Study Of Gadd45 And P21～(WAF1) Gene Expression Changes As Radiation Biodosimeter

Radiation Biodosimeters plays a vitally important role in assessing the doses of radiation victims and in the research on cell response to radiation. Many researches have been conducted during the past half-century, and hundreds of targets have been assessed. Ideal radiation biodosimeter possesses the following features: inducible after ionizing radiation (IR); proportionate to exposure dose; method simple and convenient. However, no Radiation Biodosimeter at present can meet all these requirements.Ionzing radiation could elicit several types of cell response. GEC(Gene Expression Change) of Gadd45 after IR has been paid great attention. Research in vitro by Armed Forces Radiobiology Research Institute showed that Gadd45 mRNA increases promptly after IR and its mRNA level is proportionate to exposure dose. To point out, increasing promptly after IR and easily test, the most obvious features of Gadd45, are defective in present Chromosome aberration analysis which is the most popular method. Whereas assessing the doses promptly after IR is vital to the diagnosis and treatment of radiation victims. Therefore, it has become a focus if Gadd45 could function as a practical Radiation Biodosimeters of GEC type.Until now, all papers describing Gadd45 mRNA is proportionate to exposure dose are based on the research of single man's peripheral blood. To evaluate whether Gadd45 could be developed into a practical radiation biodosimeter, the variance of Gadd45 mRNA in different people is needed to be evaluated.In addition, the existing methods need the non-radiation control sample which is used to compare the change scales in Gadd45 mRNA. But the non-radiation control blood of the radiation victims don't exist for most instances.With the aim of finding solutions to the above problems, we set up the relativereal-time quantitative PCR by standard curve method, usingβ-actin as internal standard.By this method, we established the dose-response curve equation of Gadd45/p-actin(y=0.216+0.258x, R²=0.650) after IR 4 hours, when Gadd45 mRNA reaches its most magnitude, based on data from 27 men's peripheral blood. The Coefficient of Determination(R) indicate the linear regression equation bears less precision, and values of Gadd45/actin vary greatly in different people.And then we replace Gadd45 with p21^WAF1, whose mRNA show greater rising proportion than Gadd45's after IR, and replaceβ-actin with C-myc, whose mRNA level declines after IR. Theoretically, GEC of p21^WAF1/C-myc will show much more obvious changes than GEC of Gadd45/p-actin after same dose IR. The dose-response curve equation equation of p21^WAF1/c-myc (y=0.482+0.773x, R²=0.855) bear more precision than equation of Gadd45/p-actin.All in all, we set up the relative real-time quantitative PCR by standard curve method, and establish the calibration curve of Gadd45/actin and p21^WAF1/c-myc. By this method and the calibration curve we have successfully coped with the existing problems—the non-radiation control blood of the radiation victims don't exist, and we can estimate the radiation dose under laboratory condition. This is a progress in developing Gadd45 and p21^WAF1 into practical radiation biodosimeters.