Heterozygous loss of Ebf1 results in increased DNA damage after UV exposure of B-cell progenitors. (A) Relative MFI obtained by flow cytometric analysis to detect γH2AX in in vitro-cultivated primary Wt or Ebf1^+/− pro-B cells 16 hours after UV exposure. The data are normalized toward the Wt control and represent 3 experiments, The statistics were performed using an unpaired t test; the error bar represents mean ± SD. ***P < .001. (B) Immunohistochemical staining of phosphorylated H2AX (γH2AX) in in vitro-cultured Wt or Ebf1^+/− pro-B cells 16 hours after UV exposure. DAPI was used to stain the nucleus. (Lower) Quantification of the signal intensity collected from 3 experiments. The representation of fold-integrated density is based on an unpaired t test with error bars representing mean ± SD. ***P < .001. (C) Representative pictures of comet assays performed 16 hours after UV exposure of in in vitro-cultivated primary Wt or Ebf1^+/− pro-B cells. (D) Quantitative RT-PCR data from in vitro-cultured Wt or Ebf1^+/− pro-B cells before and 16 hours after UV exposure. The data are normalized to the expression of HPRT in triplicate PCR reactions and represent 3 independent experiments. The Student t test represents statistical analysis. ****P < .0001. (E) Frequency of annexinV⁺ cells as estimated by flow cytometric analysis from in vitro-cultured Wt or Ebf1^+/− pro-B cells. The cells were gated on a lymphoid gate for live cells. The error bars in the diagrams indicate mean ± SD, and statistical analysis was performed using an unpaired Student t test. **P < .01.