Genomic Differential Expression Of Human Lymphocytes And Dose Response Relationships Induced By X-rays Irradiation

Objective To screen radiation responsive genes at the level of global genome to search for dose-response relationship induced by X-ray irradiation to explore the possibility of specific gene expression patterns and signal pathways as radiation biodosimetry.Methods Agilent human oligo microarray was used to screen differential expressive genes in homo sapien PBLs exposed to 0.5, 2.0, 5.0Gy X-ray irradiation. Radiation responsive genes were selected by statistics significance, fold change and intersection analysis. Dose-dependent up-regulated genes were mapped out with SOM method and confirmed by Quantitative RT-PCR. Radiation responsive signal pathways were analyzed through hierarchical clustering, Gene Ontology and GenMAPP databases. Cell apoptosis was detected with flow cytometry and laser confocal microscope.Results1. Total of 522 radiation responsive genes were screened out with oligo microarray. Among 38 coexpression radiation responsive genes, 18 were identified as dose-dependent responsive genes. A linear dose response relationship was established between IR and gene expression changes for DDB2, BBC3, PCNA, IFNG, TNFSF4, TNFSF8, ZNF788, TMEM30A, DACH2, TNFRSF10B and an exponential model for GADD45A, PHLDA3, ISG20L, APOBEC3H, E2F7, PPM1D over the dose range from 0.5 to 5.0Gy .2. The up-regulated genes of XPC, BAX, P21 and down-regulated genes of Ku70, XRCC3 were verified with Quantitative RT-PCR corresponded to the microarray results. The expression of GADD45 gene was dose-dependent ranging from 1.0Gy to 5.0Gy, rapidly increased at 1h, peaked at 4h, remained high for 72h and retuned to basal level by 96h post irradiation. A linear dose response relationship of gene expression for P21 was also verified over the range from 1.0 to 3.0 Gy.3. The radiation responsive genes were functional in DNA stress, DNA damage repair, cell cycle control, apoptosis and immune response. Among them 11 genes were downstream target genes of P53. Signal pathway analysis revealed that P53 signal pathway, Fas ligand, apoptosis modulation via HSP70 pathway, cell cycle control and inflammatory response pathways were involved in radiation response to X-ray exposure.Conclusions1. Microarray technique is a powerful tool in screening radiation responsive genes.2. Characteristic of differential expression induced by X-ray is explored in lymphocytes with specific dose-response and time-response patterns.3. X-ray induced genome changes include radiation responsive genes and signaling pathways which might be applied as potential radiation biodosimetry.