GAA repeats induced epigenetic silencing in Friedreich's ataxia.

GAA 重复在 Friedreich 共济失调中诱导表观遗传沉默。

• 批准号: 8420615
• 负责人: Marek Napierala
• 金额: $ 34.56万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-30 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8420615
• 关键词: Address; Adopted; Affect; Ataxia; Binding Sites; Boxing; Cell Line; Cell model; Cells; ChIP-seq; Chromatin; Code; Critical Pathways; DNA; DNA Sequence; DNA Structure; Data; Development; Disease; Enhancers; Environment; Epigenetic Process; Event; Friedreich Ataxia; Gene Silencing; Genes; Genetic Transcription; Genome; Genomics; Heterochromatin; Human; Hybrids; Inherited; Introns; Iron; Length; Link; Location; Mediating; Modeling; Modification; Molecular; Molecular Conformation; Mus; Mutagenesis; Neurodegenerative Disorders; Neurons; Pathogenesis; Pathway interactions; Patients; Physiological; Proto-Oncogene Proteins c-myc; RNA; Regulation; Role; Somatic Cell; Structure; Sulfur; Testing; Work; Zinc Fingers; base; chromatin modification; frataxin; gene repression; histone acetyltransferase; induced pluripotent stem cell; mutant; nervous system disorder; novel; novel therapeutic intervention; nuclease; overexpression; promoter; research study; tool

DESCRIPTION (provided by applicant): Friedreich's ataxia (FRDA) is caused by the epigenetic silencing of the FXN gene resulting in the deficiency of frataxin, a critical component of the iron-sulfur clusters synthesis pathway. Transcriptional repression of FXN results from large expansions of the intronic GAA repeats and can be partially reversed by modulating the epigenetic environment. The exact trigger of transcriptional inhibition and the mechanisms of epigenetic changes that occur in Friedreich's ataxia remain unknown. The aim of this application is to define mechanisms of epigenetic silencing induced by expanded GAA repeats, which could be used as potential targets for therapy of Friedreich's ataxia. We will address three fundamental aspects of the molecular pathogenesis responsible for Friedreich's ataxia: 1) What triggers the epigenetic changes in the mutant FXN locus? 2) What is the primary chromatin modification pathway involved in silencing? 3) What factors controlling the expression of the WT FXN gene are affected by the GAA expansion in FRDA? In order to answer these questions and to define the mechanism of the epigenetic silencing in the disease-relevant cellular models we generated FRDA and control induced pluripotent stem cell lines (iPSCs) and differentiated them to neuronal cells. We will use these novel FRDA models to test our hypothesis that the expansion of GAA repeats initiates a cascade of events that begins with DNA conformational changes within the repeats, followed by epigenetic changes in the sequences flanking the GAAs, which consequently leads to deregulation of FXN expression. First, we will identify mechanisms controlling expression of the FXN gene in physiological conditions. Based on our preliminary findings, we will define the roles of GCN5 histone acetyltransferase and c-MYC transcription factor in regulating FXN expression. Next, we will identify the trigger for GAA repeats-induced transcription by defining the conformation of the expanded GAA repeats in their natural context of the FXN gene. We will also determine a link between formation of the non canonical conformations, extent of epigenetic silencing and length of the GAA repeats. Furthermore, we will employ somatic cell reprogramming to iPSCs in the presence of various epigenetic modulators to discern the contributions of chromatin modification pathways to the GAA repeats-mediated silencing. Collectively, these experiments will define the epigenetic control of FXN expression, as well as the molecular mechanisms leading to its deregulation and silencing that occur in Friedreich's ataxia. Our combined approach of genome editing and pharmacological modulation of the epigenome during somatic cell reprogramming will fuel development of new therapeutic approaches for FRDA. PUBLIC HEALTH RELEVANCE: Friedreich's ataxia, the most common inherited ataxia, is a severe neurological disease caused by transcriptional silencing of the FXN gene. The proposed studies will identify the molecular mechanisms leading to the epigenetic silencing of this gene. This work will uncover new avenues for therapies of Friedreich's ataxia and other repeat expansion diseases.

描述（由申请人提供）：Friedreich的共济失调（FRDA）是由FXN基因的表观遗传沉默引起的，导致Frataxin的缺乏，Frataxin是铁硫簇合成途径的关键成分。 FXN对FXN的转录抑制作用是由内含子GAA重复序列的大量扩展而导致的，并且可以通过调节表观遗传环境来部分逆转。转录抑制的确切触发因素和弗里德里希共济失调中发生的表观遗传变化的机制尚不清楚。该应用的目的是定义扩展的GAA重复序列引起的表观遗传沉默的机制，这可以用作弗里德里希共济失调治疗的潜在靶标。我们将解决导致弗里德里希共济失调的分子发病机理的三个基本方面：1）是什么触发了突变体FXN基因座的表观遗传变化？ 2）沉默中涉及的主要染色质修饰途径是什么？ 3）哪些控制WT FXN基因表达的因素受FRDA中GAA扩展的影响？为了回答这些问题，并定义了与疾病相关的细胞模型中表观遗传沉默的机制，我们产生了FRDA并对照诱导的多能干细胞系（IPSC），并将它们区分开为神经元细胞。我们将使用这些新型的FRDA模型来测试我们的假设，即GAA重复的扩展会引发一系列事件，该事件始于重复序列内的DNA构象变化，然后在GAAS侧面的序列中的表观遗传变化，从而导致FXN表达放松调节。首先，我们将确定控制FXN基因在生理条件下表达的机制。根据我们的初步发现，我们将定义GCN5组蛋白乙酰转移酶和C-MYC转录因子在调节FXN表达中的作用。接下来，我们将通过在FXN基因的自然背景下定义扩展的GAA重复符构象来确定GAA重复诱导的转录的触发因素。我们还将确定非规范构象的形成，表观遗传沉默的程度和GAA重复的长度之间的联系。此外，我们将在存在各种表观遗传调节剂的情况下对IPSC采用体细胞重编程，以辨别染色质修饰途径对GAA重复介导的沉默的贡献。总的来说，这些实验将定义FXN表达的表观遗传控制，以及导致弗里德里希共济失调发生的导致其放松管制和沉默的分子机制。我们在体细胞重编程过程中对表观基因组的基因组编辑和药理学调节的结合方法将促进FRDA的新治疗方法的发展。 公共卫生相关性：最常见的共济失调Friedreich的共济失调是由FXN基因的转录沉默引起的严重神经系统疾病。拟议的研究将确定导致该基因表观遗传沉默的分子机制。这项工作将发现弗里德里希共济失调和其他重复扩张疾病的疗法的新途径。