MeCP2 is thought to be important for the localization of ATRX to pericentric heterochromatin, as loss of MeCP2 function in Mecp2-null mice or in mice carrying several RTT-associated point mutations in Mecp2 abolishes ATRX localization to pericentric heterochromatin in the brain [127,129]. The gene discussed is MECP2; the disease is Rett syndrome.