FNLS-YE1 induces no sgRNA-independent off-target effect in human embryos

We performed whole-genome sequencing (WGS) on human embryonic stem cells derived from human 8-cell embryos injected with or without FNLS-YE1, together with sgRNA that targeting PCSK9. Blood cell genomes of sperm and egg donors were also sequenced and analyzed as genetic background control to distinguish FNLS-YE1-induced off-target variants from germline variants. The high on-target efficiencies of four hESC lines derived from FNLS-YE1-treated human embryos were first confirmed by targeted deep sequencing. Whole genome sequencing results showed similar numbers of SNVs and indels between FNLS-YE1-edited hESC lines and non-edited one. Furthermore, these SNVs for each edited hESC lines exhibited no canonical C-to-T pattern, the characteristic of the off-target SNVs induced by cytosine base editors. Taken together, these results demonstrated that FNLS-YE1 induces no off-target effect in early human embryos.