Mechanisms of mutant mitochondrial genome modulation

项目总结/摘要 自从20亿年前与真核宿主形成共生关系以来，线粒体 成为蜂窝网络的组成部分。由于对线粒体兴趣的复苏， 是对这些细胞器的各种细胞和生理功能的更高认识， 在能源生产中的作用。然而，尽管对线粒体基因组的研究重新引起了人们的兴趣， （mtDNA）已经落后了。多种因素可能导致对mtDNA的低估，包括其 小的尺寸和小的遗传内容，在后生动物中进行遗传操作的困难，以及它的“混乱” 遗传学，这与简单而优雅的孟德尔遗传学的核基因组形成鲜明对比。 因此，与mtDNA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，把线粒体DNA看作是线粒体祖先过去的简单而无关紧要的遗迹。毁灭性 由mtDNA突变引起的疾病是其功能相关性的重要提示。总体 我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 大致上线粒体DNA的复制并不局限于细胞周期，而是可以在细胞的整个生命周期中持续发生。 细胞。因此，新的突变可能频繁出现，导致异质性状态，其中 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，含有数百个 到数千个拷贝，突变被评分为突变的mtDNA拷贝的百分比（即， 异质性水平）。即使是高度有害的mtDNA突变在低异质性水平下也是良性的。然而，在这方面， 当它们的水平上升超过临界阈值时，它们就成为致病性的，并且没有足够的拷贝。 正常的线粒体DNA来支持细胞功能。影响异质性的细胞和分子机制 水平知之甚少。因此，很难预测谁会遗传或发展mtDNA相关的遗传病。 疾病我的实验室的第一个主要目标是确定细胞和分子机制， 异质性动力学我们已经适应了C。elegans作为研究这些机制的模型系统的选择。 C. elegans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mtDNA突变体的异质性水平超过临界阈值的能力是突变的- 特定.然而，这种特异性的机制基础还不清楚。因此，第二 我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 程度.总的来说，我们的研究计划解决了长期存在的，但在该领域的基本问题， 线粒体遗传学在这个过程中，我们还将深入了解mtDNA生物学的更广泛的方面，如 它的复制和细胞如何计数mtDNA拷贝。

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.