原肠胚形成是胚胎形成中的一个关键事件。控制羊膜动物中原肠胚形成运动的机制不是很清楚，并且经常是从关于其他物种的研究来推断的。现在，Voiculescu等人报告了对在原肠胚形成过程中活鸡胚胎中各种细胞运动的首次时差分析（time-lapse analysis）。多光子时差显微镜分析显示了与在鱼类和两栖类中所描述的运动不同的运动，这对脊椎动物胚胎学研究及原肠胚形成的演化研究有重要意义。尤其是，这项工作显示了一个原肠胚形成之前的早期插入事件，它可能是回答关于羊膜动物原始条纹是怎样从远古胚孔演化而来这样一个经典问题的关键。
原始出处:
Nature 449, 1049-1052 (25 October 2007) | doi:10.1038/nature06211; Received 4 April 2007; Accepted 31 August 2007; Published online 10 October 2007
The amniote primitive streak is defined by epithelial cell intercalation before gastrulation
Octavian Voiculescu1, Federica Bertocchini1, Lewis Wolpert1, Ray E. Keller2 & Claudio D. Stern1
Department of Anatomy & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, Virginia 22903, USA
Correspondence to: Octavian Voiculescu1Claudio D. Stern1 Correspondence and requests for materials should be addressed to O.V. (Email: o.voiculescu@ucl.ac.uk) or C.D.S. (Email: c.stern@ucl.ac.uk).
Abstract
During gastrulation, a single epithelial cell layer, the ectoderm, generates two others: the mesoderm and the endoderm. In amniotes (birds and mammals), mesendoderm formation occurs through an axial midline structure, the primitive streak1, the formation of which is preceded by massive 'polonaise' movements2, 3 of ectoderm cells. The mechanisms controlling these processes are unknown. Here, using multi-photon time-lapse microscopy of chick (Gallus gallus) embryos, we reveal a medio-lateral cell intercalation confined to the ectodermal subdomain where the streak will later form. This intercalation event differs from the convergent extension movements of the mesoderm described in fish and amphibians (anamniotes)4, 5, 6, 7, 8: it occurs before gastrulation and within a tight columnar epithelium. Fibroblast growth factor from the extraembryonic endoderm (hypoblast, a cell layer unique to amniotes) directs the expression of Wnt planar-cell-polarity pathway components to the intercalation domain. Disruption of this Wnt pathway causes the mesendoderm to form peripherally, as in anamniotes1, 9. We propose that the amniote primitive streak evolved from the ancestral blastopore by acquisition of an additional medio-lateral intercalation event, preceding gastrulation and acting independently of mesendoderm formation to position the primitive streak at the midline.
