Nuclear-mitochondrial fitness interactions in Drosophila

描述（由申请人提供）：线粒体的正常功能需要数百个核基因和37个线粒体编码基因的协调表达。超过100种人类疾病可以追溯到线粒体DNA或对线粒体功能重要的核编码基因的突变。然而，患有相同mtDNA突变的患者的不同表型归因于与相同mtDNA分子相关的其他多态性，或归因于可变的核遗传背景。人们对核- mtdna联合变异的功能后果知之甚少，也没有模型可以对这些相互作用进行系统分析。这些实验表明，mtDNA变异对果蝇的适应性和线粒体酶活性具有可测量的影响。这些mtDNA的影响取决于所分析动物的核遗传背景，并且有证据表明雄性比雌性的影响更大。本研究的目的是建立一个果蝇模型来解剖核线粒体功能的定量遗传学。提出了一种简单但新颖的数量性状位点（QTL）定位的扩展，其中表型在携带不同mtdna的两种细胞质环境中被定位。黑腹d.m anogaster菌株的特征是携带来自拟马鳖的mtDNA，与黑腹d.m anogaster的mtDNA有超过600个碱基对的变化。这些mtDNA渗入导致明显的表型效应，为核基因相互作用的有效定位提供了强大的线粒体“等位基因”。有四个具体目的：1)将d.s simulans和d.m anogaster的mtdna渗入到不同的d.m anogaster核背景上，并确定这些渗入对健康、耗氧量、运动活性和线粒体酶活性的影响。2)利用在俄勒冈R和D. simulans两种线粒体背景上分别携带的重组黑腹龙自交系（RI），绘制这些性状的mito-nuclear QTL。3)在分级的mtDNA背景下，对已知OXPHOS突变体配对的野生染色体进行定量互补实验。4)确定一系列mtdna与编码线粒体蛋白的核基因纯合活突变的相互作用。这些研究将确定核和线粒体联合变异对一般人群中个体健康的影响，并检验mtDNA缺陷在男性中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.