FXTAS: Mechanisms and Modifiers

FXTAS：机制和修改器

基本信息

批准号：
10669057
负责人：
David Loren Nelson
金额：
$ 58.38万
依托单位：
BAYLOR COLLEGE OF MEDICINE
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-25 至 2025-06-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10669057
关键词：
Adult Affect Age Age of Onset Alleles Animal Model Architecture Behavioral Biological Assay Biological Models Brain CGG repeat Candidate Disease Gene Cell model Cell physiology Cerebellum Collection Data Disease Dropout Exhibits FMR1 FXTAS Fragile X Premutation Fragile X Syndrome Gait Ataxia Genes Genetic Genetic Polymorphism Genetic Screening Genome Haplotypes Human Genetics Impaired cognition Individual Intention Tremor Knockout Mice Length Link Mammalian Cell Mammals Mediating Medicine Messenger RNA Michigan Modeling Molecular Mus Mutation Neurodegenerative Disorders Neurons Nuclear Inclusion PURA gene Parkinsonian Disorders Pathogenesis Pathogenicity Patients Penetrance Production RNA RNA interference screen RNA-Binding Proteins RNASE3L gene Reporter Role Sequence Analysis Symptoms System Targeted Resequencing Toxic effect Transgenic Organisms Translations Triplet Multiple Birth Ubiquitin Variant Woman Work age related college fly gain of function genetic variant hnRNP A2 human model improved male model organism mouse model mutant mutation carrier nervous system disorder neuropathology primary ovarian insufficiency protein TDP-43 protein expression therapeutic candidate therapeutic target whole genome

项目摘要

SUMMARY Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder that affects individuals with premutation alleles (55–~200 CGG repeats) in fragile X mental retardation 1 (FMR1). Common features of FXTAS include progressive intention tremor, gait ataxia, Parkinsonism, and cognitive decline. Penetrance is age-dependent and reaches ~75% in male carriers by age 80. Up to ~15% of women with premutations also show symptoms of FXTAS. The neuropathological hallmarks of FXTAS include ubiquitin- positive intranuclear inclusions throughout the brain and marked dropout of Purkinje neurons in the cerebellum. At the molecular level, FMR1 premutation alleles exhibit a 2 to 8-fold increase in FMR1 mRNA and expression of mutant mRNAs containing long (~100) CGG triplets has been shown to be toxic in cell and animal models. Current data support two non-mutually exclusive molecular pathogenesis mechanisms for FXTAS: 1) RNA gain- of-function, in which the expression of expanded CGGs in RNA (rCGG) interferes with a subset of RNA-binding proteins (RBPs), functionally limiting their availability through sequestration, and 2) Repeat-associated non-AUG (RAN) translation, whereby translation through the rCGG (and/or antisense rCCG) repeats leads to the production of toxic homo-polypeptides, the most abundant of which is FMRpolyGlycine (FMRpolyG), that in turn interfere with cellular functions. Multiple mouse models have been developed and used by us and others to study these mechanisms. Previous work by the Nelson, Todd, Allen and Jin groups using model organisms (flies, mice) and cell models has identified several RBPs affected by expression of rCGGs. Among these are Pur α, hnRNP A2/B1, DROSHA/DGCR8, and TDP43. Increasing expression of these proteins can modulate rCGG-mediated toxicity in model systems, supporting the RNA-mediated sequestration model of FXTAS. In addition, RAN translation products are found in patient inclusions and mouse models and appear to also confer toxicity in numerous studies. In studies to determine the contributions of both the RAN translation and RBP sequestration mechanisms to FXTAS pathogenesis, we have generated transgenic lines of mice that express hnRNP A2/B1 and suppression of rCGG repeat-mediated toxicity without alteration of FMRpolyG positive inclusions. Parallel efforts at the Emory Fragile X Center used whole genome sequence (WGS) analysis of premutation carriers with early or late onset of FXTAS, combined with fly genetic screens to identify additional genetic modifiers that influence age of onset of FXTAS. Understanding the role of variation in these genes could suggest candidate therapeutic targets. In this application, we propose to confirm and extend identification of genetic modifiers through sequence analysis and analyze potential modifiers of FXTAS identified at Emory using human genetics and model system studies at Baylor, Emory and Michigan using additional fly, cell and mouse models. In coordination with Projects 1 and 3, we expect to improve understanding of mechanisms that lead to FXTAS and other Fragile X-associated Disorders, such as Fragile X associated Primary Ovarian Insufficiency (FXPOI).

概括脆性 X 相关震颤/共济失调综合征 (FXTAS) 是一种成人发病的神经退行性疾病，影响具有脆性 X 智力低下 1 (FMR1) 的前突变等位基因（55-~200 个 CGG 重复）的个体。 FXTAS 的特征包括进行性意向性震颤、步态共济失调、帕金森症和认知能力下降。外显率与年龄有关，到 80 岁时，男性携带者的外显率达到约 75%。女性携带者的外显率高达约 15% FXTAS 的神经病理学特征包括泛素化。整个大脑出现阳性核内包涵体，小脑中浦肯野神经元明显缺失。在分子水平上，FMR1 前突变等位基因的 FMR1 mRNA 和表达量增加了 2 至 8 倍含有长 (~100) CGG 三联体的突变 mRNA 已被证明在细胞和动物模型中具有毒性。目前的数据支持 FXTAS 的两种非相互排斥的分子发病机制：1) RNA 增益- 功能丧失，其中 RNA 中扩展的 CGG 的表达 (rCGG) 干扰 RNA 结合的子集蛋白质 (RBP)，通过隔离在功能上限制其可用性，以及 2) 重复相关的非 AUG （RAN）翻译，通过 rCGG（和/或反义 rCCG）重复的翻译导致产生有毒的同聚肽，其中最丰富的是 FMRpolyGlycine (FMRpolyG)，而我们和其他人已经开发并使用了多种小鼠模型来进行研究。这些机制是 Nelson、Todd、Allen 和 Jin 小组之前使用模型生物（果蝇、小鼠）进行的研究。细胞模型已鉴定出几种受 rCGG 表达影响的 RBP，其中包括 Pur α、hnRNP。 A2/B1、DROSHA/DGCR8 和 TDP43 的表达增加可以调节 rCGG 介导的。模型系统中的毒性，支持 FXTAS 的 RNA 介导的隔离模型此外，RAN。翻译产物存在于患者内含物和小鼠模型中，并且似乎也赋予毒性进行了大量研究以确定 RAN 翻译和 RBP 隔离的贡献。 FXTAS 发病机制，我们已经产生了表达 hnRNP A2/B1 的转基因小鼠品系并抑制 rCGG 重复介导的毒性，而不改变 FMRpolyG 阳性平行包含物。埃默里脆弱努力 X 中心使用了前突变携带者的全基因组序列 (WGS) 分析 FXTAS 的早期或晚期发作，结合果蝇遗传筛选，以确定额外的遗传修饰因子了解这些基因变异的作用可以建议候选基因。在此应用中，我们建议确认并扩展遗传修饰剂的识别。通过序列分析并使用人类遗传学分析埃默里大学鉴定的 FXTAS 的潜在修饰因子贝勒、埃默里和密歇根大学使用额外的果蝇、细胞和小鼠模型进行模型系统研究。通过与项目 1 和 3 的协调，我们希望加深对导致 FXTAS 和其他脆性 X 相关疾病，例如脆性 X 相关原发性卵巢功能不全 (FXPOI)。