From the Departments of Molecular Medicine and.
the Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, California 90095.
J Biol Chem. 2019 Feb 8;294(6):1846-1859. doi: 10.1074/jbc.RA118.006515. Epub 2018 Dec 14.
Friedreich ataxia (FRDA) is a neurodegenerative disorder caused by transcriptional silencing of the frataxin () gene, resulting in loss of the essential mitochondrial protein frataxin. Based on the knowledge that a GAA·TTC repeat expansion in the first intron of induces heterochromatin, we previously showed that 2-aminobenzamide-type histone deacetylase inhibitors (HDACi) increase mRNA levels in induced pluripotent stem cell (iPSC)-derived FRDA neurons and in circulating lymphocytes from patients after HDACi oral administration. How the reduced expression of frataxin leads to neurological and other systemic symptoms in FRDA patients remains unclear. Similar to other triplet-repeat disorders, it is unknown why FRDA affects only specific cell types, primarily the large sensory neurons of the dorsal root ganglia and cardiomyocytes. The combination of iPSC technology and genome-editing techniques offers the unique possibility to address these questions in a relevant cell model of FRDA, obviating confounding effects of variable genetic backgrounds. Here, using "scarless" gene-editing methods, we created isogenic iPSC lines that differ only in the length of the GAA·TTC repeats. To uncover the gene expression signatures due to the GAA·TTC repeat expansion in FRDA neuronal cells and the effect of HDACi on these changes, we performed RNA-seq-based transcriptomic analysis of iPSC-derived central nervous system (CNS) and isogenic sensory neurons. We found that cellular pathways related to neuronal function, regulation of transcription, extracellular matrix organization, and apoptosis are affected by frataxin loss in neurons of the CNS and peripheral nervous system and that these changes are partially restored by HDACi treatment.
弗里德赖希共济失调(FRDA)是一种神经退行性疾病,由 frataxin()基因转录沉默引起,导致必需的线粒体蛋白 frataxin 缺失。基于在第一个内含子中的 GAA·TTC 重复扩展导致异染色质的知识,我们之前表明 2-氨基苯甲酰胺型组蛋白去乙酰化酶抑制剂(HDACi)在诱导多能干细胞(iPSC)衍生的 FRDA 神经元和患者循环淋巴细胞中增加 mRNA 水平在 HDACi 口服给药后。FRDA 患者中 frataxin 表达减少如何导致神经和其他全身症状仍不清楚。与其他三核苷酸重复疾病类似,尚不清楚为什么 FRDA 仅影响特定的细胞类型,主要是背根神经节的大型感觉神经元和心肌细胞。iPSC 技术和基因组编辑技术的结合为在 FRDA 的相关细胞模型中解决这些问题提供了独特的可能性,避免了可变遗传背景的混杂影响。在这里,我们使用“无疤痕”基因编辑方法,创建了仅在 GAA·TTC 重复长度上不同的同基因 iPSC 系。为了揭示 FRDA 神经元细胞中 GAA·TTC 重复扩展引起的基因表达特征以及 HDACi 对这些变化的影响,我们对 iPSC 衍生的中枢神经系统(CNS)和同基因感觉神经元进行了基于 RNA-seq 的转录组分析。我们发现,与神经元功能、转录调节、细胞外基质组织和细胞凋亡相关的细胞途径在中枢神经系统和周围神经系统的神经元中受到 frataxin 缺失的影响,并且这些变化部分被 HDACi 治疗恢复。