Metabolic Dysregulation in FXTAS Pathogenesis

脆性X相关震颤/共济失调综合征(FXTAS)是一种成人起病的神经退行性疾病，影响 脆性X智力低下1(FMR1)基因前突变等位基因(55-200个CGG重复)的携带者。 FXTAS的共同特征包括进行性意向震颤、步态共济失调、帕金森症和认知 拒绝。FXTAS的神经病理特征包括全程泛素阳性的核内包涵体 大脑和小脑浦肯野神经元明显缺失。目前，数据支持两种非互换 FXTAS独特的分子致病机制：1)RNA功能增益，其中rCGG重复序列- 结合蛋白(RBPs)通过长rCGG重复序列的隔离而变得功能受限，以及2) 重复相关的非Aug(RAN)翻译，通过CGG(或反义CCG)翻译 重复序列会导致有毒同源多肽的产生，如FMRPolyG，这反过来又会干扰 细胞功能的多样性。为了研究这些机制，已经建立了多个小鼠模型。大有可为 与FXTAS相关的代谢变化，特别是在大脑中，以及 受影响最严重的区域是小脑。我们之前的工作确定了与以下因素相关的代谢变化 利用我们的FXTAS小鼠模型在小脑浦肯野表达90个CGG重复序列的FXTAS发病机制 并表现出FXTAS的关键表型特征。通过将全球新陈代谢分析与 对果蝇的遗传筛选，我们发现鞘磷脂代谢途径可以调节rCGG重复 毒性。一项对5例FXTA死后大脑与年龄匹配的对照组的初步研究也被确认 鞘磷脂途径的改变。男性慢性阻塞性肺疾病患者血浆样本的非靶向代谢分析 FXTAS的症状表明，与非携带者相比，鞘磷脂途径发生了显著变化。 在这项拟议的研究中，我们将使用其他FXTAS小鼠模型--果蝇--来扩展这些发现 模型和人体样本。首先，我们将比较表达99的小鼠模型的脂肪组学特征 CGG重复和FMRPolyG蛋白在小鼠模型中表达扩大的重复序列，而不是 表达FMRPolyG蛋白。此外，我们还将测试FXTAS对果蝇致病作用的改善。 一种靶向β-葡萄糖脑苷酸酶的药物，该酶是我们已发现的鞘糖脂途径中的关键酶 能够调节rCGG重复毒性。我们还将使用其他方法调查FXTAS患者的情况 在纵向研究队列中收集的死后脑样本和血浆样本 FXTAS发病机制。我们提出的研究FXTAS代谢变化的工作将有助于 生物标志物的识别以及对疾病发病机制的理解

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder that affects carriers of premutation alleles (55–200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene. Common features of FXTAS include progressive intention tremor, gait ataxia, Parkinsonism, and cognitive decline. The neuropathological hallmarks of FXTAS include ubiquitin-positive intranuclear inclusions throughout the brain and marked dropout of Purkinje neurons in the cerebellum. Currently, data support two non-mutually exclusive molecular pathogenesis mechanisms for FXTAS: 1) RNA gain-of-function, in which rCGG repeat- binding proteins (RBPs) become functionally limited through sequestration by lengthy rCGG repeats, and 2) Repeat-associated non-AUG (RAN) translation, whereby translation through the CGG (or antisense CCG) repeats leads to the production of toxic homo-polypeptides, such as FMRpolyG, which in turn interfere with a variety of cellular functions. Multiple mouse models have been developed to study these mechanisms. Much remains unknown regarding the metabolic alterations associated with FXTAS, especially in the brain, and the most affected region, the cerebellum. Our previous work identified the metabolic alterations associated with FXTAS pathogenesis using our FXTAS mouse model that expresses 90 CGG repeats in cerebellar Purkinje neurons and exhibits the key phenotypic features of FXTAS. By combining global metabolic profiling with a Drosophila genetic screen, we have found that the sphingolipid metabolic pathway can modulate rCGG repeat toxicity. A preliminary study of 5 FXTAS postmortem brains compared to age-matched controls also identified alterations in the sphingolipid pathway. Untargeted metabolomic analysis of plasma samples from men with symptoms of FXTAS identified significant alterations in the sphingolipid pathway compared to noncarrier men. In the proposed study, we will expand on these findings using additional FXTAS mouse models, Drosophila models, and human samples. First, we will compare the lipidomic profile of a mouse model that expresses 99 CGG repeats and the FMRpolyG protein to a mouse model that expresses the expanded repeat without expressing the FMRpolyG protein. In addition, we will test for amelioration of FXTAS pathogenesis in flies with a drug that targets β-glucocerebrosidase (GBA), a key enzyme in the sphingolipid pathway that we have found is able to modulate rCGG repeat toxicity. We will also investigate the profile in FXTAS patients using additional post mortem brain samples and plasma samples that have been collected on a longitudinally-studied cohort for FXTAS pathogenesis. Our proposed work investigating the metabolic changes in FXTAS will aid in the identification of biomarkers as well as in understanding the pathogenesis of disease