RNA-mediated mechanisms of motor system dysfunction in spinal muscular atrophy

项目摘要 脊髓性肌萎缩症（SMA）是一种常染色体隐性遗传神经肌肉疾病，其特征在于： 脊髓中运动神经元的变性和骨骼肌的进行性萎缩。SMA是最 这是婴儿死亡的常见遗传原因，目前尚无治疗方法。SMA是 由于纯合性运动神经元（SMN）蛋白普遍表达的缺陷引起， SMN 1基因缺失或突变。尽管有明确的遗传基础的疾病和进展， 由于缺乏SMN生物学知识，SMA的分子机制知之甚少。SMN有一个很好的- 在对RNA至关重要的小核核糖核蛋白（snRNP）的生物发生中确立了功能 组蛋白mRNA的剪接和3'端形成。此外，越来越明显的是，SMN RNA调节中的其他功能也可能导致SMA。然而，尽管SMN发挥了 在转录后基因调控中的核心作用，特定SMN依赖性RNA途径的贡献 SMA病理学仍然难以捉摸。SMA研究的一个主要挑战是确定哪种SMN依赖性 在许多潜在的失调事件中，RNA途径和下游基因与以下因素直接相关： 疾病表型。这对于阐明这种破坏性的分子机制至关重要。 疾病，也可能有助于开发不同于SMN上调的治疗方法。这个项目 目的是确定三个特定的和完善的SMN依赖的RNA途径的直接贡献 - 小鼠模型中U12剪接、U 7 snRNP生物发生和选择性剪接-运动系统功能障碍 这种疾病在基因和表型上都能最好地再现人类的状况。 我们的假设是，这些通路中的特定缺陷与不同的功能异常有因果关系 SMA电机系统为了解决这一假设，我们将研究每种干扰的作用， SMA病理学中的这些RNA途径及其对正常运动系统发育的要求， 在小鼠模型中分别采用选择性恢复（Aim 1）和抑制（Aim 2）方法。这些研究 将与选择的运动回路神经元群体的RNA谱分析相结合，目的是鉴定运动回路神经元的功能。 SMN缺陷诱导的转录组改变与每个RNA途径特异性相关 以及它们各自的下游基因靶点，这些基因靶点可能直接导致疾病过程， 将在SMA小鼠中测试其功能相关性（目的3）。总体而言，该项目旨在 确定SMA中突触功能障碍和运动神经元死亡的RNA依赖性机制。

Project Summary Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of motor neurons in the spinal cord and progressive atrophy of skeletal muscle. SMA is the most frequent inherited cause of infant mortality and no treatment is currently available for the disease. SMA is caused by a deficiency in the ubiquitously expressed survival motor neuron (SMN) protein due to homozygous deletion or mutation of the SMN1 gene. Despite a clear genetic basis of the disease and progress in the knowledge of SMN biology, the molecular mechanisms of SMA are poorly understood. SMN has a well- established function in the biogenesis of small nuclear ribonucleoproteins (snRNPs) that are critical for RNA splicing and 3' end formation of histone mRNAs. Moreover, it is becoming increasingly clear that SMN has additional functions in RNA regulation that might also contribute to SMA. However, although SMN plays a central role in post-transcriptional gene regulation, the contribution of specific SMN-dependent RNA pathways to SMA pathology remains elusive. A major challenge in SMA research is to identify which SMN-dependent RNA pathways and downstream genes among many potentially dysregulated events are directly relevant to the disease phenotype. This is critically important to elucidate the molecular mechanisms of this devastating disease and may also help to develop therapeutic approaches distinct from SMN upregulation. This project aims to determine the direct contribution of three specific and well-established SMN-dependent RNA pathways - U12 splicing, U7 snRNP biogenesis, and alternative splicing - to motor system dysfunction in a mouse model of the disease that provides the best recapitulation of the human condition both genetically and phenotypically. Our hypothesis is that specific defects in these pathways are causally linked to distinct functional abnormalities of the SMA motor system. To address this hypothesis, we will investigate both the role of disruption of each of these RNA pathways in SMA pathology and their requirement for normal motor system development using, respectively, selective restoration (Aim 1) and inhibition (Aim 2) approaches in mouse models. These studies will be combined with RNA profiling of select motor circuit neuron populations with the aim of identifying the transcriptome alterations induced by SMN deficiency that are specifically associated with each RNA pathway and their respective downstream gene targets that may directly contribute to the disease process, the functional relevance of which will be tested in SMA mice (Aim 3). Collectively, this project is designed to determine the RNA-dependent mechanisms of synaptic dysfunction and motor neuron death in SMA.