Hedgehog regulation of superficial slow muscle fibres in Xenopus and the evolution of tetrapod trunk myogenesis
Hedgehog regulation of superficial slow muscle fibres in Xenopus and the evolution of tetrapod trunk myogenesis
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DOI：
10.1242/dev.01194
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发表时间：
2004-07-01
期刊：
影响因子：
4.6
通讯作者：
Hughes, SM
中科院分区：
文献类型：
--
作者：
Grimaldi, A;Tettamanti, G;Hughes, SM
在四足动物系统发育中，躯干的巨大变化比四肢更明显的进化受到的关注要少。在体节中，来自附近组织的信号会诱导数波肌肉前体细胞。在羊膜动物和鱼类中，最早的肌生成需要刺猬 (Hh) 蛋白携带的来自腹侧中线的分泌信号。为了确定这种相似性是否代表进化同源性，我们检查了非洲爪蟾的肌发生，非洲爪蟾是了解脊椎动物中胚层模式的主要物种。非洲爪蟾胚胎形成两种不同类型的肌肉细胞，类似于斑马鱼的浅表慢肌纤维和内侧快肌纤维。与斑马鱼一样，XMyf5 表达和尾部体节中第一波早期浅表慢肌纤维的产生需要 Hh 信号传导。因此，Hh 依赖性的近轴肌发生可能是硬骨鱼、两栖动物和羊膜动物的祖先条件。我们的证据表明，中线来源的细胞迁移到外侧体节表面并产生浅表慢肌。这种细胞重新定向有助于非洲爪蟾体节的明显旋转。非洲爪蟾躯干的肌发生与尾部的不同。在躯干中，第一波浅表慢纤维缺失，这表明祖先生肌程序在四足动物躯干进化过程中发生了显着的适应。尽管早期内侧 XMyf5 表达需要脊索，但 Hh 信号传导无法驱动这些细胞减缓肌生成。随后，躯干和尾部体节均发育出第二波独立于 Hh 的慢纤维。这些纤维可能源自表达生肌决定基因 XMyf5、XMyoD 和 Pax3 的外细胞层，其模式让人想起羊膜动物皮肌切开术。因此，爪蟾体节与鱼类和羊膜动物具有共同的特征，这揭示了体节分化的进化。我们提出了一个从鱼类到四足动物躯干过渡过程中肌发生的进化适应模型。
In tetrapod phylogeny, the dramatic modifications of the trunk have received less attention than the more obvious evolution of limbs. In somites, several waves of muscle precursors are induced by signals from nearby tissues. In both amniotes and fish, the earliest myogenesis requires secreted signals from the ventral midline carried by Hedgehog (Hh) proteins. To determine if this similarity represents evolutionary homology, we have examined myogenesis in Xenopus laevis, the major species from which insight into vertebrate mesoderm patterning has been derived. Xenopus embryos form two distinct kinds of muscle cells analogous to the superficial slow and medial fast muscle fibres of zebrafish. As in zebrafish, Hh signalling is required for XMyf5 expression and generation of a first wave of early superficial slow muscle fibres in tail somites. Thus, Hh-dependent adaxial myogenesis is the likely ancestral condition of teleosts, amphibia and amniotes. Our evidence suggests that midline-derived cells migrate to the lateral somite surface and generate superficial slow muscle. This cell re-orientation contributes to the apparent rotation of Xenopus somites. Xenopus myogenesis in the trunk differs from that in the tail. In the trunk, the first wave of superficial slow fibres is missing, suggesting that significant adaptation of the ancestral myogenic programme occurred during tetrapod trunk evolution. Although notochord is required for early medial XMyf5 expression, Hh signalling fails to drive these cells to slow myogenesis. Later, both trunk and tail somites develop a second wave of Hh-independent slow fibres. These fibres probably derive from an outer cell layer expressing the myogenic determination genes XMyf5, XMyoD and Pax3 in a pattern reminiscent of amniote dermomyotome. Thus, Xenopus somites have characteristics in common with both fish and amniotes that shed light on the evolution of somite differentiation. We propose a model for the evolutionary adaptation of myogenesis in the transition from fish to tetrapod trunk.