Satellite Cell Development and Potential

肌肉损伤刺激正常静止的肌肉卫星细胞重新进入细胞周期，并执行 生肌计划，恢复肌肉结构和功能。而本质功能是 卫星细胞在肌肉修复中的作用已经被认识到很多年了，关于 它们的胚胎学起源、发育潜力和更新机制仍未解决。这个 本提案使用独特的转基因小鼠品系和基于Cre/loxP的谱系追踪方法 重组以研究体内卫星细胞生物学的这些关键方面。为了调查竞争对手 假设卫星细胞来源于胎儿成肌细胞和血管系统的细胞(例如内皮细胞 前体)，相关的细胞类型将通过使两个细胞类型杂交而被特异性地永久标记为LacZ 小鼠品系，在一种细胞类型控制下表达Cre重组酶基因的转基因小鼠- 特异性启动子/增强子(成肌细胞为MyoD-cre，血管来源细胞为tie2-cre和flk1-cre)和 LacZ表达依赖于Cre的报告小鼠品系。这些细胞是否代表卫星 将通过使用传输评估卫星细胞的β-半乳糖苷酶标记来确定细胞前体 电子显微镜，以及单纤维制剂的标准显微镜和共聚焦显微镜。类似的研究 在受伤的肌肉中将决定卫星细胞库是通过自我更新还是由干细胞维持 来源于骨骼肌内部或外部。卫星细胞的发展潜力将被确定 通过追踪肌肉损伤和单纤维培养中卫星细胞的命运。野外实验- 类型的小鼠将与在MyoD或Myf-5突变的小鼠身上进行平行实验进行比较 这些肌肉调节基因在卫星细胞生肌承诺中的作用。分析MyoD和 Myf-5在胚胎中的功能将定义胚胎可用的全部细胞命运选择 缺乏这些调控基因的肌源性前体，将提供新的比较洞察力 对胚胎和出生后肌肉发生的调节。总的来说，这些研究将显著地 促进了卫星细胞生物学的当前知识，并将为未来的研究提供基础 调控卫星细胞命运选择的信号和基因转录途径及其作用 祖先。

Muscle injury stimulates normally quiescent muscle satellite cells to re-enter the cell cycle and execute the myogenic program, resulting in the restoration of muscle structure and function. While the essential function of satellite cells in muscle repair has been recognized for many years, fundamental questions concerning their embryological origin, developmental potential, and mechanism of renewal remain unresolved. The present proposal uses unique transgenic mouse lines and lineage tracing approaches based on Cre/loxP recombination to investigate these key aspects of satellite cell biology in vivo. To investigate the competing hypotheses that satellite cells are derived from fetal myoblasts and cells of the vasculature (e.g. endothelial precursors), relevant cell types will be specifically and permanently labeled with lacZ by intercrossing two mouse strains, transgenic mice that express the gene for Cre recombinase under the control of a cell type- specific promoter/enhancer (MyoD-cre for myoblasts, Tie2-cre and Flk1-cre for vascular-derived cells) and a reporter mouse strain in which lacZ expression is Cre-dependent. Whether these cells represent satellite cell progenitors will be determined by assessing p-galactosidase labeling of satellite cells using transmission electron microscopy, and by standard and confocal microscopy of single-fiber preparations. Similar studies in injured muscle will determine whether the satellite cell pool is maintained by self-renewal, or by a stem cell source within or outside of skeletal muscle. The developmental potential of satellite cells will be determined by tracing the fates of satellite cells following muscle injury and in single-fiber cultures. Experiments in wild- type mice will be compared to parallel experiments in mice that are mutant for either MyoD or Myf-5 to test the function of these muscle regulatory genes in satellite cell myogenic commitment. Analysis of MyoD and Myf-5 functions in the embryo will define the full repertoire of cell fate choices available to embryonic myogenic precursors in the absence of these regulatory genes and will provide new comparative insights into the regulation of embryonic and postnatal myogenesis. Collectively, these studies will significantly advance current knowledge of satellite cell biology and will provide a foundation for future investigations into the signaling and gene transcriptional pathways that regulate cell fate choices of satellite cells and their progenitors.