CDC25B is required for the metaphase I-metaphase II transition in mouse oocytes

Abstract

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/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/MYT1, or expressing EGFP-CDC25A or constitutively active EGFP-CDK1 from microinjected cRNAs. Forced CDK1 activation in Cdc25b−/- oocytes allowed resumption of meiosis, but oocytes mostly arrested at metaphase I (MI) with intact spindles. Similarly, ∼1/3 of Cdc25b+/- oocytes with reduced amount of CDC25B arrest in MI. MI arrested Cdc25b−/- oocytes also display a transient decrease in CDK1 activity similar to Cdc25b+/+ oocytes during the MI-MII transition, whereas Cdc25b+/- oocytes exhibit only a partial APC/C activation and anaphase I entry. Thus, CDC25B is necessary for resumption of meiosis and the MI-MII transition.

SGK1 is essential for meiotic resumption in mammalian oocytes

“…The fact that SGK1 is active already in the GV oocyte might seem contradictory at first glance as it could be able to keep CDC25B phosphorylated and active the whole time. However, we also noticed that at that stage SGK1 (Thr256) is strongly localized in the nucleus, while CDC25B is known to remain in the cytoplasm before meiotic resumption and it is not until PKA is inhibited (by low cAMP levels) that CDC25B is quickly translocated to the oocyte nucleus right before NEBD ( Lincoln et al, 2002 ; Solc et al, 2008 ; Ferencova et al ,). Therefore, we hypothesize that SGK1 (Thr256) is active but restricted to the nucleus, which keeps it physically apart from CDC25B, which would further activate it.…”

Methylation analysis by targeted bisulfite sequencing in large for gestational age (LGA) newborns: the LARGAN cohort

“…This gene regulates progression through the cell division cycle. Female Cdc25b -deficient mice are sterile due to permanent meiotic arrest of the oocyte [ 47 ].…”

CHK1-CDC25A-CDK1 regulate cell cycle progression in early mouse embryos to protect genome integrity

“…We suspected that the cause for the high incidence chromosome segregation errors after Chk1 depletion during the second division was due to premature mitosis due to a shortened G2 phase. Accordingly we forced H2b-Egfp transgenic embryos into premature mitosis by WEE/MYT pharmacological inhibition (Ferencova et al, 2022) at 44h post hCG administration ( Fig. 7A ).…”

“…Only embryos with two pronuclei that divided into 2-cell stage were included in the analysis. Fluorescent long-term time-lapse imaging of embryos was performed on a Viventis LS1 Live light-sheet microscope (Viventis Microscopy Sarl, Switzerland) as described in (Ferencova et al, 2022). Embryos were placed in a 100 µl of culture medium covered with 150 µl oil (OVOIL™, Vitrolife, 10029) in sample holder multi-well (Viventis Microscopy, SHM1_4W).…”

“…Inhibitors All used inhibitors were diluted in DMSO (Merck, D2650). The concentrations used were as follows: CHK1 inhibitor (CHIR-124) 250 µM, CDK1 inhibitor (RO-3306) 2.5 µM, WEE/MYT inhibitor (PD0166285) 0.5 µM (Ferencova et al, 2022).…”