ACVR1 and diffuse intrinsic pontine glioma: Since the finding of H3.3 and H3.1K27M mutations in DIPG, we and others have discovered that ~25% of DIPG patients harbor activating ACVR1 mutations, a gene that encodes for the ALK2, a receptor in the bone morphogenetic protein (BMP) signaling pathway6,13–15.