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Trichlorfon predisposes to aneuploidy and interferes with spindle formation in in vitro maturing mouse oocytes

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Title: Trichlorfon predisposes to aneuploidy and interferes with spindle formation in in vitro maturing mouse oocytes
Authors: Cukurcam, Suna1, Sun, Fengyun1, Betzendahl, Ilse1, Adler, Ilse-Dore2, Eichenlaub-Ritter, Ursula eiri@uni-bielefeld.de
Source: Mutation Research - Genetic Toxicology & Environmental Mutagenesis. Dec2004, Vol. 564 Issue 2, p165-178. 14p.
Subject Terms: *Germplasm, Gametogenesis, Chromosome abnormalities, Down syndrome
Abstract: The pesticide trichlorfon (TCF) has been implicated in human trisomy 21, and in errors in chromosome segregation at male meiosis II in the mouse. We previously provided evidence that TCF interferes with spindle integrity and cell-cycle control during murine oogenesis. To assess the aneugenic activity of TCF in oogenesis, we presently analysed maturation, spindle assembly, and chromosome constitution in mouse oocytes maturing in vitro in the presence of 50 or 100μg/ml TCF for 16h or in pulse-chase experiments. TCF stimulated maturation to meiosis II at 50μg/ml, but arrested meiosis in some oocytes at 100μg/ml. TCF at 100μg/ml was aneugenic causing non-disjunction of homologous chromosomes at meiosis I, a significant increase of the hyperploidy rate at metaphase II, and a significant rise in the numbers of oocytes that contained a ‘diploid’ set of metaphase II chromosomes (dyads). TCF elevated the rate of precocious chromatid segregation (predivision) at 50 and 100μg/ml. Pulse-chase experiments with 100μg/ml TCF present during the first 7h or the last 9h of maturation in vitro did not affect meiotic progression and induced intermediate levels of hyperploidy at metaphase II. Exposure to ≥50μg/ml TCF throughout maturation in vitro induced severe spindle aberrations at metaphase II, and over one-third of the oocytes failed to align all chromosomes at the spindle equator (congression failure). These observations suggest that exposure to high concentrations of TCF induces non-disjunction at meiosis I of oogenesis, while lower doses may preferentially cause errors in chromosome segregation at meiosis II due to disturbances in spindle function, and chromosome congression as well as precocious separation of chromatids prior to anaphase II. The data support evidence from other studies that TCF has to be regarded as a germ cell aneugen. [Copyright &y& Elsevier]
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Abstract:The pesticide trichlorfon (TCF) has been implicated in human trisomy 21, and in errors in chromosome segregation at male meiosis II in the mouse. We previously provided evidence that TCF interferes with spindle integrity and cell-cycle control during murine oogenesis. To assess the aneugenic activity of TCF in oogenesis, we presently analysed maturation, spindle assembly, and chromosome constitution in mouse oocytes maturing in vitro in the presence of 50 or 100μg/ml TCF for 16h or in pulse-chase experiments. TCF stimulated maturation to meiosis II at 50μg/ml, but arrested meiosis in some oocytes at 100μg/ml. TCF at 100μg/ml was aneugenic causing non-disjunction of homologous chromosomes at meiosis I, a significant increase of the hyperploidy rate at metaphase II, and a significant rise in the numbers of oocytes that contained a ‘diploid’ set of metaphase II chromosomes (dyads). TCF elevated the rate of precocious chromatid segregation (predivision) at 50 and 100μg/ml. Pulse-chase experiments with 100μg/ml TCF present during the first 7h or the last 9h of maturation in vitro did not affect meiotic progression and induced intermediate levels of hyperploidy at metaphase II. Exposure to ≥50μg/ml TCF throughout maturation in vitro induced severe spindle aberrations at metaphase II, and over one-third of the oocytes failed to align all chromosomes at the spindle equator (congression failure). These observations suggest that exposure to high concentrations of TCF induces non-disjunction at meiosis I of oogenesis, while lower doses may preferentially cause errors in chromosome segregation at meiosis II due to disturbances in spindle function, and chromosome congression as well as precocious separation of chromatids prior to anaphase II. The data support evidence from other studies that TCF has to be regarded as a germ cell aneugen. [Copyright &y& Elsevier]
ISSN:13835718
DOI:10.1016/j.mrgentox.2004.08.008