David Gamm, MD, PhD
University of Wisconsin School of Medicine and Public Health
Monday, January 28, 2018
11:10 am - 12:30 pm
489 Minor Hall
Mutation-specific responses to gene therapy in Best Disease
Dominantly inherited disorders are not typically considered therapeutic candidates for gene augmentation (GA). Here we tested whether GA or gene editing (GE) could serve as a solo therapy for Best disease, a macular dystrophy linked to over 200 different mutations in BEST1, a homo-pentameric calcium-activated chloride channel (CaCC) expressed in the retinal pigment epithelium (RPE). Since no suitable animal models of autosomal dominant Best disease (adBD) exist, we utilized patient-derived induced pluripotent stem cell-derived RPE (iPSC-RPE) to show that GA restored CaCC activity and improved rhodopsin degradation in a subset of adBD lines. Specifically, lines harboring adBD mutations in calcium clasp or chloride binding regions of the channel, but not in a structural region, were responsive to GA. However, all lines demonstrated reversal of the CaCC deficit following GE via CRISPR-Cas9. Over 95% of GE events resulted in premature stop codons specifically within the mutant allele, higher than the percentage predicted by machine learning. Further, single cell profiling of edited iPSC-RPE showed no adverse perturbation of mature RPE transcriptional networks. These results suggest that GA is a viable approach for a subset of adBD patients depending on the functional role of the mutated residue, and GA non-responders are amenable to GE, which can also be accomplished with high efficiency and selectivity. Similar scenarios likely exist for other genotypically diverse dominant diseases, expanding the gene therapy landscape for affected patients.