Detection of gamma-ray-induced DNA damages in malformed dominant lethal embryos of the Japanese medaka (Oryzias latipes) using AP-PCR fingerprinting.

Adult male fish of the medaka HNI strain exposed to 9.5 Gy or 19 Gy (0.95 Gy/min) of gamma-rays were mated with non-irradiated female fish of the Hd-rR strain. Genomic DNA was prepared from malformed individual embryos which were expected to be dominant lethal and used for AP-PCR fingerprinting. By the use of a part of the T3 promoter sequence (20 mer), which, to our knowledge, is not found in the medaka genome as an arbitrary primer, we found polymorphisms in genomic fingerprints which could distinguish the parental strains. On the other hand, we found that the fingerprints of F1 hybrids were the sum of those of their parents. Based on these findings, we analyzed the fingerprints of genomic DNA of each severely malformed embryo, because we expect that radiation-induced genomic damages resulting in severe malformation and eventually in dominant lethals should be detected as changes in paternal fingerprints of F1 hybrids. Indeed, we succeeded in detecting changes in genomic DNA as loss of some paternal bands in fingerprints of malformed embryos. One of 10 malformed embryos obtained from 9.5 Gy gamma-irradiated males had lost one band of the paternal origin and 4 of 12 malformed embryos obtained from 19 Gy gamma-irradiated males had lost 5 bands. These results indicated a possibility that quantitative as well as qualitative estimation of gamma-ray-induced DNA damages can be made by this method which does not require the functional selection based on a specific target gene.