Map of the Anlage fields in the avian unincubated blastoderm

Callebaut, M.; Nueten, Emmy Van; Bortier, Hilde; Harrisson, F.; Nassauw, Luc Van

doi:10.1076/ejom.34.5.347.13056

Cited by 23 publications

(19 citation statements)

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“…The fate of these sickle-shaped anlage fields in the unincubated blastoderm is at that moment, however, not yet definitively determined. This determination will occur only after 5 to 6 hr of incubation, when the deep layer elements have already influenced the upper layer (UL) as we could demonstrate for the neural anlage fields (Callebaut et al, 1996a). These observations suggest the existence of a kind of early ooplasmic and embryonic predisposition.…”

Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symsupporting

confidence: 60%

“…It bulges into the subgerminal space medially from the junctional endoblast (derived from Rauber's sickle). In its bottom, we find a sickle Callebaut et al, 1996a). Note the general eccentric sickle-shaped aspect of the anlage fields in the area centralis.…”

Section: Sickle Canalmentioning

confidence: 74%

“…All these expression domains are initially sickleshaped, i.e., spread more or less broadly and transversely to the future longitudinal axis. These expression domains are localized in the concavity of Rauber's sickle, where we have localized the similarly sickle-shaped anlage fields in the upper layer of the unincubated chicken blastoderm (Callebaut et al, 1996a).…”

Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symmentioning

confidence: 90%

“…By the use of the quail-chicken chimera technique (Callebaut et al, 1996a), we observed that, during normal blastoderm development, the upper layer of the caudal marginal zone (at the convexity of Rauber's sickle) is not undergoing gastrulation movements, in contrast to the upper layer of the area centralis (in the concavity of Rauber's sickle). This was also confirmed by Lawson and Schoenwolf (2001).…”

Section: Rauber's Sickle and Not The Caudal Marginal Zone Initiates Pmentioning

confidence: 98%

“…Once the formation of the Rauber's sickle is provoked by unidirectionally disturbing the mechanical equilibrium between the components of the blastoderm and the subgerminal ooplasm, the blastoderm becomes permanently fixed in an equilibrium in which the radial symmetry is definitively broken and replaced by bilateral symmetry characterized by the sickle shape of Rauber's sickle and also the sickle shape of the predisposed anlage fields found in the area centralis of the unincubated blastoderm (Callebaut et al, 1996a; Fig. 10).…”

Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symmentioning

confidence: 99%

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Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

Callebaut

2005

Developmental Dynamics

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In the avian oocytal germ disc region, at the end of oogenesis, we discerned four ooplasms (␣, ␤, ␥, ␦) presenting an onion-peel distribution (from peripheral and superficial to central and deep. Their fate was followed during early embryonic development. The most superficial and peripheral ␣ ooplasm plays a fundamental role during cleavage. The ␤ ooplasm, originally localized in the peripheral region of the blastodisc, becomes mainly concentrated in the primitive streak. At the moment of bilateral symmetrization, a spatially oblique, sickle-shaped uptake of ␥ and ␦ ooplasms occurs so that ␥ and ␦ ooplasms become incorporated into the deeper part of the avian blastoderm. These ooplasms seem to contain ooplasmic determinants that initiate either early neurulation or gastrulation events. The early neural plate-inducing structure that forms a deep part of the blastoderm is the ␦ ooplasm-containing endophyll (primary hypoblast). Together with the primordial germ cells, it is derived from the superficial centrocaudal part of the nucleus of Pander, which also contains ␦ ooplasm. The other structure (␥ ooplasm) that is incorporated into the caudolateral deep part of the blastoderm forms Rauber's sickle. It induces gastrulation in the concavity of Rauber's sickle and blood island formation exterior to Rauber's sickle. Rauber's sickle develops by ingrowth of blastodermal cells into the ␥ ooplasm, which surrounds the nucleus of Pander. Rauber's sickle constitutes the primary major organizer of the avian blastoderm and generates only extraembryonic tissues (junctional and sickle endoblast). By imparting positional information, it organizes and dominates the whole blastoderm (controlling gastrulation, neurulation, and coelom and cardiovascular system formation). Fragments of the horns of Rauber's sickle extend far cranially into the lateral quadrants of the unincubated blastoderm, so that often Rauber's sickle material forms three quarters of a circle. This finding explains the regulative capacities of isolated blastoderm parts, with the exception of the anti-sickle region and central blastoderm region, where no Rauber's sickle material is present. In avian blastoderms, there exists a competitive inhibition by Rauber's sickle on the primitive streak and neural plate-inducing effects of sickle endoblast. Avian primordial germ cells contain ␦ ooplasm derived from the superficial part of the nucleus of Pander. Their original deep and central ooplasmic localization has been confirmed by the use of a chicken vasa homologue. We conclude that the unincubated blastoderm consists of three elementary tissues: upper layer mainly containing ␤ ooplasm, endophyll containing ␦ ooplasm, and Rauber's sickle containing ␥ ooplasm). These elementary tissues form before the three classic germ layers have developed.

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Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symsupporting

confidence: 60%

Section: Sickle Canalmentioning

confidence: 74%

Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symmentioning

confidence: 90%

Section: Rauber's Sickle and Not The Caudal Marginal Zone Initiates Pmentioning

confidence: 98%

Section: From Radial Symmetry By Means Of Sickle-shaped Bilateral Symmentioning

confidence: 99%

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Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

Callebaut

2005

Developmental Dynamics

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Induction and patterning of the primitive streak, an organizing center of gastrulation in the amniote

Matsukawa

Poh

Kelly

et al. 2004

Developmental Dynamics

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The primitive streak is the organizing center for amniote gastrulation. It defines the future embryonic midline and serves as a conduit of cell migration for germ layer formation. The migration patterns of endodermal and mesodermal precursors through the streak have been studied in great detail. Additional new breakthroughs recently have revealed the cell biological and molecular mechanisms that govern streak induction and patterning. These findings include (1) identification of the ontogeny and inductive signals of streak precursors, (2) the potential cellular mechanism of streak extension, and (3) the molecular and functional diversification along the anterior-posterior and mediolateral axes within the primitive streak. These findings indicate that amniote embryos initiate gastrulation by using both evolutionarily conserved and divergent mechanisms. The data also provide a foundation for understanding how the midline axis is defined and maintained during gastrulation of the amniotes. Developmental Dynamics 229:422-432, 2004.

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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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Map of the Anlage fields in the avian unincubated blastoderm

Cited by 23 publications

References 0 publications

Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

Origin, fate, and function of the components of the avian germ disc region and early blastoderm: Role of ooplasmic determinants

Induction and patterning of the primitive streak, an organizing center of gastrulation in the amniote

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

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