Cell number in relation to primary pattern formation in the embryo of Xenopus laevis

Development ◽  
1979 ◽  
Vol 53 (1) ◽  
pp. 269-289
Author(s):  
Jonathan Cooke
Keyword(s):  
Cell Cycle ◽  
Pattern Formation ◽  
Cell Cycle Control ◽  
Cell Number ◽  
The Body ◽  
Morphological Evidence ◽  
Tail Bud ◽  
Cell Cycle Time ◽  
Mesodermal Cell ◽  
Body Pattern

Morphological evidence is presented that definitive mesoderm formation in Xenopus is best understood as extending to the end of the neurula phase of development. A process of recruitment of cells from the deep neurectoderm layers into mesodermal position and behaviour, strictly comparable with that already agreed to occur around the internal blastoporal ‘lip’ during gastrula stages, can be shown to continue at the posterior end of the presumptive body pattern up to stage 20 (earliest tail bud). Spatial patterns of incidence of mitosis are described for the fifteen hours of development between the late gastrula and stage 20–22. These are related to the onset of new cell behaviours and overt cyto-differentiations characterizing the dorsal axial pattern,which occur in cranio-caudal and then medio-lateral spatial sequence as development proceeds. A relatively abrupt cessation of mitosis, among hitherto asynchronously cycling cells,precedes the other changes at each level in the presumptive axial pattern. The widespread incidence of cells still in DNA synthesis, anterior to the last mitoses in the posterior-to-anteriordevelopmental sequence of axial tissue, strongly suggests that cells of notochord and somites in their prolonged, non-cycling phase are G2-arrested, and thus tetraploid. This is discussed in relation to what is known of cell-cycle control in other situations. Best estimates for cell-cycle time in the still-dividing, posterior mesoderm of the neurula lie between 10 and 15 h. The supposition of continuing recruitment from neurectoderm can resolve an apparent discrepancy whereby total mesodermal cell number nevertheless contrives to double over a period of approximately 12 h during neurulation when most of the cells are leaving the cycle. Because of pre-existing evidence that cells maintain their relative positions (despite distortion)during the movements that form the mesodermal mantle, the patterns presented in this paper can be understood in two ways: as a temporal sequence of developmental events undergone by individual, posteriorly recruited cells as they achieve their final positions in the body pattern, or alternatively as a succession of wavefronts with respect to changes of cellstate, passing obliquely across the presumptive body pattern in antero-posterior direction. These concepts are discussed briefly in relation to recent ideas about pattern formation in growing systems.

scholarly journals Cell number in relation to primary pattern formation in the embryo of Xenopus laevis

Development ◽  
1979 ◽  
Vol 51 (1) ◽  
pp. 165-182
Author(s):  
Jonathan Cooke
Keyword(s):  
Pattern Formation ◽  
Mitotic Index ◽  
Marginal Zone ◽  
Cell Number ◽  
Unoperated Control ◽  
Cell Cycle Time ◽  
Mesodermal Cell ◽  
Equivalent Number ◽  
Experimental Embryo

Results are presented which offer strong evidence that extensive alteration of the fates of embryonic Xenopus cells occurs independently of the schedule of cell division, after operations which lead to a doubling of the axial pattern of mesodermal differentiation in the gastrula. The experimental strategy was to make estimates of total mesodermal cell numbers and mitotic index in closely matched sets, each of three synchronous sibling embryos, fixed during the ten hours following the close of gastrulation. Within each set two embryos, an unoperated control and a sham-operated embryo whose own dorsal-lip (organizer) cells had been replaced with an equivalent graft, were developing normally. The third, experimental embryo had received an organizer implant to replace an equivalent number of cells from its ventral marginal zone, and was thus developing two axial mesodermal patterns of differentiation in relation to two dorsal midlines, the extra pattern embracing much host tissue. Mitotic index was also determined, in specific regions and throughout the mesoderm, in similar sets of embryos but at mid-gastrula stages. The conclusions are justified by the results of a control investigation which show that there is normally no difference in cell cycle time along the presumptive dorso-ventral mesodermal. dimension, during the interval between time of operations and the determination of patterni The lack of any enhancement of mesodermal cell number in late embryos with dual axia patterns, or intervening enhancement of mitotic index in younger operated embryos, thus suggests that new patterns may be determined in the Xenopus gastrula without generation of extra cells. The results are discussed in relation to recent ideas about pattern formation, and the concepts of morphallaxis and epimorphosis.

Properties of the primary organization field in the embryo of Xenopus laevis

Development ◽  
1973 ◽  
Vol 30 (1) ◽  
pp. 49-62
Author(s):  
J. Cooke
Keyword(s):  
Cell Cycle ◽  
Mitomycin C ◽  
Direct Method ◽  
Large Cell ◽  
Cell Number ◽  
Information Value ◽  
Cell Counting ◽  
Tail Bud ◽  
Cell Cycle Time ◽  
Essentially Normal

Visual observation of early blastulae, and counting of cell suspensions from the late blastula and subsequent stages of Xenopus development, have shown that exposure to either colcemid or mitomycin C can sustain blockage of the mitotic cycle, and hence prevent the normal increase in cell number. Such blockage is essentially complete within a period, following introduction of the drugs, which is short compared with the cell-cycle time normal to post-blastular stages. Although the cell-counting data do not allow a statistical demonstration, there is a suggestion that mitomycin C allows a greater proportion of cells to divide once, after its introduction, than does colcemid. This is in accord with its putative mode of action, in causing only intrachromatid cross-linkage within chromosones, but there are no data on the status of DNA replication within nuclei of the non-dividing cells under either drug. If blockage is begun not earlier than stage 10+, some 20 min after dorsal lip formation, essentially normal morphogenesis ensues up to tail-bud stages around 27, including histodifferentiation of ectodermal structures and notochord, and twitching of somitic muscle. Such embryos are described. In describing those arresting at earlier stages following blockage in blastulae, the possibility is mentioned that morphogenesis may fail for mechanical reasons due to low cell number and large cell size, rather than to lack of a normal field as such. Cell counting reveals that blocked embryos with qualitatively normal pattern formation by stages 22–24, in having a total cell number appropriate to stage 10+ or 10½, show about a seventh or an eighth of the number of cells normal to their stage. Between then and stage 27 when histogenesis, particularly of twitching muscle, is more clearly seen, the direct method of estimating cell number can no longer be used, but histology reveals no mitotic metaphases in any blocked embryos. In the same experiments, operations of two types described in previous papers are performed on early gastrulae so that regulation is required in the embryonic field after the cessation of mitosis. The results are as seen in the normal presence of the cell cycle, revealing that, in response to changes of positional information value, host material may change its presumptive differentiation tendency and final commitment, in the absence of cell division as such. There is some indication that the proportional numbers of cells assigned to different structures in an individuation field may deviate from normal when overall cell number is limiting.

scholarly journals Genetic and Proteomic Evidence for Roles of Drosophila SUMO in Cell Cycle Control, Ras Signaling, and Early Pattern Formation

PLoS ONE ◽  
2009 ◽  
Vol 4 (6) ◽  
pp. e5905 ◽  
Author(s):  
Minghua Nie ◽  
Yongming Xie ◽  
Joseph A. Loo ◽  
Albert J. Courey
Keyword(s):  
Cell Cycle ◽  
Pattern Formation ◽  
Cell Cycle Control ◽  
Ras Signaling

The restrictive effect of early exposure to lithium upon body pattern in Xenopus development, studied by quantitative anatomy and immunofluorescence

Development ◽  
1988 ◽  
Vol 102 (1) ◽  
pp. 85-99 ◽  
Author(s):  
J. Cooke ◽  
E.J. Smith
Keyword(s):  
Prolonged Exposure ◽  
Anatomical Study ◽  
Cell Number ◽  
The Body ◽  
General Nature ◽  
Gene Products ◽  
Fate Map ◽  
Normal Pattern ◽  
Quantitative Anatomy ◽  
Body Pattern

We have carried out an anatomical study of Xenopus larval and gastrula stages resulting from treatment of synchronous early blastulae for brief periods with Li+. We confirm the proposal that such treatment causes a particular transformation, and partial elimination, of the normal body pattern. Coordinated restriction of pattern, without appreciable loss of cell number, is seen in all three germ layers. The distortion has been investigated by quantitative study of mesoderms at a standard stage, in relation to the normal fate map for mesoderm, and with the help of immunofluorescence on sections for somitic muscle and for blood. In the extreme syndrome, mesoderm arises from all around the blastula as usual, but is symmetrical and corresponds to that arising near the dorsal/anterior meridian of the normally specified egg or embryo with a large posterior subset of the normal pattern values thus missing. The effect is independent of any inhibition of archenteron formation or mesoderm migration (i.e. the cell mechanics of gastrulation) incurred by the treatment. It is also quite separate from a syndrome caused by more prolonged exposure to Li+ during gastrulation. A small, but distinctive, anterior pattern region is also not expressed and, anomalously in relation to their general nature, these forms differentiate considerable blood tissue. We consider the implications of some details of the pattern restriction for our understanding of interaction in the normal development and propose that the Li+ embryo is likely to be useful as a specific ‘differential screen’, in relation to the normal, during the search for those gene products that mediate initial regionalization of the body.

scholarly journals Alternative splicing of pericentrin contributes to cell cycle control in cardiomyocytes

2021 ◽  
Author(s):  
Jakob Steinfeldt ◽  
Robert Becker ◽  
Silvia Vergarajauregui ◽  
Felix B Engel
Keyword(s):  
Cell Cycle ◽  
Alternative Splicing ◽  
Cell Cycle Arrest ◽  
Cell Cycle Control ◽  
Ectopic Expression ◽  
Cell Number ◽  
Cardiomyocyte Proliferation ◽  
C2c12 Myoblasts ◽  
Cycle Arrest ◽  
Heterologous System

Induction of cardiomyocyte proliferation is a promising option to regenerate the heart. Thus, it is important to elucidate mechanisms that contribute to the cell cycle arrest of mammalian cardiomyocytes. Here, we assessed the contribution of the pericentrin (Pcnt) S isoform to the cell cycle arrest in postnatal cardiomyocytes. Immunofluorescence staining of Pcnt isoforms combined with siRNA-mediated depletion indicates that Pcnt S preferentially localizes to the nuclear envelope, while the Pcnt B isoform is enriched at centrosomes. This is further supported by the localization of ectopically expressed FLAG-tagged Pcnt S and Pcnt B in postnatal cardiomyocytes. Analysis of centriole configuration upon Pcnt depletion revealed that Pcnt B but not Pcnt S is required for centriole cohesion. Importantly, ectopic expression of Pcnt S induced centriole splitting in a heterologous system, ARPE-19 cells, and was sufficient to impair DNA synthesis in C2C12 myoblasts. Moreover, Pcnt S depletion enhanced serum-induced cell cycle re-entry in postnatal cardiomyocytes. Analysis of mitosis, binucleation rate, and cell number suggests that Pcnt S depletion promotes progression of postnatal cardiomyocytes through the cell cycle resulting in cell division. Collectively, our data indicate that alternative splicing of Pcnt contributes to the establishment of cardiomyocyte cell cycle arrest shortly after birth.

Blastemal kinetics and pattern formation during amphibian limb regeneration

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 561-574
Author(s):  
M. Maden
Keyword(s):  
Cell Cycle ◽  
Pattern Formation ◽  
Limb Regeneration ◽  
Cell Number ◽  
Growth Characteristics ◽  
Distal Limb ◽  
Cycle Times ◽  
Growth Zones ◽  
Discernible Difference ◽  
Volume Cell

To investigate whether the uniqueness of proximal and distal limb regenerates could be attributed simply to differing blastemal growth characteristics, their increase in volume, cell number and cell-cycle times were determined. With respect to these parameters proximal and distal blastemas were identical and, furthermore, no evidence could be found for the existence of separate growth zones such as an apical proliferation centre or a progress zone within the blastema. It was therefore concluded that level-specific properties of the blastemal cells play the major role in determining the structure of the regenerate, not their growth characteristics. The only discernible difference was in the cell number within the two types of blastema at the onset of cartilage redifferentiation— proximal regenerates had 60 % more cells. Thus it seems that the larger the pattern to be regenerated (the more proximal the amputation plane), the larger the primordium within which that pattern first appears. These two conclusions are discussed in relation to current theories of pattern formation during limb regeneration and development and a new way of envisaging the regeneration of pattern is described

The effects of Streptomyces hyaluronidase on tissue organization and cell cycle time in rat embryos

Development ◽  
1986 ◽  
Vol 98 (1) ◽  
pp. 59-70 ◽  
Author(s):  
Gillian M. Morriss-Kay ◽  
Fiona Tuckett ◽  
Michael Solursh
Keyword(s):  
Cell Cycle ◽  
Extracellular Matrix ◽  
Cycle Time ◽  
Cell Number ◽  
Considerable Reduction ◽  
Blue Staining ◽  
Neuroepithelial Cell ◽  
Cell Cycle Time ◽  
Rat Embryos ◽  
Tissue Organization

Day 9 rat embryos (late presomite stage with cranial neural plate or very early neural folds) were cultured for various periods of time from 6–48 h in medium containing 20 TRU ml−1Streptomyces hyaluronidase. Exposure to the enzyme resulted in considerable reduction of mesenchymal extracellular matrix. Access of the enzyme to the embryo was confirmed by alcian blue staining which indicated considerable reduction of extracellular and cell surface hyaluronate. Cranial neurulation was retarded, but not inhibited, and migration of both neural crest and primary mesenchyme cells occurred. In general, morphology was normal at 48 h. The major effect was on growth: embryos were smaller, with slightly reduced neuroepithelial cell number and greatly reduced mesenchymal cell number. Neuroepithelial cell cycle time was slightly prolonged, and that of the mesenchyme more than doubled. This differential effect on the growth rates of these two tissues reflects the normal distribution of hyaluronate, which is particularly abundant in the mesenchymal extracellular matrix.

scholarly journals Alternative Splicing of Pericentrin Contributes to Cell Cycle Control in Cardiomyocytes

2021 ◽  
Vol 8 (8) ◽  
pp. 87
Author(s):  
Jakob Steinfeldt ◽  
Robert Becker ◽  
Silvia Vergarajauregui ◽  
Felix B. Engel
Keyword(s):  
Cell Cycle ◽  
Alternative Splicing ◽  
Cell Cycle Arrest ◽  
Cell Cycle Control ◽  
Ectopic Expression ◽  
Cell Number ◽  
Cardiomyocyte Proliferation ◽  
C2c12 Myoblasts ◽  
Cycle Arrest ◽  
Heterologous System

Induction of cardiomyocyte proliferation is a promising option to regenerate the heart. Thus, it is important to elucidate mechanisms that contribute to the cell cycle arrest of mammalian cardiomyocytes. Here, we assessed the contribution of the pericentrin (Pcnt) S isoform to cell cycle arrest in postnatal cardiomyocytes. Immunofluorescence staining of Pcnt isoforms combined with SiRNA-mediated depletion indicates that Pcnt S preferentially localizes to the nuclear envelope, while the Pcnt B isoform is enriched at centrosomes. This is further supported by the localization of ectopically expressed FLAG-tagged Pcnt S and Pcnt B in postnatal cardiomyocytes. Analysis of centriole configuration upon Pcnt depletion revealed that Pcnt B but not Pcnt S is required for centriole cohesion. Importantly, ectopic expression of Pcnt S induced centriole splitting in a heterologous system, ARPE-19 cells, and was sufficient to impair DNA synthesis in C2C12 myoblasts. Moreover, Pcnt S depletion enhanced serum-induced cell cycle re-entry in postnatal cardiomyocytes. Analysis of mitosis, binucleation rate, and cell number suggests that Pcnt S depletion enhances serum-induced progression of postnatal cardiomyocytes through the cell cycle resulting in cell division. Collectively, our data indicate that alternative splicing of Pcnt contributes to the establishment of cardiomyocyte cell cycle arrest shortly after birth.

Presence and expression of G2 cyclins in the coelenterate hydra

1996 ◽  
Vol 109 (5) ◽  
pp. 1063-1069 ◽  
Author(s):  
I. Scheurlen ◽  
S.A. Hoffmeister ◽  
H.C. Schaller
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Control ◽  
Amino Acid Level ◽  
Cyclin A ◽  
Growth Conditions ◽  
Rna Degradation ◽  
Cyclin B ◽  
Proliferating Cells ◽  
Cell Cycle Time ◽  
Restriction Point

In hydra all cell-cycle control occurs in the G2/M transition. Cyclins acting at this restriction point in the cell cycle belong to the cyclin A and B families. In agreement with this we isolated cDNAs coding for a cyclin A and a cyclin B from the multiheaded mutant of Chlorohydra viridissima and a cyclin B from Hydra vulgaris. The two B-type cyclins from hydra show 85.6% identity at the amino acid level, and 84.8% at the nucleotide level. The relatedness is less extensive than that found for mammals, e.g. human and mouse, and is evidence that the two hydra species diverged early in evolution. From each hydra species only one B-type cyclin was found, showing equal relatedness to the B1 and B2 subtypes of cyclins, hinting at a role as common ancestor before the split into B1 and B2 cyclins occurred. All three hydra cyclins contain regulation signals typical for G2/M cyclins, such as a ubiquitin destruction box at the amino terminus, needed for rapid degradation of the protein, and translation and polyadenylation elements in the 3′ untranslated region to regulate RNA storage and RNA degradation. In hydra cell-cycle times vary depending on feeding regime and growth conditions. Cyclin B RNA expression was found to precede the daily mitotic rhythm induced by feeding. During head regeneration cyclin B expression showed the expected drop early during regeneration and an increase later. At the cellular level strongest expression of cyclin B RNA and protein was detected in interstitial cells which possess with one day the shortest cell-cycle time in hydra. Epithelial cells with a three-day cell-cycle rhythm showed variable, and differentiated cells no cyclin B expression. Regions of hydra containing high numbers of proliferating cells, such as developing buds exhibited elevated levels of cyclin B expression.

scholarly journals Endothelial Cell Cycle State Determines Propensity for Arterial-Venous Fate

2020 ◽  
Author(s):  
Nicholas W. Chavkin ◽  
Gael Genet ◽  
Mathilde Poulet ◽  
Nafiisha Genet ◽  
Corina Marziano ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Endothelial Cells ◽  
Endothelial Cell ◽  
Cell Cycle Progression ◽  
Network Formation ◽  
Vascular System ◽  
Cell Cycle Control ◽  
The Body ◽  
Distinct Cell ◽  
Arterial Endothelial Cells

SummaryFormation and maturation of a functional blood vascular system is required for the development and maintenance of all tissues in the body. During the process of blood vessel development, primordial endothelial cells are formed and become specified toward arterial or venous fates to generate a circulatory network that provides nutrients and oxygen to, and removes metabolic waste from, all tissues1-3. Specification of arterial and venous endothelial cells occurs in conjunction with suppression of endothelial cell cycle progression4,5, and endothelial cell hyperproliferation is associated with potentially lethal arterial-venous malformations6. However, the mechanistic role that cell cycle state plays in arterial-venous specification is unknown. Herein, studying retinal vascular development in Fucci2aR reporter mice7, we found that venous and arterial endothelial cells are in distinct cell cycle states during development and in adulthood. That is, venous endothelial cells reside in early G1 state, while arterial endothelial cells reside in late G1 state. Endothelial cells in early vs. late G1 exhibited significant differences in gene expression and activity, especially among BMP/TGF-β signaling components. The early G1 state was found to be essential for BMP4-induced venous specification, whereas late G1 state is essential for TGF-β1-induced arterial specification. In a mouse model of endothelial cell hyperproliferation and disrupted vascular remodeling, pharmacological inhibition of endothelial cell cycle rescues the arterial-venous specification defects. Collectively, our results show that endothelial cell cycle control plays a key role in arterial-venous network formation, and distinct cell cycle states provide distinct windows of opportunity for the molecular induction of arterial vs. venous specification.

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