Before human induced pluripotent stem (iPS) cells can be used to treat genetically inherited human disease, it will be necessary to develop methods of correcting disease-causing mutations that are compatible with clinical applications, combining efficiency with efficacy and leaving no residual sequences in the targeted genome. Yusa et al. present a proof-of-principle experiment demonstrating the complete genetic correction of a disease-causing mutation in patient-specific iPS cells. They use zinc finger nucleases and piggyBac technology to correction a point mutation in the α1-antitrypsin gene, which is responsible for α1-antitrypsin deficiency (A1ATD). The corrected iPS cells could efficiently differentiate to form hepatocyte-like cells and engraft into an animal model for liver injury without tumour formation. Human induced pluripotent stem cells (iPSCs) represent a unique opportunity for regenerative medicine because they offer the prospect of generating unlimited quantities of cells for autologous transplantation, with potential application in treatments for a broad range of disorders1,2,3,4. However, the use of human iPSCs in the context of genetically inherited human disease will require the correction of disease-causing mutations in a manner that is fully compatible with clinical applications3,5. The methods currently available, such as homologous recombination, lack the necessary efficiency and also leave residual sequences in the targeted genome6. Therefore, the development of new approaches to edit the mammalian genome is a prerequisite to delivering the clinical promise of human iPSCs. Here we show that a combination of zinc finger nucleases (ZFNs)7 and piggyBac8,9 technology in human iPSCs can achieve biallelic correction of a point mutation (Glu342Lys) in the α1-antitrypsin (A1AT, also known as SERPINA1) gene that is responsible for α1-antitrypsin deficiency. Genetic correction of human iPSCs restored the structure and function of A1AT in subsequently derived liver cells in vitro and in vivo. This approach is significantly more efficient than any other gene-targeting technology that is currently available and crucially prevents contamination of the host genome with residual non-human sequences. Our results provide the first proof of principle, to our knowledge, for the potential of combining human iPSCs with genetic correction to generate clinically relevant cells for autologous cell-based therapies.

Targeted gene correction of α1-antitrypsin deficiency in induced pluripotent stem cells