Radiation effect on delayed chromosome instability is different between chromosomes 6 and 8

Abstract

Ionizing radiation induces chromosome instability that is transmitted over many cell divisions after radiation exposure in the progeny of surviving cells. To know the transmissible trait of genomic instability induced by radiation, we transferred a human chromosome 6 or 8 exposed to 4 Gy of soft X-rays into unirradiated mouse recipient cells by microcell fusion and examined the numerical and structural changes of the transferred human chromosomes in the microcell hybrids detected by fluorescence in situ hybridization (FISH) using a fluorescent probe specific for the whole human chromosome 6 or 8. Transferred human chromosomes were structurally stable in all of eight microcell hybrids in which unirradiated human chromosomes 6 and 8 were introduced, suggesting that chromosome transfer itself does not destabilize the transferred chromosome. Interestingly, the copy number of transferred chromosome 8 but not 6 doubled in most of microcell hybrids in which both irradiated and unirradiated human chromosomes 8 were introduced, suggesting that human chromosome 8 is numerically unstable regardless of radiation effect. Multiple rearrangements involved in the transferred human chromosome emerged in four out of five microcell hybrids in which the irradiated human chromosome 6 was introduced, but in one out of four microcell hybrids in which the irradiated human chromosome 8 was introduced. Thus, the present study demonstrates that genomic instability is transmitted to the progeny of unirradiated cells by an irradiated chromosome and suggests that radiation effect on delayed chromosome instability is different between chromosomes 6 and 8.