Development of a Biological Dosimeter for Translocation Scoring Based on Two-Color Fluorescence in Situ Hybridization of Chromosome Subsets

Recently fluorescence in situ hybridization protocols have been
developed which allow the paining of individual chromosomes using
DNA-libraries from sorted human chromosomes. This approach has the
particular advantage that radiation induced chromosome
translocations can be easily detected, if chromo-somes of
distinctly different colors take part in the translocation event.
To enhance the sensitivity of this approach two metaphase
chromosome subsets A and B (A: chromosomes 1, 2, 4, 8, 16; B: 3, 5,
9, 10, 13) were simultaneously painted in green and red color.
Counterstaining of the chromosomes with DAPI resulted in a third
subset which exhibited blue fluorescence only. Green-red,
green-blue and red-blue translocation chromosomes could be easily
detected after irradiation of lymphocyte cultures with
^Cs-γ-rays. Analyses of painted chromosomes can be
combined with conventional GTG-banding analyses. This new
biological dosimeter should become useful to monitor both long term
effects of single irradiation events and the cumulative effects of
multiple or chronic irradiation exposures. In contrast to
translocation scoring based on the analysis of banded chromosomes,
this new approach has the particular advantage that a rapid,
automated scoring of translocations can now be envisaged.