CRISPResso: sequencing analysis toolbox for CRISPR genome editing

To the Editor To the Editor References Recent progress in genome editing technologies, in particular the CRISPR-Cas9 nuclease system, has provided new opportunities to investigate the biological functions of genomic sequences by targeted mutagenesis [1-4]. Briefly, Cas9 may be directed by a chimeric single guide RNA (sgRNA) to a target genomic sequence upstream of a protospacer adjacent motif (PAM) for cleavage. Double strand breaks (DSBs) resulting from site-specific Cas9 cleavage can be resolved by endogenous DNA repair pathways such as non-homologous end joining (NHEJ) or homology-directed repair (HDR). These repair mechanisms result in a spectrum of diverse outcomes including insertions, deletions, nucleotide substitutions, and, in the case of HDR, recombination of extrachromosomal donor sequences [1-3, 5 ...