Mechanisms of neuromuscular degeneration in SBMA

摘要 脊髓和延髓肌萎缩症(SBMA)是一种神经肌肉系统的退行性疾病，由 雄激素受体(AR)基因中的CAG/谷氨酰胺途径扩展。聚谷氨酰胺受体(PolyQ AR) 经历激素依赖性的核移位和展开，这些步骤对毒性和 男性进行性肌肉无力的发展。尽管长期以来人们认为低马达 神经元是SBMA变性的主要目标，我们实验室和其他人最近的研究已经 明确了外周血多聚Q AR表达在疾病中的重要性。这部作品突出了一个中心 骨骼肌中多聚Q受体的表达在虚弱和萎缩中的作用。基于这些发现，我们 已经开发出一种SBMA发病的创新模型，在这种模型中，神经肌肉系统的退化 从骨骼肌的毒性效应开始，随着时间的推移逐渐累及脊髓运动神经元 退化。在这里，我们建议在基因靶向小鼠(AR113Q)上测试这种疾病发病机制的模型 小鼠)在内源性水平和适当的细胞类型中表达多聚Q AR。本应用程序的目标是 是对我们新的疾病发病机制模型进行实验测试。这个模型形成了我们的中心假设 由已公布和初步数据的严密基础支持。在这里，我们将使用两个互补的 检验我们中心假设的方法：首先，我们将使用反义寡核苷酸(ASO)来敲除 多聚Q-AR在AR113Q小鼠外周组织或中枢神经系统的选择性表达及检测 对迟发性运动神经元变性的影响。第二，我们将恢复一个关键转录的功能 骨骼肌中导致SBMA骨骼肌萎缩的调节因子，然后确定其程度 这会影响AR113Q的表型，包括运动神经元变性。这些目标将是 辅以旨在利用调节PolyQ AR的内源性细胞机制的研究 降解，以消除与疾病相关的人类细胞中的蛋白毒性。我们将使用生化，遗传， 以及组织学分析，以确定AR靶向ASO对症状的有益影响 AR113Q小鼠(目标1)，确定MEF2功能增强在多大程度上挽救AR113Q表型 (目标2)，并在SBMA模型中建立靶向Hsp90/Hsp70伴侣机制的效应(目标3)。 这些研究有望在实验上测试我们提出的疾病发病机制模型，并提供 为开发治疗SBMA患者的靶向疗法奠定了坚实的基础。

ABSTRACT Spinal and bulbar muscular atrophy (SBMA) is a degenerative disorder of the neuromuscular system caused by a CAG/glutamine tract expansion in the androgen receptor (AR) gene. The polyglutamine AR (polyQ AR) undergoes hormone-dependent nuclear translocation and unfolding, steps that are essential to toxicity and to the development of progressive muscle weakness in men. Although it was long considered that lower motor neurons are the primary targets of degeneration in SBMA, recent studies from our laboratory and others have established the importance of peripheral polyQ AR expression in disease. This work highlights a central contribution of polyQ AR expression in skeletal muscle to weakness and atrophy. Based on these findings, we have developed an innovative model of SBMA pathogenesis in which degeneration of the neuromuscular system begins with toxic effects in skeletal muscle and progresses over time to involve spinal motor neuron degeneration. Here, we propose to test this model of disease pathogenesis in gene targeted mice (AR113Q mice) expressing polyQ AR at endogenous levels and in appropriate cell types. The objective of this application is to experimentally test our novel model of disease pathogenesis. This model forms our central hypothesis and is supported by a rigorous foundation of published and preliminary data. Here, we will use two complementary approaches to test our central hypothesis: First, we will use antisense oligonucleotides (ASOs) to knock-down expression of polyQ AR selectively in peripheral tissues or CNS of symptomatic AR113Q mice and determine effects on late onset motor neuron degeneration. Second, we will restore function of a critical transcriptional regulator in skeletal muscle that contributes to SBMA skeletal muscle atrophy and then determine the extent to which this influences the AR113Q phenotype, including motor neuron degeneration. These aims will be complemented by studies designed to leverage the endogenous cellular machinery that regulates polyQ AR degradation in order to eliminate proteotoxicity in disease relevant human cells. We will use biochemical, genetic, and histological assays to establish beneficial effects of AR targeted ASOs administered to symptomatic AR113Q mice (Aim 1), determine the extent to which increased MEF2 function rescues the AR113Q phenotype (Aim 2), and establish effects of targeting the Hsp90/Hsp70 chaperone machinery in SBMA models (Aim 3). These studies are expected to experimentally test our proposed model of disease pathogenesis and provide a strong foundation for developing targeted therapies to treat SBMA patients.