Radiation-induced mutations in the spleen and brain of lacZ transgenic mice

Purpose: To study the dose-response and molecular nature of radiation-induced mutations in the spleen and brain of lacZ transgenic mice. Materials and methods: Line 60 transgenic mice containing the bacterial lacZ gene in a plasmid background were used. Mutants were selected using phenyl-β-D-galactoside. The nature of mutants was determined by sequencing DNAs of mutant lacZ genes found in control and irradiated tissues. Results: X-ray irradiation at 50 and 100 Gy showed linear dose-responses for mutation induction in both tissues. The slope, however, was about twice as steep in spleen than in brain. DNA sequence analyses showed that the predominant type of mutation induced by radiation in both tissues were large deletions. Conclusions: Radiation induces mutations in spleen and brain at different efficiencies but the molecular nature of the induced mutations are similar in the two issues.