Localization of radiation-induced chromosomal breakpoints along human chromosome 1 using a combination of G-banding and FISH

Abstract

Purpose : To determine the exact location of radiation-induced chromosomal breakpoints along the euchromatic or heterochromatic regions: G-light and G-dark bands, respectively. Materials and methods : The distribution of radiation-induced chromosomal breakpoints was scored in human lymphocytes irradiated in vitro with 3 Gy of gamma-radiation. Image analysis was applied to combine G-banded and FISH-painted images of the human chromosome 1. Results : A total of 195 chromosomal breakpoints in 176 cells with structural chromosomal aberrations was used for the present analysis. Radiation-induced breakpoints were found to be distributed randomly with respect to the p or q arms of chromosome 1 and specific band or band length, but more breakpoints were mapped to G-light than to G-dark bands, the difference being statistically significant. Conclusions : The results can well be interpreted in terms of concepts of existing models of nuclear architecture, chromatin structure and transcriptional activities of the chromatin, which can influence the induction of primary chromosomal aberrations by gamma-rays. Differential repair of randomly produced primary aberrations may also explain the non-random distribution of radiation-induced breakpoints.