Mechanisms of somatic mtDNA mutation detection and elimination

描述（由申请人提供）：线粒体DNA （mtDNA）突变导致许多严重的母体传播疾病，体细胞mtDNA突变的积累与衰老和老年人常见疾病有关。这些mtDNA突变通常与正常的mtDNA共存，这种情况被称为异质性。突变型与野生型mtDNA的比例在异质性疾病的发病机制中起着至关重要的作用，但影响这一比例的机制在很大程度上是未知的。我们工作的长期目标是确定控制异质体细胞组织中有害mtDNA突变频率的细胞机制。最近对帕金森病相关因子PINK1和Parkin的研究表明，这些因子是线粒体质量控制系统（MQCS）的组成部分，可以检测功能失调的线粒体，并与其他细胞因子合作，促进其自噬降解。我们假设MQCS通过检测携带突变DNA的功能失调线粒体并靶向降解它们来减少有害异质mtDNA突变的频率。为了验证这一假设，我们建议使用模式生物黑腹果蝇来追求三个目标。第一个目标是研究MQCS的遗传改变对mtDNA突变频率增加的果蝇菌株表型的影响。第二个目标将使用一种新的下一代测序方法检查MQCS遗传扰动对mtDNA突变频率的影响。最后，第三个目标将使用最近开发的线粒体周转体内试验来测试mtDNA突变是否促进线粒体周转，以及MQCS的遗传扰动是否影响mtDNA突变对周转的影响。我们的研究将有助于理解影响异质性的分子机制，这些知识最终可能导致mtDNA突变引起的疾病的治疗发展。

DESCRIPTION (provided by applicant): Mitochondrial DNA (mtDNA) mutations cause a number of severe maternally transmitted diseases, and the accumulation of somatic mtDNA mutations is implicated in aging and common diseases of the elderly. These mtDNA mutations often coexist with normal mtDNA, a condition known as heteroplasmy. The ratio of mutated to wild-type mtDNA plays a crucial role in the pathogenesis of heteroplasmic disorders, but the mechanisms that influence this ratio are largely unknown. The long-term objective of our work is to define the cellular mechanisms that govern the frequency of deleterious mtDNA mutations in heteroplasmic somatic tissues. Recent work on the Parkinson's disease-related factors PINK1 and Parkin has revealed that these factors are components of a mitochondrial quality control system (MQCS) that can detect dysfunctional mitochondria, and, in collaboration with other cellular factors, promote their autophagic degradation. We hypothesize that the MQCS acts to reduce the frequency of deleterious heteroplasmic mtDNA mutations by detecting dysfunctional mitochondria that bear mutant DNA and targeting them for degradation. To test this hypothesis, we propose to use the model organism Drosophila melanogaster to pursue three aims. The first aim will examine the influence of genetic alterations of the MQCS on the phenotypes of a Drosophila strain with an increased mtDNA mutation frequency. The second aim will examine the influence of genetic perturbations of the MQCS on the mtDNA mutation frequency using a novel next-generation sequencing method. Finally, the third aim will use a recently developed in vivo assay of mitochondrial turnover to test whether mtDNA mutations promote mitochondrial turnover, and whether genetic perturbations of the MQCS influence the effects of mtDNA mutations on turnover. Our studies will contribute to an understanding of the molecular mechanisms that influence heteroplasmy, and this knowledge could ultimately lead to the development of treatments for diseases caused by mtDNA mutations.