The histone H3.3 variant is normally enriched in chromatin regions of high turnover such as telomeres and is associated with chaperone proteins such as DAXX (death-domain associated protein) and ATRX (alpha-thalassaemia/mental retardation syndrome X-linked), which themselves are mutated in 31% of paediatric GBM and in several cancers including pancreatic neuroendocrine tumours and AML [188, 189]. The gene discussed is DAXX; the disease is glioblastoma.