DNA alterations detected in the progeny of paternally irradiated Japanese medaka fish (Oryzias latipes).

Abstract

A nonmammalian test system for germ-cell mutagenesis has been developed by using the Japanese medaka fish. We describe a system for detecting DNA alterations in F1 progeny descended from the gamma-irradiated male medaka that uses an arbitrarily primed polymerase chain reaction and fingerprinting. A combination of these two methods has some advantages for screening changes in genomic DNA of individual progeny because this detection system can (i) screen for mutational events before embryos with dominant lethal mutations are eliminated during development and (ii) detect DNA changes in the progeny of irradiated males without functional selection and bias, such as resistance to chemicals. DNA alterations are detected as changes in patterns (i.e., band loss and/or band gain) of DNA fingerprints of progeny descended from males whose spermatozoa or spermatids were gamma-irradiated (4.75 or 9.50 Gy). We determined the frequency of gamma-irradiation-induced band loss in arbitrarily primed polymerase chain reaction fingerprints of DNA from severely malformed embryos with dominant lethal mutations and hatched viable embryos. The frequency of band loss in both dominant lethal embryos and hatched viable embryos increased with increasing gamma-ray dose, although more so in the former. We detected a new band in the fingerprints as a heritable DNA alteration but not a viability- or phenotype-affecting DNA alteration in two viable mutants recovered after gamma-irradiation experiments. A cloned amplified fragment of the new band contained a repeated sequence of p(ATGT)n.