New tool for biological dosimetry: reevaluation and automation of the gold standard method following telomere and centromere staining.

PURPOSE: The dicentric chromosome (dicentric) assay is the international gold-standard method for biological dosimetry and classification of genotoxic agents. The introduction of telomere and centromere (TC) staining offers the potential to render dicentric scoring more efficient and robust. In this study, we improved the detection of dicentrics and all unstable chromosomal aberrations (CA) leading to a significant reevaluation of the dose-effect curve and developed an automated approach following TC staining.

MATERIAL AND

METHODS

Blood samples from 16 healthy donors were exposed to (137)Cs at 8 doses from 0.1 to 6Gy. CA were manually and automatically scored following uniform (Giemsa) or TC staining. The detection of centromeric regions and telomeric sequences using PNA probes allowed the detection of all unstable CA: dicentrics, centric and acentric rings, and all acentric fragments (with 2, 4 or no telomeres) leading to the precise quantification of estimated double strand breaks (DSB).

RESULTS

Manual scoring following TC staining revealed a significantly higher frequency of dicentrics (p<10(-3)) (up to 30%) and estimated DSB (p<10(-4)) compared to uniform staining due to improved detection of dicentrics with centromeres juxtaposed with other centromeres or telomeres. This improvement permitted the development of the software, TCScore, that detected 95% of manually scored dicentrics compared to 50% for the best currently available software (DCScore™).

CONCLUSION

The use of TC staining has permitted a reevaluation of the dose-response curve and the highly efficient automation of the scoring process, marking a new step in the management and follow-up of populations exposed to genotoxic agents including ionizing radiation.