ATRX together with DAXX encode a complex that deposits the histone variant H3.3 into repetitive heterochromatin, including retrotransposons, pericentric heterochromatin, and telomeres, the latter of which show deregulation in ATRX/DAXX-mutant tumours (Heaphy et al., 2011; Dyer et al., 2017). The gene discussed is DAXX; the disease is neoplasm.