Yolk Cell

2020 ◽  
Author(s):  
Keyword(s):  
Yolk Cell

Studies on the yolk cell in Bombyx mori

1955 ◽  
Vol 9 (3) ◽  
pp. 568-571 ◽  
Author(s):  
T. Takami
Keyword(s):  
Bombyx Mori ◽  
Yolk Cell

Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3067-3078 ◽  
Author(s):  
A. Rodaway ◽  
H. Takeda ◽  
S. Koshida ◽  
J. Broadbent ◽  
B. Price ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Tgf Beta ◽  
Fgf Receptor ◽  
Activin Receptor ◽  
Yolk Cell ◽  
Endogenous Expression ◽  
Vertebrate Embryo ◽  
Fgf Signalling

The endoderm forms the gut and associated organs, and develops from a layer of cells which emerges during gastrula stages in the vertebrate embryo. In comparison to mesoderm and ectoderm, little is known about the signals which induce the endoderm. The origin of the endoderm is intimately linked with that of mesoderm, both by their position in the embryo, and by the molecules that can induce them. We characterised a gene, zebrafish gata5, which is expressed in the endoderm from blastula stages and show that its transcription is induced by signals originating from the yolk cell. These signals also induce the mesoderm-expressed transcription factor no tail (ntl), whose initial expression coincides with gata5 in the cells closest to the blastoderm margin, then spreads to encompass the germ ring. We have characterised the induction of these genes and show that ectopic expression of activin induces gata5 and ntl in a pattern which mimics the endogenous expression, while expression of a dominant negative activin receptor abolishes ntl and gata5 expression. Injection of RNA encoding a constitutively active activin receptor leads to ectopic expression of gata5 and ntl. gata5 is activated cell-autonomously, whereas ntl is induced in cells distant from those which have received the RNA, showing that although expression of both genes is induced by a TGF-beta signal, expression of ntl then spreads by a relay mechanism. Expression of a fibroblast growth factor (eFGF) or a dominant negatively acting FGF receptor shows that ntl but not gata5 is regulated by FGF signalling, implying that this may be the relay signal leading to the spread of ntl expression. In embryos lacking both squint and cyclops, members of the nodal group of TGF-beta related molecules, gata5 expression in the blastoderm is abolished, making these factors primary candidates for the endogenous TGF-beta signal inducing gata5.

TELEOST YOLK CELL FUNCTION ON BLASTODERM DIFFERENTIATION AND MORPHOGENESIS

2000 ◽  
Vol 50 (1) ◽  
pp. 37-51 ◽  
Author(s):  
Geertruy Te Kronnie ◽  
Henri W.J. Stroband ◽  
Henk Schipper ◽  
Johannis Samallo
Keyword(s):  
Cell Function ◽  
Yolk Cell

scholarly journals AFM and Microrheology in the Zebrafish Embryo Yolk Cell

10.3791/56224 ◽  
2017 ◽  
Author(s):  
Maria Marsal ◽  
Ignasi Jorba ◽  
Elena Rebollo ◽  
Tomas Luque ◽  
Daniel Navajas ◽  
...  
Keyword(s):  
Zebrafish Embryo ◽  
Yolk Cell

scholarly journals Zebrafish wnt11: pattern and regulation of the expression by the yolk cell and No tail activity

1998 ◽  
Vol 71 (1-2) ◽  
pp. 165-176 ◽  
Author(s):  
Ryosuke Makita ◽  
Toshiro Mizuno ◽  
Sumito Koshida ◽  
Atsushi Kuroiwa ◽  
Hiroyuki Takeda
Keyword(s):  
Yolk Cell ◽  
No Tail

Teleost Yolk Cell Function On Blastoderm Differentiation and Morphogenesis

2000 ◽  
Vol 50 (1) ◽  
pp. 37-51
Author(s):  
Johannis Samallo ◽  
Henri W.J. Stroband ◽  
Henk Schipper ◽  
Geertruy Te Kronnie
Keyword(s):  
Cell Function ◽  
Yolk Cell

scholarly journals Studies on the Yolk Cell in Bombyx mori

CYTOLOGIA ◽  
1954 ◽  
Vol 19 (4) ◽  
pp. 299-305 ◽  
Author(s):  
Takeo Takami
Keyword(s):  
Bombyx Mori ◽  
Yolk Cell

Structurization of Cortical Layer of Loach Yolk Cell after Wounding as a “Minimal” Model of Morphogenesis

2004 ◽  
Vol 35 (3) ◽  
pp. 148-154
Author(s):  
E. G. Korvin-Pavlovskaya ◽  
I. V. Neklyudova ◽  
L. V. Beloussov
Keyword(s):  
Minimal Model ◽  
Cortical Layer ◽  
Yolk Cell

Microtubule arrays of the zebrafish yolk cell: organization and function during epiboly

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2443-2455 ◽  
Author(s):  
L. Solnica-Krezel ◽  
W. Driever
Keyword(s):  
Danio Rerio ◽  
Developmental Changes ◽  
Microtubule Network ◽  
Cell Stage ◽  
Yolk Syncytial Layer ◽  
Animal Pole ◽  
Yolk Cell ◽  
Vegetal Pole ◽  
Cell Organization ◽  
And Function

In zebrafish (Danio rerio), meroblastic cleavages generate an embryo in which blastomeres cover the animal pole of a large yolk cell. At the 500–1000 cell stage, the marginal blastomeres fuse with the yolk cell forming the yolk syncytial layer. During epiboly the blastoderm and the yolk syncytial layer spread toward the vegetal pole. We have studied developmental changes in organization and function during epiboly of two distinct microtubule arrays located in the cortical cytoplasm of the yolk cell. In the anuclear yolk cytoplasmic layer, an array of microtubules extends along the animal-vegetal axis to the vegetal pole. In the early blastula the yolk cytoplasmic layer microtubules appear to originate from the marginal blastomeres. Once formed, the yolk syncytial layer exhibits its own network of intercrossing mitotic or interphase microtubules. The microtubules of the yolk cytoplasmic layer emanate from the microtubule network of the syncytial layer. At the onset of epiboly, the external yolk syncytial layer narrows, the syncytial nuclei become tightly packed and the network of intercrossing microtubules surrounding them becomes denser. Soon after, there is a vegetal expansion of the blastoderm and of the yolk syncytial layer with its network of intercrossing microtubules. Concomitantly, the yolk cytoplasmic layer diminishes and its set of animal-vegetal microtubules becomes shorter. We investigated the involvement of microtubules in epiboly using the microtubule depolymerizing agent nocodazole and a stabilizing agent taxol. In embryos treated with nocodazole, microtubules were absent and epibolic movements of the yolk syncytial nuclei were blocked. In contrast, the vegetal expansion of the enveloping layer and deep cells was only partially inhibited. The process of endocytosis, proposed to play a major role in epiboly of the yolk syncytial layer (Betchaku, T. and Trinkaus, J. P. (1986) Am. Zool. 26, 193–199), was still observed in nocodazole-treated embryos. Treatment of embryos with taxol led to a delay in all epibolic movements. We propose that the yolk cell microtubules contribute either directly or indirectly to all epibolic movements. However, the epibolic movements of the yolk syncytial layer nuclei and of the blastoderm are not coupled, and only movements of the yolk syncytial nuclei are absolutely dependent on microtubules. We hypothesize that the microtubule network of the syncytial layer and the animal-vegetal set of the yolk cytoplasmic layer contribute differently to various aspects of epiboly. Models that address the mechanisms by which the two microtubule arrays might function during epiboly are discussed.

Cell movements during epiboly and gastrulation in zebrafish

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 569-580 ◽  
Author(s):  
R.M. Warga ◽  
C.B. Kimmel
Keyword(s):  
Dorsal Side ◽  
Epithelial Layer ◽  
Convergent Extension ◽  
Blastula Stage ◽  
Cell Movements ◽  
Yolk Cell ◽  
Radial Cell ◽  
Convergence And Extension ◽  
Embryonic Ectoderm ◽  
Anterior Posterior

Beginning during the late blastula stage in zebrafish, cells located beneath a surface epithelial layer of the blastoderm undergo rearrangements that accompany major changes in shape of the embryo. We describe three distinctive kinds of cell rearrangements. (1) Radial cell intercalations during epiboly mix cells located deeply in the blastoderm among more superficial ones. These rearrangements thoroughly stir the positions of deep cells, as the blastoderm thins and spreads across the yolk cell. (2) Involution at or near the blastoderm margin occurs during gastrulation. This movement folds the blastoderm into two cellular layers, the epiblast and hypoblast, within a ring (the germ ring) around its entire circumference. Involuting cells move anteriorwards in the hypoblast relative to cells that remain in the epiblast; the movement shears the positions of cells that were neighbors before gastrulation. Involuting cells eventually form endoderm and mesoderm, in an anterior-posterior sequence according to the time of involution. The epiblast is equivalent to embryonic ectoderm. (3) Mediolateral cell intercalations in both the epiblast and hypoblast mediate convergence and extension movements towards the dorsal side of the gastrula. By this rearrangement, cells that were initially neighboring one another become dispersed along the anterior-posterior axis of the embryo. Epiboly, involution and convergent extension in zebrafish involve the same kinds of cellular rearrangements as in amphibians, and they occur during comparable stages of embryogenesis.

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