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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762062
• 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.

维持和修复成年组织的干细胞对周围微环境提供的信号具有很大的依赖，通常称为利基市场。在骨骼肌中，这种对干细胞的细分调节特别复杂，取决于多种不同的细胞类型，分泌生长因子和具有指导性的细胞外基质（ECM），以严格调节的时空方式。肌肉干细胞（MUSC）的基本特性，例如静止，自我更新和区分能力，取决于利基的组成。 然而，尽管它在MUSC的功能中起着重要作用，但构建和启发性信号的利基市场仍未完全理解。值得注意的是，尤其仍然是神秘的，哪些细胞和细胞外提示在小裂控制MUSC静止中，这是重要的休眠维持状态，这对于哺乳动物保持肌肉的终身能力至关重要，并从伤害中恢复。我们拟议的NSERC研究计划的重点是通过研究静态MUSC的微环境调节来填补这一空白。我们的最新进展和初步实验表明，quiescent Musc雇用了一种称为dystroglycan（DAG）的受体来依靠Nichee ECM。我们观察到在他莫昔芬诱导的MUSC特异性DAG敲除小鼠模型（IDAG-KO）中DAG的损失导致断裂静止和过早分化。重要的是，我们还发现缺乏DAG配体层粘连蛋白α2（LAMA2）的小鼠过度激活了过度分化的MUSC。在这里，我们提出了许多目标，以研究DAG及其ECM配体LAMA2保持MUSC静止的分子机制。具体目标是：（i）研究DAG作为MUSC的ECM受体的作用，并为维持静态状态引起的途径提供见解。该目标将基于对IDAG-KO小鼠的分析，并将依靠基于水凝胶的新测定法，该测定方法允许研究培养物中的MUSC静止。（ii）确定丰富的DAG配体LAMA2在静止的Musc Musc niche中的作用。该目标涉及在喇嘛2耗尽的环境中对MUSC的体内和体外询问。 （iii）研究肌肉组织中喇嘛2的沉积动力学和细胞来源。该目标是基于对LAMA的创新记者小鼠模型的产生和分析。此外，我们的工作将有助于更好地理解层粘连蛋白的生物学，并对其对发育，器官结构和功能的所有重要意义。