Ataxin-2 as a genetic risk factor for ALS: New insights into neurodegeneration

描述（由申请人提供）：肌萎缩侧索硬化症（ALS）是一种毁灭性的神经退行性疾病，对运动神经元造成严重破坏。近年来，RNA结合蛋白和RNA代谢途径的核心作用已经出现。TDP-43是一种RNA结合蛋白，已被确定为大多数ALS患者神经元病理包涵体的组成部分。此外，编码TDP-43 （TARDBP）基因的致病性突变与家族性和散发性ALS病例有关。这些数据表明，TDP-43的病理活性对ALS至关重要。然而，尽管TDP-43具有核心重要性，但人们对其如何导致疾病和导致ALS的蛋白质相互作用伙伴知之甚少。这项Co-PI研究计划汇集了酵母和苍蝇遗传学方面的两位专家，他们利用这些简单但功能强大的系统，对帕金森病和肌萎缩侧索硬化症等破坏性人类年龄相关疾病的机制有了根本性的发现。重要的是，在酵母中取得的发现可以转化为果蝇疾病模型，从酵母和苍蝇到人类患者。利用这些系统，我们发现一种聚谷氨酰胺（polyQ）蛋白ataxin-2是酵母和苍蝇中TDP-43毒性的有效修饰剂，其polyQ重复扩增导致2型脊髓小脑性共济失调（SCA2）。基于这一发现，我们测试并发现人类ataxin-2基因（ATXN2）中27- 33q的多位点扩增与ALS显著相关。这些数据表明，ATXN2是一种新的、相对常见的ALS易感疾病基因，TDP-43/Atx2相互作用是ALS和其他与TDP-43病理相关的疾病的关键靶点。为了揭示这种相互作用的机制，我们提出了三个具体目标。在目标1中，我们将使用哺乳动物细胞培养和果蝇来定义TDP-43和ataxin-2蛋白的结构域，它们对变性和功能中的协同相互作用至关重要。这些研究将提供深入了解在病理情况下受影响的蛋白质和过程的活性。在Aim 2中，我们将利用果蝇遗传学的力量来定义对TDP-43和ataxin-2之间的协同作用至关重要的其他基因。这将揭示对受干扰过程的理解和治疗靶向的新途径。最后，在Aim 3中，我们将讨论ataxin-2在神经变性中的更大作用。ALS与额颞叶变性（FTLD）有共同的疾病谱系，TDP- 43是其他神经退行性疾病的病理特征。我们将评估其他疾病中ataxin-2的polyQ重复长度，以评估相关疾病中是否发生扩增。综上所述，这些发现将揭示TDP-43/ataxin-2相互作用的关键方面，ataxin-2在神经退行性疾病中的更广泛作用，并为新的治疗见解奠定基础。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that wreaks havoc on motor neurons. Recently, a central role for RNA binding proteins and RNA metabolism pathways has emerged. TDP-43 is an RNA binding protein that has been identified as a component of pathological inclusions in neurons of most ALS patients. Further, pathogenic mutations in the gene encoding TDP-43 (TARDBP) are associated with familial and sporadic ALS cases. These data argue that pathological activities of TDP-43 are critical to ALS. Despite the central importance of TDP-43, however, little is understood about how it causes disease and protein interaction partners that lead to ALS. This Co-PI research proposal brings together two experts in yeast and fly genetics who have made fundamental discoveries into mechanisms of devastating human age-related diseases such as Parkinson's disease and ALS using these simple but powerful systems. Importantly, discoveries made in yeast are translatable to Drosophila disease models, and from yeast and flies to human patients. Using these systems, we have found that ataxin-2, a polyglutamine (polyQ) protein, whose polyQ repeat expansions cause spinocerebellar ataxia type 2 (SCA2), is a potent modifier of TDP-43 toxicity in yeast and fly. Launching from this finding, we tested and found that polyQ expansions of 27-33Qs in the human ataxin-2 gene, ATXN2, are significantly associated with ALS. These data argue that ATXN2 is a new and relatively common ALS susceptibility disease gene, and that the TDP-43/Atx2 interaction is a critical target in ALS and perhaps other diseases associated with TDP-43 pathology. With the goal to reveal mechanistic insight into this interaction, we propose three Specific Aims. In Aim 1, we will use mammalian cell culture and Drosophila to define the domains of the TDP-43 and ataxin-2 proteins that are critical for the synergistic interaction in degeneration and function. These studies will provide insight into the activity of the proteins and processes affected in the pathological situation. In Aim 2, we will use the power of fly genetics to define additional genes critical for the synergy between TDP-43 and ataxin-2. This will reveal understanding of the processes perturbed and new pathways for therapeutic targeting. Finally, in Aim 3, we will address the greater role of ataxin-2 in neurodegeneration. ALS shares a disease spectrum with frontotemporal lobar degeneration (FTLD) and TDP- 43 pathology characterizes other neurodegenerative diseases. We will assess polyQ repeat lengths of ataxin-2 in other diseases to assess whether expansions occur in related disorders. Taken together, these findings will reveal key aspects of the TDP-43/ataxin-2 interaction central to ALS, the broader role of ataxin-2 in neurodegenerative disease, and the foundation for novel therapeutic insights.