PTCH1 and medulloblastoma: Moreover, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) staining showed that GADD34 mutation, either heterozygous or homozygous, did not significantly alter cell apoptosis in medulloblastoma in Ptch1+/− mice (Figure 4D–4F, 4M).