Chromosomal instability and alterations of telomeric repeats in irradiated human fibroblasts

In recent years, evidence has been presented suggesting that genomic instability can appear several generations after cellular exposure to radiations. Kadhim et al. (1992) have shown that irradiation by alpha-particles of Pu238 (LET = 120 keV/microns) induce a transmissible instability in mouse haematopoietic cells. Working with human dermis fibroblasts irradiated by heavy ions in a large range of LETs (386-13,600 keV/microns), we demonstrated that an instability could also be acquired by human cells and that particular chromosomes (13, 16, 1) were recurrently involved in telomeric associations (Sabatier et al. 1992). This instability resulted in specific chromosome imbalances and in a particular monosomy 13 (Martins et al. 1993). In this study, we wanted to determine whether telomeres are shortened with the appearance of the chromosomal instability. Our results show no drastic shortening of the mean length of telomeres by Southern blot. By in situ hybridization we are looking to see if chromosomes specifically involved in instability have alterations of the telomeres. We have observed large variations of the hybridization signal of individual telomeres with no telomeric sequences detectable at the junction of end to end associations.