UC Berkeley

The retina contributes to the first steps in processing visual information. Rods and cone photoreceptors are the two main retina cells contributing to the initial steps in sensing light and translating it to an electrical signal to the downstream neuronal cells finally to be processed in the primary visual cortex. Many cells and hundreds of genes are involved in the light response and keeping retinal cells metabolically active. This high degree of activity makes the retina more vulnerable to mutations and degeneration. The majority of mutations identified in patients affect genes involved in either the photoreceptor structural integrity or in the phototransduction cascade. Many inherited retinal degenerative (IRDs) diseases, such as retinitis pigmentosa, lead to blindness as a result of initial rod photoreceptor cell death followed by cones and remodeling of the retina.

Gene therapy has been a growing field in the past decade and has proven to be an efficient and safe way of treating single-gene mutations leading to blindness by providing therapeutic DNA to targeted cells in the retina. The clinical trials for Leber congenital amaurosis type 2 (LCA) were the first to validate the proof-of-concept for gene therapy in the retina, after the successful use of adeno-associated viruses (AAVs) to deliver a healthy copy of the RPE65 gene to the affected cells. AAV, a small and nonpathogenic virus, has been used widely in many clinical trials, due to its safety profile and efficiency at targeting a wide range of tissues and cell types.

However, many obstacles remain from the optimization of delivery and design of viral vectors to elucidating molecular mechanisms behind the heterogenous genetic complexity in retinal diseases. While over 250 gene-causing diseases have been identified, more than 30-40% of genes involved remain unknown or outside of canonical coding sequences. For these patients, a gene replacement is not yet possible or applicable and therefore requires novel approaches.

My dissertation focuses on the use and optimization of engineered AAV vectors to achieve cell-selective targeting of retinal cells and organelles, to design novel mutation-independent gene therapies adapted for progressive degenerative diseases such as retinitis pigmentosa. It also aims at elucidating and characterizing molecular mechanisms underlying non-coding region mutations, with the use of genome editing tools to engineer mouse models of untranslated region mutations found in LCA patients. My thesis provides new knowledge and AAV toolkit to better tackle patients’ unmet need for novel gene therapy strategies addressing undiagnosed and noncanonical mutations in inherited retinal diseases.