基因组的突变。这一目标的实现将证实或否认广泛持有的，但未经证实的假设，即线粒体起源的ROS导致核基因组突变率升高。第二个具体目标是表征ROS作为年龄的函数的体细胞突变效应。我们将利用一个简单而有效的体细胞突变报告转基因系统来研究同一个C. elegans遗传背景用于第一个目的。第二个目标的实现将提供必要的知识的作用，活性氧在体细胞突变的积累，和新的见解生殖细胞和体细胞突变过程耦合的程度。第三个具体的目标是确定自然发生的线粒体基因组缺失的进化原因，在C。布里格塞这一目标将通过测试两个相反的假设来实现：第一个非适应性假设，即由于与小种群进化相关的弱自然选择，缺失被动进化，第二个适应性假设，即缺失产生的ROS在保护线虫免受细胞内寄生虫感染中发挥功能性作用。第一个假设将使用实验室比较人口规模的研究，包括C。第二种假设将使用涉及杀线虫属1的感染和竞争测定来检验，杀线虫属1是一种新发现的感染C.自然界中的布里格塞缺失水平和感染状态之间的相关性也将在C中进行测试。Briggsae天然分离物。这三个目标的实现将提供前所未有的知识，ROS对核基因组突变过程的影响，并了解一个新的范例之间的相互作用，对ROS的高度负面影响的选择，和积极的选择ROS诱导的抗寄生虫的潜力。 公共卫生相关性： 突变是所有人类遗传变异的最终来源，几乎所有遗传性遗传疾病和癌症。特别是，线粒体基因组突变和活性氧水平的相关升高与衰老、阿尔茨海默病、帕金森病和许多线粒体肌病有关。了解突变的基本特性对于了解其在各种遗传疾病，癌症和衰老过程中的作用至关重要。

DESCRIPTION (provided by applicant): The main objective of the proposed research project is to provide knowledge on the mutational and evolutionary consequences of reactive oxygen species (ROS) that result from mitochondrial dysfunction. ROS are central players in a variety of human disorders and the aging process, but also play important protective roles in innate immunity against parasites. The main objective will be achieved using the model nematode Caenorhabditis elegans and its sister species C. briggsae. The first specific aim is to determine the impact of ROS on genome-wide germline mutation processes. This aim will be accomplished by first creating mutation-accumulation (MA) lines from C. elegans genetic mutants that experience higher or lower levels of ROS as compared to wild-type, and from C. briggsae strains that experience varying levels of ROS due variation in naturally-occurring mitochondrial genome deletions. The nuclear genomes of the resultant MA lines will be comprehensively analyzed for mutation using Solexa high-throughput DNA sequencing technology. The achievement of this aim will confirm or deny the widely held, but unproven hypothesis that ROS of mitochondrial origin cause elevated mutation rates in the nuclear genome. The second specific aim is to characterize the somatic mutation effects of ROS as a function of age. A simple yet powerful somatic mutation reporter transgene system will be employed to examine the mosaic somatic mutation process in the same C. elegans genetic backgrounds used for the first aim. Achievement of the second aim will provide essential knowledge on the role of ROS in somatic mutation accumulation, and novel insights into the extent to which germline and somatic mutation processes are coupled. The third specific aim is to identify the evolutionary causes of naturally- occurring mitochondrial genome deletions in C. briggsae. This aim will be accomplished by testing two opposing hypotheses: a first non-adaptive hypothesis that the deletions passively evolved due to weak natural selection associated with evolution in small populations, and a second adaptive hypothesis that ROS resulting from the deletions play a functional role in protecting nematodes against intracellular parasite infections. The first hypothesis will be tested using laboratory comparative population size studies involving C. briggsae of varying mitochondrial genome deletion levels; the second hypothesis will be tested using infection and competition assays involving Nematocida sp. 1, a newly discovered microsporidia parasite that infects C. briggsae in nature. Correlations between deletion levels and infection status will also be tested for in C. briggsae natural isolates. Achievement of the three aims will provide unprecedented knowledge on the effects of ROS on nuclear genome mutation processes, and the potential of a new paradigm for understanding the interplay between selection against the highly negative effects of ROS, and positive selection for ROS-induced resistance to parasites. PUBLIC HEALTH RELEVANCE: Mutations are the ultimate source of all human genetic variation, and virtually all heritable genetic diseases and cancers. In particular, mitochondrial genome mutations and associated elevations in reactive oxygen species levels are implicated in aging, Alzheimer's disease, Parkinson's disease and numerous mitochondrial myopathies. Understanding the fundamental properties of mutation is of central importance to understanding its role in diverse genetic disorders, cancers and the aging process.