EAGER: Exploratory Role of the Cytoskeleton in Anisotropic Regulation of Micrornas in Skeletal Muscles

目前的骨骼肌机械功能模型是建立在对产生或受力于肌肉纤维长度的肌肉的研究基础上的。这些对肌肉纵向力学行为的测量有助于在组织、细胞和分子水平上对肌肉功能的基础知识。然而，作为主要呼吸肌的横隔膜经历了一个更复杂的力学环境，在这个环境中，所施加的力可以分解为纵向和横向分量。除了沿肌肉长度的机械力之外，施加在肌肉横平面上的机械载荷的潜在生理学意义在于，在肌肉纤维的外侧表面和末端存在相似的力传递蛋白质复合体。这项研究将确定膜片是否可以分别检测和响应纵向和横向载荷。这将增加我们对横隔膜功能随年龄和疾病的了解。本科生也将从参与该项目中获得研究经验。MicroRNAs是最近发现的一类自然产生的22个核苷酸的非编码小RNA，它通过降解目标蛋白编码的mRNAs或通过抑制翻译来调节基因表达，其机制类似于小干扰RNA介导的基因沉默。关于microRNAs对机械力的调节知之甚少。此外，人们还不能很好地理解在骨骼肌中复杂的机械负荷如何改变microRNAs的调节。目前还不清楚特定的细胞骨架蛋白，如结蛋白是否调节呼吸泵中机械传感microRNAs的调节。这项研究将确定诸如let-7e-5p和miR-98-5p这样的机械传感microRNAs是否受两条独立的拉伸诱导信号通路的调控，这两条信号通路取决于机械拉伸的方向：沿着肌肉纤维和横向到肌肉纤维。还将测试特定的细胞骨架蛋白，如titin和desmin中间丝是否调节let-7e-5p和miR-98-5p基因的机械敏感性各向异性调节。

Current models of the mechanical function of skeletal muscle are founded upon studies of muscles that are generating or are subjected to forces along the length of the muscle fibers. These measurements of the longitudinal mechanical behavior of muscle have contributed to fundamental knowledge of muscle function at the tissue, cell, and molecular levels of organization. However the diaphragm, the main respiratory muscle, experiences a more complex mechanical environment in which applied forces can be resolved into longitudinal and transverse components. The potential physiological importance of mechanical loads applied to the transverse plane of the muscle in addition to mechanical forces along the length of muscle is suggested by the presence of similar populations of force-transmitting protein complexes at the lateral surface and at the ends of muscle fibers. The research will determine whether the diaphragm can detect and respond separately to longitudinal and transverse loading. This will increase our understanding of diaphragm function with age and disease. Undergraduate students also will receive research experiences form participating in the project.MicroRNAs are a recently discovered class of naturally occurring 22 nucleotides small non-coding RNAs that regulate gene expression either by degradation of target protein-coding mRNAs or by repressing translation in a mechanism similar to small interfering RNA mediated gene silencing. There is little known about the regulation of microRNAs in response to mechanical forces. Furthermore, it is not well understood how the complexity of in vivo mechanical loading in skeletal muscles such as the diaphragm alters the regulation of the microRNAs. It is also unknown whether specific cytoskeletal proteins such as desmin modulate the regulation of mechanosensing microRNAs in the ventilatory pump. The research will determine whether mechanosensing microRNAs such as let-7e-5p and miR-98-5p are regulated by two independent stretch induced signaling pathways that are dependent on the directions of applied mechanical stretch: along muscle fibers and transverse to muscle fibers. Also tested will be whether specific cytoskeletal proteins, e.g. titin and desmin intermediate filaments modulate the mechanosensitive anisotropic regulation of the let-7e-5p and miR-98-5p genes.