title: Cyclin O regulates germinal vesicle breakdown in mouse oocytes.
abstract: It is well accepted that oocyte meiotic resumption is mainly regulated by the maturation-promoting factor (MPF), which is composed of cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2). Maturation-promoting factor activity is regulated by the expression level of CCNB1, phosphorylation of CDC2, and their germinal vesicle (GV) localization. In addition to CCNB1, cyclin O (CCNO) is highly expressed in oocytes, but its biological functions are still not clear. By employing short interfering RNA microinjection of GV-stage oocytes, we found that Ccno knockdown inhibited CDC2 (Tyr15) dephosphorylation and arrested oocytes at the GV stage. To rescue meiotic resumption, cell division cycle 25 B kinase (Cdc25b) and Ccnb1 were overexpressed in the Ccno knockdown oocytes. Unexpectedly, we found that Ccno knockdown did not affect CDC25B entry into the GV, and overexpression of CDC25B was not able to rescue resumption of oocyte meiosis. However, GV breakdown (GVBD) was significantly increased after overexpression of Ccnb1 in Ccno knockdown oocytes, indicating that GVBD block caused by cyclin O knockdown can be rescued by cyclin B1 overexpression. We thus conclude that cyclin O, as an upstream regulator of MPF, plays an important role in oocyte meiotic resumption in mouse oocytes.
authors.affiliation: State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jun-Yu
authors.initials: JY
authors.lastname: Ma
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: Ou-Yang
authors.forename: Yi-Bo
authors.initials: YB
authors.lastname: Luo
authors.forename: Zhen-Bo
authors.initials: ZB
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Hou
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Han
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
authors.forename: Heide
authors.initials: H
authors.lastname: Schatten
authors.forename: Qing-Yuan
authors.initials: QY
authors.lastname: Sun
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics; D056744:Cyclin B1 / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D016200:Maturation-Promoting Factor / Q000235:genetics / Q000378:metabolism; D008540:Meiosis / Q000235:genetics*; D000090204:Mesothelin; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D008845:Microinjections; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D034741:RNA, Small Interfering
chemical_list: C534700:Ccnb1 protein, mouse; D056744:Cyclin B1; D016213:Cyclins; C000715528:Msln protein, mouse; D034741:RNA, Small Interfering; C539096:cyclin O, mouse; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D000090204:Mesothelin
keywords: CDC25B; Ccnb1; Cdc25b; cyclin B1; cyclin O; meiosis arrest; oocyte maturation