Extrinsic Regulation of Muscle Stem Cell Quiescence

肌肉干细胞静止的外在调节

• 批准号: RGPIN-2017-05490
• 负责人: Bentzinger, Florian
• 金额: $ 2.84万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=710839
• 关键词: Extrinsic; Regulation; Muscle; Stem; Cell

Stem cells maintaining and repairing adult tissues have a strong dependency on signals provided by the surrounding microenvironment, often referred to as the niche. In skeletal muscle this niche regulation of stem cells is particularly complex and depends on a multitude of different cell types secreting growth factors and instructive extracellular matrix (ECM) in a tightly regulated spatio-temporal manner. Fundamental properties of muscle stem cells (MuSCs), such as quiescence, self-renewal and the ability to differentiate, are determined by the composition of the niche. However, in spite of its important role for the function of MuSCs, the architecture and the instructive signals the niche generates remain incompletely understood. Notably, it remains particularly enigmatic which cellular and extracellular cues in the niche control MuSC quiescence, the important dormant maintenance state that is essential to the life-long ability of mammals to maintain their muscles and recover from injuries. A major focus of our proposed NSERC research program will be to fill this gap in our biological understanding of the niche by studying the microenvironmental regulation of quiescent MuSCs. Our recent progress and preliminary experiments have revealed that quiescent MuSCs employ a receptor called dystroglycan (DAG) to adhere to the niche ECM. We observed that loss of DAG in a tamoxifen inducible MuSC specific DAG knockout mouse model (iDAG-KO) leads to a break quiescence and to premature differentiation. Importantly, we also discovered that mice deficient for the DAG ligand Laminin alpha 2 (LAMA2) have hyperactivated excessively differentiating MuSCs. Here we propose a number of objectives to investigate the molecular mechanisms through which DAG and its ECM ligand LAMA2 maintain MuSC quiescence. Specific objectives are: (I) To study the role of DAG as an ECM receptor for MuSCs and provide insights into the pathways it induces to maintain the quiescent state. This objective will be based on the analysis of iDAG-KO mice and will rely on novel hydrogel based assays that allow to study MuSCs quiescence in culture. (II) To determine the role of the abundant DAG ligand LAMA2 in the quiescent MuSC niche. This objective involves the in-vivo and in-vitro interrogation of the hyperactivated phenotype MuSC in a LAMA2 depleted environment. (III) To study the deposition dynamics and cellular sources of LAMA2 in muscle tissue. This objective is based on the generation and analysis of an innovative reporter mouse model for LAMA2. Taken together, the experiments outlined in this proposal will provide fundamental insights into the niche regulation of quiescent MuSCs that may well be extrapolated from skeletal muscle to other tissues. In addition, our work will contribute to a better understanding of the biology of Laminins with all their important implications for development, organ structure and function.

干细胞维持和修复成体组织强烈依赖于周围微环境（通常称为生态位）提供的信号。在骨骼肌中，干细胞的这种生态位调节特别复杂，依赖于多种不同的细胞类型，以严格调节的时空方式分泌生长因子和指导性细胞外基质（ECM）。肌肉干细胞（MuSCs）的基本特性，如静止、自我更新和分化能力，是由生态位的组成决定的。然而，尽管它在musc的功能中起着重要的作用，但其结构和产生的指示信号仍然不完全清楚。值得注意的是，在生态位中，哪些细胞和细胞外的信号控制着MuSC的静止，这是一种重要的休眠维持状态，对哺乳动物维持肌肉和从损伤中恢复的终身能力至关重要。我们提出的NSERC研究计划的一个主要重点将是通过研究静止musc的微环境调节来填补我们对生态位的生物学理解的空白。