Abstract
To study the molecular mechanisms which determine the sensitivity to gamma-irradiation in vivo, we identified three types of mutants with high incidence of radiation induced curly tailed (ric) malformations using a low dose of irradiation. The homozygous strain from one of these mutants, ric1, which is highly fertile and easy to breed, was established. Both in the early embryo or germ cells, RIC1 strain, is highly sensitive to gamma-ray than the wild-type strain.
In Medaka, polymorphisms among wild population enable us to map genes of interest. RIC1, which belongs to the southern Japanese population, was crossed with HNI inbred strain derived from the northern ones. After backcrossing their offspring with RIC1, acquired embryos were irradiated at the organogenesis stage. Then, radiation-induced curly tailed embryos were identified as the ric1 phenotype, and their DNA were extracted. Ric1 locus was located in LG9, and 2cM genomic region containing ric1 gene was determined. In this region, gene order seems to be conserved among medaka and two puffer fish species. Now we are examining genes related to DNA double-strand break repair from pufferfish genome database as candidate gene for ric1.
