Among IDH Mut gliomas, 80% (36/45) of oligodendrogliomas and 13% (4/30) of astrocytomas exhibited a loss of H3K27me3, with a statistically significant association between 1p/19q codeletion and H3K27me3 loss (P ≤ 0.05). Here, IDH1 is linked to oligodendroglioma.