Mutagenesis Advance Access originally published online on February 8, 2005
Mutagenesis 2005 20(1):65-75; doi:10.1093/mutage/gei010
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Mutagenesis vol. 20 no. 1 © UK Environmental Mutagen Society 2005; all rights reserved.
Aneuploidy in mouse metaphase II oocytes exposed in vivo and in vitro in preantral follicle culture to nocodazole
1Institute of Genetechnology/Microbiology, Faculty of Biology, University of Bielefeld, D-33501 Bielefeld, Germany, 3Section of Toxicology and Biomedical Sciences, ENEA CR Casaccia, I-00060 Rome, Italy and 4EggCentris NV, Kranenberg 6, B-1731 Zellik, Belgium, Free University Brussels, Laarbeeklaan 101, B-1090 Brussels, Belgium
Aneuploidy tests are important in evaluating genetic hazards especially when chemical exposures are suspected to affect the fidelity of chromosome segregation in oocytes and embryos. In the current study, a newly established method, mouse preantral follicle culture, was employed to grow oocytes in vitro within follicles. The sensitivity of in vitro grown follicle enclosed oocytes was compared with oocytes maturing in vivo in the ovary. In both the cases, oocytes were exposed to the cytostatic chemical, nocodazole, from the time of hormonally stimulated resumption of meiosis. The in vivo study revealed a significant decrease in the number of ovulated mouse oocytes and an increase in meiosis I-arrested and hyperploid metaphase II oocytes at a single i.p. dose of 70 mg/kg body weight of nocodazole. A significant increase was also observed in the number of meiosis I-arrested and hyperploid mouse oocytes from preantral follicle culture, when they were cultured in the presence of 
30 nM nocodazole during the final stages of maturation. This concentration is slightly lower than that previously shown to induce nondisjunction in denuded mouse oocytes or in cultured human lymphocytes. The higher sensitivity of the in vitro matured oocytes from preantral follicle culture than that of denuded oocytes may be related to a synergistic adverse influence of nocodazole on the oocyte, on somatic cell integrity and on cell–cell communication, which possibly also affects ovulation in vivo. When expressed in molarity relative to the mouse weight, the effective dose of the acute exposure in vivo is 3–4 orders of magnitude higher than the lowest effective concentration employed continuously in vitro. Reduced bioavailability of nocodazole to the target cells due to its poor water solubility may contribute to this difference. Preantral follicle culture can be helpful in analysing mechanisms in chemically induced aneuploidy in mammalian oogenesis, and in predicting the consequences of chemical exposures in vivo.
2 Present address: The Jackson Laboratory, Bar Harbor, ME 04609, USA
* To whom correspondence should be addressed. Tel: +49 521 106 6907; Fax: +49 521 106 6015; Email: EIRI{at}uni-bielefeld.de