HBG2 and Schnyder corneal dystrophy: (2) Gene therapy for SCD is achieved by interfering with the expression and function of the HBG1/HBG2 transcriptional repressor BCL11 transcription factor A (BCL11A) or zinc finger and BTB structural domain‐containing 7A (ZBTB7A) or by inducing the hereditary persistence of HbF (HPFH), which raises the level of HbF.218, 219