Disease Mechanisms in Human Ubiquilinopathy

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS）的特征在于脑和脊髓中大运动神经元的变性，导致随意肌的进行性消耗和麻痹、呼吸衰竭并最终死亡。家族性ALS（Fals）约占所有ALS病例的10%，其中大多数（90%）疾病表现为散发性ALS（SALS）。在过去的20年里，ALS遗传病因的发现一直是ALS研究的驱动力。这些发现为发病机制和动物模型提供了新的见解。然而，尽管做出了这些努力，但ALS的全球治疗尚不可能，因为不同病因下游的共同分子机制尚未变得明显。很明显，发现其他病因和共同的下游机制将大大推进ALS的分子理解和寻找适当的治疗方法的目标。在本申请中，我们提出了这些目标的方向的进步。我们已经发现UBQLN 2突变是X连锁显性ALS和FTD型ALS/痴呆的原因。病理学是新颖、独特和独特的，ALS患者的脊髓和皮质中存在泛素2阳性包涵体，ALS/FTD患者的海马中存在额外的包涵体。令我们惊讶的是，我们在迄今为止研究的所有SALS和ALS/FTD和FALS病例中发现了相似的泛素2阳性包涵体。这些病例都没有UBQLN 2突变，这表明泛蛋白2在ALS中的翻译后作用是整体性的。我们最初的体外和体内数据表明，泛素蛋白酶体综合征（UPS）和自噬功能障碍的突变体泛素2的存在下。此外，在表达致病性UBQLN 2突变（P497 H）的转基因小鼠中观察到认知和行为缺陷以及远场记录中的长时程增强降低。在这个项目中，我们提出了四个具体的目标来了解突变体ubiquilin 2的致病机制。我们将建立病理，认知和其他行为表型和他们的电生理相关在我们目前和将要开发的突变体ubiquiln 2小鼠模型。我们还将使用我们已经建立的ubqln 2敲除小鼠模型，并开发ubqln 1敲除和ubqln 1/ubqln 2的双敲除，以测试突变体ubiquilin 2缺陷是否是ubiquilin 2与UPS和自噬系统相关的功能丧失的表现，或者突变体ubiquilin 2是否表现出新的毒性。该项目的成功完成不仅将为理解X连锁ALS的致病机制提供深入的见解，而且还将为更广泛的研究界提供有用的试剂，用于未来的研究以及筛选和测试潜在的治疗方法。该项目的结果也将对理解其他神经退行性疾病的发病机制和治疗产生重要影响。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of large motor neurons in the brain and spinal cord, resulting in progressive wasting and paralysis of voluntary muscles, respiratory failure and ultimately death. Familial ALS (FALS) accounts for around 10% of all ALS cases, with the majority (90%) of the disease presenting as sporadic ALS (SALS). Discovery of genetic etiologies of ALS has been the driving force in ALS research for the last 20 years. These discoveries have provided fresh insight into pathogenesis and animal models. However, in spite of this effort, global treatments have not been possible for ALS because a common molecular mechanism downstream from the distinct etiologies has not become apparent. It is clear that discovery of additional etiologies and common downstream mechanisms will greatly advance the goals for a molecular understanding of ALS and in finding appropriate treatments. In this application we propose an advance in direction of those goals. We have discovered mutations in UBQLN2 as cause of X-linked dominant ALS and ALS/dementia of the FTD type. The pathology is novel, distinct and unique with ubiquilin2 positive inclusions in the spinal cord and cortex in ALS patients and additional inclusions in the hippocampus of patients with ALS/FTD. To our surprise we found similar ubiquilin2 positive inclusions in all cases of SALS and ALS/FTD and FALS cases studied thus far. None of those cases had mutations in UBQLN2, arguing for a posttranslational role for ubiquilin2 in ALS as a whole. Our initial in vitro and in vivo data suggest a dysfunction of the ubiquilin proteasome syndrome (UPS) and autophagy in the presence of mutant ubiquilin2. In addition, cognitive and behavioral deficits and decreased long term potentiation in far field recordings were observed in transgenic mice expressing a pathogenic UBQLN2 mutation (P497H). In this project, we propose four specific aims to understand the disease causing mechanism(s) of mutant ubiquilin2. We will establish pathological, cognitive and other behavioral phenotypes and their electrophysiological correlates in our current and to be developed mouse models of mutant ubiquiln2. We will also use our already established ubqln2 knockout mouse model and develop ubqln1 knockout and double knockouts of ubqln1/ubqln2 to test if mutant ubiquilin2 defects are manifestation of a loss of function of ubiquilin2 in relationto the UPS and autophagy systems or whether mutant ubiquilin2 exhibits a novel toxic property. Successful completion of this project will not only provide insight into understanding the pathogenic mechanism of X-linked ALS, but also rapidly provide the wider research community with useful reagents for future studies and for screening and testing potential therapies. The outcome of this project will also have important implications in the understanding of the pathogenesis and treatment of other neurodegenerative diseases.