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

描述（由申请人提供）：我们发现Senataxin基因（SETX）突变是青少年发病的常染色体显性（AD）家族性肌萎缩性侧索硬化症（ALS）的分子基础。这种形式的ALS被称为ALS s4，本质上是一种纯粹的运动系统疾病，其特征是肢体无力、严重肌肉萎缩、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，一种称为2型共济失调-动眼肌失用症（AOA2）的共济失调形式。在AOA2中，发病率也很高，在发病后15-20年（通常为10-22岁）出现行动能力丧失。总之，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是一种含有2677个氨基酸的大型蛋白质，其确切功能在很大程度上是未知的。它包含一个保守的DNA/RNA解旋酶结构域，指向c端，表明在RNA加工中起作用。这些重要的RNA加工功能已经被鉴定为酵母同源物Sen1p。在酵母的研究中也证实了在极n端存在一个潜在的蛋白-蛋白相互作用域。我们的研究将集中在与ALS4和AOA2相关的Senataxin突变形式，并解决以下广泛的目标：(1)我们将表征我们为ALS4生产的小鼠基因靶向和转基因（Tg）模型，并测试它们是否发展为神经病变，从而进一步详细研究神经元变性途径；(2)利用基因诱捕技术建立小鼠AOA2基因敲除模型；(3)我们假设ALS4突变体Senataxin （L389S）可能导致毒性功能获得，如异常的蛋白质-蛋白质相互作用。为了验证这一点，我们采用酵母双杂交（Y2H）筛选了人类大脑表达文库中的wt和ALS4突变体n端senataxin。我们确定了ALS4与激酶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2-H分析验证了这一点。我们将进一步研究这种相互作用及其在als s4中的潜在致病作用。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被证明非常有用，最终将与其他感兴趣的研究者分享。由于目前对这些疾病没有治愈或预防性治疗方法，因此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.