Kumar Uday, Fang Chun-Yi, Roan Hsiao-Yuh, Hsu Shao-Chun, Wang Chung-Han, Chen Chen-Hui
Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, 11529, Taiwan.
Molecular and Biological Agricultural Sciences, Taiwan International Graduate Program, Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan.
EMBO J. 2024 Aug;43(15):3090-3115. doi: 10.1038/s44318-024-00136-y. Epub 2024 Jun 5.
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.
肌纤维数量和大小的急剧增加对于支持脊椎动物胚胎后期的生长至关重要。然而，促成这些增加的集体细胞行为仍然难以捉摸。在这里，我们创建了掌肌肌纤维标记和追踪系统，用于在整体上监测发育中的斑马鱼幼虫中约5000条快肌纤维的生长和命运。通过对同一幼虫个体内的单个肌纤维进行长时间的实时追踪，我们发现许多幼虫肌纤维在发育过程中很容易溶解，从而能够在原地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群体的逐渐但广泛的消除，导致在幼鱼后期几乎完全被替代。随后出现的成年肌纤维不仅持久，而且在形态和功能上与幼虫群体不同。此外，我们确定消除-替代过程依赖于自噬途径并由其驱动。总之，我们提出幼虫肌纤维的全身替代是脊椎动物胚胎后期发育过程中驱动机体肌肉生长的一个固有但以前未被注意到的过程。
