Multicolour FISH painting for the analysis of chromosomal aberrations induced by 220 kV X-rays and fission neutrons

Purpose: The quantification of radiation-induced chromosome aberrations identified by multicoloured FISH painting and classified according to different nomenclature systems (PAINT, S&S and a conventional method). Material and methods: Blood samples were irradiated with five different doses of 220 kV X-rays or fission neutrons respectively. Cell cycle-controlled, multicoloured FISH painting was performed with a cocktail of chromosomes 1, 4, 12 and a pancentromeric probe. Results: Ten aberration parameters or categories were selected according to the three nomenclature systems and dose-response curves were constructed for the observed yields. Fitted coefficients of the linear-quadratic dose-response function show the relative importance of the quadratic term for aberration parameters of the low-LET radiation (X-rays) data set and of the linear term for those of the high-LET radiation (fission neutrons) data set. The relative proportion of complex aberrations observed was larger for the densely ionizing fission neutrons than for sparsely ionizing X-rays. Conclusion: Compared with single-colour FISH painting, a multicolour approach provides extended information for a mechanistic and quantitative interpretation of radiation-induced chromosome aberrations. The choice of a nomenclature system and the selection of an appropriate aberration parameter or category depend on these specific aspects. Practical application requires a rapid and reproducible description of the observed painting patterns and should also throw light on the origin of aberrations.