Cerberus-Nodal-Lefty-Pitx signaling cascade controls left-right asymmetry in amphioxus
Cerberus-Nodal-Lefty-Pitx signaling cascade controls left-right asymmetry in amphioxus
复制标题
Cerberus-Nodal-Lefty-Pitx 信号级联控制文昌鱼的左右不对称性
DOI：
10.1073/pnas.1620519114
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发表时间：
2017-04-04
影响因子：
11.1
通讯作者：
Wang, Yiquan
中科院分区：
文献类型：
--
作者：
Li, Guang;Liu, Xian;Wang, Yiquan
许多左右对称的动物会发展出遗传上的左右不对称。在脊椎动物中，这一过程是在Nodal信号传导的控制下，Nodal信号传导被Nodal拮抗剂Cerberus和Lefty限制在左侧。文昌鱼是最早分化的脊索动物谱系，在幼体时期就具有明显的左右不对称性。我们发现，Cerberus，Nodal，Lefty和它们的靶转录因子Pitx在文昌鱼胚胎中依次被激活。然后，我们通过基于转录激活因子样效应物核酸酶（TALEN）的敲除和热休克启动子（HSP）驱动的过表达来解决它们的功能。敲除Cerberus导致Nodal、Lefty和Pitx的异位右侧表达，而Cerberus的过表达抑制它们的左侧表达。Nodal的过度表达反过来抑制Cerberus，并在右侧异位激活Lefty和Pitx。我们还发现，左撇子抑制Nodal，而Pitx激活Nodal。这些数据联合收割机组合成一个模型，其中Cerberus确定左侧基因表达盒是被激活还是被抑制。这些调节步骤对于正常的左右不对称性的发展是必不可少的，因为当它们被破坏时，胚胎可能会形成两个表型左侧或两个表型右侧。我们的研究表明，控制左右不对称的调控盒在文昌鱼和脊椎动物的祖先中就已经存在。这包括Nodal抑制剂Cerberus和Lefty，它们都在反馈回路中与Nodal和联合收割机一起工作，以建立不对称的Pitx表达。Cerberus和Lefty在大多数无脊椎动物谱系中缺失，标志着这种机制是导致现代脊索动物谱系的创新。
Many bilaterally symmetrical animals develop genetically programmed left-right asymmetries. In vertebrates, this process is under the control of Nodal signaling, which is restricted to the left side by Nodal antagonists Cerberus and Lefty. Amphioxus, the earliest diverging chordate lineage, has profound left-right asymmetry as a larva. We show that Cerberus, Nodal, Lefty, and their target transcription factor Pitx are sequentially activated in amphioxus embryos. We then address their function by transcription activator-like effector nucleases (TALEN)-based knockout and heat-shock promoter (HSP)-driven overexpression. Knockout of Cerberus leads to ectopic right-sided expression of Nodal, Lefty, and Pitx, whereas overexpression of Cerberus represses their left-sided expression. Overexpression of Nodal in turn represses Cerberus and activates Lefty and Pitx ectopically on the right side. We also show Lefty represses Nodal, whereas Pitx activates Nodal. These data combine in a model in which Cerberus determines whether the left-sided gene expression cassette is activated or repressed. These regulatory steps are essential for normal left-right asymmetry to develop, as when they are disrupted embryos may instead form two phenotypic left sides or two phenotypic right sides. Our study shows the regulatory cassette controlling left-right asymmetry was in place in the ancestor of amphioxus and vertebrates. This includes the Nodal inhibitors Cerberus and Lefty, both of which operate in feedback loops with Nodal and combine to establish asymmetric Pitx expression. Cerberus and Lefty are missing from most invertebrate lineages, marking this mechanism as an innovation in the lineage leading to modern chordates.