Our findings show that irrespective of histological subtypes and grades, and the status of 1p19q co-deletion and other genomic alterations, cells of IDH-mutant gliomas uniformly express early lineage signatures spanning pre-OPC to NFOL and are stalled in oligodendrocyte differentiation due to suppressed myelination program, which is potentially caused by IDH mutation. Here, IDH1 is linked to glioma.