title: Regulation of fusion of the nucleolar precursor bodies following activation of mouse oocytes: roles of the maturation-promoting factors and mitogen-activated protein kinases.
abstract: Fusion of nucleoli or nucleolus precursor bodies (NPBs) has been observed during somatic cell interphase and pronuclear development of human zygotes; however, the underlying mechanism is unknown. NPB fusion and its regulation by mitogen-activated protein kinase (MAPK) and maturation-promoting factor (MPF) were studied in activated mouse oocytes. Small NPBs appeared about 4 h after ethanol activation, and took about 1.5 h to fuse into a large NPB, which persisted for about 10 h before disappearance. Analysis of the temporal windows for kinase action indicated that a high MAPK activity during the first 2 h and a low MPF activity during the first 3-4 h after activation were essential for subsequent NPB fusion. A preactivation decline in MAPK activity was associated with decreased NPB fusion following activation of aged oocytes. While MAPK inactivation by regulator U0126 prevented NPB fusion in oocytes activated by ethanol or 5 min Sr2+ treatments, it had no effect on oocytes fertilized or activated by 6 h Sr2+ treatment. In most cases, while rates of pronuclear formation did not differ, rates of NPB fusion differed significantly between different treatments. Our results suggest that: (i) the MAPK and MPF activities at the initial stage of activation regulate NPB fusion after pronuclear formation; (ii) pronuclear assembly and NPB fusion are two separable events that might be controlled by different mechanisms; and (iii) high MAPK activity and low MPF activity at the initial stage of activation is essential for NPB fusion when only one calcium rise is induced by ethanol, while inhibition of MAPK activity does not affect NPB fusion when the repetitive intracellular Ca2+ rises are induced after fertilization.
authors.affiliation: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City271018, P.R. China.
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Li
authors.forename: Hua-Yu
authors.initials: HY
authors.lastname: Lian
authors.forename: Si-Yu
authors.initials: SY
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
authors.forename: Hong-Shu
authors.initials: HS
authors.lastname: Sui
authors.forename: Dong
authors.initials: D
authors.lastname: Han
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Jing-He
authors.initials: JH
authors.lastname: Tan
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D016200:Maturation-Promoting Factor / Q000378:metabolism*; D000090204:Mesothelin; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; C000715528:Msln protein, mouse; D009570:Nitriles; C113580:U 0126; D016200:Maturation-Promoting Factor; D020928:Mitogen-Activated Protein Kinases; D000090204:Mesothelin