Selective utilization of non‐homologous end‐joining and homologous recombination for DNA repair during meiotic maturation in mouse oocytes

DNA double‐strand breaks (DSBs) are highly toxic lesions that can cause genomic instability and can be repaired by non‐homologous end‐joining (NHEJ) and homologous recombination (HR) pathways. Despite extensive studies about DSB repair pathways, the roles of each pathway during meiotic maturation in oocytes are not well understood. Here we show that oocytes selectively utilize NHEJ and HR to repair DSBs during meiotic maturation. Inhibition of NHEJ impaired the meiotic maturation of oocytes with DNA damage by activating the spindle assembly checkpoint (SAC) with a concomitant increase in metaphase I (MI) arrest and DNA damage levels. In contrast, oocytes with DNA damage bypassed SAC‐mediated MI arrest despite the presence of fragmented DNA when HR was inhibited. Notably, this bypass of SAC arrest by HR inhibition was associated with a loss of centromere integrity and subsequent impairment of chromosome architecture. Our results demonstrate that, while NHEJ is critical for the meiotic maturation of oocytes with DNA damage, HR is essential to maintain centromere integrity against DNA damage during meiotic maturation, revealing distinct roles of NHEJ and HR during meiotic maturation in mouse oocytes. In oocytes with DNA damage, inhibition of NHEJ impairs meiotic maturation by increasing DNA damage levels and, subsequently, the incidence of SAC‐mediated MI arrest. In contrast, inhibition of HR decreases centromere integrity, which in turn causes DNA fragmentation during chromosome segregation.