Global screening and extended nomenclature for 230 aphidicolin-inducible fragile sites, including 61 yet unreported ones

Since the first description of human fragile sites (FS) more than 40 years ago, a variety of substances were reported to induce chromosomal breaks at non-random, breakage-prone regions. According to information available from human genome browsers aphidicolin, an inhibitor of DNA replication induces 77 of 88 known common FS. However, in the literature additional FS are reported, which are also, at least in part, inducible by aphidicolin. To the best of our knowledge, here we present the first and largest ever done systematic, whole genome-directed and comprehensive screening for aphidicolin-inducible breakage-prone regions. The study was performed on stimulated peripheral blood lymphocytes of 3 unrelated healthy individuals. Twenty-five thousand metaphase spreads were analyzed and overall 22,537 FS located in 230 different loci were recorded. Sixty-one of those FS were never observed before and 52 were already previously reported but not included in genome browsers and yet verified. Interestingly, aphidicolin was able to induce all types of rare and common FS, suggesting that these breakage-prone regions are less dependent on the inducing chemicals than originally supposed. Overall, we provide the first comprehensive genome wide map for FS and studied possible correlations of chromosome length and GTG-banding level with FS-frequency. To handle FS better in future, an extension of the already existing alphabetical nomenclature for FS on single chromosomes is suggested.