mBAND and mFISH analysis of chromosomal aberrations and breakpoint distribution in chromosome 1 of AG01522 human fibroblasts that were exposed to radiation of different qualities

High-resolution multicolour banding FISH (mBAND) and multiplex FISH (mFISH) were used to analyse the aberrations of chromosome 1 in irradiated-AG01522 human primary fibroblasts. The cells were exposed to 1Gy of a panel of radiation of different qualities, such as X-rays, low-energy protons (28keV/μm), helium-ions (62keV/μm) and carbon-ions (96 and 252keV/μm). mBAND and mFISH analysis in calyculin-A G2-condensed chromosome spreads allowed us to detect intra- and interchromosome aberrations involving chromosome 1, including simple and complex-type exchanges, inversions (both para- and pericentric ones), deletions and rings. The data indicate that the induction of chromosomal exchanges was influenced by both Linear energy transfer (LET) and particle types. Moreover, the complex-to-simple exchanges ratio (C-ratio) and interchromosome to intrachromosome exchanges ratio (F-ratio) were evaluated by mFISH and mBAND techniques, respectively. Our results indicate that the C-ratio is a more reliable marker of radiation quality, with values that increased linearly in an LET-dependent manner. In addition, by means of mBAND analysis, the distribution of radiation-induced breakpoints along chromosome 1 was analyzed and compared with the expected distributions of the breaks. The expected values were calculated assuming a random distribution of the breakpoints. The data indicate that, irrespective of the radiation that was used, the breakpoints were non-randomly distributed along chromosome 1. In particular, breaks in the pericentromeric region were encountered at a higher frequency than expected. A deeper analysis revealed that breaks were not located in the constitutive heterochromatin (G-bands 1p11/1q11 and 1q12), but rather in a region comprised between 1p11.2 and 1p22.1, which includes G-light and G-dark bands.