SARM1 functional polymorphisms and their contribution to ALS risk

SARM1 功能多态性及其对 ALS 风险的影响

• 批准号: 10320381
• 负责人: ADAM JOSEPH BLOOM
• 金额: $ 62.01万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10320381
• 关键词: ALS pathology; ALS patients; Affect; Alleles; Amino Acids; Amyotrophic Lateral Sclerosis; Attenuated; Axon; Biological Assay; Categories; Cell Death; Cessation of life; Chemicals; Clustered Regularly Interspaced Short Palindromic Repeats; Complex; Data; Development; Disease; Disease model; Dominant-Negative Mutation; Enzymes; Etiology; Face; Foundations; Functional disorder; General Population; Genes; Genetic Polymorphism; Genetic Variation; Genetic study; Human; Human Genetics; Injury; Investigation; Knock-in; Knock-in Mouse; Knockout Mice; Link; Longevity; Maintenance; Mediating; Messenger RNA; Metabolic; Methods; Modeling; Molecular; Motor; Motor Neurons; Mus; Muscle; Mutate; Mutation; NAD+ Nucleosidase; Nerve Degeneration; Nervous system structure; Neurons; Neuropathy; Paralysed; Pathogenesis; Pathogenicity; Pathology; Pathway interactions; Phenotype; Process; Proteins; Risk; Role; Route; Spinal Cord; Structure; Symptoms; TDP-43 aggregation; Testing; Therapeutic; Trauma; Variant; Viral; axon injury; axonal degeneration; base; cohort; disorder risk; druggable target; enzyme activity; experimental study; falls; gain of function; gain of function mutation; gene therapy; genetic risk factor; genetic variant; genome wide association study; genotyped patients; induced pluripotent stem cell; inhibitor therapy; innovation; loss of function; member; motor disorder; mouse model; neurodegenerative phenotype; neuron loss; novel; overexpression; programs; protein TDP-43; small molecule inhibitor; superoxide dismutase 1

Motor axon loss is a cardinal symptom of amyotrophic lateral sclerosis (ALS). Axon loss can be driven by a genetically encoded program in which the axon survival factors NMNAT2 and STMN2 inhibit the activity of the axon destruction factor SARM1. Recent data suggest that this program of axon self-destruction may contribute to pathology in ALS. First, aggregation of TDP-43, a hallmark of most ALS cases, results in the selective loss of mRNA encoding functional STMN2, a key axon survival factor. Second, loss of SARM1 suppresses some neurodegenerative phenotypes in a mouse ALS model that expresses pathogenic human TDP-43. Here we investigate the contribution of this axon degeneration pathway to ALS. We have defined the mechanism of action of SARM1, demonstrating that it is the founding member of a new class of NAD-cleaving enzymes. SARM1 enzyme activity is normally held in check via an autoinhibitory domain. Injury- or disease- induced loss of NMNAT2 and STMN2 disinhibits SARM1, leading to rapid NAD+ depletion, metabolic catastrophe, and axon fragmentation. Our structure-function studies of the SARM1 protein have identified mutations with a range of consequences, from constitutively active variants that promote cell death and axon loss, to dominant negative variants that are neuroprotective. These findings imply that human variants may exist that either promote or protect against neurodegeneration, and that understanding the phenotypic consequences of genetic variation requires functional studies of enzyme activity. In support of this hypothesis, we have identified several rare SARM1 variants in ALS patients, but not in controls, that have constitutive NADase activity and promote neuron death and axon loss. These variants also cause motor dysfunction and paralysis when expressed in the mouse CNS, suggesting that activating SARM1 mutations may contribute to ALS pathogenesis. Here we propose to define the function of SARM1 variants from ALS patients, controls, and the general population. These studies will allow us to categorize SARM1 variants as putatively pro-degenerative, neuroprotective, or neutral. In parallel, we will dissect the contribution of variation in components of the programmed axon destruction pathway to ALS phenotypes, alone and in combination with known ALS genetic risk-factors, in motor neurons differentiated from human induced pluripotent stem cells (iPSCs). Finally, we will investigate neurodegeneration in a mouse knock-in model carrying a Sarm1 allele equivalent to a pro- degenerative allele found in ALS patients, alone and in combination with a SOD1 model, based on a specific patient genotype that we identified. We will attempt to suppress ALS phenotypes with SARM1 inhibition via a proven gene therapy approach and with experimental small molecule inhibitors. Results of these studies will establish the relationship between the SARM1-mediated axon destruction program and ALS, and build the foundation to develop axoprotective therapeutics to treat this devastating disease.

运动轴突损失是肌萎缩性侧硬化症（ALS）的基本症状。轴突损失可以驱动 通过遗传编码的程序，轴突存活因子NMNAT2和STMN2抑制了活性 轴突破坏因子SARM1。最近的数据表明，该轴突自我毁灭计划可能 有助于ALS的病理学。首先，TDP-43的汇总是大多数ALS案例的标志，导致了 选择性丢失mRNA编码功能性STMN2，这是一个钥匙轴突存活因子。第二，损失SARM1 在表达致病人的小鼠ALS模型中抑制一些神经退行性表型 TDP-43。在这里，我们研究了该轴突变性途径对ALS的贡献。我们定义了 SARM1的作用机理，表明它是新的NAD纽带的创始成员 酶。 SARM1酶活性通常通过自身抑制域进行检查。受伤或疾病 - 诱导NMNAT2和STMN2 DISAMBIND SARM1的损失，导致NAD+耗竭快速，代谢 灾难和轴突碎片。我们对SARM1蛋白的结构功能研究已经确定 具有一系列后果的突变，来自促进细胞死亡和轴突的组成型活性变体 损失是神经保护性的主要负变体。这些发现暗示了人类的变体可能存在 促进或预防神经变性，并理解表型后果 遗传变异需要酶活性的功能研究。为了支持这一假设，我们已经确定了 ALS患者的几种罕见的SARM1变体，但在对照中没有具有组成型NADase活性和 促进神经元死亡和轴突丧失。这些变体还会引起运动功能障碍和瘫痪 在小鼠中枢神经系统中表达，表明激活SARM1突变可能有助于ALS发病机理。 在这里，我们建议定义来自ALS患者，对照组和一般的SARM1变体的功能 人口。这些研究将使我们能够将SARM1变体归类为预先促成的， 神经保护性或中性。同时，我们将剖析成分变异的贡献 单独并与已知的ALS遗传的编程轴突破坏途径通往ALS表型 在运动神经元中，风险因子与人类诱导的多能干细胞（IPSC）区分开。最后，我们会的 研究携带SARM1等位基因的小鼠敲入模型中的神经变性 基于特定的特定 我们确定的患者基因型。我们将尝试通过A抑制SARM1的ALS表型 经过验证的基因治疗方法以及实验性的小分子抑制剂。这些研究的结果将 建立SARM1介导的轴突破坏计划与ALS之间的关系，并建立 开发轴保护疗法以治疗这种毁灭性疾病的基础。