GATA-1 and SP1 activities in erythroid cultures derived from
(a) Patient A has thalassemia intermedia due to elevated HbF production. (b) Patient B is the niece of Patient A. She is transfusion dependent β-thalassemia major. (c) An unrelated β-thalassemia major patient. ●, GATA-1 binding activity; ○, SP1 binding activity.