The repair of endo/exogenous DNA double-strand breaks and its effects on meiotic chromosome segregation in oocytes

Abstract

Germ cell-derived genomic structure variants not only drive the evolution of species but also induce developmental defects in offspring. The genomic structure variants have different types, but most of them are originated from DNA double-strand breaks (DSBs). It is still not well known whether DNA DSBs exist in adult mammalian oocytes and how the growing and fully grown oocytes repair their DNA DSBs induced by endogenous or exogenous factors. In this study, we detected the endogenous DNA DSBs in the growing and fully grown mouse oocytes and found that the DNA DSBs mainly localized at the centromere-adjacent regions, which are also copy number variation hotspots. When the exogenous DNA DSBs were introduced by Etoposide, we found that Rad51-mediated homologous recombination (HR) was used to repair the broken DNA. However, the HR repair caused the chromatin intertwined and impaired the homologous chromosome segregation in oocytes. Although we had not detected the indication about HR repair of endogenous centromere-adjacent DNA DSBs, we found that Rad52 and RNA:DNA hybrids colocalized with these DNA DSBs, indicating that a Rad52-dependent DNA repair might exist in oocytes. In summary, our results not only demonstrated an association between endogenous DNA DSBs with genomic structure variants but also revealed one specific DNA DSB repair manner in oocytes.

Double-strand breaks induce short-scale DNA replication and damage amplification in the fully grown mouse oocytes

“…In the 24 hours oocyte, EdU signals were not totally held together with γH2A.X foci (Supplemental File S1), indicating that the DSBs could be repaired in the SN oocytes. Similar to our previous results ( Ma et al 2019a ), HR repair protein Rad51 could be detected at the γH2A.X foci in the DSB oocytes ( Figure 2B ). Interestingly, the EdU signals were found just adjacent to the Rad51 foci ( Figure 2C ).…”

“…However, it has not been fully analyzed about whether DSBs could be the contributing factor of CGR in the growing NSN and fully grown SN oocytes. Our previous works had shown that exogenous DSBs could induce the chromatin to be entangled and matted together by Rad51 in the SN oocytes ( Ma et al 2019a ). In this study, we further investigated the features of DSB repair in mouse oocytes, which would be new clues of how CGRs are formed in germ cells and somatic cells.…”

Double-strand breaks can induce DNA replication and damage amplification in G2 phase-like oocytes of mice

“…Rad52 had been proven to mediated BIR in S phase of mammalian cells (35), whereas Rad51 had been proven to be essential for the BIR in yeast (36). In this study and our previous work (27) we found Rad51 inhibitors RI-1 and IBR2 could suppress the BIR in SN oocytes, indicating BIR in late G2 phase cells was Rad51 dependent.…”

“…For the NSN and SN oocytes, both endogenous metabolites and exogenous factors can induce DSBs in their nuclear genome (23)(24)(25)(26), but whether DSBs in growing NSN and fully grown SN oocytes could be the contributing factor of CGR hasn't be analyzed. Our previous works showed Rad51 participated in the repair of oocyte DSBs (27), in this study we further analyzed the features of DSB repair in oocytes which would be new clues of CGR formation in germ cells and somatic cells.…”

Cruciform DNA in mouse growing oocytes: Its dynamics and its relationship with DNA transcription

“…In this study, to verify whether Parp1 binds to endogenous cruciform DNA, we labeled Parp1 in oocytes with antibodies. We found that Parp1 could be detected in the NSN oocytes but not in the SN oocytes and didn't colocalize with endogenous DNA damage regions (labeled by γH2A.X) in oocytes [27] (Fig 2A). Just like cruciform DNA, the Parp1 foci could also form clusters in NSN oocytes (Fig 2A).…”