Modeling the progression of SOD1-linked motor neuron disease

描述(申请人提供)：铜锌超氧化物歧化酶1(SOD1)相关的家族性肌萎缩侧索硬化症(FALS)是一种非常不同的疾病，具有多种临床症状，可起源于上或下运动神经元，病程从一年到长达20年不等。疾病的持续时间在很大程度上取决于症状沿着神经轴传播的速度，直到参与呼吸的运动神经元受到影响。这种疾病似乎是如何传播的问题是ALS研究中尚未回答的主要问题之一。在过去的几年里，越来越多的证据表明，疾病传播的一种机制可能涉及到一种有毒的错误折叠蛋白沿着中枢神经系统的解剖连接路径在细胞之间进行类似Pron的传播。可以在细胞间传播有毒构象的蛋白质通常也可以在实验中在单个生物体之间传播疾病。为了观察运动神经元病(MND)传播的易感性，我们将表达突变超氧化物歧化酶1(SOD1-G93A和G37R)的瘫痪小鼠制备的脊髓匀浆注射到遗传脆弱的SOD1转基因小鼠的脊髓中。从我们测试的各种模型中，有一种表现出高度的脆弱性。来自瘫痪G93A小鼠的组织匀浆在3-11个月时诱导了10只表达低水平G85R-SOD1与黄色荧光蛋白(G85R-YFP小鼠)融合的小鼠中的6只出现MND，并产生了广泛的脊柱包涵体病理。重要的是，从G93A→G85R-yfp小鼠的第二代匀浆返回到新生的G85R-yfp小鼠，在3个月大的4只小鼠中有4只诱发了疾病。无论注射的转基因动物是什么品系，表达G37R变体的瘫痪小鼠的匀浆都属于传播能力较差的品系，这一发现表明，品系相似的特性表现为传播MND的能力不同。尽管这些初步发现非常令人兴奋，但我们认识到，到目前为止，我们的研究力度不够，我们无法完全评估SOD1连锁运动神经元疾病(MND)在动物之间传播的容易程度，而不进行更大的努力。目标1和目标2提出了这样一种努力，以更好地了解在这些模型中传播MND的基因/表型相互作用。我们也有非常令人兴奋的证据表明，我们可能能够创建一种模型，在这种模型中，我们可以通过向脆弱的转基因模型的坐骨神经中注射来自瘫痪小鼠的“感染性”组织匀浆，来局部引发疾病。然而，同样，我们的初步数据是有限的，需要付出更大的努力。目标3提出了这样的努力。总而言之，我们的研究旨在更好地建立SOD1-MND传播性的生物学相关性，并建立模型系统，使对疾病进展机制的研究成为可能。

DESCRIPTION (provided by applicant): Cu-Zn superoxide dismutase 1 (SOD1)-linked familial amyotrophic lateral sclerosis (fALS) is an extremely heterogeneous disease phenotypically with diverse clinical symptoms that can originate in upper or lower motor neurons and with a wide range of disease durations, from as short as a year to as long as 20 years. The duration of disease is largely a function of the speed with which symptoms spread along the neuraxis until motor neurons involved in respiration become affected. The question of how the disease seems to spread is one of the major unanswered questions in the study of ALS. Over the past few years, there has been increasing evidence that one mechanism by which the disease spreads may involve a prion-like propagation of a toxic misfolded protein from cell to cell along anatomically connected pathways of the CNS. Proteins that can transmit toxic conformations between cells often can also experimentally transmit disease between individual organisms. To survey the ease with which motor neuron disease (MND) can be transmitted, we injected spinal cord homogenates prepared from paralyzed mice expressing mutant superoxide dismutase 1 (SOD1-G93A and G37R) into the spinal cords of genetically vulnerable SOD1 transgenic mice. From the various models we tested, one emerged as showing high vulnerability. Tissue homogenates from paralyzed G93A mice induced MND in 6 of 10 mice expressing low levels of G85R-SOD1 fused to yellow fluorescent protein (G85R-YFP mice) by 3-11 months, and produced widespread spinal inclusion pathology. Importantly, second passage of homogenates from G93A→G85R-YFP mice back into newborn G85R-YFP mice, induced disease in 4 of 4 mice by 3 months of age. Homogenates from paralyzed mice expressing the G37R variant were among those that transmitted poorly, regardless of the strain of recipient transgenic animal injected, a finding suggestive of strain-like properties that manifest as differing abilities to transmit MND. Although these preliminary findings are very exciting, we recognize that our studies to date are underpowered and we cannot fully assess the ease with which SOD1-linked motor neuron disease (MND) can be transmitted between animals without a much larger effort. Aims 1 and 2 propose such an effort to better understand genotype/phenotype interactions in transmitting MND in these models. We also have very exciting evidence that we might be able to create a model in which we could initiate disease focally, by injecting the "infectious" tissue homogenates from paralyzed mice in to the sciatic nerves of vulnerable transgenic models. However, again, our preliminary data is limited and much larger effort is required. Aim 3 proposes such an effort. Collectively, our studies are designed to better establish the biological relevance of SOD1-MND transmissibility and to build model systems that would enable investigations into the mechanisms of disease progression.