Centre d'Etude de la Sensori-Motricité, UMR 8194 CNRS, Université Paris Descartes, Centre Universitaire des Saints-Pères, 45 rue des Saints-Pères, Paris, France.
Dev Dyn. 2012 May;241(5):995-1007. doi: 10.1002/dvdy.23780.
Although Xenopus is a key model organism in developmental biology, little is known about the myotome formation in this species. Here, we assessed the expression of myogenic regulatory factors of the Myod family (MRFs) during embryonic development and revealed distinct MRF programs.
The expression pattern of each MRF during embryonic development highlights three successive myogenic waves. We showed that a first median and lateral myogenesis initiates before dermomyotome formation: the median cell population expresses Myf5, Myod, and Mrf4, whereas the lateral one expresses Myod, moderate levels of Myogenin and Mrf4. The second wave of myoblasts arising from the dermomyotome is characterized by the full MRF program expression, with high levels of Myogenin. The third wave is revealed by Myf5 expression in the myotome and could contribute to the formation of plurinucleated fibers at larval stages. Furthermore, Myf5- or Myod-expressing anlagen are identified in craniofacial myogenesis.
The first median and lateral myogenesis and their associated MRF programs have probably disappeared in mammals. However, some aspects of Xenopus myogenesis have been conserved such as the development of somitic muscles by successive myogenic waves and the existence of Myf5-dependent and -independent lineages.
尽管非洲爪蟾是发育生物学的重要模式生物，但人们对该物种的肌节形成知之甚少。在这里，我们评估了 Myod 家族（MRFs）的肌生成调节因子在胚胎发育过程中的表达情况，并揭示了不同的 MRF 程序。
每个 MRF 在胚胎发育过程中的表达模式突出了三个连续的肌生成波。我们表明，在真皮肌节形成之前，首先出现中间和侧方肌发生：中间细胞群体表达 Myf5、Myod 和 Mrf4，而侧方细胞群体表达 Myod、中等水平的 Myogenin 和 Mrf4。来自真皮肌节的第二个成肌细胞波的特征是完整的 MRF 程序表达，具有高水平的 Myogenin。第三个波由肌节中的 Myf5 表达揭示，可能有助于幼虫阶段形成多核纤维。此外，在颅面肌发生中鉴定出 Myf5 或 Myod 表达的原基。
哺乳动物中可能已经消失了第一次中间和侧方肌发生及其相关的 MRF 程序。然而，非洲爪蟾肌发生的某些方面已经被保留下来，例如通过连续的肌生成波发育体节肌肉，以及存在 Myf5 依赖性和非依赖性谱系。
