Spinal Muscular atrophy: is it a motor axon disease?

脊髓性肌萎缩症：是运动轴突疾病吗？

• 批准号: 8291243
• 负责人: CHRISTINE E BEATTIE
• 金额: $ 32.69万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8291243
• 关键词: Actin-Binding Protein; Actins; Address; Affect; Animal Model; Animals; Axon; Binding; Biochemistry; Biological Models; Bundling; Cells; Cellular biology; Cessation of life; Complex; Data; Defect; Degenerative Disorder; Denervation; Development; Disease; DsRed; Electrophysiology (science); Embryo; F-Actin; Fishes; Functional disorder; Genetic; Human; Image; Individual; Infant; Intermediate Filaments; Knowledge; Life; Link; Messenger RNA; Microscopy; Modeling; Molecular Genetics; Motor; Motor Neurons; Nerve; Neuromuscular Junction; Neurons; Paralysed; Pathway interactions; Patients; Phenotype; Photons; Proteins; RNA Splicing; Respiratory System; Role; SMN protein (spinal muscular atrophy); Small Nuclear Ribonucleoproteins; Spinal Muscular Atrophy; Structure; Synapses; Testing; Toddler; Transgenic Organisms; Vimentin; Xenopus; Zebrafish; base; in vivo; insight; mortality; mutant; new therapeutic target; novel; plastin; protein distribution; public health relevance; research study; survival motor neuron gene; therapeutic development

DESCRIPTION (provided by applicant): Motoneuron diseases are devastating in that they rob individuals of the ability to move and are often fatal due to denervation of the respiratory system. Spinal muscular atrophy (SMA) is an autosomal recessive disease that causes motoneuron dysfunction leading to paralysis and in severe cases death making it a leading genetic cause of infant/toddler mortality. Analysis of SMA animal models reveals, motor axon defects, immature neuromuscular junctions (NMJs), and denervation suggesting that changes at the motor nerve terminal may initiate disease. The survival motor neuron (SMN) gene is the genetic cause of SMA and has a clearly defined role in assembling RNAs and proteins needed for mRNA splicing (snRNP assembly). Data from our lab and others, however, suggest that SMN may have other functions that are compromised when SMN levels are decreased. Using zebrafish as a model system, we have shown that SMN has an snRNP independent function important for normal motor axon outgrowth. Moreover, we have shown that plastin 3, an actin binding protein and the first identified modifier of human SMA, can rescue motor axon defects in zebrafish caused by low Smn levels. In addition, zebrafish smn mutants have severely reduced plastin 3 levels. In this proposal we will test the hypothesis that plastin 3 acts with SMN via an snRNP independent pathway to facilitate normal motoneuron development and function. To directly test this hypothesis, we will ask whether other SMA phenotypes are rescued by plastin 3 (Aim 1). This includes motoneuron and NMJ electrophysiology, SV2 protein at the NMJ, and survival. We will determine how plastin 3 is functioning with respect to SMN by performing a structure/function analysis (Aim 2). For these experiments we will use both plastin 3 and SMN mutants to define relevant domains. We will also test the hypothesis that plastin 3 is unique in its ability to modify SMA phenotypes by examining other actin binding proteins. We will test the hypothesis that the SMN plastin 3 interaction is independent of the snRNP function of SMN (Aim 3). Lastly, we will use live imaging to ask where SMN and plastin 3 proteins localize in motoneurons and does decreasing Smn change the levels and/or cellular localization of plastin 3 (Aim 4). Data derived from these Aims will directly address the relationship between SMN and plastin 3 as it relates to SMA using a combination of electrophysiology, molecular genetics, biochemistry, cell biology, and imaging. Moreover, it would establish an snRNP- independent mechanism of SMN that directly affects motoneuron function thus greatly advancing our understanding of this disease and revealing new therapeutic targets. Using zebrafish is a strength in that we can directly analyze motoneurons in vivo in SMA models that we have developed and easily generate novel transgenics to ask specific questions. This is a unique feature of this model system and thus these studies are highly relevant and will advance our understanding of how low Smn levels cause SMA. PUBLIC HEALTH RELEVANCE: Spinal muscular atrophy (SMA) is a motoneuron degenerative disease that is a leading cause of infant/toddler mortality. Low levels of the survival motor neuron (SMN) protein cause SMA, but how this happens is unclear. Recently a modifier of SMA, the actin binding protein plastin 3, was identified. Experiments in this proposal will directly test the hypothesis that SMN stabilized plastin 3 thus promoting normal motor axon outgrowth and synapses. The proposed experiments will elucidate the interaction and function of plastin 3 as it relates to SMN and has the potential to reveal novel therapeutic targets.

描述（由申请人提供）：运动神经元疾病是毁灭性的，因为它们剥夺了个体的移动能力，并且由于呼吸系统的去神经支配而通常是致命的。脊髓性肌萎缩症（SMA）是一种常染色体隐性遗传疾病，可引起运动神经元功能障碍，导致瘫痪，严重时可导致死亡，是婴幼儿死亡的主要遗传原因。SMA动物模型的分析显示，运动轴突缺陷、不成熟的神经肌肉接头（NMJ）和去神经支配表明运动神经末梢的变化可能引发疾病。运动神经元存活（SMN）基因是SMA的遗传原因，在组装mRNA剪接所需的RNA和蛋白质（snRNP组装）中具有明确的作用。然而，来自我们实验室和其他实验室的数据表明，当SMN水平降低时，SMN可能具有其他功能。使用斑马鱼作为模型系统，我们已经表明，SMN有一个snRNP独立的功能重要的正常运动轴突生长。此外，我们已经表明，plastin 3，肌动蛋白结合蛋白和第一个确定的修改人SMA，可以拯救运动轴突缺陷引起的低Smn水平的斑马鱼。此外，斑马鱼smn突变体严重降低了plastin 3水平。在这个建议中，我们将测试的假设，plastin 3的行为与SMN通过snRNP独立的途径，以促进正常的运动神经元的发展和功能。为了直接检验这一假设，我们将询问其他SMA表型是否被plastin 3（Aim 1）拯救。这包括运动神经元和NMJ电生理学，NMJ的SV2蛋白和存活率。我们将通过进行结构/功能分析（目的2）来确定plastin 3与SMN的关系。对于这些实验，我们将使用plastin 3和SMN突变体来定义相关结构域。我们还将通过检查其他肌动蛋白结合蛋白来检验这一假设，即plastin 3在其修饰SMA表型的能力方面是独特的。我们将检验SMN plastin 3相互作用独立于SMN的snRNP功能的假设（目的3）。最后，我们将使用实时成像来询问SMN和plastin 3蛋白在运动神经元中的定位，以及Smn降低是否会改变plastin 3的水平和/或细胞定位（目的4）。从这些目的中获得的数据将直接解决SMN和plastin 3之间的关系，因为它与SMA相关，使用电生理学、分子遗传学、生物化学、细胞生物学和成像的组合。此外，它将建立一个snRNP-独立的机制SMN，直接影响运动神经元的功能，从而大大推进我们对这种疾病的理解，并揭示新的治疗靶点。使用斑马鱼是一种优势，因为我们可以在我们开发的SMA模型中直接分析体内运动神经元，并很容易产生新的转基因动物来提出特定的问题。这是该模型系统的一个独特特征，因此这些研究具有高度相关性，并将促进我们对低Smn水平如何导致SMA的理解。 公共卫生相关性：脊髓性肌萎缩症（SMA）是一种运动神经元退行性疾病，是婴儿/幼儿死亡的主要原因。低水平的运动神经元生存（SMN）蛋白会导致SMA，但这种情况是如何发生的尚不清楚。最近，SMA的修饰物，肌动蛋白结合蛋白质plastin 3被鉴定。在这个提议中的实验将直接测试SMN稳定化plastin 3从而促进正常的运动轴突生长和突触的假设。拟议的实验将阐明plastin 3与SMN的相互作用和功能，并有可能揭示新的治疗靶点。