ZIC1 and medulloblastoma: Our observation that the ZIC1/ZIC4 locus undergoes recurrent repression in G4 medulloblastoma through hemizygous deposition of H3K27me3 on its SE prompted us to look for additional mono-allelic SEs in a cohort of 51 medulloblastoma tumors with matching H3K27ac ChIP–seq and WGS data (Fig. 3a).