Induction of a germline mutation at a hypervariable mouse minisatellite locus by Cf-252 radiation

Male C3H/HeN mice were exposed to Cf-252 radiation and mated with unirradiated C57BL/6N females. F1 mice were analyzed for germline mutation at the paternally derived C3H/HeN allele of a hypervariable minisatellite locus, Ms6hm. This locus exhibited a high frequency of length change mutation spontaneously, and the mutation frequency of the paternally derived C3H/He allele in F1 mice born to unirradiated males was 8.4%. Exposure of male mice to Cf-252 radiation resulted in even higher frequency of germline mutation. The spermatid stage germ cells were most sensitive to neutrons, and the mutation frequencies of the paternal allele were elevated to 18%, 26% and 24% for 0.35, 0.7 and 1.02 Gy of Cf-252 radiation, respectively. Spermatozoa and spermatogonia stages were less sensitive and the mutation frequencies for 1.02 Gy of Cf-252 radiation were 16% and 19%, respectively. The Cf-252 radiation consisted of 35% gamma-rays and 65% neutrons. Assuming that these two radiations act additively, RBE of Cf-252 neutrons for the induction of minisatellite mutation was calculated to be 5.9 for spermatozoa stage irradiation, 2.6 for spermatid stage irradiation and 6.5 for spermatogonia irradiation.