Un Aperçu Comparatif De La Gastrulation Chez Les Chordés

Jl, Pasteels

doi:10.1111/j.1469-185x.1940.tb00942.x

Cited by 44 publications

(8 citation statements)

References 49 publications

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“…4 ), gastrulation of the enigmatic common ancestor of birds and mammals would most likely be accomplished by a blastoporal plate instead of a primitive streak. The primitive streak could thus have emerged twice in amniotes ( Gilland and Burke, 2004 ) as a result of a morphogenetic constraint ( Richardson and Chipman, 2003 ). The apparent kinship of experimentally generated rabbit primitive streaks with the reptilian blastoporal plate, and the rise of reptilian model organisms ( Coolen et al, 2008 ; Bertocchini et al, 2013 ), now call for further analysis of the PCP pathway in reptiles to determine whether cellular motility might have enabled convergent evolution of vertebrate gastrulation while leaving the specification of the organizer unaffected.…”

Section: Resultsmentioning

confidence: 99%

Rho kinase activity controls directional cell movements during primitive streak formation in the rabbit embryo

2015

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During animal gastrulation, the specification of the embryonic axes is accompanied by epithelio-mesenchymal transition (EMT), the first major change in cell shape after fertilization. EMT takes place in disparate topographical arrangements, such as the circular blastopore of amphibians, the straight primitive streak of birds and mammals or in intermediate gastrulation forms of other amniotes such as reptiles. Planar cell movements are prime candidates to arrange specific modes of gastrulation but there is no consensus view on their role in different vertebrate classes. Here, we test the impact of interfering with Rho kinase-mediated cell movements on gastrulation topography in blastocysts of the rabbit, which has a flat embryonic disc typical for most mammals. Time-lapse video microscopy, electron microscopy, gene expression and morphometric analyses of the effect of inhibiting ROCK activity showed – besides normal specification of the organizer region – a dose-dependent disruption of primitive streak formation; this disruption resulted in circular, arc-shaped or intermediate forms, reminiscent of those found in amphibians, fishes and reptiles. Our results reveal a crucial role of ROCK-controlled directional cell movements during rabbit primitive streak formation and highlight the possibility that temporal and spatial modulation of cell movements were instrumental for the evolution of gastrulation forms.

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Section: Resultsmentioning

confidence: 99%

Rho kinase activity controls directional cell movements during primitive streak formation in the rabbit embryo

2015

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“…The very existence in unincubated avian blastoderms of a Rauber's sickle (1876) (formerly called Koller's sickle: 1882) has been vigorously debated for decades. Principal opponents to its existence have been Peter (1938) and Pasteels (1937Pasteels ( , 1940, who consigned the sickle to oblivion. By their strong scientific impact the sickle was voluntarily or involuntarily forgotten by most investigators until the 1970s.…”

Section: Discussionmentioning

confidence: 99%

Positional information by rauber's sickle and a new look at the mechanisms of primitive streak initiation in avian blastoderms

Callebaut¹,

Nueten²,

Bortier³

et al. 2003

Journal of Morphology

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The present experimental in vitro study suggests that a primitive streak (PS) in avian blastoderms is induced by diffusion of morphogenetic substances emanating from Rauber's sickle. Indeed, even without direct contact between a quail Rauber's sickle and the reacting upper layer (by interposition of a vitelline membrane), a PS can be induced in the isolated area centralis or antisickle region of unincubated chicken blastoderms. The so-formed PSs are localized below the vitelline membrane in the immediate neighborhood of the apposed Rauber's sickle material. This seems to indicate that Rauber's sickle organizes the formation of the avian PS according to the basic concept of "positional information." The morphogenetic substances seem to have an effect only on the formation of a PS. Each part of Rauber's sickle seems to have, point by point, the same thickening and PS-inducing effect on each corresponding part of the underlying upper layer (UL). By a mechanism of sliding over the basement membrane and fusion, this finally results in the formation of one single median PS. Our study shows that a PS can be induced in the total absence of hypoblast (sickle endoblast) or caudal marginal zone, by only the presence of Rauber's sickle material. In contrast, the differentiation of mesoblast into blood islands under the influence of Rauber's sickle and neural tissue development are impaired by the interposition of a vitelline membrane. The latter could be due to the absence of a normal interaction of Rauber's sickle-derived sickle endoblast with endophyll and/or upper layer and the absence of cranial migration of the mesoblast. Thus, earlier studies and the present study indicate the existence of a temporospatially bound cascade of gastrulation and neurulation phenomena and blood island formation in the avian blastoderm, starting from Rauber's sickle, the primary major organizer with inducing, inhibiting, and dominating potencies. The latter not only plays a role by secretion of signaling molecules, but also influences development by its cell lineages (junctional endoblast and sickle endoblast).

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“…Before gastrulation, the embryo of reptiles, birds and most mammals is a large flat disc of epithelial cells (epiblast) ( Pasteels, 1940 ). In the chick, the 50,000 or so cells that comprise the embryonic epiblast (area pellucida, 3–5 mm in diameter) move as two bilaterally symmetrical whorls, known as the ‘Polonaise’ pattern ( Gräper, 1929 ; Wetzel, 1929 ) ( Figure 1 , stage EGK XI-XIV).…”

Section: Introductionmentioning

confidence: 99%

Local cell interactions and self-amplifying individual cell ingression drive amniote gastrulation

Voiculescu

Bodenstein

Lau

et al. 2014

eLife

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Gastrulation generates three layers of cells (ectoderm, mesoderm, endoderm) from a single sheet, while large scale cell movements occur across the entire embryo. In amniote (reptiles, birds, mammals) embryos, the deep layers arise by epithelial-to-mesenchymal transition (EMT) at a morphologically stable midline structure, the primitive streak (PS). We know very little about how these events are controlled or how the PS is maintained despite its continuously changing cellular composition. Using the chick, we show that isolated EMT events and ingression of individual cells start well before gastrulation. A Nodal-dependent ‘community effect’ then concentrates and amplifies EMT by positive feedback to form the PS as a zone of massive cell ingression. Computer simulations show that a combination of local cell interactions (EMT and cell intercalation) is sufficient to explain PS formation and the associated complex movements globally across a large epithelial sheet, without the need to invoke long-range signalling.DOI: http://dx.doi.org/10.7554/eLife.01817.001

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Un Aperçu Comparatif De La Gastrulation Chez Les Chordés

Cited by 44 publications

References 49 publications

Rho kinase activity controls directional cell movements during primitive streak formation in the rabbit embryo

Rho kinase activity controls directional cell movements during primitive streak formation in the rabbit embryo

Positional information by rauber's sickle and a new look at the mechanisms of primitive streak initiation in avian blastoderms

Local cell interactions and self-amplifying individual cell ingression drive amniote gastrulation

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