DAXX forms a complex with α-thalassemia and mental retardation X-linked (ATRX) DNA helicase to act as a histone chaperone for the histone variant H3.3 to facilitate its deposition into pericentric heterochromatin, telomeres, silenced imprinted loci and endogenous retrovirus elements.43, 44, 45, 46 Like DAXX, ATRX can associate with both heterochromatin and PML NBs.30, 47 We therefore wanted to investigate if PML NB loss during differentiation disrupted the association of ATRX and DAXX at heterochromatin. The gene discussed is ATRX; the disease is thalassemia.