ANTI-CRISPR PROTEIN REGULATES CRISPR Cas9 ACTIVITY IN HUMAN EMBRYOS

Abstract

Genome editing of human embryos using CRISPR-Cas9 frequently leads to mosaicism, chromosome loss, and unintended off-target editing. To avoid mosaicism and allow inference of the inner cell mass (ICM) genotype from a trophectoderm biopsy, Cas9 editing has to be limited to the 1-cell stage. Reducing the time that Cas9 is active in a cell may also decrease off-target effects which tend to be delayed relative to on-target edits. This study aims to determine if the anti-CRISPR protein, AcrIIA4, can effectively regulate Cas9 activity by minimizing off-target editing and mosaicism in human embryos while still allowing for on-target editing of the germline.