Effective HBB gene correction in human embryos by BE3. (A) Schematic of repairing HBB −28 (A>G) in cloned human embryos by BE3 and gRNA-1. Cloned HBB −28 (A>G) mutant homozygous human embryos were generated by fusing lymphocyte cell, from peripheral blood of the patient, with in vitro matured oocytes. And the BE3 mRNA and gRNA mixture was injected after the appearance of pronucleus. HBB site from each embryo was amplified by PCR and deep sequenced. PB1, the 1st polar body. PN, pronucleus. ZP, zonapellucida. (B) Summary of base editing-mediated point mutation repairing by BE3 in cloned human embryos. The repaired embryo contains G>A conversion at the HBB −28 site. *, The target G at the HBB −28 site was converted to C instead of A. (C) Deep sequencing to detect successful repairing by BE3 in human embryos. Target site PCR amplicons from these embryos were deep sequenced