Pre-oral gut contributes to facial structures in non-teleost fishes
Pre-oral gut contributes to facial structures in non-teleost fishes
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DOI：
10.1038/nature23008
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发表时间：
2017-07-13
期刊：
影响因子：
64.8
通讯作者：
Cerny, Robert
中科院分区：
文献类型：
--
作者：
Minarik, Martin;Stundl, Jan;Cerny, Robert
尽管脊椎动物的口腔和面部区域有各种各样的适应性修改，但它们的早期口咽发育被认为是严格一致的。它涉及口和咽囊的顺序形成，外胚层形成外表面，内胚层形成内表面，通常（1，2）。在脊椎动物胚胎的最前部区域，外胚层和内胚层直接并置，并且该最早的外-内胚层界面的初始发育，即初级口（3），通常涉及限制前肠内胚层的前部扩张的外胚层口膜内陷（3，4）。在这里，我们提出的证据表明，在现存的非硬骨鱼的胚胎，口（stomodeal）的形成之前，突出的口前肠憩室（POGD）之间的前脑和屋顶的形成口的发展。微计算机断层扫描（micro-CT）成像的bichir，鲟鱼和加尔胚胎显示，前肠outpocketing在口前域开始，甚至在咽囊的顺序形成。口前部的前肠衍生细胞的存在通过体内实验进一步证实，该实验允许对早期内胚层衬里进行特异性追踪。我们表明，POGD在鲟鱼有助于口面的表面，其幼虫，包括口腔牙齿，嘴唇，和感觉触须。据我们所知，这是第一个完整的证据，内胚层起源的外部颅面结构在任何脊椎动物。在bichir和gar胚胎中，POGD形成突出的颅粘附器官，这是自由生活的脊索动物幼虫的古老bauplan的特征。POGD因此似乎可以说是祖先的所有射线鳍鱼类，其拓扑结构，咽状形态发生和基因表达表明，它们是进化相关的前肠衍生憩室的早期脊索动物和半脊索动物胚胎。因此，POGD的形成可能代表了一个祖先的发展模块与深后口起源。
Despite the wide variety of adaptive modifications in the oral and facial regions of vertebrates, their early oropharyngeal development is considered strictly uniform. It involves sequential formation of the mouth and pharyngeal pouches, with ectoderm outlining the outer surface and endoderm the inner surface, as a rule(1,2). At the extreme anterior domain of vertebrate embryos, the ectoderm and endoderm directly juxtapose and initial development of this earliest ecto-endoderm interface, the primary mouth(3), typically involves ectodermal stomodeal invagination that limits the anterior expansion of the foregut endoderm(3,4). Here we present evidence that in embryos of extant non-teleost fishes, oral (stomodeal) formation is preceded by the development of prominent pre-oral gut diverticula (POGD) between the forebrain and roof of the forming mouth. Micro-computed tomography (micro-CT) imaging of bichir, sturgeon and gar embryos revealed that foregut outpocketing at the pre-oral domain begins even before the sequential formation of pharyngeal pouches. The presence of foregut-derived cells in the front of the mouth was further confirmed by in vivo experiments that allowed specific tracing of the early endodermal lining. We show that POGD in sturgeons contribute to the orofacial surface of their larvae, comprising oral teeth, lips, and sensory barbels. To our knowledge, this is the first thorough evidence for endodermal origin of external craniofacial structures in any vertebrate. In bichir and gar embryos, POGD form prominent cranial adhesive organs that are characteristic of the ancient bauplan of free-living chordate larvae. POGD hence seem arguably to be ancestral for all ray-finned fishes, and their topology, pharyngeal-like morphogenesis and gene expression suggest that they are evolutionarily related to the foregut-derived diverticula of early chordate and hemichordate embryos. The formation of POGD might thus represent an ancestral developmental module with deep deuterostome origins.