Investigation on Ataxin2 and Matrin3 in neurodegenerative disease

RNA结合蛋白（RBP）的功能障碍或突变与越来越多的 神经退行性疾病（NDD），包括肌萎缩侧索硬化症（ALS）、AD/ADRD和脊髓小脑共济失调2型（SCA 2）。RBP Ataxin-2是ALS的有效调节剂，靶向治疗已经在临床试验中。然而，Ataxin-2在ALS和痴呆中的潜在致病机制及其与其他致病RBP相互作用的作用知之甚少。我们发现核基质RBP Matrin-3与Ataxin-2相互作用，并建议在ALS/FTD相关神经元中研究功能上的相互作用。Matrin-3突变导致FTD、家族性ALS和多系统蛋白病 （MSP）。与TDP-43一样，Matrin-3蛋白质病在ALS/FTD中观察到，即使它没有突变。在阿尔茨海默病（AD）患者神经元中也观察到Matrin-3的细胞质聚集。我们的初步数据表明，靶向MATR 3可能对这些疾病有治疗作用：我们观察到，在ALS和FTD患者的成纤维细胞中，Matrin-3过量，这些患者具有C9 ORF 72和TDP-43突变，通过RNAi降低ATXN 2表达使其正常化。FTD/ALS相关Matrin 3-S85 C小鼠模型显示广泛的选择性浦肯野细胞（PC）损失。PC是SCA 2中受影响的神经元， 对Ataxin-2突变最敏感的人群。Matrin-3 S85 C小鼠中的重度小脑神经变性表明Matrin-3和共济失调蛋白-2之间存在病理学联系，可定义与其他NDD（包括FTD）相关的神经元死亡途径。我们提出，在疾病的背景下，Ataxin-2与Matrin-3的相互作用将有助于病理学的发展，并且靶向Ataxin-2将减轻Matrin-3病理学和神经元死亡。我们计划在分离的培养神经元中研究与Ataxin-2，Matrin-3和ALS相关的病理学，这些神经元来自Ataxin-2敲除，Ataxin-2扩增和TDP-43突变 小鼠我们将通过表达Matrin-3突变和/或用腺病毒和已经开发的反义寡核苷酸策略敲低Ataxin-2来确定不同RBP的贡献。我们建议研究的病理表型包括Matrin-3水平、定位、溶解度变化、聚集成凝聚物和对神经元的毒性，以及ALS分子读数，包括TDP-43聚集和定位。我们还将研究其他相关蛋白质病生物分子成核到冷凝物中。在正常、扩增和敲除Ataxin-2和突变的TDP-43的背景下分析这些将告知Ataxin-2、Matrin-3的作用以及RBP在SCA 2和ALS/FTD的发病机制中的相互作用。本研究将为直接靶向ATXN 2和MATR 3治疗伴有MATR 3突变的ALS和FTD患者以及伴有Matrin-3蛋白病的其他AD/ADRD患者提供初步概念验证。

Dysfunction or mutation of RNA binding proteins (RBPs) is associated with a growing number of neurodegenerative diseases (NDDs), including amyotrophic lateral sclerosis (ALS), AD/ADRDs and spinocerebellar ataxia type 2 (SCA2). The RBP Ataxin-2 is a potent modifier of ALS and targeting therapeutics are already in clinical trials. However, the underlying pathogenic mechanisms of Ataxin-2 in ALS and dementias, and the roles of its interaction with other pathogenic RBPs are poorly understood. We found that the nuclear matrix RBP Matrin-3 interacts with Ataxin-2 and propose to study the interaction functionally in ALS/FTD-relevant neurons. Mutations in Matrin-3 cause FTD, familial ALS and multisystem proteinopathy (MSP). Like TDP-43, Matrin-3 proteinopathy has been observed in ALS/FTD even when it is not mutated. Cytoplasmic aggregation of Matrin-3 has also been observed in Alzheimer’s disease (AD) patient neurons. Our preliminary data suggest that targeting MATR3 may be therapeutic for these disorders: We observed Matrin-3 overabundance in fibroblasts from ALS and FTD patients with C9ORF72 and TDP-43 mutations, that was normalized by lowering ATXN2 expression by RNAi. The FTD/ALS-relevant Matrin3-S85C mouse model displays extensive selective Purkinje cell (PC) loss. PCs are the neurons affected in SCA2 and the neuronal population with the greatest susceptibility to Ataxin-2 mutations. The severe cerebellar neurodegeneration in Matrin-3 S85C mice suggests a pathological link between Matrin-3 and Ataxin-2 that could define a neuronal death pathway relevant to other NDDs including FTD. We propose that in the context of disease, Ataxin-2 interaction with Matrin-3 will contribute to the development of pathology, and that targeting Ataxin-2 will mitigate Matrin-3 pathology and neuronal death. We plan to study pathology linked to Ataxin-2, Matrin-3 and ALS in isolated cultured neurons derived from Ataxin-2 knockout, Ataxin-2 expansion and TDP-43 mutation mice. We will determine the contribution of the different RBPs by expressing Matrin-3 mutations and/or knocking down Ataxin-2 with adenovirus and antisense oligonucleotide strategies already developed. The pathological phenotypes we propose to study include Matrin-3 levels, localization, changes in solubility, aggregation into condensates and toxicity to neurons, as well as ALS molecular readouts including TDP-43 aggregation and localization. We will also investigate the nucleation of other relevant proteinopathy biomolecules into the condensates. Analyzing these in the context of normal, expanded and knockout Ataxin-2 and mutated TDP-43 will inform on the roles of Ataxin-2, Matrin-3 and the interplay of RBPs in the pathogenetic mechanisms in SCA2 and ALS/FTD. This study will provide the initial proof-of-concept for directly targeting ATXN2 and MATR3 in ALS and FTD patients with MATR3 mutations, as well as in other AD/ADRD patients with Matrin-3 proteinopathy.