Development of Microtubule-Dependence of the Chromosome Cycle at the Midblastula Transition in Xenopus laevis Embryos. (Xenopus/cell cycle/chromosomes/microtubutes/midblastula transition)

1992 ◽  
Vol 34 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Paul Clute ◽  
Yoshio Masui
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Midblastula Transition ◽  
Chromosome Cycle ◽  
Xenopus Laevis Embryos

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 Reducing inositol lipid hydrolysis, Ins(1,4,5)P3 receptor availability, or Ca2+ gradients lengthens the duration of the cell cycle in Xenopus laevis blastomeres.

1992 ◽  
Vol 116 (1) ◽  
pp. 147-156 ◽  
Author(s):  
J K Han ◽  
K Fukami ◽  
R Nuccitelli
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Xenopus Laevis ◽  
Mitotic Cell ◽  
Embryonic Cell ◽  
Cycle Duration ◽  
Cell Stage ◽  
Stage Embryo ◽  
Rate Of Hydrolysis ◽  
Xenopus Laevis Embryos

We have microinjected a mAb specifically directed to phosphatidylinositol 4,5-bisphosphate (PIP2) into one blastomere of two-cell stage Xenopus laevis embryos. This antibody binds to endogenous PIP2 and reduces its rate of hydrolysis by phospholipase C. Antibody-injected blastomeres undergo partial or complete arrest of the cell cycle whereas the uninjected sister blastomeres divided normally. Since PIP2 hydrolysis normally produces diacylglycerol (DG) and inositol 1,4,5-triphosphate (Ins[1,4,5]P3), we attempted to measure changes in the levels of DG following stimulation of PIP2 hydrolysis in antibody-injected oocytes. The total amount of DG in antibody-injected oocytes was significantly reduced compared to that of water-injected ones following stimulation by either acetylcholine or progesterone indicating that the antibody does indeed suppress PIP2 hydrolysis. We also found that the PIP2 antibodies greatly reduced the amount of intracellular Ca2+ released in the egg cortex during egg activation. As an indirect test for Ins(1,4,5)P3 involvement in the cell cycle we injected heparin which competes with Ins(1,4,5)P3 for binding to its receptor, and thus inhibits Ins(1,4,5)P3-induced Ca2+ release. Microinjection of heparin into one blastomere of the two-cell stage embryo caused partial or complete arrest of the cell cycle depending upon the concentration of heparin injected. We further investigated the effect of reducing any [Ca2+]i gradients by microinjecting dibromo-BAPTA into the blastomere. Dibromo-BAPTA injection completely blocked mitotic cell division when a final concentration of 1.5 mM was used. These results suggest that PIP2 turnover as well as second messenger activity influence cell cycle duration during embryonic cell division in frogs.

scholarly journals Dissection of the XChk1 Signaling Pathway in Xenopus laevis Embryos

2000 ◽  
Vol 11 (9) ◽  
pp. 3101-3108 ◽  
Author(s):  
Nicholas C. Kappas ◽  
Pamela Savage ◽  
Katherine C. Chen ◽  
Allan T. Walls ◽  
Jill C. Sible
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Signaling Pathway ◽  
Embryonic Cell ◽  
Midblastula Transition ◽  
Cell Cycles ◽  
Cyclin Dependent Kinases ◽  
Xenopus Embryos ◽  
Egg Extracts ◽  
Sperm Nuclei

Checkpoint pathways inhibit cyclin-dependent kinases (Cdks) to arrest cell cycles when DNA is damaged or unreplicated. Early embryonic cell cycles of Xenopus laevis lack these checkpoints. Completion of 12 divisions marks the midblastula transition (MBT), when the cell cycle lengthens, acquiring gap phases and checkpoints of a somatic cell cycle. Although Xenopus embryos lack checkpoints prior to the MBT, checkpoints are observed in cell-free egg extracts supplemented with sperm nuclei. These checkpoints depend upon the Xenopus Chk1 (XChk1)-signaling pathway. To understand why Xenopus embryos lack checkpoints,xchk1 was cloned, and its expression was examined and manipulated in Xenopus embryos. Although XChk1 mRNA is degraded at the MBT, XChk1 protein persists throughout development, including pre-MBT cell cycles that lack checkpoints. However, when DNA replication is blocked, XChk1 is activated only after stage 7, two cell cycles prior to the MBT. Likewise, DNA damage activates XChk1 only after the MBT. Furthermore, overexpression of XChk1 inXenopus embryos creates a checkpoint in which cell division arrests, and both Cdc2 and Cdk2 are phosphorylated on tyrosine 15 and inhibited in catalytic activity. These data indicate that XChk1 signaling is intact but blocked upstream of XChk1 until the MBT.

scholarly journals Changes in Oscillatory Dynamics in the Cell Cycle of Early Xenopus laevis Embryos

PLoS Biology ◽  
2014 ◽  
Vol 12 (2) ◽  
pp. e1001788 ◽  
Author(s):  
Tony Y.-C. Tsai ◽  
Julie A. Theriot ◽  
James E. Ferrell
Keyword(s):  
Cell Cycle ◽  
Xenopus Laevis ◽  
Oscillatory Dynamics ◽  
Xenopus Laevis Embryos

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.

scholarly journals Antisense Knockdown of Cyclin E does not affect the Midblastula Transition in Xenopus laevis Embryos

Cell Cycle ◽  
2005 ◽  
Vol 4 (10) ◽  
pp. 1396-1402 ◽  
Author(s):  
Michael K. Slevin ◽  
Gillian Lyons-Levy ◽  
Daniel L. Weeks ◽  
Rebecca S. Hartley
Keyword(s):  
Xenopus Laevis ◽  
Cyclin E ◽  
Midblastula Transition ◽  
Antisense Knockdown ◽  
Xenopus Laevis Embryos
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