The toxicity of the RNA CGG repeats in FXTAS

FXTAS 中 RNA CGG 重复序列的毒性

• 批准号: 8536413
• 负责人: LUBOV T TIMCHENKO
• 金额: $ 9.11万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8536413
• 关键词: 5' Untranslated Regions; Affect; Age; Age-Months; Agreement; Animal Model; Ataxia; Atrophic; Autopsy; Basic Science; Binding; Brain Pathology; CGG repeat; Cell Line; Cell model; Cerebellum; Cognitive; Cytoplasmic Granules; Data; Defect; Disease; Early identification; Event; FMR1 Gene; FXTAS; Fragile X Syndrome; Genes; Genetic Transcription; Genetic Translation; Intellectual functioning disability; Kinetics; Knock-in Mouse; Length; Mediating; Messenger RNA; Modeling; Molecular; Molecular Abnormality; Mus; Mutation; Myotonic Dystrophy; Names; Nerve Degeneration; Neurodegenerative Disorders; Neurons; Nuclear; Pathogenesis; Pathologic; Pathology; Proteins; Purkinje Cells; RNA; RNA-Binding Proteins; Recruitment Activity; Role; Staging; Stress; System; Testing; Tetanus Helper Peptide; Toxic effect; Transgenic Organisms; Tremor; Trinucleotide Repeats; Ubiquitin; Ubiquitination; Work; base; biological adaptation to stress; cerebral atrophy; mouse model; multicatalytic endopeptidase complex; nervous system disorder; older patient; progressive neurodegeneration; protein aggregation; protein complex; therapeutic development; therapy development

DESCRIPTION (provided by applicant): Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is a progressive neurodegenerative disease characterized by tremor with ataxia, brain atrophy and cognitive defects. FXTAS is caused by CGG expansions, varying in the length from ~55 to 200 repeats (CGG55-200), in the 5' UTR of the FMR1 gene. The CGG expansions of more than 200 repeats in the same gene cause the Fragile X Syndrome (FXS), an intellectual disability, distinct from FXTAS. Long CGG expansions silence the transcription of the FMR1 gene; while short expansions elevate the transcription of the FMR1. Numerous models show that the FMR1 mRNA with CGG55-200 repeats or RNA CGG55-200 repeats outside of the FMR1 mRNA cause neurodegeneration. The main pathologic feature of FXTAS is the formation of the ubiquitin (Ub)-positive inclusions that contain the proteasome, RNA-binding proteins and proteins associated with stress response. The role of these inclusions in FXTAS pathogenesis is not well understood. We have examined the activity of the ubiquitin-proteasome system (UPS) in the FXTAS mouse model, rCGG ki mice, and found accumulation of the Ub-protein conjugates in the cerebellum in these mice. We also observed that rCGG repeats increase the levels of un-phosphorylated at S302 form of RNA-binding protein, CUGBP1, named CUGBP1REP. One of the known functions of CUGBP1REP is inhibition of translation of mRNAs by recruiting them into Stress Granules. We generated a mouse model, CUGBP1-S302A knock in mice, which express only CUGBP1REP. We found that S302A ki mice develop brain atrophy at 6-months of age with the loss of the Purkinje cells. The brain atrophy in the S302A ki mice is accompanied by the accumulation of the Ub-proteins in cerebellum showing that CUGBP1REP inhibits the UPS. Since CUGBP1REP is increased in the cerebellum of rCGG ki mice, we suggest that the rCGG repeats inhibit the UPS, at least in part, through the elevation of CUGBP1REP. Based on these data, we propose a hypothesis that rCGG repeats trigger FXTAS pathology by the increase of CUGBP1REP at early stages and that this increase leads to inhibition of the UPS at late stages of the disease contributing to brain pathology. This hypothesis will be tested in the tet-regulated cell lines expressing rCGG repeats (Aim 1) and in rCGG ki, rCGG transgenic and in S302A ki mice (Aim 2). We will determine if the increase of CUGBP1REP precedes the inhibition of the UPS and formation of the Ub- positive inclusions. The identification of the early toxic events which trigger progression of FXTAS will provide a basis for the development of the therapeutic approaches for FXTAS.

描述(申请人提供)：脆性X相关震颤/共济失调综合征(FXTAS)是一种进行性神经退行性疾病，以震颤伴共济失调、脑萎缩和认知缺陷为特征。FXTAS是由FMR1基因5‘非编码区的CGG扩增引起的，其长度从~55到200个重复(CGG55-200)不等。同一基因中超过200个重复的CGG扩展导致了脆性X综合征(FXS)，这是一种与FXTAS不同的智力残疾。长CGG扩增抑制FMR1基因的转录，而短扩增则上调FMR1的转录。大量模型表明，FMR1基因外含有CGG55-200重复序列或RNA CGG55-200重复序列的FMR1基因可导致神经退行性变。FXTAS的主要病理特征是形成泛素(Ub)阳性包涵体，其中包含蛋白酶体、RNA结合蛋白和与应激反应相关的蛋白。这些包涵体在FXTAS发病机制中的作用尚不清楚。我们检测了FXTAS小鼠模型rCGG Ki小鼠的泛素-蛋白酶体系统(UPS)的活性，发现Ub-蛋白结合物在这些小鼠的小脑中积聚。我们还观察到，rCGG重复增加了RNA结合蛋白CUGBP1的S302非磷酸化水平，称为CUGBP1REP。已知的CUGBP1REP功能之一是通过将mRNAs重新招募到应激颗粒来抑制mRNAs的翻译。我们建立了一种仅表达CUGBP1REP的小鼠模型CUGBP1-S302A敲击小鼠。我们发现S302AKI小鼠在6个月龄时出现脑萎缩，浦肯野细胞丢失。S302AKI小鼠脑萎缩伴有小脑Ub蛋白积聚，表明CUGBP1REP对UPS有抑制作用。由于rCGG Ki小鼠小脑中的CUGBP1REP增加，我们认为rCGG重复序列至少部分地通过提高CUGBP1REP来抑制UPS。基于这些数据，我们提出了一种假说，即rCGG重复触发FXTAS病理在早期通过CUGBP1REP的增加，这种增加导致在疾病的晚期抑制UPS，从而促进脑病理。这一假设将在表达rCGG重复序列的tet调控的细胞系(Aim 1)、rCGG Ki、rCGG转基因和S302a Ki小鼠中得到验证(Aim 2)。我们将确定CUGBP1REP的增加是否先于UPS的抑制和Ub阳性夹杂物的形成。早期引发FXTAS进展的毒性事件的识别将为FXTAS治疗方法的发展提供基础。