scholarly journals Transcription-dependent induction of G1 phase during the zebra fish midblastula transition.

1997 ◽  
Vol 17 (2) ◽  
pp. 529-536 ◽  
Author(s):  
E Zamir ◽  
Z Kam ◽  
A Yarden
Keyword(s):  
Cell Cycle ◽  
Early Development ◽  
Actinomycin D ◽  
Flow Cytometric Analysis ◽  
G1 Phase ◽  
Fish Cell ◽  
Zebra Fish ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Zygotic Transcription

The early development of the zebra fish (Danio rerio) embryo is characterized by a series of rapid and synchronous cell cycles with no detectable transcription. This period is followed by the midblastula transition (MBT), during which the cell cycle gradually lengthens, cell synchrony is lost, and zygotic transcription is initially detected. In this work, we examined the changes in the pattern of the cell cycle during MBT in zebra fish and whether these changes are dependent on the initiation of zygotic transcription. To characterize the pattern of the early zebra fish cell cycles, the embryonic DNA content was determined by flow cytometric analysis. We found that G1 phase is below detection levels during the first 10 cleavages and can be initially detected at the onset of MBT. Inhibition of zygotic transcription, by microinjection of actinomycin D, abolished the appearance of G1 phase at MBT. Premature activation of zygotic transcription, by microinjection of nonspecific DNA, induced G1 phase before the onset of MBT, while coinjection of actinomycin D and nonspecific DNA abolished this early appearance of G1 phase. We therefore suggest that during the early development of the zebra fish embryo, G1 phase appears at the onset of MBT and that the activation of transcription at MBT is essential and sufficient for the G1-phase induction.

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.

Expression of the cell cycle control gene, cdc25, is constitutive in the segmental founder cells but is cell-cycle-regulated in the micromeres of leech embryos

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3035-3043 ◽  
Author(s):  
S.T. Bissen
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Control ◽  
Control Gene ◽  
Cdc25 Phosphatase ◽  
Cell Cycles ◽  
Cell Divisions ◽  
Zygotic Transcription ◽  
Founder Cells ◽  
Drosophila Embryos

The identifiable cells of leech embryos exhibit characteristic differences in the timing of cell division. To elucidate the mechanisms underlying these cell-specific differences in cell cycle timing, the leech cdc25 gene was isolated because Cdc25 phosphatase regulates the asynchronous cell divisions of postblastoderm Drosophila embryos. Examination of the distribution of cdc25 RNA and the zygotic expression of cdc25 in identified cells of leech embryos revealed lineage-dependent mechanisms of regulation. The early blastomeres, macromeres and teloblasts have steady levels of maternal cdc25 RNA throughout their cell cycles. The levels of cdc25 RNA remain constant throughout the cell cycles of the segmental founder cells, but the majority of these transcripts are zygotically produced. Cdc25 RNA levels fluctuate during the cell cycles of the micromeres. The levels peak during early G2, due to a burst of zygotic transcription, and then decline as the cell cycles progress. These data suggest that cells of different lineages employ different strategies of cell cycle control.

Investigation of cell cycle arrest effects of actinomycin D at G1 phase using proteomic methods in B104-1-1 cells

2005 ◽  
Vol 37 (9) ◽  
pp. 1921-1929 ◽  
Author(s):  
Hyae-Kyeong Kim ◽  
Mi-Young Kong ◽  
Moon-Jin Jeong ◽  
Dong-Cho Han ◽  
Jung-Do Choi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Actinomycin D ◽  
G1 Phase ◽  
Cycle Arrest ◽  
Proteomic Methods

scholarly journals Chromosome Association of Minichromosome Maintenance Proteins in Drosophila Mitotic Cycles

1997 ◽  
Vol 139 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Tin Tin Su ◽  
Patrick H. O'Farrell
Keyword(s):  
Cell Cycle ◽  
Cyclin E ◽  
Embryonic Cell ◽  
Cyclin B ◽  
Chromatin Interaction ◽  
G1 Phase ◽  
Minichromosome Maintenance ◽  
Cell Cycles ◽  
Mcm Proteins ◽  
Replication Factors

Minichromosome maintenance (MCM) proteins are essential DNA replication factors conserved among eukaryotes. MCMs cycle between chromatin bound and dissociated states during each cell cycle. Their absence on chromatin is thought to contribute to the inability of a G2 nucleus to replicate DNA. Passage through mitosis restores the ability of MCMs to bind chromatin and the ability to replicate DNA. In Drosophila early embryonic cell cycles, which lack a G1 phase, MCMs reassociate with condensed chromosomes toward the end of mitosis. To explore the coupling between mitosis and MCM–chromatin interaction, we tested whether this reassociation requires mitotic degradation of cyclins. Arrest of mitosis by induced expression of nondegradable forms of cyclins A and/or B showed that reassociation of MCMs to chromatin requires cyclin A destruction but not cyclin B destruction. In contrast to the earlier mitoses, mitosis 16 (M16) is followed by G1, and MCMs do not reassociate with chromatin at the end of M16. dacapo mutant embryos lack an inhibitor of cyclin E, do not enter G1 quiescence after M16, and show mitotic reassociation of MCM proteins. We propose that cyclin E, inhibited by Dacapo in M16, promotes chromosome binding of MCMs. We suggest that cyclins have both positive and negative roles in controlling MCM–chromatin association.

scholarly journals Histone titration against the genome sets the DNA-to-cytoplasm threshold for the Xenopus midblastula transition

2015 ◽  
Vol 112 (10) ◽  
pp. E1086-E1095 ◽  
Author(s):  
Amanda A. Amodeo ◽  
David Jukam ◽  
Aaron F. Straight ◽  
Jan M. Skotheim
Keyword(s):  
Cell Cycle ◽  
Transcriptional Activation ◽  
Cell Cycle Checkpoints ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Egg Extract ◽  
Activation Of Transcription ◽  
Maternal To Zygotic Transition ◽  
Synchronous Cell

During early development, animal embryos depend on maternally deposited RNA until zygotic genes become transcriptionally active. Before this maternal-to-zygotic transition, many species execute rapid and synchronous cell divisions without growth phases or cell cycle checkpoints. The coordinated onset of transcription, cell cycle lengthening, and cell cycle checkpoints comprise the midblastula transition (MBT). A long-standing model in the frog, Xenopus laevis, posits that MBT timing is controlled by a maternally loaded inhibitory factor that is titrated against the exponentially increasing amount of DNA. To identify MBT regulators, we developed an assay using Xenopus egg extract that recapitulates the activation of transcription only above the DNA-to-cytoplasm ratio found in embryos at the MBT. We used this system to biochemically purify factors responsible for inhibiting transcription below the threshold DNA-to-cytoplasm ratio. This unbiased approach identified histones H3 and H4 as concentration-dependent inhibitory factors. Addition or depletion of H3/H4 from the extract quantitatively shifted the amount of DNA required for transcriptional activation in vitro. Moreover, reduction of H3 protein in embryos induced premature transcriptional activation and cell cycle lengthening, and the addition of H3/H4 shortened post-MBT cell cycles. Our observations support a model for MBT regulation by DNA-based titration and suggest that depletion of free histones regulates the MBT. More broadly, our work shows how a constant concentration DNA binding molecule can effectively measure the amount of cytoplasm per genome to coordinate division, growth, and development.

Effects of Cadmium on Differentiation and Cell Cycle Progression in Cultured Xenopus Kidney Distal Epithelial (A6) Cells

2007 ◽  
Vol 35 (3) ◽  
pp. 343-348 ◽  
Author(s):  
Henning F. Bjerregaard
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Visual Inspection ◽  
Single Cells ◽  
Flow Cytometric Analysis ◽  
Cell Number ◽  
Cellular Growth ◽  
G1 Phase ◽  
Epithelial Cell Line ◽  
A6 Cells

Cadmium (Cd) is an important industrial and environmental pollutant, and the kidney is the primary organ to be affected. To elucidate the effects of Cd on cell proliferation, an epithelial cell line (A6) originally derived from the distal part of the Xenopus laevis kidney was cultured in media containing 10% fetal bovine serum. The effects of Cd (added as CdCl2) on cellular growth and differentiation from single cells to confluent epithelia were investigated by visual inspection and by measurement of the degree to which living cells covered a unit area. Over a concentration range from 5 to 50μM, Cd did not affect the settling and adherence of single cells to the bottom of the culture well. The addition of 5μM Cd for 4 days did not affect the ability of the A6 cells to develop confluent epithelia, measured as the area covered by adherent living epithelial cells (99 ± 4% of the control value). However, 10μM Cd did effectively inhibit development of confluent epithelia to 13 ± 5% compared to control. Visual inspection of adherent cells exposed to 50μM Cd for 7 days revealed no increase in cell number or in cell death, which indicated the induction of cell cycle arrest. Flow cytometric analysis showed that treatment of cells with Cd (0.4mM) for 24 hours induced a significant increase in the proportion of G1 phase cells from 58.6 ± 3.9 to 80.6 ± 3.7%, and a corresponding reduction in the proportion of cells in both the S and G2 phases from 24.0 ± 3.6 to 13.4 ± 3.3% and 17.2 ± 1.7 to 5.8 ± 2.1%, respectively. This study showed that Cd stopped cell proliferation in a very narrow concentration range, between 5 and 10μM, and cell cycle analysis indicated that Cd arrested the cells in the G1 phase of the cell cycle.

Hispolon from Phellinus linteus Induces G0/G1 Cell Cycle Arrest and Apoptosis in NB4 Human Leukaemia Cells

2013 ◽  
Vol 41 (06) ◽  
pp. 1439-1457 ◽  
Author(s):  
Yi-Chuan Chen ◽  
Heng-Yuan Chang ◽  
Jeng-Shyan Deng ◽  
Jian-Jung Chen ◽  
Shyh-Shyun Huang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Flow Cytometric Analysis ◽  
G1 Phase ◽  
Dependent Manner ◽  
Phellinus Linteus ◽  
Nb4 Cells ◽  
Cycle Arrest ◽  
Bax Protein ◽  
Flow Cytometric

Hispolon (a phenolic compound isolated from Phellinus linteus) has been shown to possess strong antioxidant, anti-inflammatory, anticancer, and antidiabetic properties. In this study, we investigated the antiproliferative effect of hispolon on human hepatocellular carcinoma NB4 cells using the MTT assay, DNA fragmentation, DAPI (4, 6-diamidino-2-phenylindole dihydrochloride) staining, and flow cytometric analysis. Hispolon inhibited the cellular growth of NB4 cells in a dose-dependent manner through the induction of cell cycle arrest at G0/G1 phase measured using flow cytometric analysis and apoptotic cell death, as demonstrated by DNA laddering. Exposure of NB4 cells to hispolon-induced apoptosis-related protein expressions, such as the cleavage form of caspase 3, caspase 8, caspase 9, poly (ADP ribose) polymerase, and the proapoptotic Bax protein. Western blot analysis showed that the protein levels of extrinsic apoptotic proteins (Fas and FasL), intrinsic related proteins (cytochrome c), and the ratio of Bax/Bcl-2 were increased in NB4 cells after hispolon treatment. Hispolon-induced G0/G1-phase arrest was associated with a marked decrease in the protein expression of p53, cyclins D1, and cyclins E, and cyclin-dependent kinases (CDKs) 2, and 4, with concomitant induction of p21waf1/Cip1 and p27Kip1. We conclude that hispolon induces both of extrinsic and intrinsic apoptotic pathways in NB4 human leukemia cells in vitro.

scholarly journals Titration of Four Replication Factors Is Essential for the Xenopus laevis Midblastula Transition

Science ◽  
2013 ◽  
Vol 341 (6148) ◽  
pp. 893-896 ◽  
Author(s):  
Clara Collart ◽  
George E. Allen ◽  
Charles R. Bradshaw ◽  
James C. Smith ◽  
Philip Zegerman
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Xenopus Laevis ◽  
Replication Initiation ◽  
Midblastula Transition ◽  
Multiple Events ◽  
Zygotic Transcription ◽  
Replication Factors

The rapid, reductive early divisions of many metazoan embryos are followed by the midblastula transition (MBT), during which the cell cycle elongates and zygotic transcription begins. It has been proposed that the increasing nuclear to cytoplasmic (N/C) ratio is critical for controlling the events of the MBT. We show that four DNA replication factors—Cut5, RecQ4, Treslin, and Drf1—are limiting for replication initiation at increasing N/C ratios in vitro and in vivo in Xenopus laevis. The levels of these factors regulate multiple events of the MBT, including the slowing of the cell cycle, the onset of zygotic transcription, and the developmental activation of the kinase Chk1. This work provides a mechanism for how the N/C ratio controls the MBT and shows that the regulation of replication initiation is fundamental for normal embryogenesis.

scholarly journals Zygotic Regulation of Maternal Cyclin A1 and B2 mRNAs

2001 ◽  
Vol 21 (5) ◽  
pp. 1662-1671 ◽  
Author(s):  
Yann Audic ◽  
Christina Anderson ◽  
Robert Bhatty ◽  
Rebecca S. Hartley
Keyword(s):  
Cell Cycle ◽  
Embryonic Cell ◽  
Untranslated Regions ◽  
Specific Mechanism ◽  
Cyclin A1 ◽  
Midblastula Transition ◽  
Zygotic Transcription ◽  
Adult Cell ◽  
Embryonic Cell Cycle ◽  
Zygotic Control

ABSTRACT At the midblastula transition, the Xenopus laevis embryonic cell cycle is remodeled from rapid alternations between S and M phases to become the complex adult cell cycle. Cell cycle remodeling occurs after zygotic transcription initiates and is accompanied by terminal downregulation of maternal cyclins A1 and B2. We report here that the disappearance of both cyclin A1 and B2 proteins is preceded by the rapid deadenylation of their mRNAs. A specific mechanism triggers this deadenylation. This mechanism depends upon discrete regions of the 3′ untranslated regions and requires zygotic transcription. Together, these results strongly suggest that zygote-dependent deadenylation of cyclin A1 and cyclin B2 mRNAs is responsible for the downregulation of these proteins. These studies also raise the possibility that zygotic control of maternal cyclins plays a role in establishing the adult cell cycle.

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