The CRISPR system is a genome engineering tool derived from bacteria. The CRISPR system can directly modify and repair DNA in animal and cell models of human eye disease. This technology couples an endonuclease enzyme with a targeting guide. It has been adapted to allow for specific gene editing at an exact site in the genome. Our lab has used this technology to repair patient mutations in their own stem cells and and introduce disaease causing mutations into mouse models. This allows for more accurately replicating diseases and creates an opportunity to better understand the molecular mechanisms causing disease and to test therapies.
In addition to using CRISPR to create patient mutations in stem cells and mouse models, we have also used CRISPR to correct patient mutations. We did this by first culturing fibroblasts from a skin-punch biopsy of a patient who carried an RPGR point mutation that causes X-linked retinitis pigmentosa (XLRP). These patient cells were reprogrammed into pluripotent stem cells (iPSCs) carrying the patient's c.3070G > T mutation. CRISPR was then used to correct the mutation in the iPSCs. In the future these corrected cells may yield grafts for transplantation that require no patient immunosuppression. This was the first report using CRISPR to correct a pathogenic mutation in iPSCs derived from a patient with photoreceptor degeneration.
Our lab also used CRISPR editing to correct a blinding gene mutation in mice. This was performed in a common model of retinitis pigmentosa called the “rodless” (rd1) mouse. The first generation of corrected animals showed preserved vision despite not all cells being corrected. Furthermore, second-generation CRISPR-repaired mice showed an even more robust rescue and no disease. This study was the among the first examples of gene correction (homolgy directed repair) in the visual system.