Indel and HDR-mediated gene-targeting efficiency analyses. Liver DNA was isolated from FIX-KO mice at 8 and 32 weeks posttreatment with dual gene–targeting vectors or untargeted vectors. DNA from an untreated FIX-KO mouse served as control. Indel analysis on the targeted mFIX locus was performed by deep sequencing on liver DNA isolated at 8 and 32 weeks posttreatment. HDR-mediated gene-targeting efficiency was analyzed by LMU-PCR, following digestion with StyI or TaqαI (see supplemental Figure 5), on liver DNA isolated at 32 weeks posttreatment. Indel frequency in mice treated as neonates (A) or as adults (B). HDR frequency in mice treated as neonates (C) or as adults (D). Each data point represents an individual mouse. Data are mean ± SD. *P < .05, 2-tailed Mann-Whitney U test. n.s., not statistically significant.