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，因为他们剥夺了个人的移动能力，并且由于呼吸系统的去神经而经常致命。脊柱肌肉萎缩（SMA）是一种常染色体隐性疾病，会引起运动神经元功能障碍，导致麻痹，在严重的情况下死亡，使其成为婴儿/幼儿死亡率的主要遗传原因。对SMA动物模型的分析揭示了运动轴突缺陷，未成熟的神经肌肉连接（NMJS）和神经保护，表明运动神经末端的变化可能引发疾病。生存运动神经元（SMN）基因是SMA的遗传原因，并且在组装RNA和mRNA剪接所需的蛋白质（SNRNP组装）中具有明确定义的作用。但是，来自我们实验室和其他实验室的数据表明，SMN可能具有降低SMN水平时受到损害的其他功能。使用斑马鱼作为模型系统，我们已经证明SMN对正常运动轴突生长具有重要的SNRNP独立函数。此外，我们已经表明，帕拉蛋白3，一种肌动蛋白结合蛋白和人类SMA的首次鉴定的修饰剂，可以挽救由低SMN水平引起的斑马鱼中的运动轴突缺陷。另外，斑马鱼SMN突变体严重降低了塑蛋白3水平。在此提案中，我们将检验以下假设：Plastin 3通过SNRNP独立途径与SMN起作用，以促进正常的运动神经元的发育和功能。为了直接检验该假设，我们将询问Plastin 3（AIM 1）是否拯救了其他SMA表型。这包括运动神经元和NMJ电生理学，NMJ处的SV2蛋白以及存活率。我们将通过执行结构/功能分析（AIM 2）来确定Plastin 3如何相对于SMN的功能。对于这些实验，我们将同时使用Plastin 3和SMN突变体来定义相关域。我们还将检验以下假设：Plastin 3通过检查其他肌动蛋白结合蛋白来修饰SMA表型的能力是独一无二的。我们将检验以下假设：SMN Plastin 3相互作用与SMN的SNRNP函数无关（AIM 3）。最后，我们将使用实时成像询问SMN和Plastin 3蛋白在运动神经元中定位的位置，并且SMN确实会改变Plastin 3的水平和/或细胞定位（AIM 4）。从这些目标得出的数据将直接解决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。此外，它将建立一种直接影响运动神经元功能的SNRNP独立机制，从而大大推进了我们对这种疾病的理解并揭示了新的治疗靶标。使用斑马鱼是一种优势，因为我们可以在SMA模型中直接分析体内运动神经元，并在我们开发并轻松生成新颖的转基因以提出特定问题的情况下。这是该模型系统的独特特征，因此这些研究具有很高的相关性，并将促进我们对SMN水平如何引起SMA的理解。 公共卫生相关性：脊柱肌肉萎缩（SMA）是一种运动神经元退行性疾病，是婴儿/幼儿死亡率的主要原因。较低的生存运动神经元（SMN）蛋白会导致SMA，但是这种情况尚不清楚。最近发现了SMA的修饰剂，即肌动蛋白结合蛋白质塑料3。该提案中的实验将直接检验以下假设：SMN稳定塑料3，从而促进正常运动轴突的生长和突触。提出的实验将阐明与SMN相关的塑料3的相互作用和功能，并具有揭示新型治疗靶标的潜力。