Induction of inclusion formation and disruption of lamin A/C structure by premutation CGG-repeat RNA in human cultured neural cells
Induction of inclusion formation and disruption of lamin A/C structure by premutation CGG-repeat RNA in human cultured neural cells
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DOI：
10.1093/hmg/ddi394
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发表时间：
2005-12-01
影响因子：
3.5
通讯作者：
Hagerman, PJ
中科院分区：
文献类型：
--
作者：
Arocena, DG;Iwahashi, CK;Hagerman, PJ
脆性X相关震颤/共济失调综合征(FXTAS)是一种神经退行性疾病，影响一些携带脆性X智力低下1(FMR1)基因突变前等位基因(55-200个CGG重复)的成年人。FXTAS被认为是由扩展的CGG-Repeat FMR1 mRNA的有毒“功能获得”引起的，这种mRNA存在于与这种疾病相关的神经元和星形细胞核内包裹体中。利用带有FMR1 5‘非翻译区的报告结构，我们证明了在原代神经前体细胞和已建立的神经细胞系中都可以形成核内包涵体。与身体组织中发现的包涵体一样，由扩展的CGG重复序列引起的包涵体是αB晶体蛋白阳性；然而，培养中的包涵体与泛素无关，这表明泛素化蛋白的掺入是疾病过程中的较晚事件。泛素化蛋白质的缺乏也反对一种模型，在该模型中，包涵体的形成是由于蛋白酶体降解机制的故障。扩展的CGG重复序列的存在，如RNA，导致细胞活力降低，以及核内层蛋白A/C的正常结构被破坏。这一观察结果以及FXTAS患者的包涵体和细胞培养中的包涵体均存在层蛋白A/C的发现，提示层蛋白A/C失衡可能是FXTAS发病机制的一个组成部分；尤其是与FXTAS相关的Charcot-Marie-Tooth类型的神经病可能代表一种功能性椎板病。
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder that affects some adult carriers of pre-mutation alleles (55-200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene. FXTAS is thought to be caused by a toxic 'gain-of-function' of the expanded CGG-repeat FMR1 mRNA, which is found in the neuronal and astrocytic intranuclear inclusions associated with the disorder. Using a reporter construct with a FMR1 5' untranslated region harboring an expanded (premutation) CGG repeat, we have demonstrated that intranuclear inclusions can be formed in both primary neural progenitor cells and established neural cell lines. As with the inclusions found in post-mortem tissue, the inclusions induced by the expanded CGG repeat are alpha B-crystallin-positive; however, inclusions in culture are not associated with ubiquitin, indicating that incorporation of ubiquitinated proteins is a later event in the disease process. The absence of ubiquitinated proteins also argues against a model in which inclusion formation is due to a failure of the proteasomal degradative machinery. The presence of the expanded CGG repeat, as RNA, results in reduced cell viability as well as the disruption of the normal architecture of lamin A/C within the nucleus. This last observation, and the findings that lamin A/C is present in both the inclusions of FXTAS patients and the inclusions in cell culture, suggests that lamin A/C dysregulation may be a component of the pathogenesis of FXTAS; in particular, the Charcot-Marie-Tooth-type neuropathy associated with FXTAS may represent a functional laminopathy.