title: Elevated spontaneous mutation rate in Bloom syndrome fibroblasts.
abstract: The rates of spontaneous mutation to 6-thioguanine resistance were determined in fibroblasts derived from normal and two Bloom syndrome individuals (GM 2548 and GM 1492). Two methods were utilized to determine the rates. Method I obtained the spontaneous mutation rate from the increase in the mutation frequency of a cell population in logarithmic-phase growth over 10 days. The two Bloom syndrome strains had spontaneous mutation rates of 16 X 10(-6) and 17 X 10(-6) mutations per cell per generation, whereas two normal strains had rates of 1.5 X 10(-6) and 1.1 X 10(-6). Method II utilized fluctuation analysis to measure the rate of spontaneous mutation. This method resulted in rates of 19 X 10(-6) and 23 X 10(-6) mutations per cell per generation in Bloom syndrome cells, compared to rates of 4.6 X 10(-6) and 4.9 X 10(-6) in the control strains. These data suggest that Bloom syndrome may be a mutator mutation, a previously unrecognized phenomenon in humans, and that an elevated spontaneous mutation rate in vivo may be responsible for the clinical phenotype of primordial dwarfism and increased cancer incidence.
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D002455:Cell Division; D002460:Cell Line; D005347:Fibroblasts / Q000502:physiology; D006801:Humans; D007700:Kinetics; D009154:Mutation; D012867:Skin / Q000503:physiopathology; D013577:Syndrome; D013684:Telangiectasis / Q000235:genetics*