pLenti-EF1a-DEST-HBB-SFB plasmids were transfected together with psPAX2 (Addgene, #12260) and pMD2.G (Addgene, #12259) into 293T cells to produce lentivirus. 48 h after transfection, the virus was harvested and used to infect 293T cells. 24 h after infection, the infected cells were selected with 1 μg/mL puromycin. After puromycin selection, 3 clones were picked and expanded. The integrated exogenous HBB fragment was amplified and sequenced using FP1 and RP1 (Table S4).