Amnion formation in the mouse embryo: the single amniochorionic fold model
Amnion formation in the mouse embryo: the single amniochorionic fold model
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DOI：
10.1186/1471-213x-11-48
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发表时间：
2011-08-01
影响因子：
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通讯作者：
Zwijsen, A. N.
中科院分区：
文献类型：
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作者：
Pereira, Paulo N. G.;Dobreva, Mariya P.;Zwijsen, A. N.
背景：尽管在过去十年中对羊膜原肠胚形成的分子调控获得了详细的知识，但在小鼠中羊膜发育过程的描述和说明很少，并且存在相互矛盾的描述。了解小鼠早期胚胎及其胚胎外组织的形态发生和发育，对于正确解释命运图谱数据和具有原肠胚发育缺陷的小鼠突变体至关重要。此外，最近从羊膜中分离出具有干细胞特征的细胞，进一步证明了对羊膜形成过程的更好理解。在这里，我们重新审视小鼠羊膜形成的高度动态过程。羊膜的发育在原肠形成早期就开始了，并且与外腔的形成和羊膜褶的扩张密切相关。权威的描述包括两个羊膜折叠融合，一个大的后折叠和一个小的前折叠。我们通过对解剖的、分期的胚胎进行详细的组织形态学分析，并使用历史切片进行3D重建，挑战了这种“双羊膜折叠”模型。结果：胚外胚层和相关外胚层的后褶在原肠胚形成过程中早期由胚外胚层在原始条纹后的积累形成。以前被称为“羊膜后襞”，我们将其重新命名为“羊膜褶”（ACF），因为它形成羊膜和绒毛膜。ACF内的外腔形成似乎不涉及中胚层内的细胞凋亡。ACF和外腔在不破坏外胚层、胚外胚层和内脏内胚层前交界处的情况下扩张。没有形成单独的前襞；在三维重建中证实了它的缺失。羊膜和绒毛膜闭合偏心，靠近卵筒前缘：我们称之为“前分离点”。结论：在这里，我们调和先前对羊膜形成的描述，并提供新的命名法，以及动画，澄清和强调有助于羊膜发育的组织的排列和过程的动力学。根据我们的数据，羊膜和绒毛膜是由一个单一的羊膜绒毛膜折叠形成的。最后，我们对羊膜发育受损的突变小鼠模型进行了综述。
Background: Despite the detailed knowledge obtained over the last decade on the molecular regulation of gastrulation in amniotes, the process of amnion development has been poorly described and illustrated in mice, and conflicting descriptions exist. Understanding the morphogenesis and development not only of the early mouse embryo, but also of its extraembryonic tissues, is crucial for correctly interpreting fate-mapping data and mouse mutants with gastrulation defects. Moreover, the recent isolation from amnion of cells with stem cell features further argues for a better understanding of the process of amnion formation. Here, we revisit the highly dynamic process of amnion formation in the mouse. Amnion development starts early during gastrulation and is intimately related to the formation of the exocoelom and the expansion of the amniotic fold. The authoritative description involves the fusion of two amniotic folds, a big posterior and a smaller anterior fold. We challenged this 'two amniotic folds' model by performing detailed histomorphological analyses of dissected, staged embryos and 3D reconstructions using historical sections.Results: A posterior fold of extraembryonic ectoderm and associated epiblast is formed early during gastrulation by accumulation of extraembryonic mesoderm posterior to the primitive streak. Previously called the "posterior amniotic fold", we rename it the "amniochorionic fold" (ACF) because it forms both amnion and chorion. Exocoelom formation within the ACF seems not to involve apoptosis within the mesoderm. The ACF and exocoelom expand without disrupting the anterior junction of epiblast, extraembryonic ectoderm and visceral endoderm. No separate anterior fold is formed; its absence was confirmed in 3D reconstructions. Amnion and chorion closure is eccentric, close to the anterior margin of the egg cylinder: we name it the "anterior separation point".Conclusions: Here, we reconcile previous descriptions of amnion formation and provide new nomenclature, as well as an animation, that clarify and emphasize the arrangement of the tissues that contribute to amnion development and the dynamics of the process. According to our data, the amnion and the chorion are formed by a single amniochorionic fold initiated posteriorly. Finally, we give an overview on mutant mouse models with impaired amnion development.