In vivo genome editing restores haemostasis in a mouse model of haemophilia

Gene correction in a blood disorder Direct editing of disease-causing mutations has obvious attractions for the treatment of genetic disorders if the many practical obstacles to the technique can be overcome. One promising line of research centres on the development of zinc finger nucleases (ZFNs) produced by fusing an engineered zinc finger DNA-binding domain to an endonuclease. These artificial enzymes induce efficient gene correction in cultured cells. Li et al. now report that zinc finger nucleases induce double-strand breaks in specifically selected locations on the genome and stimulate genome editing at a clinically meaningful level in vivo. In a proof-of-principle experiment, ZFNs delivered to the liver in a mouse model of haemophilia B achieved a level of gene replacement that was sufficient to correct the clotting defect, and the effect persisted following liver regeneration.