alexa Maternal aging and chromosomal abnormalities: new data drawn from in vitro unfertilized human oocytes.
Genetics & Molecular Biology

Genetics & Molecular Biology

Journal of Down Syndrome & Chromosome Abnormalities

Author(s): Pellestor F, Andro B, Arnal F, Humeau C, Demaille J

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Abstract The effect of maternal age on the incidence of chromosomal abnormalities was investigated on a large sample of 3,042 in vitro unfertilized human oocytes II obtained from 792 women aged 19-46 years and participating in an in vitro fertilization program for various indications. The chromosomal analysis combined a gradual fixation of oocytes and an adapted R-banding technique. A total of 1,397 interpretable karyotypes were obtained. Various types of numerical aberration were observed, involving conventional chromosome nondisjunction (3.5\%), single-chromatid nondisjunction (5.9\%), complex (0.8\%) or extreme aneuploidy (0.5\%), diploidy (5.4\%), and set of single chromatids (3.8\%). No significant difference was found in the mean age of women according to the various types of chromosomal abnormalities. A positive relationship was found between maternal age and the global rate of aneuploidy, in agreement with the findings of epidemiological studies. The incidence of both whole-chromosome nondisjunction and precocious chromatid separation were correlated to maternal aging but the most significant correlation was found between maternal aging and single-chromatid nondisjunction. The rate of diploidy was also correlated to a slight extent to maternal aging, whereas no correlation was found between maternal age and the rate of single-chromatid sets. These data reveal that single-chromatid malsegregation is an essential factor in the age-dependent occurrence of nondisjunction in human oocytes. Disturbance in sister-chromatid cohesion might be a causal mechanism predisposing to premature chromatid separation and subsequently to nondisjunction in female meiosis. This article was published in Hum Genet and referenced in Journal of Down Syndrome & Chromosome Abnormalities

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