Klein, A. J. | Search bioRxiv

bioRxiv2025

Mini-Pcdh15b Gene Therapy Rescues Visual Deficits in a Zebrafish Model of Usher Syndrome Type 1F

Usher syndrome type 1F (USH1F) is a severe inherited disorder caused by mutations in PCDH15, resulting in congenital deafness, vestibular dysfunction, and progressive retinal degeneration leading to blindness. While cochlear implantation can restore hearing, no therapeutic interventions currently exist for vision loss. Gene augmentation therapy represents a promising approach; however, the PCDH15 coding sequence ([~]5.3 kb) exceeds the packaging capacity of adeno-associated virus (AAV) vectors. To overcome this limitation, we previously engineered shortened "mini-PCDH15" constructs that retain key structural and functional domains while fitting within a single AAV. Among these, the mini-PCDH15-V4 variant successfully restored hearing in Pcdh15-deficient mice. Here, we investigated the ability of a cone-targeted mini-pcdh15b-V4 transgene to rescue vision in a zebrafish model of USH1F. Untreated pcdh15b-deficient zebrafish exhibited severe structural and functional defects of the retina, including disorganized and shortened photoreceptor outer segments, disrupted calyceal processes, and markedly reduced electroretinogram (ERG) and optokinetic response (OKR) performance. Targeted expression of mini-pcdh15b-V4 recapitulated typical localization of Pcdh15b to calyceal processes and outer segment membranes, rescued photoreceptor architecture, and re-established both structural organization and functional output. Treated mutants exhibited improved visual tracking behavior and full recovery of ERG a-wave and b-wave amplitudes, indicating restoration of photoreceptor and synaptic function. Importantly, mini-pcdh15b-V4 expression produced no adverse effects in wild-type or heterozygous fish, supporting the safety of cone-specific expression. Together, these findings demonstrate that mini-pcdh15b-V4 can restore both photoreceptor structure and visual function in pcdh15b-deficient zebrafish. This work establishes the pcdh15b mutant zebrafish as a powerful preclinical model for studying USH1F retinopathy and supports the translational potential of rationally engineered mini-PCDH15 constructs as a feasible gene therapy approach for preventing or reversing vision loss in individuals with USH1F.

neuroscience↗

bioRxiv2023

PCDH15 Dual-AAV Gene Therapy for Deafness and Blindness in Usher Syndrome Type 1F

Usher syndrome type 1F (USH1F), resulting from mutations in the protocadherin-15 (PCDH15) gene, is characterized by congenital lack of hearing and balance, and progressive blindness in the form of retinitis pigmentosa. In this study, we explore a novel approach for USH1F gene therapy, exceeding the single AAV packaging limit by employing a dual adeno-associated virus (AAV) strategy to deliver the full-length PCDH15 coding sequence. We demonstrate the efficacy of this strategy in mouse USH1F models, effectively restoring hearing and balance in these mice. Importantly, our approach also proves successful in expressing PCDH15 in clinically relevant retinal models, including human retinal organoids and non-human primate retina, showing efficient targeting of photoreceptors and proper protein expression in the calyceal processes. This research represents a major step toward advancing gene therapy for USH1F and the multiple challenges of hearing, balance, and vision impairment.

neuroscience↗