PDF(Pubmed)
Abstract：
Introduction: Huntington\'s disease (HD) remains an incurable and fatal neurodegenerative disease long after CAG-expansion mutation in the huntingtin gene (HTT) was identified as the cause. The underlying pathological mechanism, whether HTT loss of function or gain of toxicity results from mutation, remains a matter of debate. Methods: In this study, we genetically modulated wild-type or mutant HTT expression levels in isogenic human embryonic stem cells to systematically investigate their contribution to HD-specific phenotypes. Results: Using highly reproducible and quantifiable in vitro micropattern-based assays, we observed comparable phenotypes with HD mutation and HTT depletion. However, halving endogenous wild-type HTT levels did not strongly recapitulate the HD phenotypes, arguing against a classical loss of function mechanism. Remarkably, expression of CAG-expanded HTT in non-HD cells induced HD like phenotypes akin to HTT depletion. Discussion: By corollary, these results indicate a dominant negative effect of mutated HTT on its wild-type counterpart. Complementation with additional copies of wild-type HTT ameliorated the HD-associated phenotypes, strongly supporting a classical dominant negative mechanism. Understanding the molecular basis of this dominant negative effect will guide the development of efficient clinical strategies to counteract the deleterious impact of mutant HTT on the wild-type HTT function.
摘要：
简介：亨廷顿病（HD）仍然是一种无法治愈和致命的神经退行性疾病，在亨廷顿基因（HTT）的CAG扩增突变被确定为原因后很久。潜在的病理机制，HTT功能丧失或毒性增加是否由突变引起，仍然是一个辩论的问题。方法:在本研究中,我们对等基因人类胚胎干细胞中野生型或突变型HTT的表达水平进行了基因调控,以系统地研究它们对HD特异性表型的影响.结果：使用高度可重复和可量化的体外微模式为基础的测定，我们观察到具有HD突变和HTT耗竭的可比较表型。然而,将内源性野生型HTT水平减半并不能强烈概括HD表型，反对经典的功能丧失机制。值得注意的是,CAG扩增的HTT在非HD细胞中的表达诱导类似于HTT耗竭的HD样表型。讨论：根据推论，这些结果表明突变的HTT对其野生型对应物有明显的负作用.补充野生型HTT的额外拷贝改善了HD相关表型，强烈支持经典的显性消极机制。了解这种显性负面影响的分子基础将指导有效临床策略的开发，以抵消突变HTT对野生型HTT功能的有害影响。
