Novel gene therapy strategies for Usher syndrome

Abstract

Hearing loss is the most prevalent neurological disorder in the world and has a profound impact on quality of life. Hearing loss can present on its own as non-syndromic, or together with other maladies as syndromic hearing loss. One of the most common forms of syndromic hearing loss is Usher Syndrome, which is a rare genetic multi-sensory loss disorder responsible for sensorineural hearing loss, blindness due to retinitis pigmentosa and vestibular areflexia. Extensive work over the past decades has elucidated the causative genes and pathogenic mutations underlying the three clinical Usher subtypes (USH-1, -2 and -3). Despite the emergence of etiological data and promising therapeutic candidates for hearing restoration, no biological treatment exists for these patients. In murine models of Usher syndrome type IID and autosomal recessive hearing loss 31 (DFNB31), harboring mutations in the protein whirlin, we developed a viral-mediated gene replacement strategy to reverse the auditory and balance dysfunction as well as disentangle the relative contributions of whirlin isoforms in stereocilia morphology and maintenance. Additionally, we have optimized a cutting-edge gene editing strategy to precisely target a pathogenic point mutation underlying Usher syndrome type IC in vitro. Using an RNA- programmable deaminase, we are able to efficiently reverse the disease-associated single nucleotide polymorphism. Lastly, we have developed and begun to characterize a CRISPR- generated swine model of Usher syndrome type IIA. In contrast to other established rodent models, these pigs more accurately recapitulate human anatomy, which may translate to the disease phenotype. This porcine model has the potential to address a major limitation in translational studies for genetic hearing loss.