Unintended on-target chromosomal instability following CRISPR/Cas9 single gene targeting

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) seminal studies in mammalian cells1–3 have resulted in gene editing being broadly adopted in basic research. However, it has become apparent that the CRISPR/Cas9 system induces unintended off- and on-target genomic alterations4 and that there is a need for stricter clone screening methods before phenotypic characterisation is made, particularly before the technology is adopted for clinical purposes.