Genetics Modifiers and Longevity of MnSOD Mutant Mice

描述(申请人提供)：这项建议是基于氧自由基参与线粒体衰老，进而导致整个生物体衰老的前提。线粒体中产生的超氧阴离子自由基可导致大分子损伤，导致线粒体缺陷。这个过程最终会导致生物体的衰老和死亡。我们推测，保护线粒体免受自由基损伤的因子有可能维持能量产生和组织功能，最终延缓衰老的开始，延长生物体的寿命。MnSOD缺陷小鼠(Sod2-/-)是一种线粒体超氧阴离子自由基增加、组织损伤加速、早期死亡的动物模型。我们已经证明，遗传修饰物在确定Sod2-/-小鼠的预期寿命方面发挥着重要作用。因此，遗传背景较长的Sod2-/-小鼠的寿命是遗传背景较短的突变小鼠的5倍。我们将基因修饰基因命名为KOLEGs(基因敲除延长寿命基因)，并设计了一系列实验来定位KOLEG基因座和识别可能的修饰基因。到目前为止，我们已经在纯B6背景上产生了含有KOLEG的同源小鼠，将主要的KOLEG定位到一个10 cM的区域，并在含有KOLEG的区域确定了一个可能的修饰基因。修饰基因编码烟酰胺核苷酸转氢酶(NNT)，它是一种位于线粒体内膜的膜结合蛋白。为了以我们目前的发现为基础，并最终确定能够调节线粒体对氧化应激增加的抵抗力并延长突变和野生型小鼠寿命的新的遗传修饰物，提出了以下具体目标：目标1：通过精细定位和功能注释识别额外的修饰基因。目标2：NNT作为Sod2-/-的遗传修饰物的机理分析。目标3：验证NNT作为长寿保证基因(LAG)的有效性。

DESCRIPTION (provided by applicant): This proposal is based on the premise that oxygen free radicals are involved in mitochondrial aging and in turn, aging of the whole organism. Superoxide radicals generated in the mitochondria can lead to damage of macromolecules and result in defective mitochondria. This process ultimately leads to the state of senescence and the demise of the organism. We hypothesize that factors that can protect the mitochondria from free radical damage have the potential to maintain energy production and tissue function, and ultimately to delay the onset of senescence and prolong the lifespan of the organism. MnSOD deficient mice (Sod2-/-) represent an animal model with increased mitochondrial superoxide radicals, accelerated tissue damage, and early demise. We have showed that genetic modifiers play an important role in the determination of the life expectancy of Sod2-/- mice. Thus, Sod2-/- mice on a long-lived genetic background have a lifespan 5 times longer than that of the mutant mice on a short-lived background. We designated the genetic modifiers KOLEGs (KnockOut Life-Extending Genes) and designed a series of experiments to map the KOLEG loci and to identify putative modifier genes. To date, we have generated congenic KOLEG-containing mice on an otherwise pure B6 background, mapped the major KOLEG to a 10 cM region, and identified a putative modifier gene in the KOLEG-containing region. The modifier gene encodes the nicotinamide nucleotide transhydrogenase (NNT), which is a membrane-bound protein located in the inner membrane of the mitochondria. To build upon our current findings and ultimately identify novel genetic modifiers capable of "modulating mitochondrial resistance to increased oxidative stress and extending the lifespans of mutant as well as wild type mice, the following specific aims are proposed. Aim 1: Identification of additional modifier genes by fine mapping and functional annotation. Aim 2: Mechanistic analysis of Nnt as the genetic modifier of Sod2-/-. Aim 3: Validation of Nnt as a longevity assurance gene (LAG).