The Friedreich ataxia GAA repeat expansion mutation induces comparable epigenetic changes in human and transgenic mouse brain and heart tissues
The Friedreich ataxia GAA repeat expansion mutation induces comparable epigenetic changes in human and transgenic mouse brain and heart tissues
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DOI：
10.1093/hmg/ddm346
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发表时间：
2008-03-01
影响因子：
3.5
通讯作者：
Pook, Mark
中科院分区：
文献类型：
--
作者：
Al-Mahdawi, Sahar;Pinto, Ricardo Mouro;Pook, Mark
弗里德赖希共济失调（FRDA）是由FXN基因内含子1内纯合子GAA重复扩增突变引起的，导致frataxin蛋白表达减少。有证据表明，该突变可能诱导表观遗传变化和异染色质形成，从而阻碍基因转录。特别是，使用FRDA患者血液和淋巴母细胞细胞系的研究发现，GAA重复序列上游特定CpG位点的DNA甲基化增加，GAA重复序列侧翼区域的组蛋白修饰增加。在本报告中，我们发现这种表观遗传变化也存在于FRDA患者的大脑、小脑和心脏组织中，这些组织是该疾病的主要受影响系统。对FXN侧翼GAA区域的亚硫酸酯序列分析揭示了FRDA DNA甲基化谱的变化，上游CpG位点持续高甲基化，下游CpG位点持续低甲基化。我们还在FXN启动子内的三个特定CpG位点和外显子1内的一个CpG位点发现了差异的DNA甲基化。此外，我们通过染色质免疫沉淀分析表明，FRDA脑组织中组蛋白H3K9乙酰化总体降低，H3K9甲基化增加。我们对含有GAA重复扩增的FRDA YAC转基因小鼠的大脑、小脑和心脏组织的进一步研究显示，与在FRDA患者组织中检测到的表观遗传变化相似。因此，我们开发了一种小鼠模型，该模型将为未来针对FXN基因的表观遗传修饰来增加fraataxin表达的治疗研究提供有价值的资源。
Friedreich ataxia (FRDA) is caused by a homozygous GAA repeat expansion mutation within intron 1 of the FXN gene, leading to reduced expression of frataxin protein. Evidence suggests that the mutation may induce epigenetic changes and heterochromatin formation, thereby impeding gene transcription. In particular, studies using FRDA patient blood and lymphoblastoid cell lines have detected increased DNA methylation of specific CpG sites upstream of the GAA repeat and histone modifications in regions flanking the GAA repeat. In this report we show that such epigenetic changes are also present in FRDA patient brain, cerebellum and heart tissues, the primary affected systems of the disorder. Bisulfite sequence analysis of the FXN flanking GAA regions reveals a shift in the FRDA DNA methylation profile, with upstream CpG sites becoming consistently hypermethylated and downstream CpG sites becoming consistently hypomethylated. We also identify differential DNA methylation at three specific CpG sites within the FXN promoter and one CpG site within exon 1. Furthermore, we show by chromatin immunoprecipitation analysis that there is overall decreased histone H3K9 acetylation together with increased H3K9 methylation of FRDA brain tissue. Further studies of brain, cerebellum and heart tissues from our GAA repeat expansion-containing FRDA YAC transgenic mice reveal comparable epigenetic changes to those detected in FRDA patient tissue. We have thus developed a mouse model that will be a valuable resource for future therapeutic studies targeting epigenetic modifications of the FXN gene to increase frataxin expression.