Comparative morphology and development of extra-ocular muscles in the lamprey and gnathostomes reveal the ancestral state and developmental patterns of the vertebrate head.
Comparative morphology and development of extra-ocular muscles in the lamprey and gnathostomes reveal the ancestral state and developmental patterns of the vertebrate head.
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DOI：
10.1186/s40851-016-0046-3
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发表时间：
2016
影响因子：
2.7
通讯作者：
Wada H
中科院分区：
文献类型：
--
作者：
Suzuki DG;Fukumoto Y;Yoshimura M;Yamazaki Y;Kosaka J;Kuratani S;Wada H
脊椎动物头部的祖先形态一直是比较形态学和进化生物学中一个有趣的话题。脊椎动物头部的一个特殊组成部分是眼外肌（EOM）的存在，其发育机制和进化仍有待确定。板鳃类的头部中胚层经过局部上皮化形成三个头部腔，即眼外膜的前体。相反，在鸟类中，这些肌肉似乎主要从间充质头部中胚层发育。重要的是，在基底脊椎动物七鳃鳗，头部中胚层没有明显的头部腔或节段边界的迹象，和EOMs的发展没有得到很好的描述。此外，七鳃鳗EOMs的处置不同于其他脊椎动物，其中EOMs的形态模式是强烈保守的。为了更好地了解脊椎动物外胚层的进化和发育起源，我们详细探讨了七鳃鳗头部中胚层和外胚层的发育。我们发现，七鳃鳗EOM原基的处置不同，在有颚类，即使在最早的发展时期。我们还发现，近轴头中胚层的三个组成部分可以区分遗传（下颌前中胚层：Gsc+/TbxA-;下颌中胚层：Gsc-/TbxA-;舌骨中胚层：Gsc-/TbxA+），表明EOMs的遗传机制是保守的所有脊椎动物。我们的结论是，三方发展的起源EOMs很可能已经拥有的最新的共同祖先的脊椎动物。该祖先的EOM发育模式也被认为更类似于七鳃鳗，并且有颚动物EOM的配置很可能是通过冠状有颚动物共同祖先中发生的二次修饰而建立的。本文的在线版本（doi：10.1186/s40851-016-0046-3）包含补充材料，可供授权用户使用。
The ancestral configuration of the vertebrate head has long been an intriguing topic in comparative morphology and evolutionary biology. One peculiar component of the vertebrate head is the presence of extra-ocular muscles (EOMs), the developmental mechanism and evolution of which remain to be determined. The head mesoderm of elasmobranchs undergoes local epithelialization into three head cavities, precursors of the EOMs. In contrast, in avians, these muscles appear to develop mainly from the mesenchymal head mesoderm. Importantly, in the basal vertebrate lamprey, the head mesoderm does not show overt head cavities or signs of segmental boundaries, and the development of the EOMs is not well described. Furthermore, the disposition of the lamprey EOMs differs from those the rest of vertebrates, in which the morphological pattern of EOMs is strongly conserved. To better understand the evolution and developmental origins of the vertebrate EOMs, we explored the development of the head mesoderm and EOMs of the lamprey in detail. We found that the disposition of lamprey EOM primordia differed from that in gnathostomes, even during the earliest period of development. We also found that three components of the paraxial head mesoderm could be distinguished genetically (premandibular mesoderm: Gsc+/TbxA–; mandibular mesoderm: Gsc–/TbxA–; hyoid mesoderm: Gsc–/TbxA+), indicating that the genetic mechanisms of EOMs are conserved in all vertebrates. We conclude that the tripartite developmental origin of the EOMs is likely to have been possessed by the latest common ancestor of the vertebrates. This ancestor’s EOM developmental pattern was also suggested to have resembled more that of the lamprey, and the gnathostome EOMs’ disposition is likely to have been established by a secondary modification that took place in the common ancestor of crown gnathostomes. The online version of this article (doi:10.1186/s40851-016-0046-3) contains supplementary material, which is available to authorized users.