Mitochondrial DNA Mutations in Skeletal Muscles in Aging

描述(申请人提供)：本资助是先前申请1 R03 AG024640-01的修订版。这项资助申请的总体目标是研究线粒体在衰老中的作用，特别是测试小鼠骨骼肌中线粒体衰老的理论。根据这一理论，体细胞线粒体DNA(MtDNA)突变会导致电子传递缺陷，增加破坏性活性氧(ROS)的产生，进而产生更多的mtDNA突变。这种恶性循环可能会导致线粒体功能受损，包括能量产生减少。随之而来的组织退化将导致各种衰老表型。有间接证据支持这一理论，据报道，一些特定的mtDNA突变在衰老过程中在各种组织中积累。然而，关于线粒体DNA突变(包括低丰度突变在内的各种突变在同一细胞中共存)在衰老过程中的累积，目前还没有全面的研究。也许更重要的是，与衰老相关的mtDNA突变的生理后果在很大程度上尚不清楚。我们最近开发了一种新的方法来将mtDNA从小鼠骨骼肌转移到体外细胞培养系统中，并改进了分离和鉴定mtDNA突变的方法。结合已建立的技术，我们将通过评估年轻、中年和老年小鼠肌肉中的单个mtDNA，研究骨骼肌在衰老过程中整体mtDNA突变的积累，并进一步分离和鉴定与年龄相关的mtDNA突变。这项研究的成功将有助于我们深入了解衰老的分子机制以及与衰老相关的人类退行性疾病。

DESCRIPTION (provided by applicant): This grant is a revised version of previous application 1 R03 AG024640-01. The overall goal of this grant application is to examine the role of mitochondria in aging, and, in particular, to test the mitochondrial theory of aging in mouse skeletal muscles. According to this theory, somatic mitochondrial DNA (mtDNA) mutations cause defective electron transfer, increasing the generation of damaging reactive oxygen species (ROS), that, in turn, produce further mtDNA mutations. This vicious cycle presumably results in compromised mitochondrial function including decreased energy production. The ensuing tissue degeneration will lead to various aging phenotypes. There are circumstantial evidences to support this theory, and some specific mtDNA mutations have been reported to accumulate in various tissues during aging. However, there is still no comprehensive study on the overall mtDNA mutation (all kinds of mutations co-exist in the same cell including those with low abundance) accumulation during aging. Perhaps more importantly, the physiological consequences of the aging related mtDNA mutations are largely unclear. We recently developed a novel approach to transfer mtDNA from mouse skeletal muscle to an in vitro cell culture system, and improved methods to isolate and identify mtDNA mutations. Combined with the established technologies, we will investigate the accumulation of overall mtDNA mutations in skeletal muscle during aging by evaluating individual mtDNA from the muscle in young, middle-age and old mice, and further isolate and identify age-associated mtDNA mutations. The success of study will help us to gain insights of molecular mechanism of aging and aging-related human degenerative diseases.