<i>Cebpd−/−</i> mice had increased apoptosis and mitotic index and decreased levels of γ-H2AX in intestinal crypts, post-TBI.

<p>(A) Representative images of radiation-induced DNA fragmentation (TUNEL, green staining), DNA-damage marker γ -H2AX (red staining), and cellular nuclei (DAPI, blue staining) of proximal jejunums harvested from <i>Cebpd +/+</i> and <i>Cebpd</i>−/− mice at indicated times after exposure to 7.4 Gy TBI (magnification 10X). (B, C) Quantification of TUNEL-positive cells in intestinal crypts and stromal cells of the villi at indicated time-points after exposure to IR. (D, E) Quantification of γ-H2AX expression levels in intestinal crypts and villi at indicated time-points after exposure to IR. Values are presented as mean ± SEM, n = 4 per genotype per group. (F) Proximal jejunums of <i>Cebpd+/+</i> and <i>Cebpd</i>−/− mice were harvested at 0 h (No IR) and 24 h (IR) after exposure to 7.4 Gy TBI; representative images of immunohistochemical staining of phospho-histone H3 (Ser28) taken at 40× magnification. (G) Phospho-histone H3 (Ser28)-positive cells across approximately 100 intestinal crypts from unirradiated (No IR) and irradiated (IR) <i>Cebpd +/+</i> and <i>Cebpd</i>−/− mice were scored and represented as mean ± SEM, n = 4 per group.