原腸胚形成是胚胎形成中的一個(gè)關(guān)鍵事件,?？刂蒲蚰?dòng)物中原腸胚形成運(yùn)動(dòng)的機(jī)制不是很清楚,，并且經(jīng)常是從關(guān)于其他物種的研究來(lái)推斷的?，F(xiàn)在,，Voiculescu等人報(bào)告了對(duì)在原腸胚形成過(guò)程中活雞胚胎中各種細(xì)胞運(yùn)動(dòng)的首次時(shí)差分析（time-lapse analysis）,。多光子時(shí)差顯微鏡分析顯示了與在魚(yú)類(lèi)和兩棲類(lèi)中所描述的運(yùn)動(dòng)不同的運(yùn)動(dòng),，這對(duì)脊椎動(dòng)物胚胎學(xué)研究及原腸胚形成的演化研究有重要意義。尤其是,，這項(xiàng)工作顯示了一個(gè)原腸胚形成之前的早期插入事件,，它可能是回答關(guān)于羊膜動(dòng)物原始條紋是怎樣從遠(yuǎn)古胚孔演化而來(lái)這樣一個(gè)經(jīng)典問(wèn)題的關(guān)鍵。
原始出處:
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: [email protected]) or C.D.S. (Email: [email protected]).
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.
