2-methoxyestradiol induces spindle aberrations, chromosome congression failure, and nondisjunction in mouse oocytes.
2-Methoxyestradiol (2-ME) is a metabolite of 17beta-estradiol and a natural component of follicular fluid. Local concentrations of 2-ME may be increased by exposure to environmental pollutants that activate the expression of enzymes in the metabolic pathway from 17beta-estradiol to 2-ME. It has been suspected that this may have adverse effects on spindle formation in maturing oocytes, which would affect embryo quality. To study the dose-response patterns, we exposed denuded mouse oocytes to 2-ME during in vitro maturation. Meiotic progression, spindle morphology, centrosome integrity, and chromosome congression were examined by immunofluorescence and noninvasive polarizing microscopy (PolScope). Chromosomal constituents were assessed after spreading and C-banding. 2-ME sustained MAD2L1 expression at the centromeres and increased the number of meiosis I-blocked oocytes in a dose-dependent manner. 2-ME also caused dramatic dose-dependent increases in the hyperploidy of metaphase II oocytes. Some of these meiosis II oocytes contained anaphase I-like chromosomes, which suggests that high concentrations of the catecholestradiol interfere with the physical separation of chromosomes. Noninvasive PolScope analysis and tubulin immunofluorescence revealed that perturbations in spindle organization, which resulted in severe disturbances of the chromosome alignment at the spindle equator (congression failure), were caused by 2-ME at meiosis I and II. Pericentrin-positive centrosomes failed to align at the spindle poles, and multipolar spindles and prominent arrays of cytoplasmic microtubule asters were induced in 2-ME-exposed metaphase II oocytes. In conclusion, a micromolar level of 2-ME is aneugenic for mammalian oocytes. Therefore, exposure to 2-ME and conditions that increase the intrinsic local concentration of 2-ME in the ovary may affect fertility and increase risks for chromosomal aberrations in the oocyte and embryo.
Eichenlaub-Ritter
Ursula
U
University of Bielefeld, Faculty of Biology, Institute of Gene Technology/Microbiology, D-33501 Bielefeld, Germany. EiRi@uni-bielefeld.de
Winterscheidt
Ulrike
U
Vogt
Edgar
E
Shen
Ying
Y
Tinneberg
Hans-Rudolf
HR
Sorensen
Ralph
R
D000077584:2-Methoxyestradiol; D000782:Aneuploidy; D000818:Animals; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002869:Chromosome Aberrations / Q000139:chemically induced*; D020090:Chromosome Segregation / Q000187:drug effects*; D002875:Chromosomes / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005455:Fluorescent Antibody Technique; D064246:Mad2 Proteins; D008540:Meiosis / Q000187:drug effects; D008677:Metaphase / Q000187:drug effects; D051379:Mice; D009630:Nondisjunction, Genetic / Q000187:drug effects*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D009865:Oocytes / Q000187:drug effects* / Q000648:ultrastructure; D011247:Pregnancy; D008941:Spindle Apparatus / Q000187:drug effects*; D014404:Tubulin / Q000096:biosynthesis / Q000235:genetics
D018797:Cell Cycle Proteins; D064246:Mad2 Proteins; C577698:Mad2l1 protein, mouse; D009687:Nuclear Proteins; D014404:Tubulin; D004958:Estradiol; D000077584:2-Methoxyestradiol