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 (fluorescence in situ hybridization) in both micronuclei 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 aneuploidy in lymphocytes may result from both an excess of X chromosome losses and a better survival of cells with a monosomy X.