BCL11A and beta thalassemia: Cas9-mediated modification and BE have so far been used to modify the enhancer of transcription factor B-cell lymphoma/leukemia 11A (BCL11A), the core sequence of which is required to repress fetal hemoglobin (alpha2gamma2) in adult-stage erythroid cells to ameliorate beta-thalassemia-derived disorders [16,27,28,29,30,31,32,33,34,35].