Molecular evidence for deep evolutionary roots of bilaterality in animal development
Molecular evidence for deep evolutionary roots of bilaterality in animal development
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DOI：
10.1073/pnas.0601257103
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发表时间：
2006-07-25
影响因子：
11.1
通讯作者：
Martindale, Mark Q.
中科院分区：
文献类型：
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作者：
Matus, David Q.;Pang, Kevin;Martindale, Mark Q.
几乎所有的后生动物都显示出两侧性的迹象，但据信两侧性动物是在数亿年前从径向对称的形式中产生的。刺胞动物（珊瑚、海葵和“刺胞鱼”）在双壁藻辐射之前就与其他动物分化了。它们是双胚层的，通常以围绕其纵轴（口-背口）径向对称为特征。我们已经研究了部署的直系同源物的一些家庭成员的发育调控基因，不对称表达的两侧胚胎发生过程中的海葵，Nematostella vectensis。研究了分泌的TGF-β基因Nv-dpp、Nv-BMPS-8、六种TGF-β拮抗剂（NvChordin、NvNoggin 1、NvNoggin 2、NvGremlin、NvFollistatin和NvFollistatin样）、同源结构域蛋白NvGoosecoid（NvGsc）和NvGbx以及分泌的导向因子NvNetrin。NvDpp、NvChordin、NvNoggin 1、NvGsc和NvNetrin沿着垂直于口-背口轴（定向轴）的轴不对称地表达。此外，NvGbx和NvChordin在身体的左侧和右侧的限制性结构域中表达，表明方向轴与双侧背腹轴同源。NvNoggin 1和NvGsc的不对称表达似乎是由经典Wnt信号通路维持的。NvNoggin 1、NvNetrin和Hox直系同源物NvAnthox 7、NvAnthox 8、NvAnthox 1a和NvAnthox 6的不对称表达，以及NvNoggin 1能够在非洲爪蟾胚胎中诱导第二轴的观察结果表明，N. vectensis可能具有双侧中枢神经系统组织的前体。
Nearly all metazoans show signs of bilaterality, yet it is believed the bilaterians arose from radially symmetric forms hundreds of millions of years ago. Cnidarians (corals, sea anemones, and "jelly-fish") diverged from other animals before the radiation of the Bilateria. They are diploblastic and are often characterized as being radially symmetrical around their longitudinal (oral-aboral) axis. We have studied the deployment of orthologs of a number of family members of developmental regulatory genes that are expressed asymmetrically during bilaterian embryogenesis from the sea anemone, Nematostella vectensis. The secreted TGF-beta genes Nv-dpp, Nv-BMPS-8, six TGF-beta antagonists (NvChordin, NvNoggin 1, NvNoggin2, NvGremlin, NvFollistatin, and NvFollistatin-like), the homeodomain proteins NvGoosecoid (NvGsc) and NvGbx, and the secreted guidance factor, NvNetrin, were studied. NvDpp, NvChordin, NvNoggin1, NvGsc, and NvNetrin are expressed asymmetrically along the axis perpendicular to the oral-aboral axis, the directive axis. Furthermore, NvGbx, and NvChordin are expressed in restricted domains on the left and right sides of the body, suggesting that the directive axis is homologous with the bilaterian dorsal-ventral axis. The asymmetric expression of NvNoggin1 and NvGsc appear to be maintained by the canonical Wnt signaling pathway. The asymmetric expression of NvNoggin1, NvNetrin, and Hox orthologs NvAnthox7, NvAnthox8, NvAnthox1a, and NvAnthox6, in conjunction with the observation that NvNoggin1 is able to induce a secondary axis in Xenopus embryos argues that N. vectensis could possess antecedents of the organization of the bilaterian central nervous system.