Fig. 4. Abnormal neuronal cell death in Polβ^–/– embryo brains is associated with neurogenesis. Dorsolateral regions of cortices of (A–E) wild-type and (F–J) Polβ^–/– embryo brains at the developmental stages indicated were stained with TUNEL reagents. Arrows indicate TUNEL-positive apoptotic nuclei. CP, cortical plate; IZ, intermediate zone; ne, neuroepithelium; VZ, ventricular zone.