Nuclear-mitochondrial fitness interactions in Drosophila

描述（由申请人提供）：转录子的正常功能需要数百个核基因和37个转录子编码基因的协调表达。超过100种人类疾病已被追溯到线粒体DNA或线粒体功能中重要的核编码基因的突变。然而，患有相同mtDNA突变的患者之间的可变表型归因于相同mtDNA分子上的其他多态性，或可变的核遗传背景。联合核mtDNA变异的功能后果知之甚少，没有模型存在这些相互作用的系统分析。PI表明，线粒体DNA变异对果蝇的适应性和线粒体酶活性有可测量的影响。这些mtDNA效应取决于所检测动物的核遗传背景，并显示出雄性比雌性更强的效应。本研究的目的是建立一个果蝇模型，以剖析核-线粒体功能的数量遗传学。提出了一种简单但新颖的数量性状基因座（QTL）定位的扩展，其中表型定位在两个细胞质环境中携带不同的mtDNA。菌株D. melanogaster的特征是携带来自D. simulans与D.黑腹果蝇mtDNA这些线粒体基因渗入导致明确的表型效应，为核基因相互作用的有效作图提供了强大的线粒体“等位基因”。有四个具体目标：1）内向D。simulans和D.将黑腹果蝇mtDNA分别克隆到不同的D.黑腹果蝇核背景，并确定这些基因渗入对健身，耗氧量，运动活性和线粒体酶活性的影响。2)利用重组自交系对这些性状进行了QTL定位。黑腹果蝇携带两种线粒体背景：俄勒冈州R和D。simulans。3)在一系列分级的mtDNA背景中，对与已知OXPHOS突变体配对的野生型染色体进行定量互补分析。4)确定一系列mtDNA与编码线粒体蛋白的核基因中纯合可行突变的相互作用。这些研究将确定联合核和线粒体变异对一般人群中个体健康的影响，并检验男性线粒体DNA缺陷比女性更严重的假设。

DESCRIPTION (provided by applicant): The proper function of the mitochondrion requires the coordinated expression of hundreds of nuclear genes and 37 mitochondrial-encoded genes. Over 100 human diseases have been traced to mutations in mitochondrial DNA or in nuclear-encoded genes important in mitochondrial function. However, variable phenotypes among patients suffering from the same mtDNA mutations have been attributed to other polymorphisms linked on the same mtDNA molecule, or to variable nuclear genetic background. The functional consequences of joint nuclear-mtDNA variation are poorly understood, and no models exist for the systematic analysis of these interactions. The PIs have shown that mtDNA variation has measurable effects on fitness and mitochondrial enzyme activity in Drosophila. These mtDNA effects depend on the nuclear genetic background of the animals assayed, and show evidence for stronger effects in males than females. The goal of this research is to develop a Drosophila model to dissect the quantitative genetics of nuclear-mitochondrial function. A simple but novel extension of quantitative trait locus (QTL) mapping is proposed where phenotypes are mapped in two cytoplasmic environments carrying divergent mtDNAs. Strains of D. melanogaster are characterized that carry mtDNA from D. simulans with over 600 base pair changes from D. melanogaster mtDNA. These mtDNA introgressions result in clear phenotypic effects, providing a strong mitochondrial "allele" for efficient mapping of nuclear gene interactions. There are four specific aims: 1) Introgress D. simulans and D. melanogaster mtDNAs onto different D. melanogaster nuclear backgrounds and determine the effects of these introgressions on fitness, oxygen consumption, locomotor activity and mitochondrial enzyme activity. 2) Map mito-nuclear QTL for these traits using recombinant inbred (RI) lines of D. melanogaster carried on each of two mitochondrial backgrounds: Oregon R and D. simulans. 3) Conduct a quantitative complementation assay of wild chromosomes paired with known OXPHOS mutants in a graded series of mtDNA backgrounds. 4) Determine the interaction of a range of mtDNAs with homozygous viable mutations in nuclear genes encoding mitochondrial proteins. These studies will determine the impact of joint nuclear and mitochondrial variation on the health of individuals in general populations and test the hypothesis that mtDNA defects are more severe in males than females.