Oxidative stress-induced DNA damage of mouse zygotes triggers G2/M checkpoint and phosphorylates Cdc25 and Cdc2

Area of Science:

• Reproductive Biology
• Cell Cycle Regulation
• Oxidative Stress Research

Background:

• In vitro fertilized (IVF) embryos can experience cell cycle and developmental arrest.
• Oxidative damage in sperm activates the ATM→Chk1→Cdc25B/Cdc25C cascade, causing G2/M arrest for repair.
• Mechanisms of zygote developmental delay due to oxidative damage remain unclear.

Purpose of the Study:

• To investigate the mechanisms of G2/M cell cycle arrest in oxidatively damaged mouse zygotes.
• To establish a model for studying oxidative stress effects on zygotes.
• To identify key molecular players in the G2/M checkpoint activation.

Main Methods:

• Mouse zygotes were treated with varying concentrations of hydrogen peroxide (H2O2).
• In vitro zygote development and S phase duration (BrdU incorporation) were assessed.
• Reactive oxygen species (ROS) levels were measured.
• Immunofluorescence detected γH2AX, Cdc2, and Cdc25 activation.

Main Results:

• Oxidatively damaged zygotes exhibited delayed G2/M phase progression and increased ROS levels.
• γH2AX, a marker of DNA damage, was detected in damaged zygotes.
• Phosphorylated forms of Cdc25B (Ser323), Cdc25C (Ser216), and Cdc2 (Tyr15) were observed.

Conclusions:

• Oxidative stress-induced DNA damage in mouse zygotes triggers cell cycle checkpoints, resulting in G2/M arrest.
• Phospho-Cdc25B (Ser323), phospho-Cdc25C (Ser216), and phospho-Cdc2 (Tyr15) are involved in activating the G2/M checkpoint.
• These findings elucidate molecular pathways underlying developmental delays in early embryos exposed to oxidative stress.