Mechanisms of SPG4 Hereditary Spastic Paraplegia

SPG4遗传性痉挛性截瘫的机制

• 批准号: 10683171
• 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/10683171
• 关键词: Accounting; Address; Adult; Alleles; Animals; Applications Grants; Autophagocytosis; Axon; Back; Behavioral; Brain; Cell physiology; Code; Communities; Corticospinal Tracts; Coupled; Curiosities; Data; Defect; Development; Disease; Down-Regulation; Enzymes; Etiology; Experimental Models; Gait; 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 Paraparesis; Spinal Cord; Swelling; Symptoms; Techniques; Testing; Toxic effect; Transgenic Mice; Transgenic Organisms; Translations; UCHL1 gene; Work; autosomal dominant mutation; axonal degeneration; casein kinase II; cytotoxic; effective therapy; fast axonal transport; forging; 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; transgene expression

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.

项目概要/摘要 遗传性痉挛性截瘫 (HSP) 是一种遗传性神经退行性疾病，其中进行性进展 皮质脊髓轴突束变性导致四肢无力、痉挛和步态缺陷。这些 症状是由皮质脊髓轴突退化的死亡模式引起的，这些轴突也表现出突出的症状 病理意义不明的肿胀。最常见的 HSP 形式称为 SPG4-HSP，是由 SPAST 基因发生突变，该基因编码一种称为 spastin 的微管切断蛋白。迄今为止， SPG4-HSP病因学的普遍机制假设是单倍体不足，这意味着 由于功能性 spastin 不足，皮质脊髓束退化。然而，几种重大疾病 这种病因学无法轻易解释这些特征，并且尚不清楚减少微管切断会如何进行 促进皮质脊髓轴突变性。提供可能填补我们的重大空白的新颖信息 随着对 SPG4-HSP 发病机制的了解，主要研究人员最近的工作揭示了 SPG4-HSP 的毒性特性 突变的 spastin 蛋白，表明 SPG4-HSP 中存在功能获得机制。奇怪的是，两者 机制对快速轴突运输（FAT）产生负面影响，这是一种由分子运动蛋白驱动的细胞过程 这允许囊泡货物沿着轴突双向运动。基于强有力的实验前提， 在这项多 PI 拨款提案中，假设微管组织异常与 spastin 水平降低会导致 FAT 缺陷和轴突肿胀（功能丧失）。另一方面，毒性作用 突变 spastin 蛋白会导致由酪蛋白激酶 2 (CK2) 介导的不同 FAT 缺陷，并且这些 缺陷会促进皮质脊髓轴突变性（功能获得）。前者使轴突更脆弱， 但后者足以导致皮质脊髓轴突变性。拟议的工作旨在测试这些 通过直接将具有单个 SPAST 等位基因 (SPAST +/-) 的小鼠模型与转基因小鼠进行比较来提出假设 具有完整的内源性小鼠 SPAST 等位基因的模型，还表达带有 与 SPG4-HSP（spastin-C448Y 小鼠）相关的致病突变。在目标 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 的小鼠单独杂交，从而 可以研究功能丧失和功能获得对疾病的影响。在目标 2 中，将研究 FAT 缺陷 在从这些动物培养的神经元中，将测试缺陷病因的具体假设。在 目标 3，建议使用转基因 spastin-C448Y 小鼠进行研究，其中自噬是实验性的 实验性地增强或降低 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。本次活动的总体意义 该项目的目的是建立 SPG4-HSP 的潜在机制，并开辟一条有效治疗的道路 患者。