By showing that mutant ACVR1 is sufficient to arrest the differentiation of oligodendroglial lineage cells (Figure 8), our results provide mechanistic explanations for the presence of ACVR1 mutations among the earliest oncogenic events in a subset of DIPG, and for the recent discovery that DIPG malignant cells harbor features of OPCs (Filbin et al., 2018). This evidence concerns the gene ACVR1 and diffuse intrinsic pontine glioma.