The genetic basis for tissue specific sensitivities to mitochondrial stress

描述(由申请人提供)：本提案的目标是了解破坏一般线粒体功能的突变和抑制物如何导致具有明显组织特异性的综合征。这个团队正在开发新的实验模型，在这些模型中，他们可以利用果蝇强大的遗传工具来解决这个问题。其目的是测试遗传和化学应激源的组织特异性是否因为它们针对一般线粒体功能和组织特异性基因之间的相互作用而发生。果蝇细胞色素氧化酶亚基1的一个特定突变体是雄性不育的，其他情况下是正常的。据推测，这种高度特异的表型是该等位基因未能与另一种呼吸链蛋白的睾丸特异性亚型一起工作的结果。的确，细胞色素c的体细胞异位表达抑制了不育症的表型。拟议中的实验将严格测试这种不育是否由于突变的细胞色素氧化酶和睾丸特定的细胞色素c亚型的伙伴关系中的特定缺陷。此外，苍蝇眼将被设计为一个生物传感器，用于破坏线粒体功能的异构体特异性相互作用，并将用于识别干扰这些相互作用的突变和化学物质。还将检查两种缺陷协同作用所产生的组织特异性，其中组织特异性改变使组织对不同的遗传和化学应激源敏感。眼部特异的E2F基因敲除会影响生长，导致眼睛轻微缩小。它还使眼睛对线粒体压力敏感。一种低剂量的寡霉素，在其他组织中没有明显的效果，在眼睛中与E2F：RNAi协同作用，产生组织转化(例如，触角长出眼睛)和肥大。有人假设，这种发育不全/肥大依赖于两个具有生物学普遍关系的输入。任何抑制特定组织生长的突变都会创造一种选择性的环境，有利于细胞通过转化为另一种细胞类型来逃避生长限制(转定)。第二个破坏发展命运稳定的强调将为这一选择提供素材。线粒体压力似乎提供了这种不稳定的输入。将对该模型进行测试和筛选，以确定自然突变和有助于协同投入的环境化学物质。由于哺乳动物以组织特异性异构体的形式表达大量蛋白质，它们携带许多基因，这些基因可以突变来产生转译决定的选择。如果没有协同作用的投入，这些突变将几乎没有影响，可能会累积。因此，人们怀疑人类群体有一个巨大而隐蔽的“多态”池，这种多态造成了各种化学敏感性。对致敏突变的识别应该能够使DNA测序应用于个性化的医疗保健。 与公共健康相关：项目叙事化学物质或突变阻止线粒体发挥其作为细胞能量主要提供者的作用会导致死亡，而轻微的线粒体应激会对人类健康造成令人惊讶的复杂破坏。我们已经开发了强大的实验模型，在该模型中，我们将研究健康缺陷的复杂性的基础，并可以探索线粒体功能的化学扰动对人类健康的影响比人们普遍认为的更普遍的可能性。

DESCRIPTION (provided by applicant): The goal of this proposal is to understand how mutations and inhibitors that disrupt general mitochondrial functions can cause syndromes with marked tissue specificity. This team is developing new experimental models in which they can exploit the powerful genetic tools in Drosophila to bear on this question. The intent is to test whether tissue specificity of genetic and chemical stressors occurs because they target interactions between general mitochondrial functions and tissue specific genes. A particular mutant of Drosophila Cytochrome oxidase subunit 1 is male sterile, and otherwise normal. It is hypothesized that this highly specific phenotype is the result of failure by this allele to work in conjunction with a testis specific isoform of one of the other respiratory chain proteins. Indeed, ectopic expression of the somatic version of Cytochrome c in testis suppresses the sterility phenotype. The proposed experiments will rigorously test whether this sterility is due to a specific deficit in the partnership of the mutant Cytochrome oxidase and the testis specific isoform of Cytochrome c. Additionally, the fly eye will be engineered as a biosensor for disruption of isoform-specific interactions of mitochondrial functions, and will be applied to identify mutations and chemicals interfering with these interactions. Tissue specificity resulting from synergy of two defects will also be examined, where a tissue specific alteration sensitizes the tissue to diverse genetic and chemical stressors. Eye specific knockdown of E2F compromised growth to produce a slightly reduced eye. It also sensitized the eye to mitochondrial stress. A low dose of oligomycin that is without notable effect in other tissues, synergizes with E2F:RNAi in the eye to produce tissue transformations (e.g. antennae growing out of the eye) and hypertrophy. It is hypothesized that this dysgenesis/hypertrophy relies on two inputs with a biologically universal relationship. Any mutation that inhibits growth of a specific tissue creates a selective environment favoring cells that can escape the growth limitation by transforming to another cell type (transdetermination). A second stress that destabilizes developmental fate would produce the fodder for this selection. Mitochondrial stress appears to provide this destabilizing input. This model will be tested and screened for natural mutations and environmental chemicals contributing to the synergizing inputs. Since mammals express numerous proteins as tissue-specific isoforms, they carry many genes that can mutate to create a selection for transdetermination. Without synergizing input, these mutations would have little impact and could accumulate. Thus, it is suspected that the human population has a large and insidious pool of "polymorphisms" that creates a diversity of chemical sensitivities. Recognition of sensitizing mutations should empower application of DNA sequencing to personalized health-care. PUBLIC HEALTH RELEVANCE: Project Narrative Chemicals or mutations that prevent mitochondria from fulfilling their role as the primary providers of cellular energy cause death, whereas mild mitochondrial stress causes surprisingly complex disruptions in human health. We have developed powerful experimental model in which we will investigate the basis for the complexity of the health defects, and in which we can explore the possibility that chemical perturbation of mitochondrial function has more pervasive influence on human health than is generally recognized.