Monogenic hereditary diseases are often caused by a single mutation to the more than three billion base pairs of DNA sequence that constitutes the human genome. For the last three decades, a fundamental limitation to the field of gene therapy has been the inability to specifically correct these mutations. As a result, gene therapies to date have almost exclusively focused on methods that insert extra genetic material into random locations within a cell’s genome. The inability to make targeted modifications to cellular genomes has resulted in a myriad of unforeseen negative consequences in experimental and clinical trials of gene therapies. To address these limitations, we are engineering synthetic enzymes that can be programmed to target any location in the genome and catalyze the addition, removal, or exchange of specific gene sequences. Our work falls within the larger field of genome editing for gene and cell therapy that can be applied to diverse diseases and disorders (Maeder and Gersbach, Molecular Therapy 2016).
A primary example of our work in this area is developing genome editing methods such as zinc finger nucleases, TALENs, and CRISPR/Cas9 to correct mutations to the dystrophin gene that cause Duchenne muscular dystrophy, one of the most common fatal genetic diseases, which also currently has no effective treatment. We have used genome editing to correct mutations in patient cells and demonstrated restored dystrophin expression in cell culture and after transplantation into skeletal muscle in mouse models (Ousterout et al., Molecular Therapy 2013; Molecular Therapy 2015; Nature Communications 2015). More recently, we have extended this work to correcting dystrophin mutations in vivo in mouse models of Duchenne (Nelson et al., Science 2016).
Figure 1. CRISPR-based genome editing restores dystrophin expression in mouse models of Duchenne muscular dystrophy. Cross-sections of muscle tissue where the dystrophin protein has been labeled green, including normal, healthy tissue (left), tissue from a mouse model of Duchenne muscular dystrophy (middle), and tissue from the same mouse model that has been treated with the CRISPR gene editing system (right). Nelson et al., Science (2016).
1. Nelson CE, Gersbach CA. Engineering Delivery Vehicles for Genome Editing. Annual Review of Chemical and Biomolecular Engineering. 7:637-62 (2016).
2. DJ Landau, ED Brooks, P Perez-Pinera, H Amarasekara, AMefferd, S Li, A Bird, CA Gersbach, DD Koeberl. In Vivo Zinc Finger Nuclease-mediated Targeted Integration of a Glucose-6-phosphatase Transgene Promotes Survival in Mice with Glycogen Storage Disease Type IA. Molecular Therapy 24(4):697-706 (2016).
3. ML Maeder and CA Gersbach. Genome Editing Technologies for Gene and Cell Therapy. Molecular Therapy 24(3):430-46 (2016).
4. CE Nelson, CH Hakim, DG Ousterout, PI Thakore, EA Moreb, RM Castellanos Rivera, S Madhavan, X Pan, FA Ran, WX Yan, A Asokan, F Zhang, D Duan, CA Gersbach. In Vivo Genome Editing Improves Muscle Function in a Mouse Model of Duchenne Muscular Dystrophy. Science 351(6271):403-7 (2016).
- Highlighted by New York Times (Jan 1, 2016, A13), Nature 529:130 (2016), Science Magazine, New England Journal of Medicine 374(17):1686 (2016), BMJ 351 (2016), Nature Reviews Genetics, Nature Reviews Neurology, Nature Reviews Drug Discovery 15(3):160 (2016), Molecular Therapy 24:414-416 (2016), NIH Research Matters, The Guardian, BBC, Stat News, GEN News, and Rare Disease Report.
5. DG Ousterout, AM Kabadi, PI Thakore, WH Majoros, TE Reddy, and CA Gersbach. Multiplex CRISPR/Cas9-Based Genome Editing for Correction of Dystrophin Mutations that Cause Duchenne Muscular Dystrophy. Nature Communications 6:6244 (2015).
- Highlighted by Nature Reviews Neurology 11, 184 (2015), FierceBiotech, and the Muscular Dystrophy Association
6. DG Ousterout, AM Kabadi, PI Thakore, P Perez-Pinera, MT Brown, WH Majoros, TE Reddy, CA Gersbach. Correction of Dystrophin Expression in Cells from Duchenne Muscular Dystrophy Patients through Genomic Excision of Exon 51 by Zinc Finger Nucleases. Molecular Therapy 23(3):523-32 (2015).
7. DG Ousterout, P Perez-Pinera, PI Thakore, AM Kabadi, MT Brown, X Qin, O Fredrigo, V Mouly, JP Tremblay, CA Gersbach. Reading Frame Correction by Targeted Genome Editing Restores Dystrophin Expression in Cells from Duchenne Muscular Dystrophy Patients. Molecular Therapy 21(9):1718-26 (2013).
-Highlighted by Genetic Engineering and Biotechnology News, Muscular Dystrophy Association, and Biotechniques.