A single morphogenetic field gives rise to two retina primordia under the influence of the prechordal plate

Development ◽  
1997 ◽  
Vol 124 (3) ◽  
pp. 603-615 ◽  
Author(s):  
H. Li ◽  
C. Tierney ◽  
L. Wen ◽  
J.Y. Wu ◽  
Y. Rao
Keyword(s):  
Expression Pattern ◽  
Lineage Tracing ◽  
Chick Embryos ◽  
Median Region ◽  
Prechordal Plate ◽  
Prechordal Mesoderm ◽  
New Gene ◽  
Vertebrate Embryos ◽  
Migration Of Cells ◽  
Anterior Neural Plate

Two bilaterally symmetric eyes arise from the anterior neural plate in vertebrate embryos. An interesting question is whether both eyes share a common developmental origin or they originate separately. We report here that the expression pattern of a new gene ET reveals that there is a single retina field which resolves into two separate primordia, a suggestion supported by the expression pattern of the Xenopus Pax-6 gene. Lineage tracing experiments demonstrate that retina field resolution is not due to migration of cells in the median region to the lateral parts of the field. Removal of the prechordal mesoderm led to formation of a single retina both in chick embryos and in Xenopus explants. Transplantation experiments in chick embryos indicate that the prechordal plate is able to suppress Pax-6 expression. Our results provide direct evidence for the existence of a single retina field, indicate that the retina field is resolved by suppression of retina formation in the median region of the field, and demonstrate that the prechordal plate plays a primary signaling role in retina field resolution.

Cardiac neural crest ablation inhibits compaction and electrical function of conduction system bundles

2007 ◽  
Vol 292 (3) ◽  
pp. H1291-H1300 ◽  
Author(s):  
Abhijit Gurjarpadhye ◽  
Kenneth W. Hewett ◽  
Charles Justus ◽  
Xuejun Wen ◽  
Harriett Stadt ◽  
...  
Keyword(s):  
Neural Crest ◽  
Conduction System ◽  
Lineage Tracing ◽  
Chick Embryos ◽  
Myocardial Cells ◽  
Cardiac Neural Crest ◽  
His Bundle ◽  
Electrical Connections ◽  
Migration Of Cells ◽  
Ventricular Conduction

Retroviral and transgenic lineage-tracing studies have shown that neural crest cells associate with the developing bundles of the ventricular conduction system. Whereas this migration of cells does not provide progenitors for the myocardial cells of the conduction system, the question of whether neural crest affects the differentiation and/or function of cardiac specialized tissues continues to be of interest. Using optical mapping of voltage-sensitive dye, we determined that ventricles from chick embryos in which the cardiac neural crest had been laser ablated did not progress to apex-to-base activation by the expected stage [i.e., Hamburger and Hamilton (HH) 35] but instead maintained basal breakthroughs of epicardial activation consistent with immature function of the conduction system. In direct studies of activation, waves of depolarization originating from the His bundle were found to be uncommon in control hearts from HH34 and HH35 embryos. However, activations propagating from septal base, at or near the His bundle, occurred frequently in hearts from HH34 and HH35 neural crest-ablated embryos. Consistent with His bundle cells maintaining electrical connections with adjacent working myocytes, histological analyses of hearts from neural crest-ablated embryos revealed His bundles that had not differentiated a lamellar organization or undergone a process of compaction and separation from surrounding myocardium observed in controls. Furthermore, measurements on histological sections from optically mapped hearts indicated that, whereas His bundle diameter in control embryos thinned by almost one-half between HH30 and HH34, the His bundle in ablated embryos underwent no such compaction in diameter, maintaining a thickness at HH30, HH32, and HH34 similar to that observed in HH30 controls. We conclude that the cardiac neural crest is required in a novel function involving lamellar compaction and electrical isolation of the basally located His bundle from surrounding myocardium.

Interruption of cardiac output does not affect short-term growth and metabolic rate in day 3 and 4 chick embryos

2000 ◽  
Vol 203 (24) ◽  
pp. 3831-3838 ◽  
Author(s):  
W.W. Burggren ◽  
S.J. Warburton ◽  
M.D. Slivkoff
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Body Mass ◽  
Regression Line ◽  
Heart Beat ◽  
Chick Embryos ◽  
Simple Diffusion ◽  
Significant Difference ◽  
Vertebrate Embryos ◽  
Cervical Flexure

The heart beat of vertebrate embryos has been assumed to begin when convective bulk transport by blood takes over from transport by simple diffusion. To test this hypothesis, we measured eye growth, cervical flexure and rates of oxygen consumption (V(O2)) in day 3–4 chick embryos denied cardiac output by ligation of the outflow tract and compared them with those of embryos with an intact cardiovascular system.Eye diameter, used as the index for embryonic growth, increased at a rate of approximately 4.5-5 % h(−)(1) during the observation period. There was no significant difference (P>0.1) in the rate of increase in eye diameter between control (egg opened), sham-ligated (ligature present but not tied) and ligated embryos. Similarly, the normal progression of cervical flexure was not significantly altered by ligation (P>0.1). V(O2) (ml O(2)g(−)(1)h(−)(1)) at 38 degrees C, measured by closed respirometry, was not significantly different (P>0.1) on day 3 in sham-ligated (14.5+/−1.9 ml O(2)g(−)(1)h(−)(1)) and ligated 17.6+/−1.8 ml O(2)g(−)(1)h(−)(1)) embryos. Similarly, on day 4, V(O2) in sham-ligated and ligated embryos was statistically the same (sham-ligated 10. 5+/−2.9 ml O(2)g(−)(1)h(−)(1); ligated 9.7+/−2.9 ml O(2)g(−)(1)h(−)(1)). Expressed as a linear function of body mass (M), V(O2) in sham-ligated embryos was described by the equation V(O2)=−0.48M+24.06 (r(2)=0.36, N=18, P<0.01), while V(O2) in ligated embryos was described by the equation V(O2)=−0.53M+23.32 (r(2)=0.38, N=16, P<0.01). The regression line describing the relationship between body mass and V(O2) for pooled sham-ligated and ligated embryos (the two populations being statistically identical) was V(O2)=−0.47M+23.24. The slope of this regression line, which was significantly different from zero (r(2)=0.30, N=34, P<0.01), was similar to slopes calculated from previous studies over the same range of body mass.Collectively, these data indicate that growth and V(O2) are not dependent upon cardiac output and the convective blood flow it generates. Thus, early chick embryos join those of the zebrafish, clawed frog and axolotl in developing a heart beat and blood flow hours or days before required for convective oxygen and nutrient transport. We speculate that angiogenesis is the most likely role for the early development of a heart beat in vertebrate embryos.

Inductive interactions direct early regionalization of the mouse forebrain

Development ◽  
1997 ◽  
Vol 124 (14) ◽  
pp. 2709-2718 ◽  
Author(s):  
K. Shimamura ◽  
J.L. Rubenstein
Keyword(s):  
Sonic Hedgehog ◽  
Bone Morphogenetic Proteins ◽  
Molecular Mechanisms ◽  
Neural Plate ◽  
Gene Encoding ◽  
Prechordal Plate ◽  
Optic Vesicles ◽  
The Central Nervous System ◽  
Anterior Neural Plate ◽  
Anterior Posterior

The cellular and molecular mechanisms that regulate regional specification of the forebrain are largely unknown. We studied the expression of transcription factors in neural plate explants to identify tissues, and the molecules produced by these tissues, that regulate medial-lateral and local patterning of the prosencephalic neural plate. Molecular properties of the medial neural plate are regulated by the prechordal plate perhaps through the action of Sonic Hedgehog. By contrast, gene expression in the lateral neural plate is regulated by non-neural ectoderm and bone morphogenetic proteins. This suggests that the forebrain employs the same medial-lateral (ventral-dorsal) patterning mechanisms present in the rest of the central nervous system. We have also found that the anterior neural ridge regulates patterning of the anterior neural plate, perhaps through a mechanism that is distinct from those that regulate general medial-lateral patterning. The anterior neural ridge is essential for expression of BF1, a gene encoding a transcription factor required for regionalization and growth of the telencephalic and optic vesicles. In addition, the anterior neural ridge expresses Fgf8, and recombinant FGF8 protein is capable of inducing BF1, suggesting that FGF8 regulates the development of anterolateral neural plate derivatives. Furthermore, we provide evidence that the neural plate is subdivided into distinct anterior-posterior domains that have different responses to the inductive signals from the prechordal plate, Sonic Hedgehog, the anterior neural ridge and FGF8. In sum, these results suggest that regionalization of the forebrain primordia is established by several distinct patterning mechanisms: (1) anterior-posterior patterning creates transverse zones with differential competence within the neural plate, (2) patterning along the medial-lateral axis generates longitudinally aligned domains and (3) local inductive interactions, such as a signal(s) from the anterior neural ridge, further define the regional organization.

scholarly journals Zebrafish Dkk1, induced by the pre-MBT Wnt signaling, is secreted from the prechordal plate and patterns the anterior neural plate

2000 ◽  
Vol 98 (1-2) ◽  
pp. 3-17 ◽  
Author(s):  
Minori Shinya ◽  
Cathrin Eschbach ◽  
Matthew Clark ◽  
Hans Lehrach ◽  
Makoto Furutani-Seiki
Keyword(s):  
Wnt Signaling ◽  
Neural Plate ◽  
Prechordal Plate ◽  
Anterior Neural Plate

Analysis of endoderm formation in the avian blastoderm by the use of quail-chick chimaeras

Development ◽  
1977 ◽  
Vol 41 (1) ◽  
pp. 209-222
Author(s):  
J. Fontaine ◽  
N. M. Le Douarin
Keyword(s):  
Neural Crest ◽  
Endocrine Cells ◽  
Primitive Streak ◽  
Germ Layer ◽  
Chick Embryos ◽  
Germ Layers ◽  
Enteric Ganglia ◽  
Gut Epithelium ◽  
Migration Of Cells ◽  
Chick And Quail Embryos

The formation of the endoderm has been investigated in chimaeric embryos resulting from the combination of the lower and upper germ layers taken from chick and quail embryos at stages 2–6 of Vakaët (1962). The ability to recognize quail from chick cells made it possible to follow the fate of each germ layer during development. It appeared that the primitive hypoblast participates in the formation of the anterolateral extra-embryonic endoderm while the embryonic endoderm is formed later by migration of cells of the ectomesoblast through Hensen's node and the primitive streak. Further interspecific combinations were carried out between ectoderm and endoderm + mesoderm from quail and chick embryos at stages 5–7 of Hamburger and Hamilton. The explants were grafted into chick embryos for several days and the intestinal structures which developed were observed. No contribution of cells from the neurectoderm to the endoderm was found. In contrast, cells coming from the neural crest colonized the intestinal structures and gave rise to the enteric ganglia. It was concluded from these observations that the enterochromaffin and endocrine cells of the gut epithelium do not originate from the neurectoderm.

New gene, nel, encoding a Mr 93 K protein with EGF-like repeats is strongly expressed in neural tissues of early stage chick embryos

1995 ◽  
Vol 203 (2) ◽  
pp. 212-222 ◽  
Author(s):  
Sachiko Matshuhashi ◽  
Sumihare Noji ◽  
Eiki Koyama ◽  
Fumio Myokai ◽  
Hideyo Ohuchi ◽  
...  
Keyword(s):  
Early Stage ◽  
Chick Embryos ◽  
Neural Tissues ◽  
New Gene

scholarly journals Hensen's node induces neural tissue in Xenopus ectoderm. Implications for the action of the organizer in neural induction

Development ◽  
1991 ◽  
Vol 113 (4) ◽  
pp. 1495-1505 ◽  
Author(s):  
C.R. Kintner ◽  
J. Dodd
Keyword(s):  
Nervous System ◽  
Neural Induction ◽  
Neural Tissue ◽  
Activin A ◽  
Chick Embryos ◽  
Vertebrate Embryos

The development of the vertebrate nervous system is initiated in amphibia by inductive interactions between ectoderm and a region of the embryo called the organizer. The organizer tissue in the dorsal lip of the blastopore of Xenopus and Hensen's node in chick embryos have similar neural inducing properties when transplanted into ectopic sites in their respective embryos. To begin to determine the nature of the inducing signals of the organizer and whether they are conserved across species we have examined the ability of Hensen's node to induce neural tissue in Xenopus ectoderm. We show that Hensen's node induces large amounts of neural tissue in Xenopus ectoderm. Neural induction proceeds in the absence of mesodermal differentiation and is accompanied by tissue movements which may reflect notoplate induction. The competence of the ectoderm to respond to Hensen's node extends much later in development than that to activin-A or to induction by vegetal cells, and parallels the extended competence to neural induction by axial mesoderm. The actions of activin-A and Hensen's node are further distinguished by their effects on lithium-treated ectoderm. These results suggest that neural induction can occur efficiently in response to inducing signals from organizer tissue arrested at a stage prior to gastrulation, and that such early interactions in the blastula may be an important component of neural induction in vertebrate embryos.

scholarly journals Six3, a murine homologue of the sine oculis gene, demarcates the most anterior border of the developing neural plate and is expressed during eye development

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 4045-4055 ◽  
Author(s):  
G. Oliver ◽  
A. Mailhos ◽  
R. Wehr ◽  
N.G. Copeland ◽  
N.A. Jenkins ◽  
...  
Keyword(s):  
Expression Pattern ◽  
Eye Development ◽  
Sequence Similarity ◽  
Neural Plate ◽  
Chromosome 17 ◽  
High Sequence Similarity ◽  
Sine Oculis ◽  
Regulatory Cascade ◽  
Murine Homologue ◽  
Anterior Neural Plate

The Drosophila sine oculis homeobox-containing gene is known to play an essential role in controlling the initial events of pattern formation in the eye disc and is also required for the development of other parts of the fly visual system including the optic lobes. In this paper, we report the isolation of a sequence-related gene referred to as Six3. Based on its amino acid sequence, this gene can be included in the new Six/sine oculis subclass of homeobox genes. Early on, Six3 expression is restricted to the anterior neural plate including areas that later will give rise to ectodermal and neural derivatives. Later, once the longitudinal axis of the brain bends, Six3 mRNA is also found in structures derived from the anterior neural plate: ectoderm of nasal cavity, olfactory placode and Rathke's pouch, and also the ventral forebrain including the region of the optic recess, hypothalamus and optic vesicles. Based on this expression pattern, we conclude that Six3 is one of the most anterior homeobox gene reported to date. The high sequence similarity of Six3 with the Drosophila sine oculis, and its expression during eye development, suggests that this gene is the likely murine homologue. This finding supports the idea that mammals and insects share control genes such as eyeless/Pax6 (Halder, G., Callaerts, P. and Gehring, W. J. (1995) Science 267, 1788–1792), and also possibly other members of the regulatory cascade required for eye morphogenesis. In Small eye (Pax6) mouse mutants Six3 expression is not affected. Finally, based on the chromosomal localization and the expression pattern of the mouse Six3 gene, the human Six3 cognate could be a good candidate to be at least one of the genes affected in patients with holoprosencephaly type 2 due to an interstitial deletion of 2p21-p22. This region shares a homology with the distal region of mouse chromosome 17 where Six3 has been mapped.

Inductive signal and tissue responsiveness defining the tectum and the cerebellum

Development ◽  
2001 ◽  
Vol 128 (13) ◽  
pp. 2461-2469 ◽  
Author(s):  
Tatsuya Sato ◽  
Isato Araki ◽  
Harukazu Nakamura
Keyword(s):  
Quantitative Analysis ◽  
Expression Pattern ◽  
Neural Tissue ◽  
Chick Embryos ◽  
Rt Pcr ◽  
Signaling Molecule ◽  
Working Hypothesis ◽  
Inductive Signal

The mes/metencephalic boundary (isthmus) has an organizing activity for mesencephalon and metencephalon. The candidate signaling molecule is Fgf8 whose mRNA is localized in the region where the cerebellum differentiates. Responding to this signal, the cerebellum differentiates in the metencephalon and the tectum differentiates in the mesencephalon. Based on the assumption that strong Fgf8 signal induces the cerebellum and that the Fgf8b signal is stronger than that of Fgf8a, we carried out experiments to misexpress Fgf8b and Fgf8a in chick embryos. Fgf8a did not affect the expression pattern of Otx2, Gbx2 or Irx2. En2 expression was upregulated in the mesencephalon and in the diencephalon by Fgf8a. Consequently, Fgf8a misexpression resulted in the transformation of the presumptive diencephalon to the fate of the mesencephalon. In contrast, Fgf8b repressed Otx2 expression, but upregulated Gbx2 and Irx2 expression in the mesencephalon. As a result, Fgf8b completely changed the fate of the mesencephalic alar plate to cerebellum. Quantitative analysis showed that Fgf8b signal is 100 times stronger than Fgf8a signal. Co-transfection of Fgf8b with Otx2 indicates that Otx2 is a key molecule in mesencephalic generation. We have shown by RT-PCR that both Fgf8a and Fgf8b are expressed, Fgf8b expression prevailing in the isthmic region. The results all support our working hypothesis that the strong Fgf8 signal induces the neural tissue around the isthmus to differentiate into the cerebellum.

A Xenopus homologue of aml-1 reveals unexpected patterning mechanisms leading to the formation of embryonic blood

Development ◽  
1998 ◽  
Vol 125 (8) ◽  
pp. 1371-1380 ◽  
Author(s):  
W.D. Tracey ◽  
M.E. Pepling ◽  
M.E. Horb ◽  
G.H. Thomsen ◽  
J.P. Gergen
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Lineage Tracing ◽  
Runt Domain ◽  
Hematopoietic Stem ◽  
Blood Island ◽  
Primitive Hematopoiesis ◽  
Vertebrate Embryos ◽  
Definitive Hematopoiesis

The Runt domain gene AML1 is essential for definitive hematopoiesis during murine embryogenesis. We have isolated Xaml, a Xenopus AML1 homologue in order to investigate the patterning mechanisms responsible for the generation of hematopoietic precursors. Xaml is expressed early in the developing ventral blood island in a pattern that anticipates that of later globin. Analysis of globin and Xaml expression in explants, in embryos with perturbed dorsal ventral patterning, and by lineage tracing indicates that the formation of the ventral blood island is more complex than previously thought and involves contributions from both dorsal and ventral tissues. A truncated Xaml protein interferes with primitive hematopoiesis. Based on these results, we propose that Runt domain proteins function in the specification of hematopoietic stem cells in vertebrate embryos.

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