Analysis of CRISPR/Cas9/Rad51-mediated gene knock-out efficiency in Hek293 and NIH3T3 cells. (A) Analysis of GAPDH knock-out efficiency of CRISPR-Cas9 system; expression level of the target gene (GAPDH) was determined by immunoblotting analysis. (B) Quantification of GAPDH levels. Protein levels of GAPDH in (A) were quantified and normalized to α-tubulin (normalized values are depicted in the bar graph). Error bars indicate the mean ± SD (n = 3). Statistical significance, *P < 0.05, **P < 0.01, ***P < 0.001. (C) Confirmation of target gene expression at mRNA level by qPCR. The bar graph indicates fold-change values of three CRISPR-Cas9 systems compared with the normal condition. Error bars indicate the mean ± SD (n = 3). (D) Immunoblot analysis for RAD51-mediated CRISPR/Cas9 system in NIH-3T3 derived from mouse embryonic fibroblast cells. (E) Quantitative data for (D) indicated the expression level of GAPDH.