Neuroprotection via XIAP gene therapy in Huntington's disease

描述（由申请人提供）：亨廷顿病（HD）是一种毁灭性的遗传性神经退行性疾病，其特征是在过早死亡前出现严重的运动障碍、情绪和情感障碍以及认知能力下降。它是由编码亨廷顿蛋白（htt）的基因中的CAG重复扩增引起的，但突变htt（mhtt）最终诱导选择性神经变性的机制仍然未知。来自多个HD模型的大量证据表明，mhtt诱导凋亡性细胞死亡过程和线粒体功能障碍。XIAP是一种有效的细胞凋亡抑制剂，因此代表了亨廷顿病神经保护的一个有吸引力的靶标。本提案的目的是确定一种新的基因递送方法的潜在治疗效用，该方法使用AAV载体方法将编码XIAP的基因递送至亨廷顿氏病中神经变性的主要部位，即新纹状体。在亨廷顿氏病的遗传小鼠模型中提出的实验源自以下观察：（i）我们已经发现XIAP在体外对mhtt诱导的毒性具有神经保护作用，（ii）该作用可能由对Smac/DIABLO或Omi的抑制作用介导，而不是半胱天冬酶抑制，（iii）我们的腺相关病毒（AAV）载体递送系统导致纹状体内广泛的基因表达，和（iv）初步实验表明XIAP基因递送改善了亨廷顿病小鼠模型的表型。具体而言，我们将通过检查AAV-dXIAP在亨廷顿病的N171- 82 Q“片段”小鼠模型和第二个“全长”HD模型YAC-128 HD小鼠中的作用，检查将抗凋亡剂XIAP递送至纹状体神经元的AAV基因治疗方法是否改善亨廷顿病动物模型的结果并减少神经变性。我们还将阐明XIAP的神经保护性抗凋亡作用是否是由于抑制Smac/DIABLO或Omi/HtrA 2，而不是直接作用于HD小鼠中的半胱天冬酶。我们将产生携带dXlAP的AAV载体，所述dXlAP具有点突变，使其不能结合Smac/DIABLO-Omi或半胱天冬酶，并在HD小鼠模型中检查它们对HD病理生物学的影响。这些研究的结果将为更大规模的研究提供坚实的基础，以确定HD发病机制的细胞损伤途径，并开发一种有效的基因递送方法来治疗亨廷顿病。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is devastating hereditary neurodegenerative disorder characterized by a severe movement disorder, mood and emotional disturbances, and cognitive decline before premature death. It is caused by a CAG repeat expansion in the gene encoding huntingtin (htt), but the mechanism whereby mutant htt (mhtt) ultimately induces selective neurodegeneration is still unknown. There is substantial evidence from multiple HD models that mhtt induces apoptotic cell death processes and mitochondrial dysfunction. XIAP is a potent inhibitor of apoptosis and thus represents an attractive target for neuroprotection in Huntington's disease. The goal of this proposal is to determine the potential therapeutic utility of a novel gene delivery approach, using an AAV-vector approach to deliver the gene encoding XIAP to the major site of neurodegeneration in Huntington's disease, the neostriatum. The proposed experiments in genetic mouse models of Huntington's disease arise from the observations that (i) we have found that XIAP has neuroprotective actions against mhtt- induced toxicity in vitro, (ii) that this effect is potentially mediated by inhibitory actions against Smac/DIABLO or Omi, rather than caspase inhibition, (iii) that our adeno-associated viral (AAV) vector delivery system results in widespread gene expression within the striatum, and (iv) pilot experiments suggest that XIAP gene delivery improves phenotype in a mouse model of Huntington's disease. Specifically, we will examine whether an AAV gene therapy approach to deliver the anti-apoptotic agent XIAP to striatal neurons improves outcome and reduces neurodegeneration in animal models of Huntington's disease, by examining AAV-dXIAP's effects in the N171-82Q "fragment" mouse model of Huntington's disease, and in a second "full length" HD model, YAC-128 HD mice. We will also elucidate whether XIAP'S neuroprotective anti-apoptotic actions are due to inhibition of Smac/DIABLO or Omi/HtrA2, rather than direct effects on caspases in HD mice. We will generate AAV vectors carrying dXlAP with point mutations either disabling its ability to bind to Smac/DIABLO-Omi, or caspases, and examine their effects on HD pathobiology in an HD mouse model. The outcomes of these studies will provide a substantial foundation for larger studies to determine cell damage pathways underlying HD pathogenesis, and to develop an effective gene-delivery approach for the treatment of Huntington's disease.