After fertilization, remodeling of the oocyte and sperm genomes is essential to convert these highly differentiated and transcriptionally quiescent cells into early cleavage-stage blastomeres that are transcriptionally active and totipotent. This developmental transition is accompanied by cell cycle adaptation, such as lengthening or shortening of the gap phases G1 and G2. However, regulation of these cell cycle changes is poorly understood, especially in mammals. Checkpoint kinase 1 (CHK1) is a protein kinase that regulates cell cycle progression in somatic cells. Here, we show that CHK1 regulates cell cycle progression in early mouse embryos by restraining CDK1 kinase activity due to CDC25A phosphatase degradation. CHK1 kinase also ensures the long G2 phase needed for genome activation and reprogramming gene expression in two-cell stage mouse embryos. Finally, Chk1 depletion leads to DNA damage and chromosome segregation errors that result in aneuploidy and infertility.
- Klíčová slova
- CDC25A phosphatase, CDK1 kinase, CHK1 kinase, cell cycle regulation, early mouse embryos,
- Publikační typ
- časopisecké články MeSH
Mammalian oocytes are arrested at meiotic prophase I. The dual-specificity phosphatase CDC25B is essential for cyclin-dependent kinase 1 (CDK1) activation that drives resumption of meiosis. CDC25B reverses the inhibitory effect of the protein kinases WEE1 and MYT1 on CDK1 activation. Cdc25b-/- female mice are infertile because oocytes cannot activate CDK1. To identify a role for CDC25B following resumption of meiosis, we restored CDK1 activation in Cdc25b-/- oocytes by inhibiting WEE1 and MYT1, or expressing EGFP-CDC25A or constitutively active EGFP-CDK1 from microinjected complementary RNAs. Forced CDK1 activation in Cdc25b-/- oocytes allowed resumption of meiosis, but oocytes mostly arrested at metaphase I (MI) with intact spindles. Similarly, approximately a third of Cdc25b+/- oocytes with a reduced amount of CDC25B arrested in MI. MI-arrested Cdc25b-/- oocytes also displayed a transient decrease in CDK1 activity similar to Cdc25b+/+ oocytes during the MI-MII transition, whereas Cdc25b+/- oocytes exhibited only a partial anaphase-promoting complex/cyclosome activation and anaphase I entry. Thus, CDC25B is necessary for the resumption of meiosis and the MI-MII transition.
- Klíčová slova
- Anaphase I, CDC25B, Meiotic maturation, Mouse oocytes, Resumption of meiosis,
- MeSH
- anafáze MeSH
- anafázi podporující komplex metabolismus MeSH
- fosfatasy cdc25 MeSH
- meióza * MeSH
- metafáze MeSH
- myši MeSH
- oocyty * metabolismus MeSH
- savci MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- anafázi podporující komplex MeSH
- Cdc25b protein, mouse MeSH Prohlížeč
- fosfatasy cdc25 MeSH
Because low levels of DNA double strand breaks (DSBs) appear not to activate the ATM-mediated prophase I checkpoint in full-grown oocytes, there may exist mechanisms to protect chromosome integrity during meiotic maturation. Using live imaging we demonstrate that low levels of DSBs induced by the radiomimetic drug Neocarzinostatin (NCS) increase the incidence of chromosome fragments and lagging chromosomes but do not lead to APC/C activation and anaphase onset delay. The number of DSBs, represented by γH2AX foci, significantly decreases between prophase I and metaphase II in both control and NCS-treated oocytes. Transient treatment with NCS increases >2-fold the number of DSBs in prophase I oocytes, but less than 30% of these oocytes enter anaphase with segregation errors. MRE11, but not ATM, is essential to detect DSBs in prophase I and is involved in H2AX phosphorylation during metaphase I. Inhibiting MRE11 by mirin during meiotic maturation results in anaphase bridges and also increases the number of γH2AX foci in metaphase II. Compromised DNA integrity in mirin-treated oocytes indicates a role for MRE11 in chromosome integrity during meiotic maturation.
- Klíčová slova
- DNA damage, MRE11, double strand DNA breaks, meiotic maturation, mouse oocytes,
- MeSH
- ATM protein genetika MeSH
- DNA vazebné proteiny genetika MeSH
- dvouřetězcové zlomy DNA účinky léků MeSH
- enzymy opravy DNA genetika MeSH
- histony genetika MeSH
- homologní protein MRE11 MeSH
- meióza genetika MeSH
- metafáze genetika MeSH
- myši MeSH
- oocyty růst a vývoj metabolismus MeSH
- poškození DNA účinky léků genetika MeSH
- zinostatin aplikace a dávkování MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- Atm protein, mouse MeSH Prohlížeč
- ATM protein MeSH
- DNA vazebné proteiny MeSH
- enzymy opravy DNA MeSH
- H2AX protein, mouse MeSH Prohlížeč
- histony MeSH
- homologní protein MRE11 MeSH
- Mre11a protein, mouse MeSH Prohlížeč
- zinostatin MeSH
