FXN Promoter Silencing in the Humanized Mouse Model of Friedreich Ataxia.
FXN Promoter Silencing in the Humanized Mouse Model of Friedreich Ataxia.
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DOI：
10.1371/journal.pone.0138437
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Bidichandani SI
中科院分区：
文献类型：
--
作者：
Chutake YK;Costello WN;Lam CC;Parikh AC;Hughes TT;Michalopulos MG;Pook MA;Bidichandani SI
弗里德赖希共济失调是由FXN基因内含子1中的扩展的GAA三联体重复序列引起的，其导致FXN启动子的表观遗传沉默。这种沉默机制见于患者来源的淋巴母细胞样细胞，但它是否是一种影响多种细胞类型和组织的普遍现象仍不清楚。弗里德赖希共济失调（YG8sR）的人源化小鼠模型携带在内含子1中具有扩展的GAA三联体重复的人FXN基因的单个转基因插入物，当与缺乏扩展的重复（Y47R）的同基因转基因小鼠相比时，其缺乏FXN转录物。我们发现，在YG8sR中，FXN转录物的缺陷延伸到扩展的GAA三联体重复序列的上游和下游，表明转录起始缺陷。在所有测试的组织中均观察到这种缺陷模式，无论它们是否已知在疾病发病机制中受到影响或幸免，在神经元和非神经元组织中，以及在培养的原代成纤维细胞中。FXN启动子功能通过成纤维细胞中新合成的转录物的代谢标记来直接测量，这揭示了与Y47R小鼠相比，YG8sR小鼠在转录起始方面显著缺陷。转录起始缺陷导致Friedreich共济失调的人源化小鼠模型中FXN转录缺陷，类似于患者来源的细胞，并且Friedreich共济失调中启动子沉默的潜在机制在多种细胞类型和组织中广泛存在。
Friedreich ataxia is caused by an expanded GAA triplet-repeat sequence in intron 1 of the FXN gene that results in epigenetic silencing of the FXN promoter. This silencing mechanism is seen in patient-derived lymphoblastoid cells but it remains unknown if it is a widespread phenomenon affecting multiple cell types and tissues. The humanized mouse model of Friedreich ataxia (YG8sR), which carries a single transgenic insert of the human FXN gene with an expanded GAA triplet-repeat in intron 1, is deficient for FXN transcript when compared to an isogenic transgenic mouse lacking the expanded repeat (Y47R). We found that in YG8sR the deficiency of FXN transcript extended both upstream and downstream of the expanded GAA triplet-repeat, suggestive of deficient transcriptional initiation. This pattern of deficiency was seen in all tissues tested, irrespective of whether they are known to be affected or spared in disease pathogenesis, in both neuronal and non-neuronal tissues, and in cultured primary fibroblasts. FXN promoter function was directly measured via metabolic labeling of newly synthesized transcripts in fibroblasts, which revealed that the YG8sR mouse was significantly deficient in transcriptional initiation compared to the Y47R mouse. Deficient transcriptional initiation accounts for FXN transcriptional deficiency in the humanized mouse model of Friedreich ataxia, similar to patient-derived cells, and the mechanism underlying promoter silencing in Friedreich ataxia is widespread across multiple cell types and tissues.