Mitochondrial DNA Mutations and the Aging Process

描述（由申请人提供）：为了增加对衰老分子基础的理解，我们已经生成了一个小鼠模型（PolgD257A），该模型应该显示线粒体DNA （mtDNA）的自发突变率增加。该动物模型是通过在胚胎干细胞中引入小鼠DNA聚合酶γ (POLG)外切酶结构域的特定突变而产生的。携带线粒体dna“突变”表型的小鼠将使研究人员能够阐明衰老研究中尚未解决的核心问题之一，即线粒体突变对衰老过程的贡献。要验证的中心假设是，已知与许多有丝分裂后组织衰老相关的mtDNA突变在衰老过程中起因果作用。

DESCRIPTION (provided by applicant): In order to increase understanding of the molecular basis of aging, we have generated a mouse model (PolgD257A) that should display increased spontaneous mutation rates in mitochondrial DNA (mtDNA). This animal model was generated by introducing a specific mutation in the exonuclease domain of mouse DNA Polymerase Gamma (POLG) in ES cells. Mice carrying a "mutator" phenotype in mtDNA will allow investigators to elucidate one of the central unresolved issues in aging research, the contribution of mitochondrial mutations to the aging process. The central hypothesis to be tested is that mutations in mtDNA, known to be associated with aging in many postmitotic tissues, play a causal role in the aging process. Specific Aim 1. Characterization of skeletal muscle in mitochondrial mutator mice. Mice carrying the PolgD257A mutation are viable and display no obvious developmental defects. We propose to determine the mutational spectrum in mtDNA of these animals in order to estimate mutational frequency in vivo. We also propose to determine the level of electron transport system (ETS) abnormalities, as determined by loss of cytochrome c oxidase (COX) activity along individual muscle fibers of 5-month, 15-month and 30-month PolgD257A and wild-type control animals. Isolated mitochondria will also be characterized for age-related biochemical abnormalities, including alterations in metabolic potential and OS markers. Specific Aim 2. Gene expression profiling in skeletal muscle. We propose to characterize the gene expression profile of skeletal muscle of PolgD257A mice over the adult lifespan in order to determine if mitochondrial mutations accelerate the aging process at the molecular level. Specifically, mice will be studied at 5 months, 15 months and 30 months of age. These experiments will involve both wild-type and PolgD257A mice and utilize high density oligonucleotide arrays, which provide data on over 12,000 genes and ESTs. Specific Aim 3. Survival and Disease Patterns in PolgD257A Mice. We propose to determine the survival and disease patterns of PolgD257A mice. Animals will be backcrossed to the B6 (C57BL/6 mice) genetic background, which our laboratory has extensively characterized for disease patterns and mortality. Survival patterns, including survival curves and calculation of mortality rates, will be performed for PolgD257A mice and wild-type controls. Animals will be observed for the development of neoplastic, neurologic and cardiac phenotypes and characterized at the histopathology level accordingly.