Mechanisms of Mitochondrial Distribution

描述（由申请方提供）：膜锚定Miro GTP酶及其接头蛋白将线粒体附着于细胞骨架马达，细胞骨架马达将细胞器分布在整个细胞中。这一过程在神经元中尤为重要，因为在神经元中，线粒体从细胞体到突触之间移动了很长的距离，然后又返回。在大量人类神经退行性疾病中观察到异常的线粒体运动和分布，包括痉挛性截瘫、阿尔茨海默病、亨廷顿病和帕金森病。一个流行的模型提出，能量（ATP）剥夺和线粒体分布缺陷引起的钙缓冲的变化导致与这些疾病相关的神经元变性。然而，在这些病例中，线粒体运动缺陷是疾病进展的主要原因还是次要后果尚不清楚。本申请中提出的研究将直接测试该模型。 使用条件（floxed）等位基因，我们产生了两种不同的Miro 1突变小鼠模型。第一种是Miro 1神经元特异性KO，其允许小鼠在出生后存活，但引起以震颤、后肢僵硬、脊柱后凸（脊柱弯曲）运动缺陷和出生后数周死亡为特征的进行性神经病。这些表型是神经退行性疾病的标志。第二种是全动物敲除（KO），完成胚胎发育，但无法呼吸，出生时死亡。初步研究表明，在一个特定的神经回路的缺陷负责这种新生儿呼吸缺陷。使用这些小鼠以及这些动物的组织和原代细胞培养物，我们将确定Miro 1缺失对线粒体分布和功能的影响。我们还将确定任何线粒体缺陷是否/如何导致神经元变性和死亡。这些研究将首次对哺乳动物中Miro 1功能和特定线粒体运动缺陷进行生理分析。因为我们的研究是基于具有已证实的神经功能障碍的小鼠模型，所以我们所了解的将促进对线粒体运动在神经元健康的发育和维持中的作用的理解。

DESCRIPTION (provided by applicant): Membrane-anchored Miro GTPases and their adaptor proteins attach mitochondria to cytoskeletal motors that distribute the organelle throughout the cell. This process is particularly important in neurons, where mitochondria are moved long distances from the cell body to the synapse and back again. Aberrant mitochondrial movement and distribution is observed in a large number of human neurodegenerative disorders including Spastic paraplegias, Alzheimer's, Huntington's and Parkinson's diseases. A popular model proposes that energy (ATP) deprivation and changes in calcium buffering caused by mitochondrial distribution defects causes the neuronal degeneration associated with these diseases. However, whether mitochondrial motility defects are a primary cause or a secondary consequence of disease progression in these cases is not clear. The research proposed in this application will directly test this model. Using a conditional (floxed) allele, we generated two different Miro1 mutant mouse models. The first is a Miro1 neuron-specific KO that allows mice to survive postnatally, but causes a progressive neuropathy characterized by tremors, hind limb stiffness, kyphosis (spinal curvature) movement defects and death several weeks after birth. These phenotypes are hallmarks of neurodegenerative disorders. The second is a whole animal knockout (KO), which completes embryogenesis but fails to breathe and dies at birth. Preliminary studies indicate that defects in a specific neuronal circuit are responsible for this neonatal breathing defect. Using these mice as well as tissues and primary cell cultures from these animals, we will determine the effects of Miro1 loss on mitochondrial distribution and function. We will also determine whether/how any mitochondrial defects lead to neuronal degeneration and death. These studies will provide the first physiological analysis of Miro1 function and specific mitochondrial movement defects in mammals. Because our studies are based on mouse models with demonstrated neurological dysfunction, what we learn will advance understanding of the role of mitochondrial movement in the development and maintenance of neuronal health.