Senataxin mutations in familial motor neuron disease (ALS4) and Ataxia (AOA2)

描述(申请人提供)：我们发现了一种少年型常染色体显性遗传性家族性肌萎缩侧索硬化症(ALS)的分子基础--Senataxin基因(SETX)突变。这种形式的ALS，被称为ALS4，本质上是一种纯运动系统疾病，其特征是四肢无力、严重的肌肉萎缩、锥体体征和缓慢的疾病进展。有趣的是，SETX的隐性突变会导致第二种疾病，一种被称为共济失调-动眼运动性失用症2型(AOA2)的共济失调。AOA2的发病率也很高，通常在10-22岁之间，发病后15-20年内丧失活动能力。综上所述，这些发现证明了SETX突变的基因型-表型相关性，并证实了Senataxin是一种重要的神经元蛋白。Senataxin是一种由2677个氨基酸组成的大型蛋白质，其确切功能在很大程度上尚不清楚。它在C末端含有一个保守的DNA/RNA解旋酶结构域，表明它在RNA加工中具有功能。酵母同源物Sen1p具有如此重要的RNA处理功能。在N端还有一个潜在的蛋白质-蛋白质相互作用结构域，这是由酵母中的研究支持的。我们的研究将集中在与ALS4和AOA2相关的Senataxin的突变形式上，并解决下列广泛目标：(1)我们将鉴定我们为ALS4制备的小鼠基因靶向和转基因(TG)模型，并测试它们是否会发展成神经病变，从而进一步详细研究神经元退变途径；(2)利用基因陷阱技术，我们将建立AOA2的小鼠基因敲除模型；以及(3)我们假设ALS4突变体Senataxin(L389S)可能会导致有毒的功能获得，例如异常的蛋白质与蛋白质的相互作用。为了验证这一点，我们进行了酵母双杂交(Y2H)筛选，筛选了人脑表达文库的wt和ALS4突变型N端Senataxin。我们确定了ALS4与KIF1B的特异性相互作用，并通过进一步的Y2H重新测试和哺乳动物的2-H实验进行了验证。我们将在ALS4中进一步研究这种相互作用及其潜在的致病效应。公共卫生相关性：从这项研究中获得的潜在知识是对家族性ALS和共济失调中神经元死亡原因的更好理解。作为研究的一部分，正在开发的小鼠模型也可能被证明非常有用，最终将与其他感兴趣的研究人员分享。由于目前还没有针对这些疾病的治愈或预防性治疗，所获得的任何知识都有可能为这些患者提供未来的诊断和治疗干预措施。

DESCRIPTION (provided by applicant): We discovered mutations in the Senataxin gene (SETX) as the molecular basis of a juvenile-onset, autosomal dominant (AD) form of familial amyotrophic lateral sclerosis (ALS). This form of ALS, known as ALS4, is an essentially pure motor systems disorder characterized by limb weakness, severe muscle wasting, pyramidal signs, and slow disease progression. Intriguingly, recessive mutations of SETX cause a second disease, a form of ataxia known as Ataxia-Oculomotor Apraxia type 2 (AOA2). In AOA2, morbidity is also high with loss of ambulation occurring ~15-20 years following onset which normally ranges from 10-22 years of age. Together these findings demonstrate genotype-phenotype correlation for SETX mutations and confirm senataxin as an important neuronal protein. Senataxin is a large protein at 2677 amino acids and its precise function is largely unknown. It contains a conserved DNA/RNA helicase domain towards the C-terminal suggesting a function in RNA processing. Such important RNA processing functions have been characterized for the yeast orthologue, Sen1p. There is also a potential protein-protein interaction domain in the extreme N-terminal which is supported by studies in yeast. Our studies will focus on mutant forms of Senataxin associated with ALS4 and AOA2 and address the following broad aims: (1) We will characterize murine gene targeted and transgenic (Tg) models we have produced for ALS4 and test if they develop neuropathies allowing further detailed study of neuronal degeneration pathways; (2) Using gene trap technology we will develop a murine knock-out model for AOA2; and (3) we have hypothesized that ALS4 mutant Senataxin (L389S) may lead to toxic gain-of-function such as aberrant protein-protein interaction. To test this we undertook yeast two-hybrid (Y2H) screens with wt and ALS4 mutant N-terminal senataxin of a human brain expression library. We identified a ALS4 specific interaction with the kinesin, KIF1B, that was validated with further Y2H re-testing and mammalian 2-H assays. We will further examine this interaction and its potential pathogenic effects in ALS4. PUBLIC HEALTH RELEVANCE: The potential knowledge gained from this research is an improved understanding of the causes of neuronal death in familial forms of ALS and Ataxia. Murine models being developed as part of the study could also prove highly useful and would eventually be shared with other interested investigators. Since there is currently no cure or preventive treatment for these conditions, any knowledge gained has the potential to provide future diagnostic and therapeutic interventions for these patients.