Mechanisms of mitochondrial mutation rate variation across eukaryotes

真核生物线粒体突变率变异的机制

基本信息

批准号：
10549690
负责人：
Daniel Benjamin Sloan
金额：
$ 38.36万
依托单位：
COLORADO STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-06-01 至 2028-05-31
项目状态：
未结题

项目摘要

PROJECT SUMMARY High mutation rates in mitochondrial DNA (mtDNA) are a major cause of inherited and age-related diseases. There is a longstanding view that the mutation-prone nature of mitochondrial genomes in humans and animal models is a byproduct of the intense metabolic activity associated with oxidative phosphorylation and energy conversion. However, recent evidence has challenged this idea, and there is growing recognition that differences in the enzymatic machinery responsible for mtDNA replication and repair are a key cause of high mutation rates in human mtDNA. Variation in mtDNA replication and repair pathways may also explain why some eukaryotic lineages (e.g., plants) are able to suppress mutation rates in their mitochondrial genomes to exceptionally low levels. An overarching theme of our research program is to identify the mechanisms responsible for variation in mitochondrial mutation rates across eukaryotes and thereby help resolve the long- term uncertainties about why rates are so high in humans. To overcome the technical challenges associated with investigating rare events like de novo mutations, we have applied multiple innovative sequencing technologies that can detect new DNA sequence variants present at ultra-low frequencies, essentially capturing mutations and damaged bases as they occur and mapping them to nucleotide-level resolution. Our future work will address two major questions. First, how do plant mitochondria achieve some of the lowest rates of point mutations ever observed (less than one substitution per site per billion years)? This line of investigation will build off our recent discovery that plant-MSH1 is necessary for maintaining low mutation rates in plant organelle genomes. MSH1 is enigmatic member of the MutS gene family which was likely acquired by horizontal transfer from giant viruses. We will test the hypothesis that it is part of a novel mechanism of mismatch repair that induces double-stranded breaks followed by template-based recombinational repair. Second, how do mitochondria repair bulky DNA damage introduced by UV? We will test the hypothesis that mitochondria contain a previously unrecognized repair pathway with similarities to classic nucleotide excision repair (NER). This hypothesis is motivated by our recent observation that exposure of divergent eukaryotic model systems to UV light results in the release of mtDNA-derived oligonucleotides that carry damaged bases at consistent positions and exhibit characteristic length profiles, a hallmark of NER. Overall, this research program will help determine why mitochondrial genomes exhibit such extreme mutation rate variation across the eukaryotic tree of life.

项目摘要线粒体DNA（mtDNA）的高突变率是遗传性疾病和年龄相关的主要原因。长期以来的观点是，人类和动物中线粒体基因组的突变性质模型是与氧化磷酸化和能量相关的强烈代谢活性的副产品转换。但是，最近的证据挑战了这一想法，并且越来越认识到负责mtDNA复制和修复的酶机制的差异是高度的关键原因人mtDNA的突变率。 mtDNA复制和修复途径的变化也可以解释为什么一些真核生物谱系（例如植物）能够抑制其线粒体基因组中的突变率极低的水平。我们研究计划的总体主题是确定机制负责真核生物之间线粒体突变率的变化，从而有助于解决长期关于为什么人类的费率如此之高的术语不确定性。克服相关的技术挑战通过调查诸如从头突变之类的罕见事件，我们应用了多个创新测序可以检测到具有超低频率的新的DNA序列变体的技术，本质上是捕获突变并在发生时损坏的碱基，并将其映射到核苷酸级分辨率。我们的未来的工作将解决两个主要问题。首先，植物线粒体如何达到最低的一些观察到的点突变发生率（每十亿年的替代少于一个替代）？这条线调查将建立我们最近发现的，即植物-MSH1对于保持低突变率是必要的在植物细胞器基因组中。 MSH1是Muts基因家族的神秘成员，很可能是由从巨型病毒中的水平转移。我们将检验以下假设：它是一种新型机制的一部分不匹配的修复会导致双链断裂，然后是基于模板的重组维修。其次，线粒体修复紫外线引入的大量DNA损伤如何？我们将检验以下假设线粒体包含先前未识别的修复途径，与经典核苷酸切除相似维修（NER）。我们最近的观察结果激发了这一假设紫外线的模型系统会导致释放mtDNA衍生的寡核苷酸，这些寡核苷酸载有受损的碱基在一致的位置和展示特征长度曲线上，NER的标志。总体而言，这项研究程序将有助于确定为什么线粒体基因组在整个范围内表现出如此极端的突变率变化真核的生命树。