The frequency of micronuclei with X chromosome increases with age in human females

The rate of micronuclei counted on lymphocyte cultures from five healthy female donors, 27–80 years old, increased with age. Using pXBR1 probe, specific for the alphoid DNA of the X chromosome, the presence of this chromosome was investigated by FISH (fluoroscence in sity hybridization) in both micronucleic and metaphases. Both X aneuploidy and frequency of X chromosome per micronuclei increased with age. However, this overinvolvement of X chromosome was not sufficient to explain the overall increase of micronuclei with age, suggesting that autosomes are also involved. Thus, the higher increase of X than autosome aneyploidy in lymphocytes may result from both an excess of X choromosome losses and a better survival of cells with a monoosomy X.