Genomic DNA was extracted using DNeasy Blood and Tissue Kit (Qiagen). Genomic regions flanking cut sites of sgRNAs were individually amplified by PCR using Phusion Flash High Fidelity PCR Master Mix (Thermo). Amplicons derived from the same samples were then pooled at equimolar, and then subjected to library preparation using NEBNext® Ultra™ II DNA Library Prep Kit (NEB) using Index primers. Amplicon sequencing