title: DNA double-strand breaks disrupted the spindle assembly in porcine oocytes.
abstract: We used etoposide (25-100 µg/mL) to induce DNA double-strand breaks (DSBs) in porcine oocytes at the germinal vesicle (GV) stage to determine how such damage affects oocyte maturation. We observed that DNA damage did not delay the rate of germinal vesicle breakdown (GVBD), but did inhibit the final stages of maturation, as indicated by the failure to extrude the first polar body. Oocytes with low levels of DSBs failed to effectively activate ataxia telangiectasia-mutated (ATM) kinase, while those with severe DNA DSBs failed to activate checkpoint kinase 1 (CHK1)--the two regulators of the DNA damage response pathway--indicating that porcine oocytes lack an efficient G2/M phase checkpoint. DSBs induced spindle defects and chromosomal misalignments, leading to the arrest of these oocytes at meiotic metaphase I. The activity of maturation-promoting factor also did not increase appropriately in oocytes with DNA DSBs, although its abundance was sufficient to promote GVBD and chromosomal condensation. Following parthenogenetic activation, embryos from etoposide-treated oocytes formed numerous micronuclei. Thus, our results indicate that DNA DSBs do not efficiently activate the ATM/CHK1-dependent DNA-damage checkpoint in porcine oocytes, allowing these DNA-impaired oocytes to enter M phase. Oocytes with DNA damage did, however, arrest at metaphase I in response to spindle defects and chromosomal misalignments, which limited the ability of these oocytes to reach meiotic metaphase II.
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: HaiYang
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: YiBo
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Zhao
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: ZiLi
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: Jeongwoo
authors.initials: J
authors.lastname: Kwon
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: Xiang-Shun
authors.initials: XS
authors.lastname: Cui
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Naesudong-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Korea.
authors.forename: Nam-Hyung
authors.initials: NH
authors.lastname: Kim
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D053903:DNA Breaks, Double-Stranded; D059565:G2 Phase Cell Cycle Checkpoints; D059566:M Phase Cell Cycle Checkpoints; D009865:Oocytes / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D013552:Swine
chemical_list: D011494:Protein Kinases; D064007:Ataxia Telangiectasia Mutated Proteins; D000071877:Checkpoint Kinase 1