Investigating the Contribution of ALS/FTD-Associated Mutations in the NEK1 Kinase to Disease Pathophysiology

肌萎缩侧索硬化症（ALS）是一种破坏性的神经退行性疾病，其特征在于： 逐渐失去控制肌肉运动的能力。ALS患者经常与额颞叶共病， 痴呆症（FTD），也称为ALS/FTD。ALS的临床表现是由选择性的 连接CNS和肌肉组织的上下运动神经元（MN）的功能障碍和变性。 绝大多数ALS在性质上是散发性的，而10%的患者患有家族性形式的ALS。 疾病，这使得致病基因变异的鉴定。ALS可以由突变引起 在编码蛋白质的基因中，这些蛋白质涉及多种细胞功能，从RNA代谢、蛋白质稳定 和细胞骨架稳态。最近的遗传学研究强调了NIMA相关激酶1（NEK 1）作为一种主要的 ALS的遗传因素NEK 1中的功能丧失遗传变异使多达200人易患ALS。 占所有病例的2%。NEK 1在中枢神经系统中的具体作用和功能尚未得到解决。还剩下什么 导致突变型NEK 1 ALS病理生理学的细胞机制是难以捉摸的。在本研究中，我们将 使用NEK 1细胞模型、诱导多能干细胞（iPSC）患者来源的MN、体内果蝇模型 和ALS-NEK 1死后患者CNS组织的研究，以：a）确定ALS相关的CNS组织的机制， 突变损害MN功能; B）表征NEK 1依赖性磷酸化的生理底物; 以及c）验证这些变化对ALS中神经病理学的贡献。我们将检验这个假设 NEK 1突变通过破坏激酶对细胞通路的调节作用而引起神经毒性， 对于MN功能至关重要。在初步实验中，我们发现NEK 1缺陷的iPSC衍生的MN 表现出微管（MT）动力学破坏和核输入受损。在目标1中，我们将确定 这些缺陷与大量的无义和错义ALS相关的NEK 1相关 变体。在初步的实验中，我们发现NEK 1相互作用物在MT中的功能是丰富的， 细胞骨架和核输入以及NEK 1水平的降低导致蛋白质的差异表达 参与这些途径。在目标2中，我们将确定NEK 1磷酸化的生理底物 通过进行磷酸化蛋白质组学质谱分析和询问 差异磷酸化在初步实验中，我们确定尼基是最接近的果蝇同源物， 通过对NEK 1基因的研究，并使用RNAi细胞系，我们发现它对运动功能和生存至关重要。在目标3中， 确定NEK 1在果蝇完整神经系统中的功能，并验证我们对 体内的细胞模型。我们的研究将揭示细胞机制， 神经元中的突变NEK 1，并可能发现潜在的治疗靶点， ALS/FTD患者。

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that is characterized by a progressive inability to control muscle movement. ALS patients are often comorbid with frontotemporal dementia (FTD), also known as ALS/FTD. The clinical manifestation of ALS is mediated by the selective dysfunction and degeneration of upper and lower motor neurons (MNs) that connect the CNS to the musculature. The overwhelming majority of ALS is sporadic in nature, while 10% of patients suffer from familial forms of disease, which have enabled the identification of causative genetic variants. ALS can be caused by mutations in genes that encode proteins involved in diverse cellular functions ranging from RNA metabolism, proteostasis and cytoskeletal homeostasis. Recent genetic studies have highlighted NIMA-related kinase 1 (NEK1) as a major genetic contributor to ALS. Loss-of-function genetic variants in NEK1 confer susceptibility to ALS in as many as 2% of all cases. The specific role and function of NEK1 in the CNS remains unresolved. What also remains elusive is the cellular mechanisms that lead to mutant NEK1 ALS pathophysiology. In the present study, we will use NEK1 cellular models, induced pluripotent stem cell (iPSC) patient-derived MNs, in vivo Drosophila models and ALS-NEK1 postmortem patient CNS tissue to: a) determine the mechanisms by which ALS-associated mutations impair MN function; b) characterize the physiological substrates for NEK1-dependent phosphorylation; and, c) validate the contribution of these changes towards neuropathology in ALS. We will test the hypothesis that NEK1 mutations cause neurotoxicity by disrupting the regulatory role of the kinase on cellular pathways that are essential for MN function. In preliminary experiments, we found that NEK1-deficient iPSC-derived MNs exhibit disrupted microtubule (MT) dynamics and impaired nuclear import. In Aim 1 we will determine whether these defects are relevant in the context of an extensive set of nonsense and missense ALS-associated NEK1 variants. In preliminary experiments, we found that NEK1 interactors are enriched for function in the MT cytoskeleton and nuclear import and that reduction of NEK1 levels results in differential expression of proteins involved in these pathways. In Aim 2 we will determine the physiological substrates for NEK1 phosphorylation in MNs by conducting phosphoproteomic mass spectrometry analysis and interrogating the functional effects of differential phosphorylation. In preliminary experiments we identified Niki as the closest Drosophila homologue of NEK1 and using RNAi lines we found that it is essential for motor function and survival. In Aim 3 we will determine the function of NEK1 in the intact nervous system of flies and validate our findings on the effects of the cellular models in vivo. Our studies will shed light into the cellular mechanisms that are compromised by mutant NEK1 in neurons and will likely uncover potential therapeutic targets for a significant percentage of ALS/FTD patients.