A,B) γH2AX, strongly detectable 4 hours after xRT resolved by 48 hours, consistent with effective DNA repair. C,D) Between 4 and 48 hours after xRT, M-Smo;Baxfloxed medulloblastomas developed a differentiated histology, marked by the elaboration of eosinophilic neuropil and the formation of Homer Wright rosettes. E,F) IHC for NeuN demonstrates the dramatic increase in NeuN expression that was consistently seen 48 hours after radiation of Bax-deleted tumors. Scale bars: 100 µm (A–D and insets), 1 mm (E,F).