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Effect of inhibitors of DNA replication on early zebrafish embryos: evidence for coordinate activation of multiple intrinsic cell-cycle checkpoints at the mid-blastula transition

Published online by Cambridge University Press:  26 September 2008

Richard Ikegami ,
Alma K. Rivera-Bennetts ,
Deborah L. Brooker  and
Thomas D. Yager
Richard Ikegami
Affiliation:
Division of Developmental Biology and Research Institute, Hospital for Sick Children, Toronto, Graduate Department of Molecular and Medical Genetics, University of Toronto, and Naiad Systems, Toronto, Ontario, Canada
Alma K. Rivera-Bennetts
Affiliation:
Division of Developmental Biology and Research Institute, Hospital for Sick Children, Toronto, Graduate Department of Molecular and Medical Genetics, University of Toronto, and Naiad Systems, Toronto, Ontario, Canada
Deborah L. Brooker
Affiliation:
Division of Developmental Biology and Research Institute, Hospital for Sick Children, Toronto, Graduate Department of Molecular and Medical Genetics, University of Toronto, and Naiad Systems, Toronto, Ontario, Canada
Thomas D. Yager*
Affiliation:
Division of Developmental Biology and Research Institute, Hospital for Sick Children, Toronto, Graduate Department of Molecular and Medical Genetics, University of Toronto, and Naiad Systems, Toronto, Ontario, Canada
*
T.D. Yager, Division of Developmental Biology and Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M59 1X8.
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Summary

We address the developmental activation, in the zebrafish embryo, of intrinsic cell-cycle checkpoints which monitor the DNA replication process and progression through the cell cycle. Eukaryotic DNA replication is probably carried out by a multiprotein complex containing numerous enzymes and accessory factors that act in concert to effect processive DNA synthesis (Applegren, N. et al. (1995) J. Cell. Biochem. 59, 91–107). We have exposed early zebrafish embryos to three chemical agents which are predicted to specifically inhibit the DNA polymerase α, topoisomerase I and topoisomerase II components of the DNA replication complex. We present four findings: (1) Before mid-blastula transition (MBT) an inhibition of DNA synthesis does not block cells from attempting to proceed through mitosis, implying the lack of functional checkpoints. (2) After MBT, the embryo displays two distinct modes of intrinsic checkpoint operation. One mode is a rapid and complete stop of cell division, and the other is an ‘adaptive’ response in which the cell cycle continues to operate, perhaps in a ‘repair’ mode, to generate daughter nuclei with few visible defects. (3) The embryo does not display a maximal capability for the ‘adaptive’ response until several hours after MBT, which is consistent with a slow rranscriptional control mechanism for checkpoint activation. (4) The slow activation of checkpoints at MBT provides a window of time during which inhibitors of DNA synthesis will induce cytogenetic lesions without killing the embryo. This could be useful in the design of a deletion-mutagenesis strategy.

Keywords

Cell-cycle checkpointsDeletion-mutagenesisDNA replicationMid-blastula transitionZebrafish
Type
Article
Information
Zygote , Volume 5 , Issue 2 , May 1997 , pp. 153 - 175
Copyright
Copyright © Cambridge University Press 1997

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