Patterns of junctional communication during development of the early amphibian embryo

Development ◽  
1988 ◽  
Vol 103 (4) ◽  
pp. 769-783 ◽  
Author(s):  
S. Guthrie ◽  
L. Turin ◽  
A. Warner
Keyword(s):  
Gap Junctions ◽  
Lucifer Yellow ◽  
Dorsal Side ◽  
Cell Stage ◽  
Animal Pole ◽  
Amphibian Embryo ◽  
Grey Crescent ◽  
The Future ◽  
Junctional Permeability ◽  
Side Gap

Cell-cell communication through gap junctions was examined in Xenopus laevis embryos between the 16-cell and early blastula stages using Lucifer Yellow, Fluorescein, lead EDTA and dicyanoargentate as probes of junctional permeability. Injections were made into cells whose position was identified with respect to the primary cleavage axis and the grey crescent. FITC dextrans revealed cytoplasmic bridges between the injected cell and its sister only. In the animal pole at the 16-cell stage at the future dorsal side of the embryo, Lucifer Yellow was frequently and extensively transferred between cells through gap junctions. At the future ventral side gap junctional transfer of Lucifer Yellow was significantly less frequent and less extensive. The asymmetry of transfer between future dorsal and ventral sides of the animal pole was more marked at the 32-cell stage. In the vegetal pole also at the 32-cell stage, a dorsoventral difference in junctional permeability to Lucifer Yellow was observed. At the 64-cell stage the transfer of Lucifer Yellow was relatively frequent between cells lying in the same radial segment in the animal pole; transfer into cells outside each segment was infrequent, except at the grey crescent. At the 128-cell stage, Lucifer transfer between future dorsal or future ventral cells in the equatorial region was infrequent. A high incidence of transfer was restored at the future dorsal side at the 256-cell stage. At the 32-cell stage, fluorescein was infrequently transferred between animal pole cells although lead EDTA moved from cell to cell with high, comparable frequency in future dorsal and ventral regions. Dicyanoargentate always transferred extensively, both at the 32- and 64-cell stages. Treatment of embryos with methylamine raised intracellular pH by 0.15 units, increased the electrical conductance of the gap junction and produced a 10-fold increase in the frequency of Lucifer Yellow transfer through gap junctions in future ventral regions of the animal pole at the 32-cell stage.

Gap-junctional permeability in early and cleavage-arrested ascidian embryos

Development ◽  
1991 ◽  
Vol 112 (1) ◽  
pp. 153-160 ◽  
Author(s):  
B. Dale ◽  
L. Santella ◽  
E. Tosti
Keyword(s):  
Gap Junctions ◽  
Lucifer Yellow ◽  
Cell Voltage ◽  
Spatial Location ◽  
Cell Stage ◽  
Junctional Conductance ◽  
Junctional Permeability ◽  
Cell Embryo ◽  
Ascidian Embryos ◽  
Two Stages

Using the whole-cell voltage clamp technique, we have studied junctional conductance (Gj), and Lucifer Yellow (LY) coupling in 2-cell and 32-cell ascidian embryos. Gj ranges from 17.5 to 35.3 nS in the 2-cell embryo where there is no passage of LY, and from 3.5 to 12.2 nS in the later embryo where LY dye spread is extensive. In both cases, Gj is independent of the transjunctional potential (Vj). Manually apposed 2-cell or 32-cell embryos established a junctional conductance of up to 10 nS within 30 min of contact. Furthermore, since we did not observe any significant number of cytoplasmic bridges at the EM and Gj is sensitive to octanol, it is probable that blastomeres in the 2-cell and 32-cell embryos are in communication by gap junctions. In order to compare Gj in the two stages and to circumvent problems of cell size, movement and spatial location, we used cytochalasin B to arrest cleavage. Gj in cleavage-arrested 2-cell embryos ranged from 25.0 to 38.0 nS and remained constant over a period of 2.5 h. LY injected into a blastomere of these arrested embryos did not spread to the neighbour cell until they attained the developmental age of a 32- to 64-cell control embryo. Our experiments indicate a change in selectivity of gap junctions at the 32-cell stage that is not reflected by a macroscopic change in ionic permeability.

scholarly journals The oral-aboral axis of a sea urchin embryo is specified by first cleavage

Development ◽  
1989 ◽  
Vol 106 (4) ◽  
pp. 641-647 ◽  
Author(s):  
R.A. Cameron ◽  
S.E. Fraser ◽  
R.J. Britten ◽  
E.H. Davidson
Keyword(s):  
Sea Urchin ◽  
Cleavage Plane ◽  
Strongylocentrotus Purpuratus ◽  
Cell Stage ◽  
Animal Pole ◽  
Sea Urchin Embryo ◽  
The Future ◽  
Axis Specification ◽  
The Right ◽  
Lines Of Evidence

Several lines of evidence suggest that the oral-aboral axis in Strongylocentrotus purpuratus embryos is specified at or before the 8-cell stage. Were the oral-aboral axis specified independently of the first cleavage plane, then a random association of this plane with the blastomeres of the four embryo quadrants in the oral-aboral plane (viz. oral, aboral, right and left) would be expected. Lineage tracer dye injection into one blastomere at the 2-cell stage and observation of the resultant labeling patterns demonstrates instead a strongly nonrandom association. In at least ninety percent of cases, the progeny of the aboral blastomeres are associated with those of the left lateral blastomeres and the progeny of the oral blastomeres with the right lateral ones, respectively. Thus, ninety percent of the time the oral pole of the future oral-aboral axis lies 45 degrees clockwise from the first cleavage plane as viewed from the animal pole. The nonrandom association of blastomeres after labeling of the 2-cell stage implies that there is a mechanistic relation between axis specification and the positioning of the first cleavage plane.

The correlation between patterns of dye transfer junctions and future developmental fate in Xenopus: u.v. irradiation and lithium treatment

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 747-752 ◽  
Author(s):  
D.J. Nagajski ◽  
S.C. Guthrie ◽  
C.C. Ford ◽  
A.E. Warner
Keyword(s):  
Lucifer Yellow ◽  
Lithium Treatment ◽  
Cell Communication ◽  
Embryonic Axis ◽  
Axis Formation ◽  
Dye Transfer ◽  
Cell Stage ◽  
The Future ◽  
Vegetal Pole ◽  
Cell Embryo

The correlation between cell-to-cell communication junctions at the 32-cell stage and the subsequent embryonic axis has been examined in Xenopus laevis Disturbances of embryonic axis formation were u.v. irradiation at the vegetal pole before 0.6 in the which generates embryos with dorsal axial embryos were treated with 100mM-lithium chloride 32-cell stage, which generates embryos with ventral The cell-to-cell transfer of Lucifer Yellow was used junctional permeability. Injections were made into cells, lying in tiers 1 and 2 of the 32-cell embryo, relative to the future dorsoventral axis of the embryo on the basis of differences in pigmentation. The Yellow transfer in the future dorsal half of the compared with that in the future ventral half for u.v.-irradiated and Li-treated embryos. Injected subsequently scored for axial developmenf for transfer frequencies. In control embryos at the 32- Yellow transfer was both more frequent and more dorsal regions than in future ventral regions, as In embryos that had been u.v. irradiated before 0.6 in cycle, Lucifer transfer was the same in both light and the animal hemisphere and at the low level ventral regions in normal embryos. These embryos reductions in dorsal axial structures. Embryos the first cell cycle, when u.v. irradiation no longer cytoplasmic movements initiated at fertilization, dorsoventral difference in Lucifer Yellow transfer and normal dorsoventral polarity. Embryos exposed to

Reduced gap junctional communication is associated with the lethal condition characteristic of DDK mouse eggs fertilized by foreign sperm

Development ◽  
1987 ◽  
Vol 101 (3) ◽  
pp. 449-459 ◽  
Author(s):  
M. Buehr ◽  
S. Lee ◽  
A. McLaren ◽  
A. Warner
Keyword(s):  
Gap Junctions ◽  
Lucifer Yellow ◽  
Blastocyst Stage ◽  
Weak Base ◽  
Cell Stage ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Condition Characteristic ◽  
Gap Junctional ◽  
Mouse Eggs

Communication through gap junctions was examined in 8-cell zygotes generated by fertilization of eggs of the DDK inbred strain of mice with spermatozoa of the C3H strain. These zygotes spontaneously begin to extrude cells at the late 16-cell stage and 95% die by the blastocyst stage. The transfer of Lucifer Yellow between cells of DDK/C3H zygotes that had not yet begun to express the defect was significantly slower than in DDK/DDK controls or in controls from other strains. Treatment with the weak base methylamine, to raise intracellular pH, speeded the transfer of Lucifer in all strains; transfer between cells of DDK/C3H zygotes became as fast as that between cells of control zygotes. DDK/C3H zygotes cultured in methylamine either from the 4- to 8-cell stage to the early 16-cell stage (19h) or from the early to the late 16-cell stage (6 h) showed significant rescue to the blastocyst stage. Once spontaneous decompaction of cells from DDK/C3H zygotes had begun (the late 16-cell stage onwards) methylamine treatment was no longer able to bring about rescue. We conclude that zygotes developed from eggs of the DDK strain fertilized by foreign spermatozoa are characterized physiologically by defective gap junctional communication. Improving gap junctional communication is sufficient to allow many zygotes to maintain the compacted state, suggesting a link between compaction and communication through gap junctions.

scholarly journals Establishment of the Dorso-ventral Axis in Xenopus Embryos Is Presaged by Early Asymmetries in β-Catenin That Are Modulated by the Wnt Signaling Pathway

1997 ◽  
Vol 136 (5) ◽  
pp. 1123-1136 ◽  
Author(s):  
Carolyn A. Larabell ◽  
Monica Torres ◽  
Brian A. Rowning ◽  
Cynthia Yost ◽  
Jeffrey R. Miller ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Glycogen Synthase ◽  
Dorsal Side ◽  
Glycogen Synthase Kinase ◽  
Nuclear Accumulation ◽  
Glycogen Synthase Kinase 3 ◽  
Early Cleavage ◽  
Cell Stage ◽  
The Future ◽  
Cleavage Stages

Eggs of Xenopus laevis undergo a postfertilization cortical rotation that specifies the position of the dorso-ventral axis and activates a transplantable dorsal-determining activity in dorsal blastomeres by the 32-cell stage. There have heretofore been no reported dorso-ventral asymmetries in endogenous signaling proteins that may be involved in this dorsal-determining activity during early cleavage stages. We focused on β-catenin as a candidate for an asymmetrically localized dorsal-determining factor since it is both necessary and sufficient for dorsal axis formation. We report that β-catenin displays greater cytoplasmic accumulation on the future dorsal side of the Xenopus embryo by the two-cell stage. This asymmetry persists and increases through early cleavage stages, with β-catenin accumulating in dorsal but not ventral nuclei by the 16- to 32cell stages. We then investigated which potential signaling factors and pathways are capable of modulating the steady-state levels of endogenous β-catenin. Steadystate levels and nuclear accumulation of β-catenin increased in response to ectopic Xenopus Wnt-8 (Xwnt-8) and to the inhibition of glycogen synthase kinase-3, whereas neither Xwnt-5A, BVg1, nor noggin increased β-catenin levels before the mid-blastula stage. As greater levels and nuclear accumulation of β-catenin on the future dorsal side of the embryo correlate with the induction of specific dorsal genes, our data suggest that early asymmetries in β-catenin presage and may specify dorso-ventral differences in gene expression and cell fate. Our data further support the hypothesis that these dorso-ventral differences in β-catenin arise in response to the postfertilization activation of a signaling pathway that involves Xenopus glycogen synthase kinase-3.

Morphogenetic Interactions before Gastrulation in the Amphibian, Xenopus laevis—Regulation in Blastulae

Development ◽  
1962 ◽  
Vol 10 (3) ◽  
pp. 451-463
Author(s):  
A. S. G. Curtis
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction ◽  
Considerable Degree ◽  
Cell Stage ◽  
Grey Crescent ◽  
Ring Type ◽  
The Future

The site of the future dorsal lip of the gastrula is already determined to a considerable degree at the grey-crescent region by the 8-cell stage, probably by means of interactions within the cortex (Curtis, 1962b). But this determination is still easily disturbed because excision of the grey-crescent cortex from the 8-cell stage does not prevent the appearance of a dorsal lip. The embryo forms a new dorsal lip by a process of regulation. Similarly, Votquenne (1933) destroyed the blastomere containing the grey crescent at the 8-cell stage in Rana fusca and nevertheless obtained nearly normal embryos; which result indicated that regulation had happened. At a later stage, late blastula, excision of the cells of the presumptive dorsal Up region does not prevent a dorsal lip forming and subsequent neural induction occurring (Goerttler, 1926) although the embryos are of the abnormal ‘ring’ type.

Cardiovascular development in the zebrafish. I. Myocardial fate map and heart tube formation

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 31-40 ◽  
Author(s):  
D.Y. Stainier ◽  
R.K. Lee ◽  
M.C. Fishman
Keyword(s):  
Single Cell ◽  
Tube Formation ◽  
Cardiovascular Development ◽  
Heart Tube ◽  
Cell Stage ◽  
Animal Pole ◽  
Cardiac Progenitors ◽  
Somite Stage ◽  
The Future ◽  
Heart Tube Formation

We have analyzed the origin of cardiac progenitors in the zebrafish embryo by injection of single blastomeres with a lineage tracer dye, and examined the formation of the zebrafish heart tube by serial sectioning of immunostained embryos. At the 512-cell stage (early blastula), most cardiac progenitors lie in a marginal zone that extends from 90 degrees longitude (midway between the future dorsal and ventral axis) through 180 degrees longitude (the future ventral axis) to 270 degrees longitude. By focusing on myocardial progenitors located at 90 degrees (and 270 degrees) longitude, we found that a single cell injected in the early blastula can contribute progeny to both the atrium and ventricle. A cell injected in the midblastula contributes progeny to either the atrium or ventricle, but not both. This analysis suggests that, at least for these myocardial progenitors, the atrial and ventricular lineages separate in the midblastula. Precardiac cells involute early during gastrulation and turn towards the animal pole with other early involuting cells. These cardiogenic cells reach the embryonic axis around the 8-somite stage, and there they coalesce to form a pair of myocardial tubular primordia on either side of the midline. By the 21-somite stage, the tropomyosin-immunoreactive myocardial tubes have moved closer to each other, and a distinct group of cells, the endocardial progenitor cells, sits medially between them. The myocardial tubes then fuse to enclose the endocardial cells and form the definitive heart tube. By 22 hours postfertilization (26-somite stage), the heart tube is clearly beating. The regionalization of cardiac myosin heavy chain expression distinguishes the cardiac chambers at this stage, although they are not morphologically delineated until 36 hours. This work shows that cardiogenic regions can be identified in the early blastula, and that chamber restriction seems to arise in the midblastula. Additionally, it provides the basis for embryological perturbation at the single cell level, as well as for the genetic analysis of heart tube formation in the zebrafish.

Activation of dorsal development by contact between the cortical dorsal determinant and the equatorial core cytoplasm in eggs of Xenopus laevis

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1543-1551 ◽  
Author(s):  
H. Kageura
Keyword(s):  
Xenopus Laevis ◽  
Dorsal Side ◽  
Equatorial Region ◽  
Normal Embryo ◽  
Dorsal Region ◽  
The Core ◽  
Dorsal Axis ◽  
The Future ◽  
Vegetal Pole ◽  
Cell Embryo

In eggs of Xenopus laevis, dorsal development is activated on the future dorsal side by cortical rotation, after fertilization. The immediate effect of cortical rotation is probably the transport of a dorsal determinant from the vegetal pole to the equatorial region on the future dorsal side. However, the identity and action of the dorsal determinant remain problematic. In the present experiments, individual isolated cortices from various regions of the unfertilized eggs and embryos were implanted into one of several positions of a recipient 8-cell embryo. The incidence of secondary axes was used not only to locate the cortical dorsal determinant at different times but also to locate the region of the core competent to respond to the dorsal determinant. The dorsal axis-inducing activity of the cortex occurred around the vegetal pole of the unfertilized egg. During cortical rotation, it shifted from there to a wide dorsal region. This is apparently the first evidence for the presence of a dorsal determinant in the egg cortex. The competence of the core of the 8-cell embryo was distributed in the form of gradient with the highest responsiveness at the equator. These results suggest that, in the normal embryo, dorsal development is activated by contact between the cortical dorsal determinant and the equatorial core cytoplasm, brought together through cortical rotation.

Heat-shock-induced grey crescent formation in axolotl eggs and oocytes: the role of gravity

Development ◽  
1987 ◽  
Vol 100 (4) ◽  
pp. 599-609
Author(s):  
J.-C. Beetschen ◽  
J. Gautier
Keyword(s):  
Protein Synthesis ◽  
Heat Shock ◽  
Synergistic Action ◽  
Nuclear Factor ◽  
Crescent Formation ◽  
Animal Pole ◽  
Grey Crescent ◽  
Cytoskeletal Structure

Axolotl eggs were heat shocked (36.8°C, 10min) inside their jelly layers. Heat shock (HS) was shown to induce the precocious appearance of a grey crescent (GC) in a number of eggs immediately after fertilization (Benford & Namenwirth, 1974). It was also demonstrated that this phenomenon occurs in fertilized or artificially activated eggs only when they are shocked within 11/2h after spawning. The GC forms still later in heated unfertilized, nonactivated eggs. The role of the jelly layers is considered to be mechanical: a proportion of eggs is maintained in a tilted position until the egg is able to orient animal pole upwards under the influence of gravity as a late consequence of activation. The jelly layers are not essential if the eggs are artificially tilted or rotated during HS. GC formation can also be induced in in vitro maturing oocytes, provided they are tilted during HS. Gravity thus plays an essential role in the cytoplasmic rearrangements leading to HS-induced GC formation. Our results indicate a synergistic action between heat and gravity in this process. The cytological appearance of the GC formed in those experiments is that of a ‘Born's crescent’ with a conspicuous ‘vitelline wall’ (Pasteels, 1964). When oocytes are enucleated before maturation, HS has no effect on GC formation. A nuclear factor is therefore essential, as has been demonstrated in early GC formation induced by inhibitors of protein synthesis. Finally, incorporation of amino acids into oocyte proteins appears to be rapidly inhibited by HS (from 5 min). However, we cannot conclude that GC formation is in fact triggered by inhibition of protein synthesis. It is also likely that HS disrupts cytoskeletal structure, hence facilitating cytoplasmic rearrangements. Nevertheless, these results are in agreement with the scheme we recently proposed for GC formation in the rotated axolotl oocyte (Gautier & Beetschen, 1985).

scholarly journals Gap junction structures after experimental alteration of junctional channel conductance.

1985 ◽  
Vol 101 (5) ◽  
pp. 1741-1748 ◽  
Author(s):  
T M Miller ◽  
D A Goodenough
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Electron Micrographs ◽  
Time Course ◽  
Structural Changes ◽  
Lucifer Yellow ◽  
Freeze Fracture ◽  
Channel Conductance ◽  
Experimental Alteration ◽  
Quick Freezing

Gap junctions are known to present a variety of different morphologies in electron micrographs and x-ray diffraction patterns. This variation in structure is not only seen between gap junctions in different tissues and organisms, but also within a given tissue. In an attempt to understand the physiological meaning of some aspects of this variability, gap junction structure was studied following experimental manipulation of junctional channel conductance. Both physiological and morphological experiments were performed on gap junctions joining stage 20-23 chick embryo lens epithelial cells. Channel conductance was experimentally altered by using five different experimental manipulations, and assayed for conductance changes by observing the intercellular diffusion of Lucifer Yellow CH. All structural measurements were made on electron micrographs of freeze-fracture replicas after quick-freezing of specimens from the living state; for comparison, aldehyde-fixed specimens were measured as well. Analysis of the data generated as a result of this study revealed no common statistically significant changes in the intrajunctional packing of connexons in the membrane plane as a result of experimental alteration of junctional channel conductance, although some of the experimental manipulations used to alter junctional conductance did produce significant structural changes. Aldehyde fixation caused a dramatic condensation of connexon packing, a result not observed with any of the five experimental uncoupling conditions over the 40-min time course of the experiments.

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