PTCH1 and medulloblastoma: Thus, GADD34 homozygous mutation significantly reduced the incidence of medulloblastoma in Ptch1+/− mice (9 out of 60 Ptch1+/−; Gadd34−/− mice vs 23 out of 76 Ptch1+/−; Gadd34+/+ mice, Figure 2B).