BACKGROUND The concerted activity of Meis and Hoxa11 transcription factors is essential for the subdivision of tetrapod limbs into proximo-distal (PD) domains; however, little is know about the evolution of this patterning mechanism. Here, we aim to study the expression of meis and hoxa11 orthologues in the median and paired rayed fins of zebrafish and in the lobed fins of the Australian lungfish. RESULTS First, a late phase of expression of meis1.1 and hoxa11b in zebrafish dorsal and anal fins relates with segmentation of endochondral elements in proximal and distal radials. Second, our zebrafish in situ hybridization results reveal spatial and temporal changes between pectoral and pelvic fins. Third, in situ analysis of meis1, meis3 and hoxa11 genes in Neoceratodus pectoral fins identifies decoupled domains of expression along the PD axis. CONCLUSIONS Our data raise the possibility that the origin of stylopod and zeugopod lies much deeper in gnathostome evolution and that variation in meis and hoxa11 expression has played a substantial role in the transformation of appendage anatomy. Moreover, these observations provide evidence that the Meis/Hoxa11 profile considered a hallmark of stylopod/zeugopod patterning is present in Neoceratodus.

中文翻译：

---

meis 和 hoxa11 在 dipnoan 和硬骨鱼鳍中的表达为脊椎动物附属物的进化提供了新的见解。

背景 Meis 和 Hoxa11 转录因子的协同活性对于将四足动物肢体细分为近-远（PD）结构域是必不可少的。然而，人们对这种模式机制的演变知之甚少。在这里，我们旨在研究 meis 和 hoxa11 直系同源物在斑马鱼的中位和成对的鳍状鳍以及澳大利亚肺鱼的裂鳍中的表达。结果 首先，斑马鱼背鳍和臀鳍中 meis1.1 和 hoxa11b 的晚期表达与近端和远端桡骨中软骨内元件的分割有关。其次，我们的斑马鱼原位杂交结果揭示了胸鳍和腹鳍之间的空间和时间变化。第三，对新角鲨胸鳍中的 meis1、meis3 和 hoxa11 基因的原位分析确定了沿 PD 轴的解耦表达域。结论 我们的数据提出了一种可能性，即 stylopod 和 zeugopod 的起源在 gnathostome 进化中的位置更深，而 meis 和 hoxa11 表达的变化在附件解剖学的转变中发挥了重要作用。此外，这些观察提供的证据表明，Meis/Hoxa11 轮廓被认为是新角龙中存在的 stylopod/zeugopod 模式的标志。