142 Transcriptome Analysis Captures Radiation Exposure in a Dose-sensitive Manner and Predicts Short-term Survival in a Mouse Model

Abstract

\n \n \n A mass exposure to irradiation would be a challenge to health care systems. A simple tool or test that indicates the intensity of the absorbed radiation or the chances of survivability would be invaluable in this scenario. To identify biomarkers that potentially could provide novel biodosimetry tools, we have conducted a radiation dose-response and time-course experiment in mice that includes an assessment of the transcriptome of the skin.\n \n \n \n Groups of mice (n=5) received whole-body X-ray exposures (0, 1, 3, 6, or 20Gy) and skin biopsies were obtained from each animal at times post-irradiation (h2, Days 4, 7, 21, 28). Biopsies were collected from the 20Gy cohort for only days 0, 4, and 7. Total RNA was isolated and microarrays were performed and analyzed using custom R scripts to obtain lists of probe sets differentially expressed. Changes in gene expression at Benjamini-Hochberg FDR adjusted P < 0.05 and FC >2 were deemed significant. Analyses were performed comparing the different doses of X-ray exposure over all time points.\n \n \n \n Mice in the 20Gy group were euthanized by d7 and the dose was considered lethal. Animals in 1, 3, and 6Gy groups completed the full experiment to d28. Sammon plot analysis of transcriptomes showed clear separation of samples based on the irradiation levels and time after exposure. The clearest separation was between samples of lethal and sublethal doses. Samples from animals exposed to sublethal doses separated more based on timepoints rather than the IR dose suggesting a level of similarity in the progression of the response to sublethal doses. Downregulation was the dominant modulation in the significantly differentially transcribed genes (SDTGs) in the 20Gy group. Temporal changes in ratios of upregulated/downregulated SDTGs (P < 0.05 and FC > 2) revealed further the difference between of transcriptome responses after exposure to lethal and sublethal doses and indicated a delayed peaks response with increasing IR doses within the sublethal range. About 59% of the SDTGs in 20gy were common to all timepoints while no more than 11% were common at the same duration in the other groups. Ratios of the number of SDTGs at h2 to those common to all TPs decreased in a dose-dependent manner with potential radiation dosimetric applications.\n \n \n \n These results demonstrate a solid ability in detecting IR exposure, differentiating lethal and sublethal exposures, and differentiating among the exposure to sublethal doses.\n