Schlueter J, Brand T
Cell and Developmental Biology, University of Würzburg, Würzburg, Germany.
Cytogenet Genome Res. 2007;117(1-4):256-67. doi: 10.1159/000103187.
Left-right asymmetry of internal organs is widely distributed in the animal kingdom. The chick and mouse embryos have served as important model organisms to analyze the mechanisms underlying the establishment of the left-right axis. In the chick embryo many genes have been found to be asymmetrically expressed in and around the node, while the same genes in the mouse show symmetric expression patterns. In the mouse there is strong evidence for an establishment of left-right asymmetry through nodal cilia. In contrast, in the chick and in many other organisms left-right asymmetry is probably generated by an early-acting event involving membrane depolarization. In both birds and mammals a conserved Nodal-Lefty-Pitx2 module exists that controls many aspects of asymmetric morphogenesis. This review also gives examples of divergent mechanisms of establishing asymmetric organ formation. Thus there is ample evidence for conserved and non-conserved strategies to generate asymmetry in birds and mammals.
内脏器官的左右不对称在动物界广泛存在。鸡和小鼠胚胎已成为分析左右轴建立机制的重要模式生物。在鸡胚胎中，许多基因在节点及其周围呈不对称表达，而在小鼠中相同的基因则表现出对称的表达模式。在小鼠中，有强有力的证据表明通过节点纤毛建立了左右不对称。相比之下，在鸡和许多其他生物中，左右不对称可能是由涉及膜去极化的早期作用事件产生的。在鸟类和哺乳动物中都存在一个保守的Nodal-Lefty-Pitx2模块，它控制着不对称形态发生的许多方面。本综述还给出了建立不对称器官形成的不同机制的例子。因此，有充分的证据表明在鸟类和哺乳动物中存在保守和非保守的产生不对称的策略。
