Post-transcriptional Regulation of Satellite Cell Function

 描述(申请人提供)：骨骼肌出生后的生长和修复需要称为卫星细胞的成年肌肉干细胞。位于肌纤维质膜和基底膜之间的卫星细胞通常保持有丝分裂的静止群体，直到受到刺激而激活和退出静止。在激活过程中，卫星 细胞上调MyoD的表达，MyoD是肌肉中的主要调控转录因子。然而，控制退出静止状态和随后MyoD表达的机制尚不清楚。体内卫星细胞激活的基因表达谱显示编码参与mRNA衰退的蛋白的转录显著减少，强烈暗示转录后mRNA调控卫星细胞的激活。在这项提案中，我提出了证据表明，其中一种信使核糖核酸衰变的因子，雷公藤红素(TTP)，通过破坏MyoD信使核糖核酸的稳定来抑制卫星细胞的激活。因此，TTP对转录后mRNA的调控可能在卫星细胞激活后自我更新所需的卫星细胞静止的稳态维持和重新获得中发挥重要作用。这项建议将涉及：1)TTP/Tis11家族在肌肉再生过程中的功能，2)mRNA靶标在卫星细胞激活过程中介导TTP/Tis11家族功能，以及3)在肉瘤发生和发展过程中这种稳态网络的破坏/重新连接。这些研究目标与高级小鼠遗传学、RNA生物化学和生物信息学的实践培训部分相结合，补充了我之前研究癌症(研究生院)和成人干细胞信号(之前的博士后培训)的经验。这项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，专门为独立研究健康和疾病中干细胞激活的转录后机制而量身定做。科罗拉多大学博尔德分校卓越的研究环境，以及肌肉和干细胞生物学(Olwin、Leinwand和Yi博士)、信使核糖核酸生物化学(Roy Parker博士)和临床前小鼠肉瘤模型(David Kirsch博士)专家的密切指导/合作，将使这些研究工作得以成功完成。最终，这项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在疾病中如何放松调控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.