SNP array for Cas9 treated human oocytes and embryos

Human eggs were fertilized with sperm carrying a homozygous mutation in the EYS gene at rs758109813 and treated with a Cas9 RNP targeting this mutation at either fertilization or at the 2-cell stage. The purpose of this analysis was to determine loss of heterozygosity due to CRISPR-induced chromosomal changes. We find that However, in half of the embryos, the break remains unrepaired throughout the first cell cycle, resulting in both segmental, as well as whole chromosome loss. These embryos appear as corrected non-mosaic wild type embryos in an on-target sequence analysis, but are not viable. These results show a surprising tolerance of the human embryo for mitotic entry with unrepaired DNA double strand breaks, and suggest that pericentromeric cleavage by Cas9 may enable the allele-specific removal of chromosomes in trisomic embryos. SNP array for Cas9 treated human oocytes and embryos