Department of Anatomy, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand.
Dev Dyn. 2013 Sep;242(9):1043-55. doi: 10.1002/dvdy.23998. Epub 2013 Jul 22.
Vertebrate muscles are defined and patterned at the stage of primary myotube formation, but there is no clear description of how these cells form in vivo. Of particular interest is whether primary myotubes are "seeded" by a unique myoblast population that differentiates as mononucleated myocytes, similar to the founder myoblasts of insects.
We analyzed the cell populations and processes leading to initiation of primary myogenesis in limb buds of rats and mice. Pax3(+ve) myogenic precursors migrate into the limb bud and initially consolidate into dorsal and ventral muscle masses in the absence of Pax7 expression. Approximately a day later, Pax7(+ve) cells appear in the central aspect of the limb base and subsequently throughout the limb muscle masses. Primary myogenesis is initiated within each muscle mass at a time when only Pax3, and not Pax7, protein can be detected. Primary myotubes form initially as elongate mononucleated myocytes, well before cleavage of the muscle masses has occurred. Multinucleate myotubes appear approximately a day later. A similar process is seen during initiation of chick limb primary myogenesis.
Primary myotubes of vertebrate limb muscles are initiated by mononucleated myocytes, that appear structurally analogous to the founder myoblasts of insects.
脊椎动物的肌肉在初级肌管形成阶段被定义和定型，但对于这些细胞如何在体内形成还没有明确的描述。特别感兴趣的是，初级肌管是否是由分化为单核肌细胞的独特成肌细胞群体“播种”的，类似于昆虫的创始成肌细胞。
我们分析了导致大鼠和小鼠肢芽中初级肌发生起始的细胞群体和过程。Pax3(+ve)成肌前体细胞迁移到肢芽中，在没有 Pax7 表达的情况下，最初整合到背侧和腹侧肌肉块中。大约一天后，Pax7(+ve)细胞出现在肢基部的中央部分，随后出现在整个肢肌肉块中。在每个肌肉块中，当只能检测到 Pax3 蛋白而不能检测到 Pax7 蛋白时，初级肌管就开始形成。初级肌管最初形成长形单核肌细胞，远早于肌肉块的分裂。多核肌管大约一天后出现。在鸡肢初级肌发生的起始过程中也可以看到类似的过程。
脊椎动物肢体肌肉的初级肌管由单核肌细胞启动，这些细胞在结构上类似于昆虫的创始成肌细胞。
