Occurrence of dorsal axis-inducing activity around the vegetal pole of an uncleaved Xenopus egg and displacement to the equatorial region by cortical rotation

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 163-170 ◽  
Author(s):  
M. Fujisue ◽  
Y. Kobayakawa ◽  
K. Yamana
Keyword(s):  
Cell Cycle ◽  
Close Association ◽  
Dorsal Side ◽  
Equatorial Region ◽  
Cell Stage ◽  
Assay Procedure ◽  
Axis Specification ◽  
Vegetal Pole ◽  
Cell Embryo ◽  
Dorsal Cells

Specification of the dorsoventral axis is a subject of great importance in amphibian embryogenesis. We have found that cytoplasm of the vegetal dorsal cells of a 16-cell embryo of Xenopus laevis, when injected into the ventral vegetal cells of a recipient at the same stage, can induce formation of a second axis. In the present experiments, using the same assay procedure, we found that the cytoplasm around the vegetal pole of an egg before cortical rotation is also active in inducing a second axis, that the activity decreases throughout the second half of the cell cycle and appears in a presumptive dorsal equatorial region at the 2- to 16-cell stages. This is the first demonstration of the localization of dorsal forming activity in any specific region of an egg. After UV irradiation, a treatment that is known to block cortical rotation and thereby inhibit axis specification, the activity remains near the vegetal pole beyond the first cell cycle and does not appear in an equatorial region, at least at the 16-cell stage. This suggests that cortical rotation or a related force is in some way involved in changes in distribution of the activity. We also found that UV-irradiated 8-cell embryos can rescue dorsal development when they are cut into halves along the first cleavage plane. Histological examination revealed that the rescued embryos have a neural tube and notochord. In the half embryo, the animal and vegetal regions came into contact during wound healing, an event that enables the activity to localize in the new equator of an embryo. Therefore this rescue suggests that, if the activity is distributed only in the equatorial region, dorsal specification occurs. In fact, the dorsal side of the rescued embryos seems to correspond to the plane through which the embryos have been cut. Based on our results, we propose (1) that a determinant that carries axis-inducing activity is first present around the vegetal pole, (2) that the determinant shifts from the vegetal pole to an equatorial region by or in close association with cortical rotation and (3) that occurrence of the determinant in the equatorial region is a prerequisite for axis specification.

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.

The vegetal determinants required for the Spemann organizer move equatorially during the first cell cycle

Development ◽  
1996 ◽  
Vol 122 (7) ◽  
pp. 2207-2214 ◽  
Author(s):  
M. Sakai
Keyword(s):  
Cell Cycle ◽  
Formation Process ◽  
Lithium Treatment ◽  
Axis Formation ◽  
Cell Stage ◽  
Spemann Organizer ◽  
Dorsal Axis ◽  
Vegetal Pole ◽  
Organizing Center ◽  
Cell Embryo

Embryos with no dorsal axis were obtained when more than 15% of the egg surface was deleted from the vegetal pole of the early 1-cell embryo of Xenopus laevis. The timing of the deletion in the first cell cycle was critical: dorsal-deficient embryos were obtained when the deletion began before time 0.5 (50% of the first cell cycle) whereas normal dorsal axis usually formed when the deletion was done later than time 0.8. The axis deficiency could be restored by lithium treatment and the injection of vegetal but not animal cytoplasm. Bisection of the embryo at the 2-cell stage, which is known to restore the dorsal structures in the UV-ventralized embryos, had no effect on the vegetal-deleted embryos. These results show clearly that, in Xenopus, (1) the dorsal determinants (DDs) localized in the vegetal pole region at the onset of development are necessary for dorsal axis development and (2) the DDs move from the vegetal pole to a subequatorial region where they are incorporated into gastrulating cells to form the future organizing center. A model for the early axis formation process in Xenopus is proposed.

A cytoplasmic determinant for dorsal axis formation in an early embryo of Xenopus laevis

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1051-1056 ◽  
Author(s):  
M. Yuge ◽  
Y. Kobayakawa ◽  
M. Fujisue ◽  
K. Yamana
Keyword(s):  
Xenopus Laevis ◽  
Direct Evidence ◽  
Early Embryo ◽  
Dorsal Side ◽  
Axis Formation ◽  
Secondary Axis ◽  
Dorsal Axis ◽  
Cell Embryo ◽  
Dorsal Cells ◽  
Cytoplasmic Determinant

In Xenopus laevis, dorsal cells that arise at the future dorsal side of an early cleaving embryo have already acquired the ability to cause axis formation. Since the distribution of cytoplasmic components is markedly heterogeneous in an egg and embryo, it has been supposed that the dorsal cells are endowed with the activity to form axial structures by inheriting a unique cytoplasmic component or components localized in the dorsal region of an egg or embryo. However, there has been no direct evidence for this. To examine the activity of the cytoplasm of dorsal cells, we injected cytoplasm (dorsal cytoplasm) from dorsal vegetal cells of a Xenopus 16-cell embryo into ventral vegetal cells of a simultaneous recipient. The cytoplasm caused secondary axis formation in 42% of recipients. Histological examination revealed that well-developed secondary axes included notochord, as well as a neural tube and somites. However, injection of cytoplasm of ventral vegetal cells never caused secondary axis and most recipients became normal tailbud embryos. Furthermore, about two-thirds of ventral isolated halves injected with dorsal cytoplasm formed axial structures. These results show that dorsal, but not ventral, cytoplasm contains the component or components responsible for axis formation. This can be the first step towards identifying the molecular basis of dorsal axis formation.

Brief cytochalasin-induced disruption of microfilaments during a critical interval in 1-cell C. elegans embryos alters the partitioning of developmental instructions to the 2-cell embryo

Development ◽  
1990 ◽  
Vol 108 (1) ◽  
pp. 159-172 ◽  
Author(s):  
D.P. Hill ◽  
S. Strome
Keyword(s):  
Cell Cycle ◽  
Asymmetric Cell Division ◽  
Critical Time ◽  
Time Interval ◽  
Critical Interval ◽  
Cell Stage ◽  
C Elegans ◽  
Daughter Cells ◽  
Correct Pattern ◽  
Cell Embryo

We are investigating the involvement of the microfilament cytoskeleton in the development of early Caenorhabditis elegans embryos. We previously reported that several cytoplasmic movements in the zygote require that the microfilament cytoskeleton remain intact during a narrow time interval approximately three-quarters of the way through the first cell cycle. In this study, we analyze the developmental consequences of brief, cytochalasin D-induced microfilament disruption during the 1-cell stage. Our results indicate that during the first cell cycle microfilaments are important only during the critical time interval for the 2-cell embryo to undergo the correct pattern of subsequent divisions and to initiate the differentiation of at least 4 tissue types. Disruption of microfilaments during the critical interval results in aberrant division and P-granule segregation patterns, generating some embryos that we classify as ‘reverse polarity’, ‘anterior duplication’, and ‘posterior duplication’ embryos. These altered patterns suggest that microfilament disruption during the critical interval leads to the incorrect distribution of developmental instructions responsible for early pattern formation. The strict correlation between unequal division, unequal germ-granule partitioning, and the generation of daughter cells with different cell cycle periods observed in these embryos suggests that the three processes are coupled. We hypothesize that (1) an ‘asymmetry determinant’, normally located at the posterior end of the zygote, governs asymmetric cell division, germ-granule segregation, and the segregation of cell cycle timing elements during the first cell cycle, and (2) the integrity or placement of this asymmetry determinant is sensitive to microfilament disruption during the critical time interval.

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

Timing of the phases of the cell cycle during the period of asynchronous division up to the 49-cell stage in Lymnaea

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 367-391
Author(s):  
J. A. M. van den Biggelaar
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Bilateral Symmetry ◽  
Supporting Evidence ◽  
Cell Stage ◽  
Vegetative Cells ◽  
Animal Pole ◽  
Cell Cycles ◽  
Cell Embryo ◽  
In Cells

The duration of the phases of the cell cycle (M-G1–S-G2) has been determined from the 8-up to the 49-cell stage in eggs of Lymnaea, using autoradiography and cytophotometry of Feulgen-stained nuclei. Division asynchrony of corresponding cells in different quadrants is primarily caused by unequal lengthening of the G2 phases. In general it appeared that in the vegetative cells lengthening of the cell cycles is chiefly due to an extension of the G2 phases, whereas in the cells of the animal half the duration of both the S and the G2 phases are extended. DNA synthesis is not blocked in cells which stop dividing and start to differentiate. A conspicuous lengthening of the cell cycles is observed in the 16- and 24-cell embryo; this is accompanied with the reappearance of distinct nucleoli. Supporting evidence has been obtained for the assumption that bilateral symmetry at the animal pole of the embryo is induced by cells from the vegetative hemisphere, presumably by the macromere 3D, during the 24-cell stage.

Cell cycle redistribution of U3 snRNA and fibrillarin. Presence in the cytoplasmic nucleolus remnant and in the prenucleolar bodies at telophase

1994 ◽  
Vol 107 (2) ◽  
pp. 463-475 ◽  
Author(s):  
M.C. Azum-Gelade ◽  
J. Noaillac-Depeyre ◽  
M. Caizergues-Ferrer ◽  
N. Gas
Keyword(s):  
Cell Cycle ◽  
Immunofluorescence Microscopy ◽  
Close Association ◽  
Ultrastructural Level ◽  
Small Nuclear Rna ◽  
Cho Cell ◽  
Nucleolar Proteins ◽  
Nuclear Rna ◽  
Active Nors

The distribution of the U3 small nuclear RNA during the cell cycle of the CHO cell line was studied by in situ hybridization using digoxigenin-labelled oligonucleotide probes. The location of the hybrids by immunofluorescence microscopy and at the ultrastructural level was correlated with the distribution of two nucleolar proteins, nucleolin and fibrillarin. The U3 snRNA molecules persist throughout mitosis in close association with the nucleolar remnant. U3 snRNA is present in the prenucleolar bodies (PNBs) and could participate in nucleologenesis in association with several nucleolar proteins such as nucleolin and fibrillarin. The interaction of U3 snRNP with the 5′ external spacer of pre-RNA newly synthesized by active NORs is proposed to be the promoting event of nucleologenesis.

Distribution of microvilli on dissociated blastomeres from mouse embryos: evidence for surface polarization at compaction

Development ◽  
1981 ◽  
Vol 62 (1) ◽  
pp. 339-350
Author(s):  
W. J. D. Reeve ◽  
C. A. Ziomek
Keyword(s):  
Ligand Binding ◽  
Single Cells ◽  
Progressive Increase ◽  
Mouse Embryos ◽  
Cell Stage ◽  
Characteristic Distribution ◽  
Surface Polarization ◽  
Cell Embryo ◽  
Fluorescent Ligand ◽  
Scanning Electron

Cells of mouse embryos develop a polarization of microvillous distribution at compaction. Cells of the 4-cell embryo show a uniform pattern of fluorescent-ligand binding and an even distribution of microvilli. Each cell of the early 8-cell embryo has a uniform distribution both of microvilli and of fluorescent ligand. During the 8-cell stage, there is a progressive increase in the incidence of cells which show microvilli restricted to a region normally on the exposed surface of the embryo. When late 8-cell embryos were disaggregated to single cells, and these sorted by pattern of fluorescent-ligand binding, each of the four patterns of staining related consistently to a characteristic distribution of microvilli as viewed by scanning electron microscopy. The 16-cell embryo possessed an inside population of uniformly labelled cells with a sparse microvillous distribution, and an outside population of cells, each of which had a microvillous pole.

scholarly journals Characterization of p96h2bk: immunoreaction with an anti-Erk(extracellular-signal-regulated kinase) peptide antibody and activity in Xenopus oocytes and eggs

1998 ◽  
Vol 335 (1) ◽  
pp. 43-50
Author(s):  
Dong-Hua CHEN ◽  
Chin-Tin CHEN ◽  
Yong ZHANG ◽  
Mei-Ann LIU ◽  
Roberto CAMPOS-GONZALEZ ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Xenopus Oocytes ◽  
Protein Kinase Activity ◽  
Cell Stage ◽  
Extracellular Signal Regulated Kinase ◽  
Oncogenic Ras ◽  
Cycle Arrest ◽  
Extracellular Signal ◽  
M Phase

We have shown previously that oncogenic Ras induces cell cycle arrest in activated Xenopus egg extracts [Pan, Chen and Lin (1994) J. Biol. Chem. 269, 5968–5975]. The cell cycle arrest correlates with the stimulation of a protein kinase activity that phosphorylates histone H2b in vitro (designated p96h2bk) [Chen and Pan (1994) J. Biol. Chem. 269, 28034–28043]. We report here that p96h2bk is likely to be p96ram, a protein of approx. 96 kDa that immunoreacts with a monoclonal antibody (Mk-1) raised against a synthetic peptide derived from a sequence highly conserved in Erk1/Erk2 (where Erk is extracellular-signal-regulated kinase). This is supported by two lines of evidence. First, activation/inactivation of p96h2bk correlates with upward/downward bandshifts of p96ram in polyacrylamide gels. Secondly, both p96h2bk and p96ram can be immunoprecipitated by antibody Mk-1. We also studied the activity of p96h2bk/p96ram in Xenopus oocytes and eggs. p96h2bk/p96ram was inactive in stage 6 oocytes, was active in unfertilized eggs, and became inactive again in eggs after fertilization. Since stage 6 oocytes are at G2-phase of the cell cycle, unfertilized eggs arrest at M-phase and eggs exit M-phase arrest after fertilization, the results thus indicate that p96h2bk/p96ram activity is cell cycle dependent. Moreover, microinjection of oncogenic Ras into fertilized eggs at the one-cell stage arrests the embryos at the two-cell stage, and this induced arrest is correlated with an inappropriate activation of p96h2bk/p96ram. The data are consistent with the concept that inappropriate activation of p96h2bk/p96ram plays a role in the cell cycle arrest induced by oncogenic Ras.

When and how does cell division order influence cell allocation to the inner cell mass of the mouse blastocyst?

Development ◽  
1987 ◽  
Vol 100 (2) ◽  
pp. 325-332
Author(s):  
C.L. Garbutt ◽  
M.H. Johnson ◽  
M.A. George
Keyword(s):  
Cell Division ◽  
Cell Population ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Lineage ◽  
The Other ◽  
Mouse Blastocyst ◽  
Short Term ◽  
Cell Stage ◽  
Cell Embryo

Aggregate 8-cell embryos were constructed from four 2/8 pairs of blastomeres, one of which was marked with a short-term cell lineage marker and was also either 4 h older (derived from an early-dividing 4-cell) or 4 h younger (derived from a late-dividing 4-cell) than the other three pairs. The aggregate embryos were cultured to the 16-cell stage, at which time a second marker was used to label the outside cell population. The embryos were then disaggregated and each cell was examined to determine its labelling pattern. From this analysis, we calculated the relative contributions to the inside cell population of the 16-cell embryo of older and younger cells. Older cells were found to contribute preferentially. However, if the construction of the aggregate 8-cell embryo was delayed until each of the contributing 2/8 cell pairs had undergone intercellular flattening and then had been exposed to medium low in calcium to reverse this flattening immediately prior to aggregation, the advantage possessed by the older cells was lost. These results support the suggestion that older cells derived from early-dividing 4-cell blastomeres contribute preferentially to the inner cell mass as a result of being early-flattening cells.

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