Mechanisms of SPG4 Hereditary Spastic Paraplegia

SPG4遗传性痉挛性截瘫的机制

• 批准号: 10267690
• 负责人: PETER W. BAAS
• 金额: $ 64.1万
• 依托单位: DREXEL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-30 至 2025-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10267690
• 关键词: Accounting; Address; Adult; Alleles; Animals; Applications Grants; Autophagocytosis; Axon; Back; Behavioral; Brain; Cell physiology; Code; Communities; Corticospinal Tracts; Coupled; Data; Defect; Development; Disease; Down-Regulation; Enzymes; Etiology; Experimental Models; Genes; Genetic; Hereditary Spastic Paraplegia; Heritability; Human; Individual; Knowledge; Limb structure; Link; Lower Extremity; Mediating; Membrane; Microtubules; Modeling; Molecular Motors; Motor Neurons; Movement; Mus; Mutation; Neurodegenerative Disorders; Neurons; Organelles; Pathogenesis; Pathogenicity; Pathologic; Patients; Pattern; Phenotype; Principal Investigator; Property; Protein Isoforms; Proteins; Reporter; Reporting; Spastic Gait; Spinal Cord; Swelling; Symptoms; Techniques; Testing; Toxic effect; Transgenic Mice; Transgenic Organisms; Translations; UCHL1 gene; Work; autosomal dominant mutation; axonal degeneration; base; casein kinase II; cytotoxic; effective therapy; fast axonal transport; gain of function; in vivo; innovation; loss of function; motor neuron degeneration; mouse model; mutant; negative affect; nervous system disorder; novel; prevent; selective expression; spasticity; spastin; tool

PROJECT SUMMARY / ABSTRACT Hereditary Spastic Paraplegias (HSP) are heritable neurodegenerative diseases in which progressive degeneration of corticospinal axonal tracts results in limb weakness, spasticity and gait deficiencies. These symptoms result from a dying back pattern of degeneration of corticospinal axons, which also display prominent swellings of unclear pathological significance. The commonest form of HSP, termed SPG4-HSP, is caused by mutations in the SPAST gene, which codes for a microtubule-severing protein called spastin. To date, the prevailing mechanistic hypothesis for the etiology of SPG4-HSP is haploinsufficiency, meaning that the corticospinal tracts degenerate because of insufficient functional spastin. However, several major disease features are not readily explained by this etiology, and it is not clear how reduced microtubule severing would promote corticospinal axonal degeneration. Providing novel information that may fill a major gap in our knowledge of SPG4-HSP pathogenesis, recent work of the Principal Investigators revealed toxic properties of mutant spastin proteins, suggesting that a gain-of-function mechanism operates in SPG4-HSP. Curiously, both mechanisms negatively affect fast axonal transport (FAT), a cellular process fueled by molecular motor proteins that allows bidirectional movement of vesicular cargoes along axons. Based on a strong experimental premise, it is hypothesized in this multi-PI grant proposal that abnormalities in microtubule organization associated with reduced spastin levels cause FAT deficits and axonal swellings (loss-of-function). On the other hand, toxic effects of mutant spastin protein cause different FAT deficits that are mediated by casein kinase 2 (CK2), and these deficits promote corticospinal axon degeneration (gain-of-function). The former makes the axon more vulnerable, but it is the latter that suffices for corticospinal axon degeneration. The proposed work seeks to test these hypotheses by directly comparing a mouse model with a single SPAST allele (SPAST +/-) with a transgenic mouse model with both endogenous mouse SPAST alleles intact that additionally expresses human spastin bearing a pathogenic mutation associated with SPG4-HSP (spastin-C448Y mice). In Aim 1, these models will be individually crossed with mice that selectively express eGFP in corticospinal motor neurons (CSMN), so that loss-of and gain-of-function contributions to the disease can be investigated. In Aim 2, FAT deficits will be studied in neurons cultured from these animals, and specific hypotheses for the etiology of the deficits will be tested. In Aim 3, studies are proposed using transgenic spastin-C448Y mice in which autophagy is experimentally enhanced or CK2 levels are experimentally reduced, to test the hypothesis that these manipulations will prevent or reduce corticospinal axon degeneration and associated behavioral deficits. The overall significance of this project is to establish mechanisms underlying SPG4-HSP and forge a path toward effective therapies for patients.

项目摘要 /摘要 遗传性痉挛性截瘫（HSP）是可遗传的神经退行性疾病 皮质脊髓轴突的变性会导致肢体无力，痉挛和步态缺陷。这些 症状是由于皮质脊髓轴突变性的垂死的背部模式而导致的，该模式也表现出突出 不清楚病理意义的肿胀。 HSP的最常见形式称为SPG4-HSP，是由 翼峰基因中的突变，该突变代码为微管的蛋白质称为痉挛。迄今为止， SPG4-HSP病因的普遍机械假设是单倍不足，这意味着 皮质脊髓束由于功能不足而退化。但是，几种主要疾病 该病因不容易解释特征，尚不清楚微管切断如何减少 促进皮质脊髓轴突变性。提供可能填补我们的主要空白的新颖信息 对SPG4-HSP发病机理的了解，主要研究人员的最新工作揭示了 突变的翼丁蛋白蛋白，表明功能收益机制在SPG4-HSP中起作用。奇怪的是，两者 机制负面影响快速轴突运输（FAT），这是一种由分子运动蛋白燃料的细胞过程 这允许在轴突上双向运动。基于强大的实验前提 在这项多PI赠款提案中假设，微管组织中的异常 降低的痉挛水平会导致脂肪缺陷和轴突肿胀（功能丧失）。另一方面，有毒作用 突变的痉挛蛋白会导致不同的脂肪缺陷，这些脂肪缺陷是由酪蛋白激酶2（CK2）介导的，这些脂肪缺陷 缺陷促进皮质脊髓轴突变性（功能获得）。前者使轴突更加脆弱， 但是，后者足以用于皮质脊髓轴突变性。拟议的工作旨在测试这些 通过直接将小鼠模型与单个示波器等位基因（SPAST +/-）与转基因小鼠进行比较，假设 两种内源性小鼠翼线等位基因完整的模型，可另外表达具有人数的轴承 与SPG4-HSP（Spastin-C448Y小鼠）相关的致病突变。在AIM 1中，这些模型将是 与在皮质脊髓运动神经元（CSMN）中选择性表达EGFP的小鼠单独交叉，以便 可以研究对该疾病的丧失和功能贡献。在AIM 2中，将研究脂肪缺陷 在这些动物培养的神经元中，将测试缺陷病因的特定假设。在 AIM 3，使用转基因Spastin-C448Y小鼠提出了研究，其中自噬是实验 实验降低了增强或CK2水平，以检验这些操作将阻止的假设 或减少皮质脊髓轴突变性和相关的行为缺陷。总体意义 项目是建立SPG4-HSP的基础机制，并为有效疗法的途径建立 患者。