The modified type II CRISPR/Cas, including the human codon–optimized versions of Cas9 and the specific gRNA, was first shown to work efficiently in HEK 293T cells, human leukemia K562 cell line, murine cell lines, and PGP1 iPS cells, using the adeno-associated virus integration site 1 (AAVS1) or empty spiracles homeobox 1 (EMX1) loci as target genes in February 2013 [28], [29]. Here, EMX1 is linked to leukemia.