Reversal of female infertility by Chk2 ablation reveals the oocyte DNA damage checkpoint pathway

Area of Science:

• Reproductive biology
• Molecular genetics
• Cellular surveillance mechanisms

Background:

• Genetic errors during meiosis can cause birth defects and pregnancy loss.
• Oocyte quality control mechanisms eliminate eggs with unrepaired DNA damage, but their nature is largely unknown.
• Recombination-defective mice exhibit sterility due to failed oocyte elimination.

Purpose of the Study:

• To identify the molecular mechanisms responsible for eliminating oocytes with DNA damage during female meiosis.
• To investigate the role of checkpoint kinase 2 (Chk2) in oocyte surveillance.
• To determine the signaling pathway involved in DNA double-strand break (DSB) response in oocytes.

Main Methods:

• Analysis of Chk2-mutant mice.
• Induction of DNA double-strand breaks (DSBs) via irradiation and meiotic mutations.
• Assessment of oocyte elimination and female fertility.
• Western blotting to detect activation of p53 and p63.

Main Results:

• Checkpoint kinase 2 (Chk2) is essential for eliminating mouse oocytes with unrepaired meiotic or induced DNA double-strand breaks (DSBs).
• Mutation of Chk2 rescued female infertility in mice with meiotic recombination defects or following irradiation.
• Both programmed and induced DSBs activated Chk2, leading to the activation of p53 and p63, which mediated oocyte elimination.

Conclusions:

• Chk2 acts as a critical DNA damage surveillance factor in female meiosis.
• The oocyte DNA double-strand break (DSB) response involves a pathway where ataxia telangiectasia and Rad3-related (ATR) signals to Chk2, which then activates p53 and p63.
• Targeting the Chk2-mediated pathway could offer therapeutic strategies for infertility associated with meiotic errors.