Gene therapeutic approaches for dominant retinopathies

Over the past two decades, significant progress has been made in defining the molecular pathogenesis of hereditary retinal degenerations. Many of these are characterised by immense genetic heterogeneity. For example, in retinitis pigmentosa (RP), the most common form of this group of disorders, over 50 disease causing genes have been implicated, 20 of which are inherited in an autosomal dominant manner. Knowledge of the underlying genetic pathogenesis together with the availability of animal models and vectors for delivery has enabled exploration of gene-based therapies for inherited retinopathies. Notably, many studies have focused on treatment of recessive forms of these disorders and significant progress including ongoing clinical trials have been achieved. Progress in developing gene therapies for dominant retinopathies has been slower. One reason for this is that gene therapies for many dominant diseases, which are targeted to correcting the primary genetic defect, are likely to require suppression of the mutant gene. Alternative therapeutic approaches, which involve modulating secondary features associated with the disease pathology (such as ER stress or apoptosis) are also being explored. This review is focused on the development of gene-based therapies for dominantly inherited retinopathies. The main topics discussed are suppression technologies, preclinical animal models, retinal gene delivery and therapeutic strategies.