title: Non-homologous DNA increases gene disruption efficiency by altering DNA repair outcomes.
abstract: The Cas9 endonuclease can be targeted to genomic sequences by programming the sequence of an associated single guide RNA (sgRNA). For unknown reasons, the activity of these Cas9-sgRNA combinations varies widely at different genomic loci and in different cell types. Thus, disrupting genes in polyploid cell lines or when using poorly performing sgRNAs can require extensive downstream screening to identify homozygous clones. Here we find that non-homologous single-stranded DNA greatly stimulates Cas9-mediated gene disruption in the absence of homology-directed repair. This stimulation increases the frequency of clones with homozygous gene disruptions and rescues otherwise ineffective sgRNAs. The molecular outcome of enhanced gene disruption depends upon cellular context, stimulating deletion of genomic sequence or insertion of non-homologous DNA at the edited locus in a cell line specific manner. Non-homologous DNA appears to divert cells towards error-prone instead of error-free repair pathways, dramatically increasing the frequency of gene disruption.
authors.affiliation: Innovative Genomics Initiative, University of California, Berkeley 94720, USA.|Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Richardson
authors.affiliation: Innovative Genomics Initiative, University of California, Berkeley 94720, USA.|Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Ray
authors.affiliation: Innovative Genomics Initiative, University of California, Berkeley 94720, USA.|Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: N L
authors.initials: NL
authors.lastname: Bray
authors.affiliation: Innovative Genomics Initiative, University of California, Berkeley 94720, USA.|Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Corn
mesh_terms: D001483:Base Sequence; D064130:CRISPR-Associated Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism*; D004260:DNA Repair; D017353:Gene Deletion; D056426:Genetic Loci; D057809:HEK293 Cells; D006720:Homozygote; D006801:Humans; D009841:Oligonucleotides / Q000378:metabolism
chemical_list: D064130:CRISPR-Associated Proteins; D009841:Oligonucleotides; D004247:DNA