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Intercellular bridges in vertebrate gastrulation.

Caneparo L, Pantazis P, Dempsey W, Fraser SE - PLoS ONE (2011)

Bottom Line: The developing zebrafish embryo has been the subject of many studies of regional patterning, stereotypical cell movements and changes in cell shape.To better study the morphological features of cells during gastrulation, we generated mosaic embryos expressing membrane attached Dendra2 to highlight cellular boundaries.These findings reveal a surprising feature of the cellular landscape in zebrafish embryos and open new possibilities for cell-cell communication during gastrulation, with implications for modeling, cellular mechanics, and morphogenetic signaling.

View Article: PubMed Central - PubMed

Affiliation: Beckman Institute and Division of Biology, California Institute of Technology, Pasadena, California, United States of America. caneparo@caltech.edu

ABSTRACT
The developing zebrafish embryo has been the subject of many studies of regional patterning, stereotypical cell movements and changes in cell shape. To better study the morphological features of cells during gastrulation, we generated mosaic embryos expressing membrane attached Dendra2 to highlight cellular boundaries. We find that intercellular bridges join a significant fraction of epiblast cells in the zebrafish embryo, reaching several cell diameters in length and spanning across different regions of the developing embryos. These intercellular bridges are distinct from the cellular protrusions previously reported as extending from hypoblast cells (1-2 cellular diameters in length) or epiblast cells (which were shorter). Most of the intercellular bridges were formed at pre-gastrula stages by the daughters of a dividing cell maintaining a membrane tether as they move apart after mitosis. These intercellular bridges persist during gastrulation and can mediate the transfer of proteins between distant cells. These findings reveal a surprising feature of the cellular landscape in zebrafish embryos and open new possibilities for cell-cell communication during gastrulation, with implications for modeling, cellular mechanics, and morphogenetic signaling.

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Intercellular Bridge Formation and Embryo Distribution.(A-A”’) Image series from a confocal time-lapse of a dividing cell forming an intercellular bridge during the blastula stage. Nuclei are labeled with H2B-mCherry (in red) and mDendra2 (in green) highlights the cellular boundary (see also Movie S1). (B) Animal pole view of blastula zebrafish showing several pairs of interconnecting cells (white arrows). (C, C’’) Persistence of the intercellular bridge (red arrow) from mid-gastrula (C) to the end of gastrulation (C’) (see also Movie S2). (D) Schematic showing several intercellular bridges mapped in an ideal embryo, shown here in an animal pole view. Different colors show different portions of the embryos: (red) neural plate region; (dark blue) non-neural territory; (green) presumptive lateral plate. The subdivision into territories has been made aligning each embryo by the embryonic shield and the anterior neural border. The dorsal side of the idealized embryo is shown by the white asterisk (*). (E, F) Quantification of the length of the intercellular bridges at midgastrula. (E) The boxplot shows the median length of intercellular bridges (red line). The first quartile (blue box) and the minimum and maximum value of the intercellular bridges (whiskers) are depicted for a total of n = 30 cells from 20 independent embryos. The average length of the intercellular bridges is 215 µm. (F) The histogram shows the same distribution represented in the boxplot. Scale bar (A-C’): 20 µm.
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pone-0020230-g002: Intercellular Bridge Formation and Embryo Distribution.(A-A”’) Image series from a confocal time-lapse of a dividing cell forming an intercellular bridge during the blastula stage. Nuclei are labeled with H2B-mCherry (in red) and mDendra2 (in green) highlights the cellular boundary (see also Movie S1). (B) Animal pole view of blastula zebrafish showing several pairs of interconnecting cells (white arrows). (C, C’’) Persistence of the intercellular bridge (red arrow) from mid-gastrula (C) to the end of gastrulation (C’) (see also Movie S2). (D) Schematic showing several intercellular bridges mapped in an ideal embryo, shown here in an animal pole view. Different colors show different portions of the embryos: (red) neural plate region; (dark blue) non-neural territory; (green) presumptive lateral plate. The subdivision into territories has been made aligning each embryo by the embryonic shield and the anterior neural border. The dorsal side of the idealized embryo is shown by the white asterisk (*). (E, F) Quantification of the length of the intercellular bridges at midgastrula. (E) The boxplot shows the median length of intercellular bridges (red line). The first quartile (blue box) and the minimum and maximum value of the intercellular bridges (whiskers) are depicted for a total of n = 30 cells from 20 independent embryos. The average length of the intercellular bridges is 215 µm. (F) The histogram shows the same distribution represented in the boxplot. Scale bar (A-C’): 20 µm.

Mentions: Three-dimensional imaging revealed that the cells linked by intercellular bridges resided within the epiblast layer; bridges were not observed linking cells in either the EVL or the hypoblast. A quantitative analysis of 51 intercellular bridges from 38 independent embryos at late gastrula stages showed that the protrusions averaged 215 µm in length (see Figure 2E). The imaging confirmed the presence of pseudopodia and other cellular extensions in the epiblast, but the length of such projections was a small fraction of the length of the intercellular bridges. Interestingly, previous reports of the cell morphologies during chick neurulation [11] and of deep cells in the medaka fish suggested the presence of intercellular bridges; in medaka a fraction of fixed and dissociated deep cells were found to be linked by short (up to 30 µm) intercellular extensions [12].


Intercellular bridges in vertebrate gastrulation.

Caneparo L, Pantazis P, Dempsey W, Fraser SE - PLoS ONE (2011)

Intercellular Bridge Formation and Embryo Distribution.(A-A”’) Image series from a confocal time-lapse of a dividing cell forming an intercellular bridge during the blastula stage. Nuclei are labeled with H2B-mCherry (in red) and mDendra2 (in green) highlights the cellular boundary (see also Movie S1). (B) Animal pole view of blastula zebrafish showing several pairs of interconnecting cells (white arrows). (C, C’’) Persistence of the intercellular bridge (red arrow) from mid-gastrula (C) to the end of gastrulation (C’) (see also Movie S2). (D) Schematic showing several intercellular bridges mapped in an ideal embryo, shown here in an animal pole view. Different colors show different portions of the embryos: (red) neural plate region; (dark blue) non-neural territory; (green) presumptive lateral plate. The subdivision into territories has been made aligning each embryo by the embryonic shield and the anterior neural border. The dorsal side of the idealized embryo is shown by the white asterisk (*). (E, F) Quantification of the length of the intercellular bridges at midgastrula. (E) The boxplot shows the median length of intercellular bridges (red line). The first quartile (blue box) and the minimum and maximum value of the intercellular bridges (whiskers) are depicted for a total of n = 30 cells from 20 independent embryos. The average length of the intercellular bridges is 215 µm. (F) The histogram shows the same distribution represented in the boxplot. Scale bar (A-C’): 20 µm.
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Related In: Results  -  Collection

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pone-0020230-g002: Intercellular Bridge Formation and Embryo Distribution.(A-A”’) Image series from a confocal time-lapse of a dividing cell forming an intercellular bridge during the blastula stage. Nuclei are labeled with H2B-mCherry (in red) and mDendra2 (in green) highlights the cellular boundary (see also Movie S1). (B) Animal pole view of blastula zebrafish showing several pairs of interconnecting cells (white arrows). (C, C’’) Persistence of the intercellular bridge (red arrow) from mid-gastrula (C) to the end of gastrulation (C’) (see also Movie S2). (D) Schematic showing several intercellular bridges mapped in an ideal embryo, shown here in an animal pole view. Different colors show different portions of the embryos: (red) neural plate region; (dark blue) non-neural territory; (green) presumptive lateral plate. The subdivision into territories has been made aligning each embryo by the embryonic shield and the anterior neural border. The dorsal side of the idealized embryo is shown by the white asterisk (*). (E, F) Quantification of the length of the intercellular bridges at midgastrula. (E) The boxplot shows the median length of intercellular bridges (red line). The first quartile (blue box) and the minimum and maximum value of the intercellular bridges (whiskers) are depicted for a total of n = 30 cells from 20 independent embryos. The average length of the intercellular bridges is 215 µm. (F) The histogram shows the same distribution represented in the boxplot. Scale bar (A-C’): 20 µm.
Mentions: Three-dimensional imaging revealed that the cells linked by intercellular bridges resided within the epiblast layer; bridges were not observed linking cells in either the EVL or the hypoblast. A quantitative analysis of 51 intercellular bridges from 38 independent embryos at late gastrula stages showed that the protrusions averaged 215 µm in length (see Figure 2E). The imaging confirmed the presence of pseudopodia and other cellular extensions in the epiblast, but the length of such projections was a small fraction of the length of the intercellular bridges. Interestingly, previous reports of the cell morphologies during chick neurulation [11] and of deep cells in the medaka fish suggested the presence of intercellular bridges; in medaka a fraction of fixed and dissociated deep cells were found to be linked by short (up to 30 µm) intercellular extensions [12].

Bottom Line: The developing zebrafish embryo has been the subject of many studies of regional patterning, stereotypical cell movements and changes in cell shape.To better study the morphological features of cells during gastrulation, we generated mosaic embryos expressing membrane attached Dendra2 to highlight cellular boundaries.These findings reveal a surprising feature of the cellular landscape in zebrafish embryos and open new possibilities for cell-cell communication during gastrulation, with implications for modeling, cellular mechanics, and morphogenetic signaling.

View Article: PubMed Central - PubMed

Affiliation: Beckman Institute and Division of Biology, California Institute of Technology, Pasadena, California, United States of America. caneparo@caltech.edu

ABSTRACT
The developing zebrafish embryo has been the subject of many studies of regional patterning, stereotypical cell movements and changes in cell shape. To better study the morphological features of cells during gastrulation, we generated mosaic embryos expressing membrane attached Dendra2 to highlight cellular boundaries. We find that intercellular bridges join a significant fraction of epiblast cells in the zebrafish embryo, reaching several cell diameters in length and spanning across different regions of the developing embryos. These intercellular bridges are distinct from the cellular protrusions previously reported as extending from hypoblast cells (1-2 cellular diameters in length) or epiblast cells (which were shorter). Most of the intercellular bridges were formed at pre-gastrula stages by the daughters of a dividing cell maintaining a membrane tether as they move apart after mitosis. These intercellular bridges persist during gastrulation and can mediate the transfer of proteins between distant cells. These findings reveal a surprising feature of the cellular landscape in zebrafish embryos and open new possibilities for cell-cell communication during gastrulation, with implications for modeling, cellular mechanics, and morphogenetic signaling.

Show MeSH
Related in: MedlinePlus