title: Role of cytoskeleton in regulating fusion of nucleoli: a study using the activated mouse oocyte model.
abstract: Although fusion of nucleoli was observed during pronuclear development of zygotes and the behavior of nucleoli in pronuclei has been suggested as an indicator of embryonic developmental potential, the mechanism for nucleolar fusion is unclear. Although both cytoskeleton and the nucleolus are important cellular entities, there are no special reports on the relationship between the two. Role of cytoskeleton in regulating fusion of nucleoli was studied using the activated mouse oocyte model. Mouse oocytes were cultured for 6 h in activating medium (Ca²⁺-free CZB medium containing 10 mM SrCl₂) supplemented with or without inhibitors for cytoskeleton or protein synthesis before pronuclear formation, nucleolar fusion, and the activity of maturation-promoting factor (MPF) were examined. Whereas treatment with microfilament inhibitor cytochalasin D or B or intermediate filament inhibitor acrylamide suppressed nucleolar fusion efficiently, treatment with microtubule inhibitor demecolcine or nocodazole or protein synthesis inhibitor cycloheximide had no effect. The cytochalasin D- or acrylamide-sensitive temporal window coincided well with the reported temporal window for nucleolar fusion in activated oocytes. Whereas a continuous incubation with demecolcine prevented pronuclear formation, pronuclei formed normally when demecolcine was excluded during the first hour of activation treatment when the MPF activity dropped dramatically. The results suggest that 1) microfilaments and intermediate filaments but not microtubules support nucleolar fusion, 2) proteins required for nucleolar fusion including microfilaments and intermediate filaments are not de novo synthesized, and 3) microtubule disruption prevents pronuclear formation by activating MPF.
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Hua-Yu
authors: HY
authors: Lian
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Guang-Zhong
authors: GZ
authors: Jiao
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Hui-Li
authors: HL
authors: Wang
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Xiu-Wen
authors: XW
authors: Tan
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Tian-Yang
authors: TY
authors: Wang
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Liang-Liang
authors: LL
authors: Zheng
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China.
authors: Qiao-Qiao
authors: QQ
authors: Kong
authors: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, P.R. China tanjh@sdau.edu.cn.
authors: Jing-He
authors: JH
authors: Tan
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism*; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D004477:Ectogenesis / Q000187:drug effects; D046149:Embryo Culture Techniques; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D059471:In Vitro Oocyte Maturation Techniques; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism; D008297:Male; D016200:Maturation-Promoting Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008561:Membrane Fusion / Q000187:drug effects; D000090204:Mesothelin; D008815:Mice, Inbred Strains; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009866:Oogenesis / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: C000715528:Msln protein, mouse; D011500:Protein Synthesis Inhibitors; D050257:Tubulin Modulators; D016200:Maturation-Promoting Factor; C025700:strontium chloride; D000090204:Mesothelin; D013324:Strontium
keywords: cytoskeleton; nucleoli; oocytes; pronuclei