Development of mini-USH2A gene therapy to treat Usher syndrome type 2A.

About This Grant

Project Summary Usher syndrome type 2 (USH2) is the most common inherited condition for combined loss of hearing and vision worldwide. Several pathogenic variants in the USH2A gene have been reported to cause USH2 and non- syndromic retinitis pigmentosa (RP). The development of genetic therapies for USH2A has been mainly hampered due to the large size of the gene (15.6kb). The payload capacity of AAV restricts the USH2A gene from being included in a single vector. The USH2A protein contains several repetitive domains, and we hypothesize that some of these repetitive domains in the USH2A protein could be dispensable for its function, which is evidenced by recent exon skipping studies. This proposal exploits an innovative minigene approach by systematically deleting repetitive regions in USH2A and screening the functional efficacy of USH2A minigenes (mini-USH2A) both in vitro and in vivo. In addition, the proposed work also aims to deliver mini-USH2A to the retina and cochlea to rescue the USH2A phenotype. Our preliminary data has identified a mini-USH2A (mini- USH2A-4) and validated its functional efficacy in vitro using the Ush2a knock-out cell line. In this proposal, we aim to further characterize and functionally evaluate mini-USH2A-4 and generate novel mini-USH2A by sequential deletion of EGF-Laminin domains in mini-USH2A-4. This work will evaluate the functional efficacy of mini-USH2A through a detailed investigation of biochemical interactions using cell and animal models. The proposed work will also aim to develop an AAV-based approach to deliver mini-USH2A to the retina and cochlea to evaluate the therapeutic efficacy in the Ush2a knock-out mouse model. Successful completion of this study will set the stage for future clinical applications for treating USH2. The proposed research is clinically significant and will contribute to the mission to develop therapies targeting IRDs.