Evolution of the therian face through complete loss of the premaxilla
Evolution of the therian face through complete loss of the premaxilla
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DOI：
10.1111/ede.12417
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发表时间：
2022-08
影响因子：
2.9
通讯作者：
Hiroki Higashiyama;D. Koyabu;Hiroki Kurihara
中科院分区：
文献类型：
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作者：
Hiroki Higashiyama;D. Koyabu;Hiroki Kurihara
颌骨的解剖结构在大多数硬骨鱼类中是高度保守的，包括四足动物。然而，我们最近的研究表明，前上颌骨，吻上颌骨，在兽目哺乳动物的进化过程中，被重新安排，被取代的中隔上颌至少在侧部。在本研究中，为了更多地了解从祖先上颌到兽面的进化过程，我们重新研究了兽前颌骨（切牙）的发育。通过比较小鼠、蝙蝠、山羊和牛胎儿，我们证实了兽前颌骨具有双重发育起源，即侧体和腭突。这种双重发展在兽目哺乳动物中广泛保留。使用Dlx 1-CreERT 2小鼠进行的细胞谱系追踪实验显示，腭突起源于下颌前区的腹侧部分，鼻腭神经分布于此，而侧体则从上颌神经区域的上颌突发育而来。通过对各种四足动物的比较分析，我们得出结论，腭突不应被认为是祖先前颌骨的一部分。它相当于非哺乳动物四足动物犁骨的前部区域。因此，目前的研究结果表明，真正的前上颌骨在兽目哺乳动物的进化过程中完全消失了，导致建立了独特的兽目面孔作为进化的新奇事物。根据胚胎发育过程中骨化中心的地形关系，重新考虑颅骨的同源框架是必要的。
The anatomical framework of the jawbones is highly conserved among most of the Osteichthyes, including the tetrapods. However, our recent study suggested that the premaxilla, the rostralmost upper jaw bone, was rearranged during the evolution of therian mammals, being replaced by the septomaxilla at least in the lateral part. In the present study, to understand more about the process of evolution from the ancestral upper jaw to the therian face, we re‐examined the development of the therian premaxilla (incisive bone). By comparing mouse, bat, goat, and cattle fetuses, we confirmed that the therian premaxilla has dual developmental origins, the lateral body and the palatine process. This dual development is widely conserved among the therian mammals. Cell‐lineage‐tracing experiments using Dlx1‐CreERT2 mice revealed that the palatine process arises in the ventral part of the premandibular domain, where the nasopalatine nerve distributes, whereas the lateral body develops from the maxillary prominence in the domain of the maxillary nerve. Through comparative analysis using various tetrapods, we concluded that the palatine process should not be considered part of the ancestral premaxilla. It rather corresponds to the anterior region of the vomerine bone of nonmammalian tetrapods. Thus, the present findings indicate that the true premaxilla was completely lost during the evolution of the therian mammals, resulting in the establishment of the unique therian face as an evolutionary novelty. Reconsideration of the homological framework of the cranial skeleton based on the topographical relationships of the ossification center during embryonic development is warranted.