Post-transcriptional Regulation of Satellite Cell Function

 描述（由申请人提供）：骨骼肌的出生后生长和修复需要称为卫星细胞的成体肌肉干细胞。卫星细胞位于肌纤维质膜和基底层之间，通常维持为有丝分裂静止群体，直到被刺激激活并退出静止。在启动过程中，卫星 细胞上调MyoD，肌肉中的主要调节转录因子。然而，从静止退出和随后的MyoD表达的机制知之甚少。体内卫星细胞活化的基因表达谱显示，参与mRNA衰变的编码蛋白质的转录本显著耗尽，强烈暗示了卫星细胞活化中的转录后mRNA调控。在这个建议中，我提出的证据表明，这些mRNA衰变因子之一，Tristetraprolin（TTP），抑制卫星细胞激活的不稳定MyoD mRNA。因此，转录后的mRNA调控TTP可能发挥重要作用，在稳态维持和重新收购卫星细胞的静止所需的卫星细胞自我更新激活后。该提案将涉及：1）肌肉再生过程中TTP/Tis 11-家族功能，2）卫星细胞活化过程中介导TTP/Tis 11-家族功能的mRNA靶点，3）肉瘤发生和进展过程中这种稳态网络的破坏/重新布线。这些研究目标与先进的小鼠遗传学，RNA生物化学和生物信息学的实践培训部分相结合，并补充了我以前研究癌症（研究生院）和成人干细胞信号传导（之前的博士后培训）的经验。本提案中概述的机会旨在为我提供一个多学科的概念背景和实验工具集，专门针对健康和疾病中干细胞激活的转录后机制的独立研究。科罗拉多大学博尔德分校的特殊研究环境以及与肌肉和干细胞生物学（Olwin，Leinwand和Yi博士），mRNA生物化学（Roy帕克博士）和临床前小鼠肉瘤模型（大卫基尔希博士）专家的密切指导/合作，将使这些研究工作顺利完成。最终，本提案中概述的研究和培训计划将为建立致力于了解肌肉干细胞稳态的基本机制以及这些过程如何在疾病中解除管制的学术研究生涯奠定基础。

 DESCRIPTION (provided by applicant): Postnatal growth and repair of skeletal muscle requires adult muscle stem cells called satellite cells. Located between the myofiber plasma membrane and the basal lamina, satellite cells are generally maintained as a mitotically quiescent population until stimulated to activate and exit quiescence. During activation, satellite cells upregulate MyoD, a master regulatory transcription factor in muscle. However, the mechanisms governing exit from quiescence and subsequent MyoD expression are poorly understood. Gene expression profiling of in vivo satellite cell activation revealed significant depletion of transcripts encoding proteins involved in mRNA decay, strongly implicating post-transcriptional mRNA regulation in satellite cell activation. In this proposal, I present evidence that one of these mRNA decay factors, Tristetraprolin (TTP), suppresses satellite cell activation by destabilizing MyoD mRNA. Thus, post-transcriptional mRNA regulation by TTP may play an important role in the steady-state maintenance and re-acquisition of satellite cell quiescence required for satellite cell self-renewal following activation. This proposal will address: 1) TTP/Tis11-family function during muscle regeneration, 2) mRNA targets mediating TTP/Tis11-family function during satellite cell activation, and 3) corruption/rewiring of this homeostatic network during sarcoma initiation and progression. These research aims are coupled with hands-on training components in advanced mouse genetics, RNA biochemistry, and bioinformatics, and complement my previous experiences studying cancer (graduate school) and adult stem cell signaling (prior postdoctoral training). The opportunities outlined in this proposal are designed to provide me with a multidisciplinary conceptual background and experimental toolset tailored towards independent study of post-transcriptional mechanisms of stem cell activation in health and disease. An exceptional research environment at the University of Colorado-Boulder as well as close mentorship by/collaboration with experts in muscle and stem cell biology (Drs. Olwin, Leinwand and Yi), mRNA biochemistry (Dr. Roy Parker) and pre-clinical mouse sarcoma models (Dr. David Kirsch), will enable successful completion of these research endeavors. Ultimately, the research and training plan outlined in this proposal will lay a foundation for the establishment of an academic research career dedicated to understanding fundamental mechanisms of muscle stem cell homeostasis and how these processes are deregulated in disease.