DNA replication initiation by 6-DMAP treatment in maturing oocytes and dividing embryos from marine invertebrates

Néant, Isabelle; Dubé, François

doi:10.1002/(sici)1098-2795(199608)44:4<443::aid-mrd3>3.0.co;2-l

Cited by 4 publications

(2 citation statements)

References 44 publications

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“…These results indicate that only one round of DNA replication occurs. In marine invertebrates the effect of 6-DMAP is basically the same as that found by us except that 6-DMAP induces continuous DNA replication in meiotic cells but supports only a single round of replication in somatic cells of those species (Neant et al, 1994;Neant & Dube, 1996). The reason for this difference is unknown.…”

Section: Discussionsupporting

confidence: 67%

“…Thus, it has been shown in a variety of species that the presence of 6-DMAP in the culture medium blocks germinal vesicle breakdown (GVBD) and the initiation of maturation Rime et al, 1989;Fulka, Jr et al, 1991). On the other hand, maturing oocytes respond to 6-DMAP treatment by chromatin decondensation and the formation of nuclei (Szollosi et al, 1991;Neant et al, 1994;Neant & Dube, 1996). When metaphase II oocytes are incubated with this drug no decondensation is observed unless an activation stimulus is applied (Fulka, Jr et al, 1991;Szollosi et al, 1993;Susko-Parish et al, 1994;Ledda et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment

Fulka

First²,

C³

et al. 1997

Zygote

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Immature mouse oocytes (germinal vesicle stage, GV), oocytes at different stages during maturation (prometaphase to anaphase I) and matured oocytes (metaphase II arrested) were cultured in 6-dimethylaminopurine (6-DMAP)-supplemented medium also containing bromodeoxyuridine for the assessment of DNA replication in these cells. Immature oocytes remained arrested at the GV stage and DNA replication was never detected in them. On the other hand, oocytes at the prometaphase to anaphase-telophase I stages responded to 6-DMAP treatment by forming nuclei which synthesised DNA. Mature (metaphase II) oocytes did not respond to 6-DMAP and their chromatin remained condensed. DNA synthesis could even be induced in GV-staged oocytes, but only when they were fused to freshly activated oocytes and incubated in 6-DMAP-supplemented medium.

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Section: Discussionsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment

Fulka

First²,

C³

et al. 1997

Zygote

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On cyclins, oocytes, and eggs

1997

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Oocyte and egg are suitable model systems for studying cell division since meiotic maturation resembles a G2/M transition and early embryonic divisions are precisely timed and occur without zygotic transcription. The analysis of oocytes and eggs from different species provides the opportunity to understand the roles of proteins that are critical to the progression and maintenance of the cell cycle. Among them, cyclins are certainly worthy of investigation. Mitotic cyclins (cyclins A and B) are clearly implicated in meiosis and early embryonic cell cycles. More recent studies have revealed that G1‐type cyclins (cyclins E and D) could also play a role in both processes and cyclin H has been suggested to participate to CAK activity (cdc2‐activating kinase) in oocytes. The study of cyclins in oocytes and eggs clearly offer insights into their roles during the cell cycle. Mol. Reprod. Dev. 48:397–411, 1997. © 1997 Wiley‐Liss, Inc.

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Cdk2 Activity Is Dispensable for the Onset of DNA Replication during the First Mitotic Cycles of the Sea Urchin Early Embryo

Moreau

Marquès

Barakat

et al. 1998

Developmental Biology

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Earlier work reported the important role of Cdk2 as a regulator of DNA replication in somatic cells and in Xenopus extracts. In the present report we analyze in vivo the involvement of Cdk2 in DNA replication during early embryogenesis using the first mitotic cycles of sea urchin embryos. Unfertilized Sphaerechinus granularis eggs are arrested after the second meiotic cytokinesis. Fertilization resumes the block and induces DNA replication after a short lag period, making sea urchin early embryo a good model for studying in vivo the onset of DNA replication. We show that Cdk2 as well as its potential partner cyclin A are present in the nucleus in G1 and S phase and therefore available for DNA replication. In accordance with data obtained in Xenopus egg extracts we observed that Cdk2 kinase activity is low and stable during the entire cycle. However, in contrast with this in vitro system in which Cdk2 activity is required for the onset of DNA replication, the specific inhibition of Cdk2 kinase by microinjection of the catalytically inactive Cdk2-K33R or the inhibitor p21(Cip1) does not prevent DNA replication. Because olomoucine, DMAP, and emetine treatments did not preclude DNA synthesis, neither cyclin A/Cdk1 nor cyclin B/Cdk1 kinase activities are necessary to replace the absence of Cdk2 kinase in promoting DNA replication. These data suggest that during early embryogenesis Cdks activities, in particular Cdk2, are dispensable in vivo for the initiation step of DNA replication. However, the specific localization of Cdk2 in the nucleus from the beginning of M phase to the end of S phase suggests its involvement in other mechanisms regulating DNA replication such as inhibition of DNA re-replication and/or that its regulating role is achieved through a pathway independent of the kinase activity. We further demonstrate that even after inhibition of Cdk activities, the permeabilization of the nuclear membrane is required to allow a second round of DNA replication. However, in contrast to Xenopus egg extracts, re-replication can take place in the absence of DMAP-sensitive kinase.

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DNA replication initiation by 6-DMAP treatment in maturing oocytes and dividing embryos from marine invertebrates

Cited by 4 publications

References 44 publications

Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment

Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment

On cyclins, oocytes, and eggs

Cdk2 Activity Is Dispensable for the Onset of DNA Replication during the First Mitotic Cycles of the Sea Urchin Early Embryo

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