a, Immunohistochemistry (IHC) of γH2AX on the liver of 13.5 dpc wt and Seckel littermate embryos. b, Examples of two representative areas of ATRS/S embryos, which were chosen from organs that appear compromised on adult mice -such as the forebrain or the face-, that illustrate the generalized accumulation of p53 or apoptotic cells (as measured with activated caspase 3) on the mutant embryos. Scale bar (white) indicates 150 μm. c, Quantification of the signals from b. d, Quantification of the frequency of cells with pan-nuclear γH2AX on different organs of 13.5dpc embryo and 2 month old mice.