Micro RNAs as biomarkers and therapeutic targets in myotubular myopathy

项目总结 肌管性肌病是一种致命的神经肌肉疾病，与严重的疾病有关(包括 轮椅和呼吸机依赖)和早期死亡率。有严重的障碍阻碍了治疗 这种毁灭性的疾病。其中包括发现新的治疗策略的需要，特别是那些 适用于更广泛的先天性肌病，并开发非侵入性生物标记物， 与治疗反应相关，因此适合用于临床试验。我们的首要目标是 翻译MTM的治疗方法。在这项提案中，我们将通过建立第一个血清来解决这一目标 MTM的生物标志物，并确定一种具有广泛治疗潜力的新的治疗方法。 MTM是一种X连锁疾病，由MTM1突变引起，MTM1是一种调节内体分选的磷酸酶。 我们已经证明，MTM1突变导致三联体的破坏，三联体是一种肌肉结构，负责 兴奋-收缩偶联是MTM发病的关键驱动因素。几个 研究小组已经证明，肌纤维萎缩也是MTM病理的一个重要因素。而当 这些变化背后的确切机制仍有待阐明，DNM2的过度表达是关键 三联体缺陷的驱动因素，与AKT-TOR通路信号不平衡相关 肌纤维大小。在这项研究中，我们提出了一种旨在针对和纠正这些缺陷的治疗方法。 MicroRNAs(MiRNAs)是一种小的、非编码的RNAs，它调节基因的表达并发挥重要的作用 无数细胞过程的调节者。MiRNAs正在成为治疗效果的生物标志物和 潜在的治疗方法。在一些疾病(包括其他肌肉疾病)中，循环中的miRNAs相关 与疾病严重程度和治疗反应有关，正在考虑作为临床试验的生物标记物。 MiR-486和miR-133a与MTM的发病有直接关系。我们已经证明了miR- 486通过重新平衡AKT信号来调节肌纤维的大小，其他人已经证明miR-133a 直接下调DNM2。因此，这些miRNAs作为潜在的治疗靶点很有吸引力，这是一个概念 我们证明miR-486过表达作为DMD的治疗策略是有效的。 在初步数据中，我们对MTM小鼠肌肉中的miRNAs进行了分析，发现50 MiRNAs包括miR-486和miR-133a的下调。在此基础上，我们假设 MiRNAs的水平将与疾病状态和治疗反应相关，从而发挥理想的作用 MTM的非侵入性生物标志物。此外，我们预测miR-486和miR-133a的恢复表达将 分别增加肌纤维大小和逆转三联体缺陷，从而挽救MTM表型。我们会 在MTM的小鼠模型中，使用严格的方法学来检验这些假设。成功完成我们的 研究将确定第一个适用于临床翻译的MTM生物标志物，并建立一种新的 适用于以肌纤维萎缩和/或三联体缺陷为特征的肌肉疾病的治疗。

PROJECT SUMMARY Myotubular myopathy is a fatal neuromuscular disease associated with severe morbidities (including wheelchair and ventilator dependence) and early mortality. There are critical barriers hindering treatment for this devastating disease. These include the need to uncover new therapeutic strategies, particularly ones with applicability for a broader spectrum of congenital myopathies, and to develop non-invasive biomarkers that correlate with treatment response and are thus suitable for use in clinical trials. Our overarching goal is to translate therapies for MTM. In this proposal, we will address this goal by establishing the first serum biomarker for MTM and identifying a novel therapeutic approach with broad treatment potential. MTM is an X-linked disorder caused by mutations in MTM1, a phosphatase that regulates endosomal sorting. We have shown that MTM1 mutation results in disruption of the triad, a muscle structure responsible for excitation-contraction coupling, and that triad disorganization is a critical driver of MTM pathogenesis. Several groups have demonstrated that myofiber hypotrophy is also an important contributor to MTM pathology. While the precise mechanisms underlying these changes remain to be elucidated, overexpression of DNM2 is a key driver of the triad defects, and unbalanced AKT-TOR pathway signaling is associated with the reduced myofiber size. In this study, we propose a treatment aimed at targeting and correcting these defects. MicroRNAs (miRNAs) are small, non-coding RNAs that modulate gene expression and serve as important regulators of myriad cellular processes. MiRNAs are emerging as both treatment effect biomarkers and potential therapeutics. In several disorders (including other muscle diseases), circulating miRNAs correlate with disease severity and treatment response, and are under consideration as biomarkers in clinical trials. The miRNAs miR-486 and miR-133a have direct relevance to MTM pathogenesis. We have shown that miR- 486 regulates myofiber size by rebalancing AKT signaling, and others have demonstrated that miR-133a directly down-regulates DNM2. These miRNAs are thus attractive as potential therapeutic targets, a concept validated by our demonstration of miR-486 overexpression as a treatment strategy for DMD. In preliminary data, we profiled miRNAs from MTM mouse muscle and found significant changes in 50 miRNAs including downregulation of miR-486 and miR-133a. Based on this, we hypothesize that changes in the levels of miRNAs will correlate with disease status and treatment response, and thus function as an ideal non-invasive biomarker for MTM. Further, we predict that restoring expression of miR-486 and miR-133a will increase myofiber size and reverse triad defects respectively, and thus rescue the MTM phenotype. We will test these hypotheses using rigorous methodology in the murine model of MTM. Successful completion of our study will identify the first biomarker of MTM suitable for clinical translation, and establish a novel treatment with applicability to muscle diseases that feature myofiber hypotrophy and/or triad defects.