title: The Rho-GTPase effector ROCK regulates meiotic maturation of the bovine oocyte via myosin light chain phosphorylation and cofilin phosphorylation.
abstract: Oocyte meiosis involves a unique asymmetric division involving spindle movement from the central cytoplasm to the cortex, followed by polar body extrusion. ROCK is a Rho-GTPase effector involved in various cellular functions in somatic cells as well as oocyte meiosis. ROCK was previously shown to promote actin organization by phosphorylating several downstream targets, including LIM domain kinase (LIMK), phosphorylated cofilin (p-cofilin), and myosin light chain (MLC). In this study, we investigated the roles of ROCK and MLC during bovine oocyte meiosis. We found that ROCK was localized around the nucleus at the oocyte's germinal-vesicle (GV) stage, but spreads to the rest of the cytoplasm in later developmental stages. On the other hand, phosphorylated MLC (p-MLC) localized at the cortex, and its abundance decreased by the metaphase-II stage. Disrupting ROCK activity, via RNAi or the chemical inhibitor Y-27632, blocked both cell cycle progression and polar body extrusion. ROCK inhibition also resulted in decreased cortical actin, p-cofilin, and p-MLC levels. Similar to the phenotype associated with inhibition of ROCK activity, inhibition of MLC kinase by the chemical inhibitor ML-7 caused defects in polar body extrusion. Collectively, our results suggest that the ROCK/MLC/actomyosin as well as ROCK/LIMK/cofilin pathways regulate meiotic spindle migration and cytokinesis during bovine oocyte maturation.
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Cheong-ju, South Korea.
authors.forename: So-Rim
authors.initials: SR
authors.lastname: Lee
authors.affiliation: Department of Veterinary Medicine, College of Agriculture, Yanbian university, Yanji, Jilin Province, China.
authors.forename: Yong-Nan
authors.initials: YN
authors.lastname: Xu
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Cheong-ju, South Korea.
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Jo
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Cheong-ju, South Korea.
authors.forename: Suk
authors.initials: S
authors.lastname: Namgoong
authors.affiliation: Department of Animal Sciences, Chungbuk National University, Cheong-ju, South Korea.
authors.forename: Nam-Hyung
authors.initials: NH
authors.lastname: Kim
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D048749:Cytokinesis / Q000502:physiology; D008540:Meiosis / Q000502:physiology*; D018994:Myosin Light Chains / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D008941:Spindle Apparatus / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism*
chemical_list: D051339:Actin Depolymerizing Factors; D018994:Myosin Light Chains; D054460:rho-Associated Kinases