CRISPR/Cas9-mediated gene editing of VKORC1 and VKORC1L1 in HEK293T cells. (A) The wild-type sequence for both genes (c.70-116 of VKORC1 and c.88-131 of VKORC1L1) is shown on the top, deletions are indicated by dashes, and insertion and substitution is shown in bold type. (B) Measurement of FIX activity after transfection of human F9 cDNA and supplementation of 12 µM vitamin K₁ in different genetically engineered cells. Columns represent measurements of endogenous VKORC1 and VKORC1L1 activity in HEK 293T WT, endogenous VKORC1 activity (VKORC1L1 KO), endogenous VKORC1L1 activity (VKORC1 KO), and in cells lacking both VKOR enzymes (VKORC1/VKORC1L1 DKO cells). Columns show mean of triplicates ± standard error of the mean.