The arrangement of myonuclei in skeletal muscle tissue has long been used as a biomarker for muscle health, but there is a dearth of in vivo exploration of potential effects of myonuclear organization on the function and regeneration of skeletal muscle because traditional nuclear stains are performed on postmortem tissue. Therefore, we sought a transgenic method to produce a selective and persistent myonuclear label in whole muscles of living mice. We bred together a mouse line with skeletal muscle fiber-selective expression of Cre recombinase and a second mouse line with a Cre-inducible fluorescently tagged histone protein to generate a mouse line that produces a myonuclear label suitable for vital imaging and histology of fixed tissue. We tested the effectiveness of this vital label in three conditions known to generate abnormal myonuclear positioning. First, we injured myofibers of young mice with cardiotoxin. Second, this nuclear label was bred into a murine model of Duchenne muscular dystrophy. Finally, we examined old mice from this line that have undergone the natural aging process. Welch’s t test was used to compare wild type and transgenic mice. The resulting mouse line transgenically produces a vital red fluorescent label of myonuclei, which facilitates their in vivo imaging in skeletal muscle tissue. Transgenic fluorescent labeling of myonuclei has no significant effect on skeletal muscle function, as determined by twitch and tetanic force recordings. In each muscle examined, including those under damaged, dystrophic, and aged conditions, the labeled myonuclei exhibit morphology consistent with established literature, and reveal a specialized arrangement of subsynaptic myonuclei at the neuromuscular junction. Taken together, our results demonstrate that this mouse line provides a versatile tool to selectively visualize myonuclei within both living and fixed preparations of healthy, injured, diseased, and aged muscles.

中文翻译：

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独特的肌核重要标记，用于研究小鼠骨骼肌组织中的肌核排列。


骨骼肌组织中肌核的排列长期以来一直被用作肌肉健康的生物标志物，但由于传统的核染色是在死后进行，因此缺乏肌核组织对骨骼肌功能和再生的潜在影响的体内探索组织。因此，我们寻求一种转基因方法来在活体小鼠的整个肌肉中产生选择性且持久的肌核标记。我们将一个具有骨骼肌纤维选择性表达 Cre 重组酶的小鼠品系和一个具有 Cre 诱导型荧光标记组蛋白蛋白的第二个小鼠品系一起培育，以生成一个小鼠品系，该小鼠品系可产生适合固定组织的生命成像和组织学的肌核标记。我们在三种已知会产生异常肌核定位的情况下测试了这一重要标签的有效性。首先，我们用心脏毒素损伤幼鼠的肌纤维。其次，将这种核标签培育成杜氏肌营养不良症小鼠模型。最后，我们检查了该品系中经历自然衰老过程的年老小鼠。 Welch's t 检验用于比较野生型和转基因小鼠。由此产生的小鼠品系通过转基因方式产生重要的肌核红色荧光标记，这有利于它们在骨骼肌组织中的体内成像。根据抽搐和强直力记录确定，肌核的转基因荧光标记对骨骼肌功能没有显着影响。在检查的每块肌肉中，包括在受损、营养不良和老化条件下的肌肉，标记的肌核表现出与现有文献一致的形态，并揭示了神经肌肉接头处突触下肌核的特殊排列。 总而言之，我们的结果表明，该小鼠系提供了一种多功能工具，可以选择性地可视化健康、受伤、患病和衰老肌肉的活体和固定制剂中的肌核。