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端-远端(PD)结构域至关重要;但是,对这种模式机制的演变知之甚少。这里,我们旨在研究meis和hoxa11直向同源物在斑马鱼的正中和成对射线鳍以及澳大利亚肺鱼的浅鳍中的表达。
结果:首先,meis1.1和hoxa11b在斑马鱼背鳍和肛门鳍中的晚期表达与近端和远端放射状软骨内元素的分割有关。第二,我们的斑马鱼原位杂交结果揭示了胸鳍和骨盆鳍之间的时空变化。第三,新胸鳍中meis1,meis3和hoxa11基因的原位分析鉴定了沿PD轴的表达解耦结构域。
结论:我们的数据提出了这样一种可能性,即长足类和足足类的起源在下颌茎的进化中更深入,并且meis和hoxa11表达的变化在附肢解剖结构的转化中起着重要作用。此外,这些观察结果提供了证据,表明在Neoceratodus中存在被认为是stylopod/zeugopa图案标志的Meis/Hoxa11轮廓。
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.