Drastic increases in myofiber number and size are essential to support vertebrate post-embryonic growth. However, the collective cellular behaviors that enable these increases have remained elusive. Here, we created the palmuscle myofiber tagging and tracking system for in toto monitoring of the growth and fates of ~5000 fast myofibers in developing zebrafish larvae. Through live tracking of individual myofibers within the same individuals over extended periods, we found that many larval myofibers readily dissolved during development, enabling the on-site addition of new and more myofibers. Remarkably, whole-body surveillance of multicolor-barcoded myofibers further unveiled a gradual yet extensive elimination of larval myofiber populations, resulting in near-total replacement by late juvenile stages. The subsequently emerging adult myofibers are not only long-lasting, but also morphologically and functionally distinct from the larval populations. Furthermore, we determined that the elimination-replacement process is dependent on and driven by the autophagy pathway. Altogether, we propose that the whole-body replacement of larval myofibers is an inherent yet previously unnoticed process driving organismic muscle growth during vertebrate post-embryonic development.

中文翻译：

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幼虫肌纤维的全身替换在斑马鱼中产生永久性的成体肌纤维。


肌纤维数量和尺寸的急剧增加对于支持脊椎动物胚胎后生长至关重要。然而，导致这些增加的集体细胞行为仍然难以捉摸。在这里，我们创建了手掌肌纤维标记和跟踪系统，用于全面监测发育中的斑马鱼幼虫中约 5000 条快速肌纤维的生长和命运。通过长时间对同一个体内的单个肌纤维进行实时跟踪，我们发现许多幼虫肌纤维在发育过程中很容易溶解，从而能够现场添加新的和更多的肌纤维。值得注意的是，对多色条形码肌纤维的全身监测进一步揭示了幼虫肌纤维种群的逐渐而广泛的消除，导致幼虫后期几乎完全被替换。随后出现的成虫肌纤维不仅持久，而且在形态和功能上与幼虫种群不同。此外，我们确定消除替代过程依赖于自噬途径并由自噬途径驱动。总而言之，我们认为幼虫肌纤维的全身替换是脊椎动物胚胎后发育过程中驱动有机体肌肉生长的固有但以前未被注意到的过程。