Characterization of the unusually rapid cell cycles during rat gastrulation

Development ◽  
1993 ◽  
Vol 117 (3) ◽  
pp. 873-883 ◽  
Author(s):  
A. Mac Auley ◽  
Z. Werb ◽  
P.E. Mirkes
Keyword(s):  
Cell Cycle ◽  
Cycle Time ◽  
Mammalian Cells ◽  
Primitive Streak ◽  
Cycle Duration ◽  
Embryonic Cells ◽  
Cell Cycle Time ◽  
Cell Cycles ◽  
A Cell ◽  
Cycle Regulation

The onset of gastrulation in rodents is associated with the start of differentiation within the embryo proper and a dramatic increase in the rate of growth and proliferation. We have determined the duration of the cell cycle for mesodermal and ectodermal cells of rat embryos during gastrulation (days 8.5 to 9.5 of gestation) using a stathmokinetic analysis. These embryonic cells are the most rapidly dividing mammalian cells yet described. Most cells of the ectoderm and mesoderm had a cell cycle time of 7 to 7.5 hours, but the cells of the primitive streak divided every 3 to 3.5 hours. Total cell cycle time was reduced by shortening S and G2, as well as G1, in contrast to cells later in development, when cell cycle duration is modulated largely by varying the length of G1. In the ectoderm and mesoderm, G1 was 1.5 to 2 hours, S was 3.5 to 4 hours, and G2 was 30 to 40 minutes. G1, S and G2 were shortened even further in the cells of the primitive streak: G1 was less than 30 minutes, S was 2 to 2.75 hours, and G2 was less than 20 minutes. Thus, progress of cells through all phases of the cell cycle is extensively modified during rodent embryogenesis. Specifically, the increased growth rate during gastrulation is associated with radical changes in cell cycle structure and duration. Further, the commitment of cells to become mesoderm and endoderm by entering the primitive streak is associated with expression of a very short cell cycle during transit of the primitive streak, such that developmental decisions determining germ layer fate are reflected in differences in cell cycle regulation.

scholarly journals Positive Feedback Between PU.1 and the Cell Cycle Controls Myeloid Differentiation

Science ◽  
2013 ◽  
Vol 341 (6146) ◽  
pp. 670-673 ◽  
Author(s):  
Hao Yuan Kueh ◽  
Ameya Champhekar ◽  
Stephen L. Nutt ◽  
Michael B. Elowitz ◽  
Ellen V. Rothenberg
Keyword(s):  
Cell Cycle ◽  
Cell Fate ◽  
Positive Feedback ◽  
Regulatory Gene ◽  
Control Cell ◽  
Stem Cell Differentiation ◽  
Myeloid Differentiation ◽  
Cycle Duration ◽  
Gene Circuits ◽  
Cell Cycles

Regulatory gene circuits with positive-feedback loops control stem cell differentiation, but several mechanisms can contribute to positive feedback. Here, we dissect feedback mechanisms through which the transcription factor PU.1 controls lymphoid and myeloid differentiation. Quantitative live-cell imaging revealed that developing B cells decrease PU.1 levels by reducing PU.1 transcription, whereas developing macrophages increase PU.1 levels by lengthening their cell cycles, which causes stable PU.1 accumulation. Exogenous PU.1 expression in progenitors increases endogenous PU.1 levels by inducing cell cycle lengthening, implying positive feedback between a regulatory factor and the cell cycle. Mathematical modeling showed that this cell cycle–coupled feedback architecture effectively stabilizes a slow-dividing differentiated state. These results show that cell cycle duration functions as an integral part of a positive autoregulatory circuit to control cell fate.

Nuclear DNA content and minimum generation time in herbaceous plants

1972 ◽  
Vol 181 (1063) ◽  
pp. 109-135 ◽  
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Cycle Time ◽  
Generation Time ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Annual Species ◽  
Cell Cycle Time ◽  
Developmental Processes ◽  
The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

scholarly journals Effects of cell cycle variability on lineage and population measurements of mRNA abundance

2020 ◽  
Author(s):  
Ruben Perez-Carrasco ◽  
Casper Beentjes ◽  
Ramon Grima
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Negative Binomial ◽  
Eukaryotic Cell ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Monotonically Decreasing Function ◽  
Binomial Mixture ◽  
A Cell ◽  
The Mean

AbstractMany models of gene expression do not explicitly incorporate a cell cycle description. Here we derive a theory describing how mRNA fluctuations for constitutive and bursty gene expression are influenced by stochasticity in the duration of the cell cycle and the timing of DNA replication. Analytical expressions for the moments show that omitting cell cycle duration introduces an error in the predicted mean number of mRNAs that is a monotonically decreasing function of η, which is proportional to the ratio of the mean cell cycle duration and the mRNA lifetime. By contrast, the error in the variance of the mRNA distribution is highest for intermediate values of η consistent with genome-wide measurements in many organisms. Using eukaryotic cell data, we estimate the errors in the mean and variance to be at most 3% and 25%, respectively. Furthermore, we derive an accurate negative binomial mixture approximation to the mRNA distribution. This indicates that stochasticity in the cell cycle can introduce fluctuations in mRNA numbers that are similar to the effect of bursty transcription. Finally, we show that for real experimental data, disregarding cell cycle stochasticity can introduce errors in the inference of transcription rates larger than 10%.

The NIMA-related kinase X-Nek2B is required for efficient assembly of the zygotic centrosome in Xenopus laevis

2000 ◽  
Vol 113 (11) ◽  
pp. 1973-1984 ◽  
Author(s):  
A.M. Fry ◽  
P. Descombes ◽  
C. Twomey ◽  
R. Bacchieri ◽  
E.A. Nigg
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Basal Body ◽  
Chromatin Condensation ◽  
Embryonic Cells ◽  
Serine Threonine Kinase ◽  
Cell Cycles ◽  
Functional Studies ◽  
Mammalian Cell Cycle ◽  
Egg Extracts

Nek2 is a mammalian cell cycle-regulated serine/threonine kinase that belongs to the family of proteins related to NIMA of Aspergillus nidulans. Functional studies in diverse species have implicated NIMA-related kinases in G(2)/M progression, chromatin condensation and centrosome regulation. To directly address the requirements for vertebrate Nek2 kinases in these cell cycle processes, we have turned to the biochemically-tractable system provided by Xenopus laevis egg extracts. Following isolation of a Xenopus homologue of Nek2, called X-Nek2B, we found that X-Nek2B abundance and activity remained constant through the first mitotic cycle implying a fundamental difference in Nek2 regulation between embryonic and somatic cell cycles. Removal of X-Nek2B from extracts did not disturb either entry into mitosis or the accompanying condensation of chromosomes providing no support for a requirement for Nek2 in these processes at least in embryonic cells. In contrast, X-Nek2B localized to centrosomes of adult Xenopus cells and was rapidly recruited to the basal body of Xenopus sperm following incubation in egg extracts. Recruitment led to phosphorylation of the X-Nek2B kinase. Most importantly, depletion of X-Nek2B from extracts significantly delayed both the assembly of microtubule asters and the recruitment of gamma-tubulin to the basal body. Hence, these studies demonstrate that X-Nek2B is required for efficient assembly of a functional zygotic centrosome and highlight the possibility of multiple roles for vertebrate Nek2 kinases in the centrosome cycle.

Calcium and cell cycle control

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 525-542 ◽  
Author(s):  
M. Whitaker ◽  
R. Patel
Keyword(s):  
Cell Cycle ◽  
Sea Urchin ◽  
Mammalian Cells ◽  
Cell Cycle Regulation ◽  
Sea Urchins ◽  
Cell Cycle Control ◽  
Control Point ◽  
Control Cell ◽  
Free Calcium ◽  
Cycle Regulation

The cell division cycle of the early sea urchin embryo is basic. Nonetheless, it has control points in common with the yeast and mammalian cell cycles, at START, mitosis ENTRY and mitosis EXIT. Progression through each control point in sea urchins is triggered by transient increases in intracellular free calcium. The Cai transients control cell cycle progression by translational and post-translational regulation of the cell cycle control proteins pp34 and cyclin. The START Cai transient leads to phosphorylation of pp34 and cyclin synthesis. The mitosis ENTRY Cai transient triggers cyclin phosphorylation. The motosis EXIT transient causes destruction of phosphorylated cyclin. We compare cell cycle regulation by calcium in sea urchin embryos to cell cycle regulation in other eggs and oocytes and in mammalian cells.

scholarly journals Cilia and the cell cycle?

2005 ◽  
Vol 169 (5) ◽  
pp. 707-710 ◽  
Author(s):  
Lynne M. Quarmby ◽  
Jeremy D.K. Parker
Keyword(s):  
Cell Cycle ◽  
Kidney Disease ◽  
Polycystic Kidney Disease ◽  
Mammalian Cells ◽  
Cell Cycle Regulation ◽  
Polycystic Kidney ◽  
Unicellular Alga ◽  
Regulatory Relationship ◽  
Cycle Regulation ◽  
Multiple Signaling

A recent convergence of data indicating a relationship between cilia and proliferative diseases, such as polycystic kidney disease, has revived the long-standing enigma of the reciprocal regulatory relationship between cilia and the cell cycle. Multiple signaling pathways are localized to cilia in mammalian cells, and some proteins have been shown to act both in the cilium and in cell cycle regulation. Work from the unicellular alga Chlamydomonas is providing novel insights as to how cilia and the cell cycle are coordinately regulated.

scholarly journals Cell cycle phases in the unequal mother/daughter cell cycles of Saccharomyces cerevisiae.

1984 ◽  
Vol 4 (11) ◽  
pp. 2529-2531 ◽  
Author(s):  
B J Brewer ◽  
E Chlebowicz-Sledziewska ◽  
W L Fangman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cycle Phase ◽  
Cell Cycle Time ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Cycles ◽  
Daughter Cells ◽  
Mother And Daughter ◽  
Cell Cycle Phases ◽  
Mother Cells

During cell division in the yeast Saccharomyces cerevisiae mother cells produce buds (daughter cells) which are smaller and have longer cell cycles. We performed experiments to compare the lengths of cell cycle phases in mothers and daughters. As anticipated from earlier indirect observations, the longer cell cycle time of daughter cells is accounted for by a longer G1 interval. The S-phase and the G2-phase are of the same duration in mother and daughter cells. An analysis of five isogenic strains shows that cell cycle phase lengths are independent of cell ploidy and mating type.

Cell cycle progression and cell division are sensitive to hypoxia in Drosophila melanogaster embryos

2001 ◽  
Vol 280 (5) ◽  
pp. R1555-R1563 ◽  
Author(s):  
Robert M. Douglas ◽  
Tian Xu ◽  
Gabriel G. Haddad
Keyword(s):  
Cell Cycle ◽  
Drosophila Melanogaster ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Immunoblot Analysis ◽  
Embryonic Cell ◽  
Cell Cycle Checkpoints ◽  
Cycle Phase ◽  
Embryonic Cells

We and others recently demonstrated that Drosophila melanogaster embryos arrest development and embryonic cells cease dividing when they are deprived of O2. To further characterize the behavior of these embryos in response to O2 deprivation and to define the O2-sensitive checkpoints in the cell cycle, embryos undergoing nuclear cycles 3–13 were subjected to O2deprivation and examined by confocal microscopy under control, hypoxic, and reoxygenation conditions. In vivo, real-time analysis of embryos carrying green fluorescent protein-kinesin demonstrated that cells arrest at two major points of the cell cycle, either at the interphase (before DNA duplication) or at metaphase, depending on the cell cycle phase at which O2 deprivation was induced. Immunoblot analysis of embryos whose cell divisions are synchronized by inducible String (cdc25 homolog) demonstrated that cyclin B was degraded during low O2 conditions in interphase-arrested embryos but not in those arrested in metaphase. Embryos resumed cell cycle activity within ∼20 min of reoxygenation, with very little apparent change in cell cycle kinetics. We conclude that there are specific points during the embryonic cell cycle that are sensitive to the O2 level in D. melanogaster. Given the fact that O2deprivation also influences the growth and development of other species, we suggest that similar hypoxia-sensitive cell cycle checkpoints may also exist in mammalian cells.

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