Fig. 7. Apoptosis in early post-mitotic neurons of Xrcc2^–/– embryos. Sagittal section of (A and B) the frontal cortex and (C and D) the septal area of the developing forebrain in an E12.0 Xrcc2-null embryo, stained with propidium iodide (A and C), and double stained with TUNEL reagents (green) and the anti-β3-tubulin antibody, TUJ1 (red) (B and D). TUNEL-positive nuclei are localized predominantly within the newly generated, TUJ1-staining neuronal cell population of the PPL layer. V, lateral ventricle; VZ, ventricular zone; PPL, primordial plexiform layer.