The targeting construct is designed as a multiplex containing 10 single guide RNAs (sgRNA) driven by separate U6 promoters inserted into the 3' UTR of an EGFP reporter driven by constitutive CAG promoter. A "barcode" 276 bp array containing target sites matching each of the expressed sgRNAs is inserted upstream of the EGFP polyadenylation site. (J:290327)