RNA splicing dysfunction in Alzheimer's disease

 描述（由申请人提供）：阿尔茨海默病（AD）是最常见的痴呆症，是美国第六大死亡原因。该疾病影响约500万美国人，2012年的护理费用约为2000亿美元。尽管对AD发病机制进行了广泛的研究，并在开发AD的治疗方法方面进行了巨大的投资，但该疾病尚无治愈方法。因此，迫切需要加快研究，以开发有效的AD治疗方法。蛋白质聚集体的沉积是AD病理学的共同特征。聚集蛋白的鉴定以及遗传学研究可以为AD的分子发病机制提供重要的见解。由此产生的淀粉样蛋白级联和tau假说主导了AD研究，但它们的解释一直在发展，可溶性蛋白寡聚体作为有毒物质出现。然而，AD的病因学仍有待充分阐明。我们之前通过质谱对人脑聚集蛋白质组进行了全面的研究，鉴定了4，216种蛋白质，其中36种蛋白质在AD中积累，包括U1- 70 K和其他U1小核核糖核蛋白（U1 snRNP）剪接体组分。多个U1 snRNP亚基在AD中形成细胞质缠结样结构，但在其他神经退行性疾病中不形成[例如，帕金森氏病、额颞叶变性和皮质基底节变性（伴tau蛋白病）]，表明U1 snRNP病理学是AD特异性的，不能单独由tau蛋白病诱导。深度RNA测序揭示了AD脑中RNA加工的整体失调。重要的是，在轻度认知障碍和早期Braak阶段的AD中发现了U1- 70 K聚集，表明U1 snRNP改变发生在AD发展的早期。U1 snRNP组分也聚集在具有PS1和APP突变以及21三体的AD病例的早发遗传形式中，表明异常淀粉样蛋白级联反应可能导致人类U1 snRNP功能障碍。有趣的是，U1- 70 K敲除或U1 snRNP的反义寡核苷酸抑制增加了细胞模型和可能的小鼠模型中淀粉样前体蛋白（APP）和AAPs的产生水平，表明AAPs产生和U1 snRNP异常的恶性循环。因此，我们的假设是，U1 snRNP功能障碍可以介导神经退行性变和调节Abladder的产生，有助于AD的发病机制。我们将在三个具体目标中检验这一假设：（i）研究U1 snRNP功能障碍是否导致细胞模型中的神经毒性;（ii）研究U1 snRNP功能障碍是否导致小鼠模型中的神经退行性变;（iii）确定U1 snRNP功能障碍如何导致异常的腺苷酸产生。我们的研究结果将说明RNA剪接功能障碍在AD发病机制中的潜在作用，这可能导致开发新的策略来有效地诊断和治疗这种疾病。

 DESCRIPTION (provided by applicant): Alzheimer's disease (AD), the most common form of dementia, is the sixth-leading cause of death in the US. The disease affects ~5 million Americans, and had a care cost of ~$200 billion in 2012. Despite extensive investigation of AD pathogenesis and tremendous investment in developing therapeutics for AD, no cure is available for the disease. Thus, there is an urgent need to accelerate research to develop effective treatments for AD. Deposition of protein aggregates is a common feature of AD pathology. Identification of the aggregated proteins, together with genetic studies, can provide crucial insights into the molecular pathogenesis of AD. The resulting amyloid cascade and tau hypotheses dominate AD studies, but their interpretation has been evolving and soluble protein oligomers emerge as toxic species. However, AD etiology remains to be fully illustrated. We previously performed a comprehensive study of the human brain aggregated proteome by mass spectrometry and identified 4,216 proteins, among which 36 proteins accumulate in AD, including U1-70K and other U1 small nuclear ribonucleoprotein (U1 snRNP) spliceosome components. Multiple U1 snRNP subunits form cytoplasmic tangle-like structures in AD but not in other neurodegenerative disorders [e.g., Parkinson's disease, frontotemporal lobar degeneration, and corticobasal degeneration (with tauopathy)], indicating that U1 snRNP pathology is AD specific and cannot be induced by tauopathy alone. Deep RNA sequencing revealed global dysregulation of RNA processing in AD brain. Importantly, U1-70K aggregation was found in mild cognitive impairment and early Braak stages of AD, indicating that U1 snRNP alteration occurs early in AD development. U1 snRNP components also aggregate in early onset genetic forms of AD cases with PS1 and APP mutations as well as trisomy 21, suggesting that abnormal amyloid cascade may cause U1 snRNP dysfunction in human. Interestingly, U1-70K knockdown or antisense oligonucleotide inhibition of U1 snRNP increased the level of amyloid precursor protein (APP) and Aß production in cellular models and possibly in a mouse model, suggesting a vicious cycle of Aß production and U1 snRNP abnormality. Thus, our hypothesis is that U1 snRNP dysfunction can mediate neurodegeneration and modulate Aß production, contributing to AD pathogenesis. We will test this hypothesis in three specific aims: (i) investigate whether U1 snRNP dysfunction leads to neurotoxicity in cellular models; (ii) examine whether U1 snRNP dysfunction leads to neurodegeneration in a mouse model; and (iii) determine how U1 snRNP dysfunction causes aberrant Aß production. Our results will illustrate the potential role of RNA splicing dysfunction in AD pathogenesis, which may lead to the development of novel strategies to effectively diagnose and treat this disease.