Objective     To investigate ionizing irradiation (IR)-induced overall changes of gene expressions in small intestinal crypt and villus of mice by gene expression chip analysis

and the characteristics of genes relative to DNA damage repair and cell cycle regulation.     Methods     Twenty male C57/BL6 mice

5-week-old and 20 to 22 g body weight

were randomly grouped. Experimental groups were sacrificed at 4

8

and 24 h after a single dose of 12 Gy cobalt total body irradiation (TBI)

followed by the separation of crypt and villus cells from small intestinal epithelium. Normal mice were taken as control. Dynamic changes of gene expressions were elucidated by cDNA expression microarray analysis. Upregulated and downregulated genes were subjected to cluster analysis

and the genes related with DNA damage repair and cell cycle were also analyzed.     Results      After IR treatment

the genes that were upregulated or downregulated for more than 2-folds (P0.01) compared with control were grouped into different cell signal pathways by cluster analysis. These pathways were mainly related with p53

MAPK

apoptosis

cell cycle and immune response (P0.05). Ranking by P value

we found that p53 and MAPK pathways exhibited more significant up-regulation in the crypt than those in the villus. Representative genes of different DNA repair pathways were up-regulated to certain extent

which was coincident with the change of cell cycle. The characteristics of gene expression indicated high accurate homologous recombination

nonhomologous end joining

as well as nucleotide excision repair were the main DNA repair ways in crypt repair

however

rapid but error prone repair

mismatch repair was predominant in the villus for gene integrity maintenance.     Conclusion      IR-induced DNA damage response is related to cell differentiation status

and crypt cells are more sensitive to DNA damage.