Department of Zoology, Faculty of Science, Charles University in Prague, 12844 Prague, Czech Republic.
Department of Zoology, Comenius University in Bratislava, Bratislava, Slovakia.
Proc Biol Sci. 2023 Sep 13;290(2006):20231158. doi: 10.1098/rspb.2023.1158.
The vertebrate pharynx is a key embryonic structure with crucial importance for the metameric organization of the head and face. The pharynx is primarily built upon progressive formation of paired pharyngeal pouches that typically develop in post-oral (mandibular, hyoid and branchial) domains. However, in the early embryos of non-teleost fishes, we have previously identified pharyngeal pouch-like outpocketings also in the pre-oral domain of the cranial endoderm. This pre-oral gut (POG) forms by early pouching of the primitive gut cavity, followed by the sequential formation of typical (post-oral) pharyngeal pouches. Here, we tested the pharyngeal nature of the POG by analysing expression patterns of selected core pharyngeal regulatory network genes in bichir and sturgeon embryos. Our comparison revealed generally shared expression patterns, including , , , or between early POG and post-oral pharyngeal pouches POG thus shares pharyngeal pouch-like morphogenesis and a gene expression profile with pharyngeal pouches and can be regarded as a pre-mandibular pharyngeal pouch. We further suggest that pre-mandibular pharyngeal pouches represent a plesiomorphic vertebrate trait inherited from our ancestor's pharyngeal metameric organization, which is incorporated in the early formation of the pre-chordal plate of vertebrate embryos.
脊椎动物咽是一种关键的胚胎结构，对于头部和面部的体节组织具有至关重要的意义。咽主要通过成对咽囊的渐进形成构建而成，这些咽囊通常在口后（下颌、舌骨和鳃）区域发育。然而，在非硬骨鱼的早期胚胎中，我们之前在颅内内胚层的口前区域也发现了类似咽囊的膨出。这个口前肠（POG）通过原始肠腔的早期囊形成，随后是典型（口后）咽囊的顺序形成。在这里，我们通过分析比目鱼和鲟鱼胚胎中选定的核心咽调节网络基因的表达模式来测试 POG 的咽性质。我们的比较揭示了一般共同的表达模式，包括早期 POG 与口后咽囊之间的 、 、 或 ，因此 POG 具有类似咽囊的形态发生和与咽囊相似的基因表达谱，可以被视为前下颌咽囊。我们进一步提出，前下颌咽囊代表了从我们祖先的咽体节组织遗传而来的古脊椎动物特征，它被纳入了脊椎动物胚胎前索板的早期形成中。
