Lalonde Robert L, Akimenko Marie-Andrée
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Int J Dev Biol. 2018;62(11-12):705-716. doi: 10.1387/ijdb.180248rl.
The evolution of tetrapod limbs from paired fish fins comprised major changes to the appendicular dermal and endochondral skeleton. Fish fin rays were lost, and the endochondral bone was modified and elaborated to form three distinct segments common to all tetrapod limbs: the stylopod, the zeugopod and the autopod. Identifying the molecular mechanisms that contributed to these morphological changes presents a unique insight into our own evolutionary history. This review first summarizes previously identified cis-acting regulatory elements for the 5'HoxA/D genes and actinodin1 that were tested using transgenic swap experiments between fish and tetrapods. Conserved regulatory networks provide evidence for a deep homology between distal fin structures and the autopod, while diverging regulatory strategies highlight potential molecular mechanisms that contributed to the fin-to-limb transition. Next, we summarize studies that performed functional analysis to recapitulate fish-tetrapod diverging regulatory strategies and then discuss their potential morphological consequences during limb evolution. Finally, we also discuss here some of the advantages and disadvantages of using zebrafish to study molecular and morphological changes during the fin-to-limb transition.
从成对的鱼鳍进化而来的四足动物肢体，对附肢的真皮和软骨内骨骼产生了重大变化。鱼鳍鳍条消失，软骨内骨骼经过改造和细化，形成了所有四足动物肢体共有的三个不同部分：上肢骨、中肢骨和远端骨。确定导致这些形态变化的分子机制，为我们了解自身的进化历史提供了独特的视角。本综述首先总结了先前鉴定的5'HoxA/D基因和肌动蛋白odin1的顺式作用调控元件，这些元件是通过鱼类和四足动物之间的转基因交换实验进行测试的。保守的调控网络为远端鳍结构和远端骨之间的深度同源性提供了证据，而不同的调控策略则突出了导致鳍到肢体转变的潜在分子机制。接下来，我们总结了进行功能分析以重现鱼类 - 四足动物不同调控策略的研究，然后讨论它们在肢体进化过程中的潜在形态学后果。最后，我们还在此讨论了使用斑马鱼研究鳍到肢体转变过程中的分子和形态变化的一些优缺点。
