Neuroprotection via XIAP gene therapy in Huntington's disease

描述(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之前出现严重的运动障碍、情绪和情绪障碍以及认知能力下降。它是由亨廷顿蛋白(Huntingtin，HTT)编码基因的CAG重复序列扩大引起的，但突变的HTT(MHTT)最终导致选择性神经变性的机制尚不清楚。多个HD模型的大量证据表明，mHTT可诱导细胞凋亡过程和线粒体功能障碍。XIAP是一种有效的细胞凋亡抑制物，因此是亨廷顿病神经保护的一个有吸引力的靶点。这项建议的目的是确定一种新的基因传递方法的潜在治疗效用，使用AAV载体方法将编码XIAP的基因传递到亨廷顿病神经变性的主要部位，即新纹状体。拟议的亨廷顿病小鼠遗传模型实验源于以下观察结果：(I)我们已经发现XIAP在体外具有对抗mHTT诱导的毒性的神经保护作用，(Ii)这种作用可能是通过对Smac/Diablo或Omi的抑制作用而不是半胱氨酸酶抑制作用来介导的，(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，(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。具体地说，我们将通过检测AAV-dXIAP在亨廷顿病N171-82Q“片段”小鼠模型和第二个“全长”HD模型YAC-128 HD小鼠中的作用，来检验将抗凋亡剂XIAP输送到纹状体神经元的AAV基因治疗方法是否改善了亨廷顿病动物模型的结局并减少了神经退化。我们还将阐明XIAP的神经保护抗凋亡作用是由于抑制Smac/Diablo或Omi/HtrA2，而不是直接影响HD小鼠的caspase。我们将产生携带点突变的dXlAP的AAV载体，使其无法与Smac/Diablo-Omi或caspase结合，并在HD小鼠模型中检测它们对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发病机制背后的细胞损伤途径，并开发有效的基因传递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.