Identification of the gene for vitamin K epoxide reductase

We report the identification of a vitamin K epoxide reductase (VKOR) gene. VKOR is the target of warfarin, the most widely prescribed anticoagulant for thromboembolic disorders. Although estimated to prevent twenty strokes per induced bleeding episode, warfarin is under-utilized because of fear of inducing bleeding. Our identification of VKOR should lead to a better understanding of the mechanism of warfarin; it could result in more accurate dosing and in the design of new anticoagulants. We cloned the gene for Drosophila vitamin K-dependent γ-glutamyl carboxylase (dGC), the first γ-glutamyl carboxylase reported in invertebrates, and tried to identify the VKOR gene through a genetic approach utilizing Drosophila. Recently, warfarin resistance was mapped to rat chromosome one and the combined deficiencies of vitamin K-dependent proteins to the syntenic region of human chromosome sixteen. We synthesized siRNA pools directed towards eighteen unknown genes within this region and studied their ability to inhibit V KOR activity in A549 human lung carcinoma cells. siRNA is widely used to knock-down specific genes, but has not been previously employed for large-scale screening of mammalian genes. We report the identification of a VKOR gene using siRNA and confirmation of its identity by expression in insect cells.