T7 endonuclease I assay for genome modification
293T Cells were collected after 48 h post-transfection for genomic DNA extraction. The genomic region flanking the target site of each gene was PCR-amplified, and products were purified using DNA Clean Kit following the manufacturer’s protocol. A total of ~ 200 ng purified PCR amplicons was mixed with 1 μl NEBuffer 2 and diluted in ddH2O to 10 μl, then subjected to a re-annealing process to form a heteroduplex according to the reported procedure [44]. After re-annealing, the products were treated with T7EI following recommending protocol, and 2.5% agarose gels were used for further analysis. Indels were calculated via band intensities based on previously reported method [45].