Axonal mRNP alterations in spinal muscular atrophy

脊髓性肌萎缩症中轴突 mRNP 的改变

• 批准号: 313233411
• 负责人: Dr. Michael Briese
• 金额: --
• 依托单位: Institut für Klinische Neurobiologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/313233411?language=en
• 关键词: Axonal; mRNP; alterations; spinal; muscular

Spinal motoneurons are highly polarized cells that critically depend on subcellular mRNA transport into axons during development and for maintenance and repair in the adult. Axonal mRNA transport is disturbed in motoneuron diseases and might contribute to defective axon integrity and synaptic transmission at neuromuscular endplates, thereby causing motoneuron dysfunction and death. Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder characterized by loss of motoneurons in the spinal cord leading to weakness of corresponding muscles. Patients have a deletion of or mutations in the Survival Motor Neuron 1 (SMN1) gene leading to loss of the SMN protein. SMN has a canonical function in the biogenesis of spliceosomal snRNPs. More recent research has pointed to additional functions in the assembly and transport of messenger ribonucleoprotein particles (mRNPs). Disturbed mRNP transport and processing might contribute to motor axon degeneration and defective presynaptic differentiation seen in SMA. We have previously identified the heterogeneous nuclear ribonucleoprotein R (hnRNP R), an RNA-binding protein, as an interactor of SMN. Reduction of either Smn or hnRNP R in cultured primary mouse motoneurons leads to reduced axon growth indicating that both proteins have roles in motoneuron development. Levels of hnRNP R are severely reduced in axons of Smn-deficient motoneurons indicating reduced transport or processing of axonal hnRNP R and hnRNP R-containing mRNPs upon loss of Smn. During the first SPP 1935 funding period we further explored this possibility by characterizing the RNA interactome of hnRNP R using the iCLIP technique and observed interactions with many mRNAs encoding proteins with functions in axon growth. Additionally, we characterized the protein interactome of hnRNP R in motoneurons by proteomics and detected a large number of RNA-binding proteins, including several proteins previously implicated in amyotrophic lateral sclerosis (ALS). Beyond that, we found that the Hnrnpr transcript itself is transported into motor axons. We identified proteins interacting with the 3'UTR that might mediate its axonal translocation. During the second SPP 1935 funding period we would like to characterize the hnRNP R transport mRNPs in vivo and investigate to what extent their integrity is disturbed in motor nerves from an SMA mouse model. Additionally, we would like to examine whether transport and local translation of Hnrnpr is disrupted in Smn-deficient motoneurons and in motor nerves from SMA mice. Finally, we are planning to investigate the functions of hnRNP R for motor system development and maintenance by characterizing a new Hnrnpr knockout mouse. We anticipate that our findings are not only relevant for SMA but might also reveal new insights into the pathomechanisms of ALS, and envision that our expertise in motoneuron biology is of interest to other members of the SPP 1935.

脊髓运动神经元是一种高度极化的细胞，在发育过程中严重依赖于亚细胞mRNA向轴突的运输，并在成年后维持和修复。运动神经元疾病中轴突mRNA转运受到干扰，可能导致神经肌肉终板上轴突完整性和突触传递的缺陷，从而导致运动神经元功能障碍和死亡。脊髓性肌萎缩症(SMA)是一种常染色体隐性遗传性神经肌肉疾病，其特征是脊髓运动神经元丢失，导致相应肌肉的无力。患者存在存活运动神经元1(SMN1)基因的缺失或突变，导致SMN蛋白丢失。SMN在剪接体SnRNPs的生物发生中具有典型的作用。最近的研究指出，信使核糖核蛋白颗粒(MRNP)的组装和运输具有额外的功能。MRNP转运和加工障碍可能与SMA中运动轴突变性和突触前分化障碍有关。我们以前已经确定异质性核核糖核蛋白R(HnRNP R)是一种RNA结合蛋白，是SMN的相互作用因子。在原代培养的小鼠运动神经元中，SMN或hnRNP R的减少会导致轴突生长减少，这表明这两种蛋白在运动神经元的发育中都有作用。在SMN缺乏运动神经元的轴突中，hnRNP R的水平严重降低，这表明当SMN丢失时，轴突hnRNP R和含有hnRNP R的mRNP的运输或加工减少。在第一个SPP 1935资助期，我们通过使用iCLIP技术表征hnRNP R的RNA相互作用组，并观察到与许多编码具有轴突生长功能的蛋白质的mRNAs的相互作用，进一步探索了这种可能性。此外，我们还用蛋白质组学方法研究了hnRNP R在运动神经元中的蛋白质相互作用组，并检测到了大量的RNA结合蛋白，其中包括几个与肌萎缩侧索硬化症(ALS)相关的蛋白。除此之外，我们发现Hnrnpr转录本本身被运输到运动轴突中。我们确定了与3‘UTR相互作用的蛋白质，可能介导了它的轴突移位。在第二个SPP 1935资助期，我们想要描述体内hnRNP R转运mRNPs的特征，并从SMA小鼠模型中调查它们在运动神经中的完整性受到多大程度的干扰。此外，我们想要检查Hnrnpr的运输和局部翻译是否在SMN缺陷的运动神经元和SMA小鼠的运动神经中受到干扰。最后，我们计划通过鉴定一种新的Hnrnpr基因敲除小鼠来研究hnRNP R在电机系统开发和维护中的功能。我们预计，我们的发现不仅与SMA相关，还可能揭示ALS的病理机制的新见解，并设想我们在运动神经元生物学方面的专业知识将引起SPP 1935的其他成员的兴趣。