Spatial-temporal characteristics of intercellular junctions in early zebrafish and loach embryos before and during gastrulation

2003

Zygote

Through the injection of f-aequorin and the use of a photon imaging microscope, we have previously reported that a rhythmic series of intercellular Ca2+ waves circumnavigate zebrafish embryos over a 10 h period during gastrulation and axial segmentation. These waves first appear at about 65% epiboly and continue to arise every 5-10 min up to at least the 16-somite stage. In response to our publication, it was suggested that the waves may be an artefact caused by dechorionation of the embryos and would not be observed during the development of intact embryos (i.e. those with chorions). Here we demonstrate (again initially by aequorin imaging) that the rhythmic intercellular Ca2+ waves that traverse the blastoderm margin can also be observed in embryos that have an intact chorion. In addition, the appearance time, propagation pathway, velocity, duration and Ca2+ rise of the waves, as well as the interwave interval and the timing of wave onset, are approximately the same in both dechorionated embryos and those with an intact chorion. Furthermore, by loading intact embryos with Ca2+-green dextran at the single-cell stage and then using scanning confocal microscopy to obtain high-resolution images, we confirm the presence of circumferential Ca2+ waves and show that they pass through a population of deep cells located at the blastoderm margin. The confirmation of these pan-embryonic Ca2+ waves in zebrafish further corroborates our earlier suggestion that such waves might play a fundamental role in normal embryonic patterning during the gastrula period.

Section: Chorion Intactsupporting

confidence: 67%

Imaging intercellular calcium waves during late epiboly in intact zebrafish embryos

2003

Zygote

“…It has been suggested that the intercellular transmission of such long‐range Ca 2+ waves may result from propagation through gap junctions, possibly mediated via the diffusion of either Ca 2+ itself or IP 3 , as proposed by Berridge et al 36 . This suggestion is supported by a report that, during the GP, there is an increase in the permeability of gap junctions in a circular zone around the blastoderm margin 37 that appears to correlate with both the initiation time and propagation path of the pan‐embryonic marginal waves 34,35 …”

Section: Ca2+ Signalling During the Gpmentioning

confidence: 81%

Ca²⁺ SIGNALLING AND EARLY EMBRYONIC PATTERNING DURING ZEBRAFISH DEVELOPMENT

2007

Clin Exp Pharma Physio

1. It has been proposed that Ca2+ signalling, in the form of pulses, waves and steady gradients, may play a crucial role in key pattern-forming events during early vertebrate development. 2. With reference to the embryo of the zebrafish (Danio rerio), herein we review the Ca2+ transients reported from the cleavage to segmentation periods. This time-window includes most of the major pattern-forming events of early development, which transform a single-cell zygote into a complex multicellular embryo with established primary germ layers and body axes. 3. Data are presented to support our proposal that intracellular Ca2+ waves are an essential feature of embryonic cytokinesis and that propagating intercellular Ca2+ waves (both long and short range) may play a crucial role in: (i) the establishment of the embryonic periderm and the coordination of cell movements during epiboly, convergence and extension; (ii) the establishment of the basic embryonic axes and germ layers; and (iii) definition of the morphological boundaries of specific tissue domains and embryonic structures, including future organ anlagen. 4. The potential downstream targets of these Ca2+ transients are also discussed, as well as how they may integrate with other pattern-forming signalling pathways known to modulate early developmental events.

“…(1,14,46) This suggestion is supported by the report that in gastrula-stage embryos there is an increase in the permeability of gap junctions in a circular zone around the blastoderm margin. (47) This correlates with the initiation time and propagation path of the pan-embryonic marginal waves. (14) Morphogen gradients and propagating second messenger waves have long been proposed as carriers of putative long-range coordinating messages essential for metazoan development.…”

Section: Calcium Signalling During the Blastula Periodmentioning

confidence: 86%

Calcium signalling during zebrafish embryonic development

2000

Bioessays

Calcium signals appear throughout the first 24 hours of zebrafish development. These begin at egg activation, then continue to be generated throughout the subsequent zygote, cleavage, blastula, gastrula, and segmentation periods. They are thus associated with the major phases of pattern formation: cell proliferation, cell differentiation, axis determination, the generation of primary germ layers, the emergence of rudimentary organ systems, and therefore the establishment of the basic vertebrate body plan. When signals need to be transmitted across significant distances they take the form of waves, either intracellular waves when the cell size is large, or later in development when the cell size is reduced, intercellular waves. We will consider both types of calcium signals and their integration into signalling networks, and discuss their possible functions and developmental significance with regard to pattern formation. BioEssays 22:113–123, 2000. ©2000 John Wiley & Sons, Inc.