Proposed schematic model detailing epigenetic driver mutations in H3F3A and related pathway mutations. (a) Under normal conditions, K27 and K36 act as repressive and activating marks, respectively. (b) Mutations in H3F3A at K27M lead to decreased trimethylation on K27 by EZH2, causing gene activation and leading to abnormal gene expression. (c) Mutations in H3F3A at G34R/V lead to an alteration of K36 methylation, and are associated with abnormal gene expression. (d) Mutations in SETD2 cause a decrease in trimethylation of K36 and may potentially lead to abnormal gene regulation. (e) ATRX/DAXX mutations have been shown to play a role in the alternative lengthening of telomeres. WT, wild type.