Study on epigenetic differences of monozygotic twin atomic bomb survivors in Hiroshima

Objective: We investigated the epigenetic differences of monozygotic (MZ) twin atomic bomb (A-bomb) survivors in Hiroshima. Design: A clinical study. Materials and Methods: We analyzed 190 of MZ twin A-bomb survivors who were exposed to A-bomb on 6th August in 1945 in Hiroshima city in Japan. Male of MZ twin A-bomb survivors were 94, and female 96. The number of MZ twin in-utero exposed survivors was 14. For control study, we analyzed 90 brother A-bomb survivors. Results: Most of MZ twin A-bomb survivors were 2 year old at exposure. 24 MZ twin A-bomb survivors died. Mean survival term from exposure was 46.5 years. Main cause of death was malignancy. Liver cancer was the most of malignancy of MZ twin survivors. Conclusions: The epigenetic differences arose during the lifetime of MZ twins of A-bomb survivors. We found that, although MZ twins were epigenetically indistinguishable during the early years of life, older MZ twins exhibited remarkable differences in their overall content and life time with the same experience of A-bomb exposure.