The skeletal musculature of gnathostomes, which is derived from embryonic somites, consists of epaxial and hypaxial portions. Some hypaxial muscles, such as tongue and limb muscles, undergo de-epithelialization and migration during development. Delamination and migration of these myoblasts, or migratory muscle precursors (MMPs), is generally thought to be regulated by hepatocyte growth factor (HGF) and receptor tyrosine kinase (MET) signaling. However, the prevalence of this mechanism and the expression patterns of the genes involved in MMP development across different vertebrate species remain elusive. We performed a comparative analysis of Hgf and Met gene expression in several vertebrates, including mouse, chicken, dogfish (Scyliorhinus torazame), and lamprey (Lethenteron camtschaticum). While both Hgf and Met were expressed during development in the mouse tongue muscle, and in limb muscle formation in the mouse and chicken, we found no clear evidence for the involvement of HGF/MET signaling in MMP development in shark or lamprey embryos. Our results indicate that the expressions and functions of both Hgf and Met genes do not represent shared features of vertebrate MMPs, suggesting a stepwise participation of HGF/MET signaling in MMP development during vertebrate evolution.

中文翻译：

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HGF/MET信号在脊椎动物进化过程中逐步参与迁移肌肉前体的发育

有颚动物的骨骼肌组织来源于胚胎体节，由外轴部分和半轴部分组成。一些下轴肌肉，如舌头和四肢肌肉，在发育过程中经历去上皮化和迁移。这些成肌细胞或迁移肌前体 (MMP) 的分层和迁移通常被认为受肝细胞生长因子 (HGF) 和受体酪氨酸激酶 (MET) 信号传导的调节。然而，这种机制的普遍性和参与不同脊椎动物物种 MMP 发育的基因的表达模式仍然难以捉摸。我们对几种脊椎动物的 Hgf 和 Met 基因表达进行了比较分析，包括小鼠、鸡、角鲨 (Scyliorhinus torazame) 和七鳃鳗 (Lethenteron camtschaticum)。虽然 Hgf 和 Met 在小鼠舌肌发育过程中以及小鼠和鸡的肢体肌肉形成过程中都有表达，但我们没有发现 HGF/MET 信号传导参与鲨鱼或七鳃鳗胚胎 MMP 发育的明确证据。我们的结果表明，Hgf 和 Met 基因的表达和功能并不代表脊椎动物 MMP 的共同特征，表明 HGF/MET 信号在脊椎动物进化过程中逐步参与 MMP 发育。