T7E1 assay

The T7E1 assay was performed as previously described [23]. Briefly, mouse genomic DNA was extracted from tail biopsies. The region of DNA containing the nuclease target site was amplified using Lif_Forward 2 (5′-TAC CTT GCC TCT TAA TCC AGT GG-3′) and Lif_Reverse 2 (5′-TGA AGA GAG CAT TGG CGC TGC CA-3′) primers. The amplicons were denatured by heating and annealed to form heteroduplex DNA, which was then treated with 5 units of T7E1 (New England Biolabs, Ipswich, MA, USA) in NEB buffer 2.1 for 1 h at 37 °C, and analyzed using 2% agarose gel electrophoresis.