Li Jixue, Rozwadowska Natalia, Clark Amanda, Fil Daniel, Napierala Jill S, Napierala Marek
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL 35294, USA.
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 1825 University Blvd., Birmingham, AL 35294, USA.
Stem Cell Res. 2019 Oct;40:101529. doi: 10.1016/j.scr.2019.101529. Epub 2019 Aug 7.
Friedreich's ataxia is caused by large homozygous, intronic expansions of GAA repeats in the frataxin (FXN) gene, resulting in severe downregulation of its expression. Pathogenic repeats are located in intron one, hence patients express unaffected FXN protein, albeit in low quantities. Although FRDA symptoms typically afflict the nervous system, hypertrophic cardiomyopathy is the predominant cause of death. Our studies were conducted using cardiomyocytes differentiated from induced pluripotent stem cells derived from control individuals, FRDA patients, and isogenic cells corrected by zinc finger nucleases-mediated excision of pathogenic expanded GAA repeats. This correction of the FXN gene removed the primary trigger of the transcription defect, upregulated frataxin expression, reduced pathological lipid accumulation observed in patient cardiomyocytes, and reversed gene expression signatures of FRDA cardiomyocytes. Transcriptome analyses revealed hypertrophy-specific expression signatures unique to FRDA cardiomyocytes, and emphasized similarities between unaffected and ZFN-corrected FRDA cardiomyocytes. Thus, the iPSC-derived FRDA cardiomyocytes exhibit various molecular defects characteristic for cellular models of cardiomyopathy that can be corrected by genome editing of the expanded GAA repeats. These results underscore the utility of genome editing in generating isogenic cellular models of FRDA and the potential of this approach as a future therapy for this disease.
弗里德赖希共济失调是由frataxin（FXN）基因中GAA重复序列的大片段纯合内含子扩增引起的，导致其表达严重下调。致病重复序列位于第一内含子中，因此患者表达的FXN蛋白未受影响，尽管数量很少。虽然弗里德赖希共济失调（FRDA）症状通常累及神经系统，但肥厚型心肌病是主要的死亡原因。我们的研究使用了从对照个体、FRDA患者以及通过锌指核酸酶介导切除致病的扩增GAA重复序列而校正的同基因细胞来源的诱导多能干细胞分化而来的心肌细胞。FXN基因的这种校正消除了转录缺陷的主要触发因素，上调了frataxin的表达，减少了在患者心肌细胞中观察到的病理性脂质积累，并逆转了FRDA心肌细胞的基因表达特征。转录组分析揭示了FRDA心肌细胞特有的肥厚特异性表达特征，并强调了未受影响的和经锌指核酸酶校正的FRDA心肌细胞之间的相似性。因此，诱导多能干细胞来源的FRDA心肌细胞表现出心肌病细胞模型特有的各种分子缺陷，这些缺陷可通过对扩增的GAA重复序列进行基因组编辑来校正。这些结果强调了基因组编辑在生成FRDA同基因细胞模型中的实用性以及这种方法作为该疾病未来治疗手段的潜力。
