Circadian Clock and Muscle Health

我们已经证明，肌肉生物钟机制的破坏是通过丢失核心时钟基因， BMal1，足以导致严重的肌肉无力，令人惊讶的是，死亡率增加。基于 这些发现，这笔赠款的总体目标是寻求对 肌肉生物钟在调节基因表达的日常程序中的作用以及时钟中断是如何导致 严重的肌肉无力和全身健康状况下降。 我们发现，MyoD1可以调节核心时钟基因的表达，使其成为真正的组织- 特定的昼夜节律时钟调节器1。我们还确定了MyoD1和CLOCK：BMal1共享峰值 结合在整个肌肉基因组的3000多个位置。这些新发现为我们的研究提供了支持 将Myod1调制时钟机制的网络属性的机制(S)定义为 以及了解MyoD1作为时钟辅助因子在日常基因组和转录中的作用 成人肌肉中的风景。 在MyoD1和时钟因子的下游，我的实验室已经确定了两个肌肉特异性基因，RBM20和 TCAP，我们建议将时钟紊乱与肌肉无力联系起来。肌肉BMal1的丧失，导致显著的 RBM20和TCAP表达减少，我们发现肌节结构发生变化，包括 肌节长度、M线和Z线扭曲，肌丝取向改变。最后，全球BMal1 基因敲除小鼠BMal1KO被用作高级衰老的模型，因为它表现出显著的类似衰老的特征 患者的平均寿命为37周。在使用该全局BMal1 KO进行的初步实验中 小鼠我们利用带有肌肉特异性启动子的AAV载体在骨骼肌中拯救了BMal1。我们发现 这足以显著提高肌肉力量，但也显著延长了寿命。这些 是对我们的发现的补充，即随着肌肉BMal1的丧失，死亡率增加，并证明 仅在骨骼肌中抢救BMal1可改善全身健康。此外，随着年龄的增长和许多慢性病 表现为肌肉时钟紊乱的疾病，这些结果表明，靶向肌肉时钟机制 作为一种翻译策略具有潜力。我们建议测试以下三个具体目标： 具体目标1：确定MyoD1在核心时钟机制中的作用，并作为日常工作的辅助因素 骨骼肌中的转录剪裁景观。 特定目标2：测试时钟控制基因RBM20和/或TCAP在肌节结构中的作用 和肌肉功能。 具体目标3：确定延长BMal1寿命所需的骨骼肌特定变化 柯鼠。

We have shown that disruption of the muscle circadian clock mechanism through loss of the core clock gene, Bmal1, is sufficient to induce significant muscle weakness and surprisingly, increased mortality. Based on these findings, the overall objective of this grant is to pursue the fundamental understanding of the role of the muscle circadian clock in regulating a daily program of gene expression and how clock disruption leads to significant muscle weakness and diminished systemic health. We found that MyoD1 can modulate expression of the core clock gene, Bmal1 making it a bona fide tissue- specific circadian clock modifier1. We have also determined that MyoD1 and CLOCK:BMAL1 share peak binding at over 3000 sites across the muscle genome. These new findings provide support for our studies to define the mechanism(s) through which MyoD1 modulates the network properties of the clock mechanism as well as understanding the role of MyoD1 as a clock co-factor in the daily genomic and transcriptomic landscape in adult muscle. Downstream from MyoD1 and the clock factors, my lab has identified two muscle specific genes, Rbm20 and Tcap, that we propose link clock disruption with muscle weakness. Loss of muscle Bmal1, results in significant decreases in Rbm20 and Tcap expression and we find changes in sarcomere structure including variability of sarcomere length, distortions in M and Z lines and altered myofilament orientation. Lastly, the global Bmal1 knock out mouse, Bmal1KO, has been used as a model of advanced aging as it exhibits significant aging-like pathologies and has a median lifespan of 37wks. In preliminary experiments using this global Bmal1 KO mouse we rescued Bmal1 in skeletal muscles using an AAV vector with a muscle specific promoter. We found that this was sufficient to significantly improve muscle strength but also significantly extended lifespan. These are complementary to our findings of increased mortality with loss of muscle Bmal1 and demonstrate that rescuing Bmal1 only in skeletal muscle improves systemic health. In addition, with aging and many chronic diseases exhibiting muscle clock disruption, these results suggest that targeting the muscle clock mechanism holds potential as a translational strategy. We propose to test the following three specific aims: Specific Aim 1: To define the roles of MyoD1 within the core clock mechanism and as a co-factor for the daily transcriptomic landscape in skeletal muscle. Specific Aim 2: To test the clock controlled genes, Rbm20 and/or Tcap, for their roles in sarcomere structure and muscle function. Specific Aim 3: To determine the skeletal muscle specific changes required for improved lifespan in the Bmal1 KO mouse.