A Drosophila model to investigate prion-like transmission of Huntington's disease

描述(申请人提供)：亨廷顿病(HD)是一种遗传性神经退行性疾病，其特征是运动和认知功能的进行性恶化，其主要遗传原因是普遍表达的胞浆蛋白亨廷顿蛋白(Htt)N端附近的聚谷氨酰胺(PolyQ)束扩张。突变体Htt采用了一种细胞毒性功能获得，使其聚合成不溶的淀粉样纤维聚集体，这些聚集体最初沉积在基底节纹状体的中等刺神经元中，但在疾病的后期，扩散到邻近脑区(如海马区和皮质)的神经元。虽然Htt聚集体的沉积显然与神经细胞死亡有关，但它们促进细胞毒性或通过脑组织传播的确切机制目前尚不清楚。最近的研究表明，胞外Htt聚集体具有类似于Pron的性质，即它们可以触发可溶单体的模板构象变化，并将错误折叠状态传递给NAOVE细胞。此外，新出现的证据表明，与其他神经退行性疾病(如阿尔茨海默氏症和帕金森氏病)相关的蛋白质形成的聚集体也具有类似Pron的行为，这表明这些疾病的进展可能是通过共同的机制发生的。该方案的总体目的是建立果蝇模型，以证明Pron样HD病理传递是否可以在体内重演，并探讨这一过程中涉及的机制(S)。特定目的1研究聚集表型是否可以从表达致病多Q束的易于聚集的Htt的神经元传递到表达可溶性Htt和非致病多Q束的突触连接的神经元。具体目标2探索了另一种但不一定是相互排斥的可能性，即Htt诱导的聚集在相邻的、非突触连接的细胞之间传递。这些研究将利用果蝇嗅觉神经元电路和各种遗传工具的详细知识，在单个果蝇的不同细胞类型中表达致病和非致病Htt蛋白。具体目标3的重点是确定Htt诱导的聚集在果蝇模型中横向传递的决定因素，以深入了解这一过程所涉及的机制(S)。这些研究将采用功能丧失筛查，在该筛查中，编码细胞表面和分泌蛋白的基因被RNA干扰耗尽，并将通过检查Htt诱导的聚集扩散到突触连接和/或邻近细胞的方式来衡量影响。总之，这些方法将扩大我们目前对Htt聚集体如何在活体环境中具有Pron样属性的细胞之间传播的理解，并将有助于深入了解HD和其他神经退行性疾病的病理通过患病个体的大脑沿着刻板印象的路径发展的机制。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by a progressive deterioration in motor and cognitive function, and its primary genetic cause is the expansion of a polyglutamine (polyQ) tract near the N-terminus of the ubiquitously-expressed, cytosolic protein huntingtin (Htt). Mutant Htt adopts a cytotoxic gain-of-function that causes it to polymerize into insoluble, amyloid-like fibrillar aggregates that are initially deposited in medium spiny neurons in the striatum of the basal ganglia but in later stages of disease, spread to neurons in neighboring brain regions (e.g. the hippocampus and cortex). While it is clear that deposition of Htt aggregates correlates with neuronal cell death, the exact mechanism by which they contribute to cytotoxicity or spread through brain tissue is currently unknown. Recent studies suggest that extracellular Htt aggregates have prion-like properties; i.e. they can trigger the templated conformational change of soluble monomers and transmit the misfolded state to naove cells. Further, emerging evidence suggests that aggregates formed by proteins associated with other neurodegenerative disorders (e.g. Alzheimer's and Parkinson's diseases) also adopt prion-like behavior, suggesting that progression of these diseases may occur by a common mechanism. The overall aim of this proposal is to establish a Drosophila model to demonstrate whether prion-like transmission of HD pathology can be recapitulated in vivo and to explore the mechanism(s) involved in this process. Specific Aim 1 investigates whether the aggregation phenotype can be transmitted from neurons expressing aggregation-prone Htt containing a pathogenic polyQ tract to synaptically-connected neurons expressing soluble Htt with a non-pathogenic polyQ tract. Specific Aim 2 explores an alternative but not necessarily mutually exclusive possibility, that Htt-induced aggregation is transmitted between adjacent, non-synaptically-connected cells. These studies will exploit detailed knowledge of Drosophila olfactory neuronal circuitry and various genetic tools to express pathogenic and non-pathogenic Htt proteins in distinct cell types within an individual fly. The focus of Specific Aim 3 is to identify determinants for the lateral transmission of Htt-induced aggregation in a Drosophila model to gain insight into the mechanism(s) involved in this process. These studies will employ a loss-of-function screen in which genes encoding cell surface and secreted proteins are depleted by RNA interference, and effects will be measured by examining how the spread of Htt-induced aggregation to synaptically-connected and/or neighboring cells is altered. Together, these approaches will expand our current understanding of how Htt aggregates propagate between cells with prion-like properties in an in vivo setting, and will lend insight into the mechanism by which the pathology of HD and other neurodegenerative disorders progress along stereotypical paths through the brains of afflicted individuals.