title: Antiapoptotic role for ornithine decarboxylase during oocyte maturation.
abstract: Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is a nonredundant and essential gene in all eukaryotes. During the mitotic cell cycle, ODC exhibits two activity peaks: one at the G(1)/S transition and one during the G(2)/M transition. The physiological role of this cell cycle-dependent ODC activity dynamic is not clear. Previous studies have reported a significant elevation of ODC activity during Xenopus oocyte maturation, which resembles mitotic G(2)/M transition. In order to study the roles of ODC activity in the oocytes, we utilized antisense morpholino (xODC mo) oligonucleotides to inhibit ODC translation. We report here that xODC mo abolished ODC activity increase during oocyte maturation. xODC mo-injected oocytes underwent germinal vesicle breakdown, emitted the first polar body, and reached metaphase II, thus completing nuclear maturation. However, the metaphase II oocytes exhibited high levels of reactive oxygen species and became apoptotic. When transferred to host frogs and subsequently ovulated, these eggs were fertilized but exhibited embryo fragmentation. Translation of ODC is therefore integral to cytoplasmic maturation, protecting metaphase II oocytes from reactive oxygen species-induced apoptosis.
authors.affiliation: Ottawa Health Research Institute, Ottawa Hospital, 725 Parkdale Avenue, Ottawa K1Y 4E9, Canada.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Chunqi
authors.initials: C
authors.lastname: Ma
authors.forename: Jennifer
authors.initials: J
authors.lastname: Karmouch
authors.forename: Hadia Arabi
authors.initials: HA
authors.lastname: Katbi
authors.forename: X Johné
authors.initials: XJ
authors.lastname: Liu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045304:Cytochromes c / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000201:enzymology; D005260:Female; D008677:Metaphase / Q000187:drug effects; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D009866:Oogenesis / Q000187:drug effects; D009955:Ornithine Decarboxylase / Q000096:biosynthesis / Q000172:deficiency / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014981:Xenopus / Q000196:embryology / Q000378:metabolism*
chemical_list: D016376:Oligonucleotides, Antisense; D011073:Polyamines; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D045304:Cytochromes c; D009955:Ornithine Decarboxylase