Spontaneous level of aneuploidy of chromosomes 7 and X in interphase lymphocytes of two healthy donors of different age

Defects in the distribution of chromosomes during mitotic division such as sister chromatid nondisjunction or detachment of kinetochore microtubules at anaphase can give rise to aneuploid cells, for example to a monosomic and a trisomic daughter cell. It is well-known that aneuploidy contributes significantly to carcinogenesis. Also, a relationship between advanced chronological age and increased chromosomal aneuploidy has been reported for humans. In particular hypoploidy increases with age and several studies showed that sex chromosomes are preferentially lost, i.e. the X chromosome in females and the Y chromosome in males [1]. Changes in the copy number of chromosomes can be assessed by means of fluorescence in situ hybridisation (FISH) in both metaphase spreads and interphase cells. However, since the latter technique allows the analysis of large populations within a short time and is able to uncover aneuploidy hidden in non-proliferating cells, it is preferentially used for numerical chromosome studies. To examine the effect of donor (cell) age as well as radiation exposure on the degree of aneuploidy, we established recently the FISH-technique for the analysis of interphase cells. In a first experiment we measured the spontaneous frequency of aneuploidy for chromosomes 7 and X in interphase lymphocytes of 2 female healthy donors of different age (25 and 50 years old). Peripheral blood was collected by venipuncture. Lymphocytes were isolated, fixed and pancentromeric DNA probes specific for the centromeric regions of chromosomes 7 and X were applied. The probe for chromosomes 7 was labelled with fluorescein isothiocyanate (FITC) (Vysis, France), whereas the probe for chromosomes X was labelled with Spectrum Orange (Cambio, UK).