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.

项目总结/摘要 遗传性痉挛性截瘫（HSP）是一种遗传性神经退行性疾病， 皮质脊髓轴突束的变性导致肢体无力、痉挛和步态缺陷。这些 症状是由皮质脊髓轴突退化的垂死模式引起的，其也表现出突出的 病理意义不明的肉瘤。HSP的最常见形式，称为SPG 4-HSP，由以下引起： SPAST基因突变，该基因编码一种名为spastin的微管切断蛋白。迄今为止 SPG 4-HSP病因学的流行机制假说是单倍不足，这意味着 皮质脊髓束由于功能性痉挛不足而退化。然而，几种主要疾病 这些特征不容易用这种病因学来解释，也不清楚减少的微管切断如何 促进皮质脊髓轴突变性。提供新的信息，可能会填补我们的主要空白， SPG 4-HSP发病机制的知识，主要研究者最近的工作揭示了SPG 4-HSP的毒性特性。 突变的痉挛蛋白，表明功能获得机制在SPG 4-HSP中起作用。奇怪的是，两者 机制负面影响快速轴突运输（FAT），一个由分子马达蛋白质推动的细胞过程 允许囊泡物质沿着轴突双向运动。基于强有力的实验前提， 在这个多PI拨款提案中假设，与 痉挛素水平降低导致FAT缺陷和轴突痉挛（功能丧失）。另一方面， 突变的痉挛蛋白引起不同的脂肪缺陷，由酪蛋白激酶2（CK 2）介导，这些 缺陷促进皮质脊髓轴突变性（功能获得）。前者使轴突更脆弱， 但后者足以引起皮质脊髓轴突变性。拟议的工作旨在测试这些 通过直接比较具有单个SPAST等位基因（SPAST +/-）的小鼠模型与转基因小鼠的假设 具有两个内源性小鼠SPAST等位基因完整的模型，该模型另外表达携带 与SPG 4-HSP相关的致病性突变（spastin-C448 Y小鼠）。在目标1中，这些模型将 分别与在皮质脊髓运动神经元（CSMN）中选择性表达eGFP的小鼠杂交， 可以研究功能丧失和功能获得对疾病的贡献。在目标2中，将研究脂肪赤字 在从这些动物培养的神经元中，将测试缺陷的病因学的特定假设。在 目的3：利用转基因spastin-C448 Y小鼠进行研究， 通过实验提高或降低CK 2水平，以检验这些操作将阻止 或减少皮质脊髓轴突变性和相关的行为缺陷。这件事的整体意义 该项目旨在建立SPG 4-HSP的潜在机制，并为有效治疗 患者