Developmental Fates of Blastomeres of Eight-Cell-Stage Xenopus laevis Embryos. (intracellular injection/horseradish peroxidase/developmental fate/Xenopus embryo)

Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were observed exclusively in the anterior dorsal part of the ectoderm, and that these transients increased in number and amplitude between stages 9 to 11, just prior to the onset of neural induction. During this time, however, no increase in cytosolic free calcium was observed in the ventral ectoderm, mesoderm or endoderm. The origin and role of these dorsal calcium-signalling patterns were also investigated. Calcium transients require the presence of functional L-type voltage-sensitive calcium channels. Inhibition of channel activation from stages 8 to 14 with the specific antagonist R(+)BayK 8644 led to a complete inhibition of the calcium transients during gastrulation and resulted in severe defects in the subsequent formation of the anterior nervous system. BayK treatment also led to a reduction in the expression of Zic3 and geminin in whole embryos, and of NCAM in noggin-treated animal caps. The possible role of calcium transients in regulating developmental gene expression is discussed.

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Prospective Fates of Blastomeres at the 32 Cell Stage of Xenopus laevis Embryos

Proceedings of the Japan Academy ◽

10.2183/pjab1945.47.407 ◽

1971 ◽

Vol 47 (4) ◽

pp. 407-412 ◽

Cited By ~ 56

Author(s):

Osamu NAKAMURA ◽

Keiko KISHIYAMA

Keyword(s):

Xenopus Laevis ◽

Cell Stage ◽

Xenopus Laevis Embryos

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Reducing inositol lipid hydrolysis, Ins(1,4,5)P3 receptor availability, or Ca2+ gradients lengthens the duration of the cell cycle in Xenopus laevis blastomeres.

The Journal of Cell Biology ◽

10.1083/jcb.116.1.147 ◽

1992 ◽

Vol 116 (1) ◽

pp. 147-156 ◽

Cited By ~ 49

Author(s):

J K Han ◽

K Fukami ◽

R Nuccitelli

Keyword(s):

Cell Cycle ◽

Cell Division ◽

Xenopus Laevis ◽

Mitotic Cell ◽

Embryonic Cell ◽

Cycle Duration ◽

Cell Stage ◽

Stage Embryo ◽

Rate Of Hydrolysis ◽

Xenopus Laevis Embryos

We have microinjected a mAb specifically directed to phosphatidylinositol 4,5-bisphosphate (PIP2) into one blastomere of two-cell stage Xenopus laevis embryos. This antibody binds to endogenous PIP2 and reduces its rate of hydrolysis by phospholipase C. Antibody-injected blastomeres undergo partial or complete arrest of the cell cycle whereas the uninjected sister blastomeres divided normally. Since PIP2 hydrolysis normally produces diacylglycerol (DG) and inositol 1,4,5-triphosphate (Ins[1,4,5]P3), we attempted to measure changes in the levels of DG following stimulation of PIP2 hydrolysis in antibody-injected oocytes. The total amount of DG in antibody-injected oocytes was significantly reduced compared to that of water-injected ones following stimulation by either acetylcholine or progesterone indicating that the antibody does indeed suppress PIP2 hydrolysis. We also found that the PIP2 antibodies greatly reduced the amount of intracellular Ca2+ released in the egg cortex during egg activation. As an indirect test for Ins(1,4,5)P3 involvement in the cell cycle we injected heparin which competes with Ins(1,4,5)P3 for binding to its receptor, and thus inhibits Ins(1,4,5)P3-induced Ca2+ release. Microinjection of heparin into one blastomere of the two-cell stage embryo caused partial or complete arrest of the cell cycle depending upon the concentration of heparin injected. We further investigated the effect of reducing any [Ca2+]i gradients by microinjecting dibromo-BAPTA into the blastomere. Dibromo-BAPTA injection completely blocked mitotic cell division when a final concentration of 1.5 mM was used. These results suggest that PIP2 turnover as well as second messenger activity influence cell cycle duration during embryonic cell division in frogs.

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Reversal of dorsoventral polarity in Xenopus laevis embryos by 180° rotation of the animal micromeres at the eight-cell stage

Developmental Biology ◽

10.1016/0012-1606(88)90304-1 ◽

1988 ◽

Vol 128 (2) ◽

pp. 428-434 ◽

Cited By ~ 14

Author(s):

Pietro Cardellini

Keyword(s):

Xenopus Laevis ◽

Cell Stage ◽

Dorsoventral Polarity ◽

Xenopus Laevis Embryos

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Fate map for the 32-cell stage of Xenopus laevis

Development ◽

10.1242/dev.99.4.527 ◽

1987 ◽

Vol 99 (4) ◽

pp. 527-551 ◽

Cited By ~ 43

Author(s):

L. Dale ◽

J.M. Slack

Keyword(s):

Xenopus Laevis ◽

Short Range ◽

Three Dimensional ◽

Spatial Localization ◽

Spatial Location ◽

Fate Map ◽

Cell Stage ◽

Range Cell ◽

Early Gastrula ◽

Xenopus Laevis Embryos

A complete fate map has been produced for the 32-cell stage of Xenopus laevis. Embryos with a regular cleavage pattern were selected and individual blastomeres were injected with the lineage label fluorescein-dextran-amine (FDA). The spatial location of the clones was deduced from three-dimensional (3D) reconstructions of later stages and the volume of each tissue colonized by labelled cells in each tissue was measured. The results from 107 cases were pooled to give a fate map which shows the fate of each blastomere in terms of tissue types, the composition of each tissue by blastomere, the location of each prospective region on the embryo and the fate of each blastomere in terms of spatial localization. Morphogenetic movements up to stage 10 (early gastrula) were assessed by carrying out a number of orthotopic grafts at blastula and gastrula stages using donor embryos uniformly labelled with FDA. Although there is a regular topographic projection from the 32-cell stage this varies a little between individuals because of variability of positions of cleavage planes and because of short-range cell mixing during gastrulation. The cell mixing means that the topographic projection fails for anteroposterior segments of the dorsal axial structures and it is not possible to include short segments of notochord or neural tube or individual somites on the pregastrulation fate map.

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