It is well known that the developing embryo is especially sensitive to ionising radiation. However, to date little is known about the long-term effects of in utero exposure on mutation rates during adulthood. To evaluate the effects of in utero irradiation on mutation induction and transgenerational instability, BALB/c pregnant mice (Theiler stage 20, 12 days of gestation) were exposed to 1 Gy of acute X-rays. The in utero exposed 8-week-old males and females were mated to control partners. To evaluate the effects of in utero irradiation on mutation induction in the germline of exposed mice, all parents and offspring were profiled using two mouse-specific expanded simple tandem repeat (ESTR) probes Ms6-hm and Hm-2. The results of our study show that ESTR mutation rates in the germline of in utero irradiated male and female mice remain highly elevated during adulthood. Using single-molecule PCR, the frequency of ESTR mutation was established in DNA samples prepared from sperm, bone marrow and brain taken from the in utero irradiated animals. In all animals, a statistically significant ∼2.8-3.7 fold increase in the mean mutation frequency was found in all tissues of the in utero irradiated animals. The results of our study show that the mutagenic effects of in utero irradiation in mice are well manifested during adulthood and therefore suggest that the susceptibility of early stages of mouse development to ionising radiation may be higher than previously thought. To analyse the effects of parental irradiation on transgenerational instability, the frequency of ESTR mutation was established in DNA samples prepared from sperm, bone marrow and brain taken from the first-generation offspring of in utero irradiated male and female mice. The results of our study show that in the offspring of in utero exposed males the frequency of ESTR mutation is considerably elevated across multiple tissues, whereas in the offspring of irradiated females it does not significantly differ from that in controls. A comparison with the results of our previous studies on transgenerational in stability among the offspring of BALB/c male mice irradiated during adulthood showed that that the magnitude of transgenerational effects is not affected by the stage of paternal exposure. This work has therefore established that an instability signal induced in the germline of in utero irradiated males is manifested during adulthood. The potential implications of our findings to for further understanding of the possible mechanisms of transgenerational genomic instability will be discussed.

The non-targeted effects of human exposure to ionising radiation, including transgenerational instability manifesting in the children of irradiated parents, remains poorly understood. Employing a mouse model, we have analysed whether low-dose acute or low-dose-rate chronic paternal γ-irradiation can destabilise the genomes of their first-generation offspring. Using single-molecule PCR, the frequency of mutation at the mouse expanded simple tandem repeat (ESTR) locus Ms6-hm was established in DNA samples extracted from sperm of directly exposed BALB/c male mice, as well as from sperm and the brain of their first-generation offspring. For acute γ-irradiation from 10–100 cGy a linear dose-response for ESTR mutation induction was found in the germ line of directly exposed mice, with a doubling dose of 57 cGy. The mutagenicity of acute exposure to 100 cGy was more pronounced than that for chronic low-dose-rate irradiation. The analysis of transgenerational effects of paternal irradiation revealed that ESTR mutation frequencies were equally elevated in the germ line (sperm) and brain of the offspring of fathers exposed to 50 and 100 cGy of acute γ-rays. In contrast, neither paternal acute irradiation at lower doses (10–25 cGy), nor low-dose-rate exposure to 100 cGy affected stability of their offspring. Our data imply that the manifestation of transgenerational instability is triggered by a threshold dose of acute paternal irradiation. The results of our study also suggest that most doses of human exposure to ionising radiation, including radiotherapy regimens, may be unlikely to result in transgenerational instability in the offspring children of irradiated fathers.

It is well known that the developing embryo is especially sensitive to ionising radiation. However, to date little is known about the long-term effects of in utero exposure on mutation rates during adulthood. To evaluate the effects of in utero irradiation on mutation induction and transgenerational instability, BALB/c pregnant mice (Theiler stage 20, 12 days of gestation) were exposed to 1 Gy of acute X-rays. The in utero exposed 8-week-old males and females were mated to control partners. To evaluate the effects of in utero irradiation on mutation induction in the germline of exposed mice, all parents and offspring were profiled using two mouse-specific expanded simple tandem repeat (ESTR) probes Ms6-hm and Hm-2. The results of our study show that ESTR mutation rates in the germline of in utero irradiated male and female mice remain highly elevated during adulthood. Using single-molecule PCR, the frequency of ESTR mutation was established in DNA samples prepared from sperm, bone marrow and brain taken from the in utero irradiated animals. In all animals, a statistically significant ∼2.8-3.7 fold increase in the mean mutation frequency was found in all tissues of the in utero irradiated animals. The results of our study show that the mutagenic effects of in utero irradiation in mice are well manifested during adulthood and therefore suggest that the susceptibility of early stages of mouse development to ionising radiation may be higher than previously thought. To analyse the effects of parental irradiation on transgenerational instability, the frequency of ESTR mutation was established in DNA samples prepared from sperm, bone marrow and brain taken from the first-generation offspring of in utero irradiated male and female mice. The results of our study show that in the offspring of in utero exposed males the frequency of ESTR mutation is considerably elevated across multiple tissues, whereas in the offspring of irradiated females it does not significantly differ from that in controls. A comparison with the results of our previous studies on transgenerational in stability among the offspring of BALB/c male mice irradiated during adulthood showed that that the magnitude of transgenerational effects is not affected by the stage of paternal exposure. This work has therefore established that an instability signal induced in the germline of in utero irradiated males is manifested during adulthood. The potential implications of our findings to for further understanding of the possible mechanisms of transgenerational genomic instability will be discussed.