Mechanisms of mutant mitochondrial genome modulation

项目摘要/摘要 自从20亿年前与真核宿主形成共生关系以来，线粒体 成为蜂窝网络不可或缺的组成部分。多亏了人们对线粒体的兴趣重新燃起， 是对这些细胞器广泛的细胞和生理功能的更大的欣赏 它们在能源生产中的作用。然而，尽管重新引起了人们的兴趣，但对线粒体基因组的研究 (MtDNA)已经落后。对线粒体DNA的认识不足可能是多种因素造成的，包括它的 体型小，基因含量少，在后生动物中对其进行遗传操作的难度，以及它的“混乱” 遗传学，这与简单而优雅的孟德尔核基因组遗传学形成了鲜明对比。 因此，与线粒体DNA生物学有关的基本问题仍然没有得到解决。这是个错误， 然而，将线粒体DNA视为线粒体祖先过去的简单和无关紧要的痕迹。毁灭性的 线粒体DNA突变引起的疾病是对其功能相关性的重要提醒。最重要的是 我的实验室未来五年的研究目标是研究线粒体DNA遗传学，以及更多的线粒体DNA生物学 大体上说。线粒体DNA的复制不仅限于细胞周期，而且可以在人的整个生命周期中连续发生 这些细胞。因此，新的突变可能频繁出现，导致异质性状态，在这种状态下 线粒体DNA的两个或多个序列变体共存。因为细胞是线粒体DNA的多倍体，包含数百个 对于数千个拷贝，突变按突变的mtDNA拷贝的百分比来评分(即 异质性水平)。即使高度有害的mtDNA突变在低异质性水平上也是良性的。然而， 当它们的水平超过临界阈值并且没有足够的拷贝时，它们就会变得致病 支持细胞功能的正常线粒体DNA。影响异质性的细胞和分子机制 人们对这一水平知之甚少。因此，很难预测谁将继承或发展线粒体DNA相关的基因。 疾病。我的实验室的第一个主要目标是识别细胞和分子机制 异质性动力学。我们采用线虫作为研究这些机制的模型系统。 线虫使我们能够以前所未有的方式跟踪个体和世代之间的异质性水平 可行性。线粒体DNA突变体的异质性水平超过临界阈值的能力是突变的。 具体的。然而，这种特异性的机制基础还没有被很好地理解。因此，第二个 我的实验室的主要目标是利用一组不同的突变来解释它们异质性的差异 级别。综上所述，我们的研究计划解决了长期存在的但根本性的问题 线粒体遗传学。在这个过程中，我们还将深入了解mtdna生物学的更广泛方面，例如 它的复制和细胞如何计算线粒体DNA拷贝数。

PROJECT SUMMARY/ABSTRACT Ever since forming a symbiotic relationship with the eukaryotic host 2 billion years ago, mitochondria have become integral components of the cellular network. Thanks to the resurgence of interest in mitochondria, there is a greater appreciation for the wide variety of cellular and physiological functions for these organelles beyond their role in energy generation. Despite this renewed interest, however, research into the mitochondrial genome (mtDNA) has lagged. Multiple factors likely contribute to this underappreciation for mtDNA, including its diminutive size and small genetic content, the difficulty of genetically manipulating it in metazoans, and its ‘messy’ genetics, which stands in stark contrast to the simple and elegant mendelian genetics of the nuclear genome. Consequently, fundamental questions pertaining to mtDNA biology remain unaddressed. It is a mistake, however, to view mtDNA as simple and inconsequential vestiges of mitochondria’s ancestral past. Devastating diseases caused by mtDNA mutations serve as important reminders of its functional relevance. The overarching goal of research in my lab over the coming five years is to study mtDNA genetics, and mtDNA biology more broadly. Replication of mtDNA is not confined to the cell cycle and can occur continuously throughout the life of the cells. Consequently, new mutations can arise frequently, contributing to a state of heteroplasmy, in which two or more sequence variants of mtDNA coexist. Because cells are polyploid for mtDNA, containing hundreds to thousands of copies, mutations are scored as the percentage of mtDNA copies that are mutant (i.e. heteroplasmy levels). Even highly deleterious mtDNA mutations are benign at low heteroplasmy levels. However, they become pathogenic when their levels rise beyond a critical threshold and there are insufficient copies of the normal mtDNA to support cellular function. The cellular and molecular mechanisms that impact heteroplasmy levels are poorly understood. Consequently, it is difficult to predict who will inherit or develop mtDNA-associated diseases. The first major goal of my lab is to identify the cellular and molecular mechanisms that modulate heteroplasmy dynamics. We have adapted C. elegans as a model system of choice to study these mechanisms. C. elegans allows us to track heteroplasmy levels across individuals and generations with unprecedented feasibility. The ability of mtDNA mutants to rise in heteroplasmy levels beyond the critical threshold are mutant- specific. However, the mechanistic basis for this specificity is not well understood. Consequently, the second major goal of my lab is to utilize a diverse panel of mutations to explain the differences in their heteroplasmy levels. Taken together, our research program tackles long-standing but fundamental questions in the field of mitochondrial genetics. In the process, we will also gain insights into broader aspects of mtDNA biology such as its replication and how cells count mtDNA copies.