A simple method for simultaneous interphase-metaphase chromosome analysis in biodosimetry

Purpose: To find a simple protocol for measuring chromosome damage both in G1 and in G2/M chromosomes, to overcome problems related to low mitotic index and cell-cycle alterations in biodosimetric tests. Materials and methods: The protocol is based on the use of calyculin A to induce premature chromosome condensation in human peripheral blood lymphocytes in different phases of the cell cycle. Chromosome exchanges were measured by fluorescence in situ hybridization (chromosomes 2 and 4) in lymphocytes from four different donors. Cells were exposed to 4 Gy X-rays and the results were compared to aberrations in M phase (colcemid block) and G0 (premature chromosome condensation induced by fusion to mitotic hamster cells). Results: Treatment with calyculin A produced a high Fraction of chromosome condensation in different phases of;he cell cycle Cells in G1 and G2/M could be scored simultaneously for biodosimetry by chromosome painting. The condensation index was 5-20 times higher than the mitotic index (colcemid alone). The calyculin A treatment did not produce a significant increase in the background of chromosomal aberrations or modify the yield of chromosomal aberrations scored after exposure to X-rays. Conclusions: Induction of chromosome condensation by calyculin A is a powerful biodosimetric tool, which provides a high number of spreads for analysis and overcomes problems related to poor in vitro, growth or cell-cycle alterations.