两侧对称动物左右不对称发生机制研究进展

Progress on the mechanism of left-right asymmetrical patterning in bilateriansv

左右不对称是两侧对称动物的重要特征,其形成机制一直是发育生物学领域备受关注的科学问题之一。脊椎动物的左右不对称发生经过3个重要阶段:左右对称性的打破,左右不对称信号的建立和维持,以及左右不对称器官的形态发生。多数脊椎动物在胚胎发育阶段依赖纤毛产生定向液流打破胚胎的左右对称性,随后建立Nodal-Pitx2左右不对称信号,最后由Pitx2等基因指导左右不对称器官的形态发生过程。无脊椎动物中存在不依赖纤毛介导的Nodal-Pitx不对称信号表达机制,甚至具有完全独立的左右不对称发育机制。本文结合最新的左右不对称器官发育机制的研究进展,综述了脊椎动物和无脊椎动物胚胎左右不对称的发生过程及相关基因和信号通路,有助于深入理解左右不对称器官发育的过程,以期为追溯左右不对称器官发育机制的起源演化提供参考。

Left-right asymmetry is an essential feature in bilateral animals.The mechanism underlying the left-right asymmetrical organ morphogenesis is a central question in developmental biology.Studies in vertebrates show that left-right asymmetry formation needs three essential steps:the initial left-right symmetry breaking,the left-right asymmetrical gene expression,and the left-right asymmetrical organ morphogenesis.Many vertebrates use cilia to produce directional fluid flow to break symmetry during embryonic development,asymmetric Nodal-Pitx2 signaling to pattern the left-right asymmetry,and Pitx2 and other genes to control the morphogenesis of asymmetrical organs.In invertebrates,there are left-right mechanisms independent of cilia and even others more different from that of vertebrates.In this review,we summarize the major steps and relevant molecular mechanisms of left-right asymmetric development in vertebrates and invertebrates,aiming to provide a reference for the understanding of the origin and evolution of the left-right developmental mechanism.