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

描述（由申请人提供）：亨廷顿舞蹈病（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细胞质蛋白亨廷顿蛋白（Htt） n端附近的聚谷氨酰胺（polyQ）通道扩张。突变Htt采用细胞毒性功能获得，导致其聚合成不溶性淀粉样纤维聚集体，最初沉积在基底节区纹状体的中棘神经元中，但在疾病后期扩散到邻近大脑区域（如海马和皮层）的神经元中。虽然Htt聚集体的沉积与神经元细胞死亡相关是明确的，但它们促进细胞毒性或通过脑组织扩散的确切机制目前尚不清楚。最近的研究表明，细胞外Htt聚集体具有类似朊病毒的性质；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原始细胞。此外，新出现的证据表明，与其他神经退行性疾病（如阿尔茨海默病和帕金森病）相关的蛋白质形成的聚集体也采用朊病毒样行为，这表明这些疾病的进展可能通过共同的机制发生。本提案的总体目标是建立果蝇模型，以证明HD病理的朊病毒样传播是否可以在体内重现，并探讨这一过程所涉及的机制。特异性目的1研究聚集表型是否可以从表达具有致病性多q束的易聚集性Htt的神经元传递到表达具有非致病性多q束的可溶性Htt的突触连接神经元。特异性目标2探讨了另一种但不一定相互排斥的可能性，即http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回路的详细知识和各种遗传工具，在单个果蝇的不同细胞类型中表达致病性和非致病性Htt蛋白。特异性目标3的重点是在果蝇模型中确定htt诱导的聚集横向传播的决定因素，以深入了解这一过程中涉及的机制。这些研究将采用功能丧失筛选，其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http诱导的聚集如何传播到突触连接和/或邻近细胞来测量效果。总之，这些方法将扩展我们目前对Htt聚集体如何在体内具有朊病毒样特性的细胞之间传播的理解，并将深入了解HD和其他神经退行性疾病的病理沿着患者大脑的刻板路径进展的机制。

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.