DNA damage induces a kinetochore-based ATM/ATR-independent SAC arrest unique to the first meiotic division in mouse...

Area of Science:

• Cell Biology
• Reproductive Biology
• Genetics

Background:

• DNA damage in mouse oocytes triggers a meiotic arrest in meiosis I, preventing the formation of embryos with harmful mutations.
• This meiotic arrest relies on the spindle assembly checkpoint, which inhibits the anaphase-promoting complex (APC).

Purpose of the Study:

• To elucidate the mechanism by which DNA damage engages the spindle assembly checkpoint in mouse oocytes.
• To identify the key molecular players and localization of checkpoint activation following DNA damage.

Main Methods:

• Observation of checkpoint protein assembly at kinetochores and chromosome arms after DNA damage.
• Pharmacological inhibition of specific kinases (Mps1, aurora kinase, Haspin) to assess their role.
• Generation of oocyte-specific knockout models for DNA damage response kinases (ATM, ATR).

Main Results:

• Checkpoint proteins rapidly assemble at kinetochores within minutes of DNA damage, leading to complete APC inhibition within 30 minutes.
• This response occurs without measurable loss of k-fibres or tension across bivalents.
• The checkpoint activation is dependent on Mps1, aurora kinase, and Haspin, but not ATM or ATR kinases.
• Checkpoint activation is absent in mature oocytes during meiosis II.

Conclusions:

• Mouse oocytes possess a unique mechanism for rapid DNA damage detection, primarily through kinetochore-based checkpoint activation.
• This kinetochore-centric response ensures genomic integrity by preventing the transmission of DNA damage to the next generation.
• The absence of this checkpoint in meiosis II highlights a critical difference in DNA damage response between meiotic stages.