IDH1 and glioblastoma: To estimate the frequency of such circumscribed copy number losses affecting MGMT in H3 G34-mutant gliomas compared with glioblastoma, we analyzed the MGMT locus not only in our reference cohort 3 (Figure 2), but also in another extensive cohort of patients with IDH-wildtype glioblastoma.24 At the threshold of −0.75 (log2), focal copy number underrepresentations affecting the MGMT locus were seen more frequently in H3 G34-mutant gliomas (13%) here than in mesenchymal (MES) (0.3%), RTK1 (4%), or RTK2 (6%) glioblastoma in a large reference cohort (Supplementary Table S7).