Deciphering the roles of FXR1 in health and myopathy

项目总结/摘要 RNA结合蛋白影响肌肉功能和疾病进展的机制仍然是 大部分未知。脆性X相关蛋白1（FXR 1）是一种多功能的RNA结合蛋白， 在调节心肌细胞中RNA的时空表达方面。越来越明显的是 FXR 1是正常肌肉功能所必需的，并且与人类心脏和骨骼肌病变两者相关。 尽管小鼠中Fxr 1的整体敲除导致围产期致死性心脏和骨骼肌缺陷， 关于FXR 1的基本机制作用知之甚少。我们发现FXR 1与 并在转录后调节编码兴奋-收缩偶联所必需的蛋白质的mRNA， 包括调节肌球蛋白调节轻链（RLC）磷酸化的组分。我们还确定 FXR 1和编码utrophin的mRNA之间的相互作用，utrophin是一种可以在功能上取代 杜氏肌营养不良症中肌营养不良蛋白的丢失。我们广泛的初步数据，以及其他人的数据， 揭示人DMD肌细胞以及所有DMD模型中的FXR 1蛋白水平显著降低 测试包括来自犬、猪、小鼠和大鼠的那些。值得注意的是，在三个不同的细胞中恢复FXR 1水平， DMD的小鼠模型减弱了疾病进展，导致结构和功能的改善， 包括心肌和骨骼肌。在DMD小鼠中，肌营养蛋白表达也响应于增加的 FXR 1水平。因此，我们假设FXR 1特异性调节细胞成分，这些细胞成分对于 适当的肌肉功能和FXR 1水平/功能的改变有助于疾病进展，特别是在 DMD我们提出了一个全球性的，公正的和多学科的方法，从单分子到体内研究， 包括使用人体组织，使我们能够实现三个具体目标，重点是确定 脆性X蛋白的基本生理功能及其在肌肉发病机制中的作用。另外我们 将是第一批评估基因治疗策略以预防DMD大鼠肌肉功能障碍的小组之一（a 与人类DMD非常相似的模型）。我们预测这些发现将促进一种独特的RNA水平 改善肌肉疾病进展的治疗方法。

PROJECT SUMMARY/ABSTRACT The mechanism whereby RNA-binding proteins impact muscle function and disease progression is still largely unknown. Fragile X-related protein 1 (FXR1), an RNA-binding protein, is multi-functional and plays a role in regulating the temporal and spatial expression of RNAs in myocytes. It is becoming increasingly evident that FXR1 is essential for normal muscle function and is associated with both human cardiac and skeletal myopathies. Although global knockout of Fxr1 in mice results in perinatal lethality with cardiac and skeletal muscle defects, little is known regarding the fundamental mechanistic role(s) of FXR1. We discovered that FXR1 interacts with, and post-transcriptionally regulates, mRNAs that encode proteins essential for excitation-contraction coupling, including components that regulate phosphorylation of the myosin regulatory light chain (RLC). We also identified an interaction between FXR1 and the mRNA that encodes utrophin, a protein that can functionally substitute for the loss of dystrophin in Duchenne Muscular Dystrophy. Our extensive preliminary data, and data from others, reveal that FXR1 protein levels are significantly reduced in human DMD myocytes as well as in all DMD models tested including those from canine, pig, mouse and rat. Remarkably, restoring FXR1 levels in three different mouse models of DMD attenuates disease progression, resulting in structural and functional improvements in both cardiac and skeletal muscle. Utrophin expression is also enhanced in DMD mice in response to increased FXR1 levels. Thus, we hypothesize that FXR1 specifically regulates cellular components that are critical for proper muscle function and alterations in FXR1 levels/function contribute to disease progression, particularly in DMD. We propose a global, unbiased and multidisciplinary approach from single molecule to in vivo studies, including the use of human tissue, to allow us to accomplish three Specific Aims focused on determining the basic physiological function of a Fragile X protein and the role it plays in muscle pathogenesis. In addition, we will be among the first groups to assess gene-therapy strategies to prevent muscle dysfunction in DMD-rats (a model which closely resembles human DMD). We predict these discoveries will facilitate a unique RNA-level therapeutic approach to ameliorate muscle disease progression.