Figure 2

Establishment of the IR-mediated G1 checkpoint in E13.5/E15.5 embryonic liver cells. Pregnant mice at embryonic stages E11.5, E13.5, E15.5, and E17.5 were subjected to 0 or 6 Gy ionizing radiation (IR). At the indicated time points after IR, embryonic liver cells were isolated for PI staining and flow cytometric analysis. The cell cycle arrest patterns were determined at E11.5 (A), E13.5 (B), E15.5 (C), and E17.5 (D) using Modfit software. Each analysis was on a cell pool of 3–5 embryonic livers. The data were the means ± SD from two independent analyses i.e. the embryonic liver cells were from different pregnant mice. Following transient G2 arrest, G1 arrest was observed at E13.5, E15.5, and E17.5 but not at E11.5. (E) Representative histograms of the cell cycle distribution patterns of E11.5, E13.5, E15.5, and E17.5 liver cells after 6 Gy IR at the indicated time points. (F) Mice were subjected to 0 or 2 Gy IR at different postnatal ages. Liver cells were isolated at the indicated time points for cell cycle analysis. Percentages of G1, S, and G2/M cells were determined. The mean ± SD was from 2 independent experiments.