title: Different fates of oocytes with DNA double-strand breaks in vitro and in vivo.
abstract: In female mice, despite the presence of slight DNA double-strand breaks (DSBs), fully grown oocytes are able to undergo meiosis resumption as indicated by germinal vesicle breakdown (GVBD); however, severe DNA DSBs do reduce and delay entry into M phase through activation of the DNA damage checkpoint. But little is known about the effect of severe DNA DSBs on the spindle assembly checkpoint (SAC) during oocyte maturation. We showed that nearly no first polar body (PB1) was extruded at 12 h of in vitro maturation (IVM) in severe DNA DSBs oocytes, and the limited number of oocytes with PB1 were actually at telophase. However, about 60% of the severe DNA DSBs oocytes which underwent GVBD at 2 h of IVM released a PB1 at 18 h of IVM and these oocytes did reach the second metaphase (MII) stage. Chromosome spread at MI and MII stages showed that chromosomes fragmented after GVBD in severe DNA DSBs oocytes. The delayed PB1 extrusion was due to the disrupted attachment of microtubules to kinetochores and activation of the SAC. At the same time, misaligned chromosome fragments became obvious at the first metaphase (MI) in severe DNA DSBs oocytes. These data implied that the inactivation of SAC during the metaphase-anaphase transition of first meiosis was independent of chromosome integrity. Next, we induced DNA DSBs in vivo, and found that the number of superovulated oocytes per mouse was significantly reduced; moreover, this treatment increased the percentage of apoptotic oocytes. These results suggest that DNA DSBs oocytes undergo apoptosis in vivo.
authors.affiliation: a State Key Laboratory of Reproductive Biology; Institute of Zoology; Chinese Academy of Sciences ; Beijing , China.
authors.forename: Fei
authors.initials: F
authors.lastname: Lin
authors.forename: Xue-Shan
authors.initials: XS
authors.lastname: Ma
authors.forename: Zhen-Bo
authors.initials: ZB
authors.lastname: Wang
authors.forename: Zhong-Wei
authors.initials: ZW
authors.lastname: Wang
authors.forename: Yi-Bo
authors.initials: YB
authors.lastname: Luo
authors.forename: Lin
authors.initials: L
authors.lastname: Huang
authors.forename: Zong-Zhe
authors.initials: ZZ
authors.lastname: Jiang
authors.forename: Meng-Wen
authors.initials: MW
authors.lastname: Hu
authors.forename: Heide
authors.initials: H
authors.lastname: Schatten
authors.forename: Qing-Yuan
authors.initials: QY
authors.lastname: Sun
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin / Q000494:pharmacology; D019070:Cell Lineage / Q000187:drug effects; D002478:Cells, Cultured; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D005260:Female; D066298:In Vitro Techniques; D018386:Kinetochores / Q000187:drug effects / Q000378:metabolism; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects; D008540:Meiosis / Q000187:drug effects; D008813:Mice, Inbred ICR; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D059705:Polar Bodies / Q000166:cytology / Q000187:drug effects; D011418:Prophase / Q000187:drug effects; D013997:Time Factors
chemical_list: D001761:Bleomycin; C105427:Zeocin
keywords: DDR, DNA damage response; DNA double-strand breaks; DSBs, DNA double-strand breaks; GVBD, germinal vesicle breakdown; ICL, interstrand crosslinks; IVM, in vitro maturation; MI, the first metaphase; MII, the second metaphase; PB1, first polar body; PBE, PB1 extrusion; SAC, spindle assembly checkpoint; apoptosis; meiosis; oocyte; spindle assembly checkpoint