Nuclear-mitochondrial fitness interactions in Drosophila

描述（由申请人提供）：已知超过100种遗传疾病影响线粒体活性，使其成为最常见的人类病理之一。线粒体功能需要约1500个核编码基因和37个mtdna编码基因的协调表达。这种基因组组织有两个重要的含义：1)线粒体功能是一个大的突变目标，2)核-线粒体相互作用是正常生理表现的核心。这项研究计划的长期目标是使用果蝇作为模型来解剖影响有机体适应性的核-线粒体相互作用的遗传基础。这项研究的初始阶段已经发现了一个惊人的上位相互作用，其中一个特定的mtDNA在一个核背景（俄勒冈R）产生一套高度妥协的表型。当将相同的mtDNA放置在另一组野生染色体上时，这些表型恢复到接近野生型的水平。受影响的特征是代谢性疾病的标志：发育迟缓，生殖力下降，运动，COX活性和刚毛缺陷。目前的建议旨在确定负责这种核线粒体相互作用的位点或位点，并剖析这些基因的功能。有三个具体目标：1)利用分离、减数分裂和缺陷作图，对改变mtDNA性能的核因子进行遗传定位。我们将检验所有受影响的表型都是由于单个基因座而不是每个性状的独立基因座的假设；2)利用SNP-array定位F2后代核位点的分子特征，分析现有和新等位基因，确定导致特定表型的核苷酸变化；3)鉴定基因的组织特异性表达。我们将记录新发现基因的组织特异性表达，以及它们对线粒体基因表达的影响。我们将操纵组织特异性表达来测试这种核-线粒体相互作用对表型的影响在不同组织中是不同的假设。这些目标将确定在第一阶段研究中发现的强有丝分裂-核上位相互作用的遗传基础，并开展线粒体酶复合物在核和mtDNA编码蛋白的特定遗传操作下如何起作用的新机制研究。这些实验将提供细胞核和线粒体基因的特定突变如何相互作用以决定机体性能的基本信息。由于这些相互作用在进化上是古老且高度保守的，因此对果蝇遗传途径的解剖将与理解人类这类非常常见的疾病非常相关。

DESCRIPTION (provided by applicant): Over 100 genetic diseases are known to affect mitochondrial activity making this one of the most common classes of human pathologies. Mitochondrial function requires the coordinated expression of ~1500 nuclear-encoded genes and 37 mtDNA-encoded genes. This genomic organization has two important implications: 1) mitochondrial function is a large mutational target, and 2) nuclear-mitochondrial interactions are central to normal physiological performance. The long-term goal of this research program is to use Drosophila as a model to dissect the genetic bases of nuclear-mitochondrial interactions that affect organismal fitness. The initial phase of this research has uncovered a striking epistatic interaction where a particular mtDNA in one nuclear background (Oregon R) produces a suite of highly compromised phenotypes. When this same mtDNA is placed on an alternative set of wild chromosomes, these phenotypes are restored to near-wild type levels. The traits affected are hallmarks of metabolic disease: delayed development, reduced fecundity, locomotion, COX activity, and bristle defects. The current proposal seeks to identify the locus or loci responsible for this nuclear-mitochondrial interaction, and dissect the function of these genes. There are three specific aims: 1) Genetically map nuclear factors that modify mtDNA performance using segregation, meiotic and deficiency mapping. We will test the hypothesis that all affected phenotypes are due to a single locus, vs. independent loci for each trait; 2) Molecular characterization of the mapped nuclear loci using SNP-array mapping among F2 offspring, and analyses of existing and novel alleles to identify the nucleotide changes causing specific phenotypes and, 3) Tissue specific expression of the identified genes. We will document the tissue specific expression of the newly identified genes, and their impact on mitochondrial gene expression. We will manipulate tissue specific expression to test the hypothesis that this nuclear-mitochondrial interaction effect on phenotype is distinct in different tissues. These Aims will identify the genetic bases of strong mito-nuclear epistatic interactions uncovered in the first phase of the research, and undertake new mechanistic studies of how the mitochondrial enzyme complexes function under specific genetic manipulations of nuclear and mtDNA encoded proteins. These experiments will provide fundamental information on how specific mutations in nuclear and mitochondrial genes interact to determine organismal performance. As these interactions are evolutionarily ancient and highly conserved, the dissection of genetic pathways in Drosophila will be very relevant to understanding this very common class of diseases in humans.