[Generation and analyses of transgenic mice containing mutant p53 transgene]

p53 is known to be a suppressor oncogene product regulating the cell cycle as a check point protein. Loss of function mutations were frequently observed in various human cancers. To investigate the role of mutant form of p53 in the presence of wild-type p53 in vivo, we generated two types of transgenic mice carrying p53 transgenes with mutation at the codon 248 from Arg to Trp or at the codon 249 from Arg to Ser. We obtained seven transgenic mouse lines with Trp-mutant type and eight lines from Ser-mutant type which express mutant p53 transgenes. These transgenic mice were observed for tumor formation over a period of one year. However, no tumors were developed within the monitoring period. To test whether the mutant p53 has a dominant negative effect on the wild type p53 or not, transgenic mice were crossed with p53 knockout mice which were heterozygous for the endogenous wild type p53 gene. Lymphocytes of these mice were cultured after gamma irradiation to induce apoptosis. Viability of lymphocytes as well as fragmentation of DNAs were measured. Apoptosis of lymphocytes from p53 +/- mutant transgenic mice was not suppressed compared with lymphocytes from p53 +/- mice. From these results, the mutant p53 with point mutation at the codon 248 from Arg to Trp or at the codon 249 from Arg to Ser, has a loss of function mutation, but not a dominant negative mutation over the wild type p53.