Deep cytoplasmic rearrangements during early development in Xenopus laevis

Development ◽  
1991 ◽  
Vol 111 (4) ◽  
pp. 845-856 ◽  
Author(s):  
M.V. Danilchik ◽  
J.M. Denegre
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Xenopus Laevis ◽  
Early Development ◽  
Marginal Zone ◽  
Dorsal Side ◽  
Fluorescent Dye ◽  
Entry Point ◽  
Sperm Entry ◽  
Yolk Platelet

The egg of the frog Xenopus is cylindrically symmetrical about its animal-vegetal axis before fertilization. Midway through the first cell cycle, the yolky subcortical cytoplasm rotates 30 degrees relative to the cortex and plasma membrane, usually toward the side of the sperm entry point. Dorsal embryonic structures always develop on the side away from which the cytoplasm moves. Details of the deep cytoplasmic movements associated with the cortical rotation were studied in eggs vitally stained during oogenesis with a yolk platelet-specific fluorescent dye. During the first cell cycle, eggs labelled in this way develop a complicated swirl of cytoplasm in the animal hemisphere. This pattern is most prominent on the side away from which the vegetal yolk moves, and thus correlates in position with the prospective dorsal side of the embryo. Although the pattern is initially most evident near the egg's equator or marginal zone, extensive rearrangements associated with cleavage furrowing (cytoplasmic ingression) relocate portions of the swirl to vegetal blastomeres on the prospective dorsal side.

Provisional bilateral symmetry in Xenopus eggs is estiblished during maturation

Zygote ◽  
1994 ◽  
Vol 2 (3) ◽  
pp. 213-220 ◽  
Author(s):  
E.E. Brown ◽  
K.M. Margelot ◽  
M.V. Danilchik
Keyword(s):  
Cell Cycle ◽  
Bilateral Symmetry ◽  
Entry Point ◽  
Yolk Mass ◽  
Vegetal Cortex ◽  
Sperm Entry ◽  
Egg Cortex ◽  
The Way

SummaryDorsal–ventral patterning in the Xenopus egg becomes established midway through the first cell cycle during a 30° rotation of the subcortical yolk mass relative to the egg cortex. This rotation of symmetrisation is microtubule dependent, and its direction is thought to be cued by the usually eccentric sperm centrosome. The fact that parthenogenetically activated eggs also undergo a directed rotation, despite the absence of a sperm centrosome, suggests that an endogenous asymmetry in the unfertilised egg supports the directed polymerisation of microtubules in the vegetal cortex, in the way that an eccentric sperm centrosome would in fertilised eggs. Consistent with this idea, we noticed that the maturation spot is usually located an average of more than 15° from the geometric centre of the pigmented animal hemisphere. In parthenogenetically activated eggs, this eccentric maturation spot can be used to predict the direction of rotation. Although in most fertilised eggs the yolk mass rotates toward the sperm entry point (SEP) meridian, occasionally this relationship is perturbed significantly; in such eggs, the maturation spot is never on the same side of the egg as the SEP. In oocytes tilted 90° from upright during maturation in vitro, the maturation spot developed 15° or more from the centre of the pigmented hemisphere, always displaced towards the point on the equator that was up during maturation. This experimentally demonstrated lability is consistent with an off-axis oocyte orientation during oogenesis determining its eccentric maturation spot position, and, in turn, its endogenous rotational bias.

scholarly journals Regional expression, pattern and timing of convergence and extension during gastrulation of Xenopus laevis

Development ◽  
1988 ◽  
Vol 103 (1) ◽  
pp. 193-209 ◽  
Author(s):  
R. Keller ◽  
M. Danilchik
Keyword(s):  
Xenopus Laevis ◽  
South African ◽  
Marginal Zone ◽  
Time Lapse ◽  
Dorsal Side ◽  
Convergent Extension ◽  
Intact Embryo ◽  
Convergence And Extension ◽  
Degree Of Convergence ◽  
Degree Of Extension

We show with time-lapse micrography that narrowing in the circumblastoporal dimension (convergence) and lengthening in the animal-vegetal dimension (extension) of the involuting marginal zone (IMZ) and the noninvoluting marginal zone (NIMZ) are the major tissue movements driving blastopore closure and involution of the IMZ during gastrulation in the South African clawed frog, Xenopus laevis. Analysis of blastopore closure shows that the degree of convergence is uniform from dorsal to ventral sides, whereas the degree of extension is greater on the dorsal side of the gastrula. Explants of the gastrula show simultaneous convergence and extension in the dorsal IMZ and NIMZ. In both regions, convergence and extension are most pronounced at their common boundary, and decrease in both animal and vegetal directions. Convergent extension is autonomous to the IMZ and begins at stage 10.5, after the IMZ has involuted. In contrast, expression of convergent extension in the NIMZ appears to be dependent on basal contact with chordamesoderm or with itself. The degree of extension decreases progressively in lateral and ventral sectors. Isolated ventral sectors show convergence without a corresponding degree of extension, perhaps reflecting the transient convergence and thickening that occurs in this region of the intact embryo. We present a detailed mechanism of how these processes are integrated with others to produce gastrulation. The significance of the regional expression of convergence and extension in Xenopus is discussed and compared to gastrulation in other amphibians.

Nuclear distribution of PCNA during embryonic development in Xenopus laevis: a reinvestigation of early cell cycles

1992 ◽  
Vol 102 (1) ◽  
pp. 63-69 ◽  
Author(s):  
M. Leibovici ◽  
G. Monod ◽  
J. Geraudie ◽  
R. Bravo ◽  
M. Mechali
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Xenopus Laevis ◽  
Early Development ◽  
Nuclear Periphery ◽  
S Phase ◽  
Nuclear Antigen ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Cyclical Pattern

The immunocytological distribution of the proliferating cell nuclear antigen (PCNA), a protein involved in DNA replication, has been examined during the early development of Xenopus laevis. The protein is uniformly detected in nuclei during early stages up to the neurula stage. PCNA is detected by its distinctive cyclical pattern during early development, remaining detectable only during the period of S phase of each cell cycle. Immunological detection of PCNA is therefore a useful and specific non-isotopic marker of S-phase cells in the embryo. PCNA associates with typical karyomeric structures, suggesting that DNA replication starts before the nuclear compartment is entirely formed. At the midblastula transition, a new pattern of PCNA staining becomes apparent. First, a new type of PCNA staining is detected at the nuclear periphery. Second, mitotic clusters with different PCNA distributions suggest that the onset of desynchronization of the cell cycle at this stage is not random.

The site of fertilisation determines dorsoventral polarity but not chirality in the zebra mussel embryo

Zygote ◽  
1998 ◽  
Vol 6 (2) ◽  
pp. 125-135 ◽  
Author(s):  
Craig Marc Luetjens ◽  
Adriaan W.C. Dorresteijn
Keyword(s):  
Early Stage ◽  
Dorsal Side ◽  
Entry Point ◽  
Cleavage Furrow ◽  
Experimental Conditions ◽  
Cell Stage ◽  
Dorsoventral Axis ◽  
Dorsoventral Polarity ◽  
Sperm Entry ◽  
Two Factors

The dorsoventral polarity of unequally cleaving spiralian embryos becomes established at an early stage. The factors determining the position of the dorsoventral axis are still unknown. We present data showing that the sperm entry point (SEP) in both normal development and under experimental conditions determines the position of the first cleavage furrow in Dreissena embryos. The position of the spindles at second cleavage is directed by the site of fertilisation also, and the large, dorsal D quadrant of the 4-cell stage always forms opposite the SEP. The spiral chirality at third cleavage seems to be independent of both the fertilisation point and the arrangement of the quadrants. Dextral and sinistral third cleavages are found in a single egg batch, but sinistral cleavages prevail. We postulate that two factors coordinate the proper positioning of the dorsoventral axis. The sperm entry point as an epigenetic factor determines the dorsal side of the embryo. But since the dorsoventral axis forms oblique to the first cleavage furrow, this first decision is still ambiguous, and a second decision is required that, due to the alternative chirality of spiral cleavage, finally sets up the dorsoventral axis.

scholarly journals Dynamic Regulation of Caveolin-1 Trafficking in the Germ Line and Embryo of Caenorhabditis elegans

2006 ◽  
Vol 17 (7) ◽  
pp. 3085-3094 ◽  
Author(s):  
Ken Sato ◽  
Miyuki Sato ◽  
Anjon Audhya ◽  
Karen Oegema ◽  
Peter Schweinsberg ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Plasma Membrane ◽  
Caenorhabditis Elegans ◽  
Fluorescent Protein ◽  
Germ Line ◽  
Cortical Granule ◽  
Major Protein ◽  
Dynamic Regulation ◽  
Caveolin 1 ◽  
Green Fluorescent

Caveolin is the major protein component required for the formation of caveolae on the plasma membrane. Here we show that trafficking of Caenorhabditis elegans caveolin-1 (CAV-1) is dynamically regulated during development of the germ line and embryo. In oocytes a CAV-1-green fluorescent protein (GFP) fusion protein is found on the plasma membrane and in large vesicles (CAV-1 bodies). After ovulation and fertilization the CAV-1 bodies fuse with the plasma membrane in a manner reminiscent of cortical granule exocytosis as described in other species. Fusion of CAV-1 bodies with the plasma membrane appears to be regulated by the advancing cell cycle, and not fertilization per se, because fusion can proceed in spe-9 fertilization mutants but is blocked by RNA interference–mediated knockdown of an anaphase-promoting complex component (EMB-27). After exocytosis, most CAV-1-GFP is rapidly endocytosed and degraded within one cell cycle. CAV-1 bodies in oocytes appear to be produced by the Golgi apparatus in an ARF-1–dependent, clathrin-independent, mechanism. Conversely endocytosis and degradation of CAV-1-GFP in embryos requires clathrin, dynamin, and RAB-5. Our results demonstrate that the distribution of CAV-1 is highly dynamic during development and provides new insights into the sorting mechanisms that regulate CAV-1 localization.

Early development of dorsal column-medial lemniscal projections in the clawed toad, Xenopus laevis

1993 ◽  
Vol 74 (2) ◽  
pp. 291-294 ◽  
Author(s):  
A. Múñoz ◽  
R. de Boer-Van Huizen ◽  
I. Bergervoet-Vernooy ◽  
H.J. ten Donkelaar
Keyword(s):  
Xenopus Laevis ◽  
Early Development ◽  
Dorsal Column
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