ACVR1 and neoplasm: ACVR1 / H3.1 K27M mutant tumours appear to have a more astrocytic rather than oligodendroglial gene expression signature and morphological appearance34, although in terms of putative developmental origin it should be noted that activin A—ACVR1 signalling is associated with oligodendrocyte differentiation and myelination16,17, a developmental process actively occurring at the age and location at which DIPG arises.