AAV-mediated Ascl1 augmentation attenuates photoreceptor degeneration in a mouse model of blue light-induced retinal injury

Photo-oxidative stress is a key contributor to vision loss in older adults and involves progressive dysfunction and loss of photoreceptors and retinal pigment epithelial (RPE) cells. Effective therapies that directly preserve outer retinal cell survival under such stress remain limited. Ascl1 is a basic helix-loop-helix transcription factor best known for neurogenesis and cellular plasticity and has been widely studied in the retina for its ability to reprogram Müller glia. Here we asked whether Ascl1 gene augmentation can also confer cytoprotection in the adult outer retina under acute degenerative stress. We used a mouse model of blue light-induced retinal injury to impose photo-oxidative stress on the outer retina and RPE, and tested the protective effect of Ascl1 gene augmentation using AAV8-CAG-Ascl1-GFP (with AAV8-CAG-GFP as the control). Retinal structure and function were assessed using immunostaining, behavioral tests, and electroretinography. To explore the underlying mechanisms, we further performed a dual-luciferase reporter assay, bulk RNA sequencing, qPCR, and western blotting. Ascl1 overexpression was detected in the outer retina and RPE, where it mitigated blue light-induced degeneration, resulting in the partial preservation of outer retinal structure and retinal function (ERG b-wave responses) and light/dark preference behavior. Consistent with an anti-apoptotic effect, Ascl1 markedly reduced TUNEL-positive cells in the ONL and was accompanied by decreased cleaved Caspase-8 and BAX and increased Bcl2. Dual-luciferase assays confirmed that Ascl1 directly activates the Bcl2 promoter. In parallel, Ascl1 increased PI3K and AKT phosphorylation, suggesting engagement of pro-survival signaling. Injury-associated glial/microglial activation and RPE junctional disruption were also attenuated in Ascl1-treated eyes. These data support a cytoprotective dimension of Ascl1 augmentation in addition to its reprogramming-associated role and demonstrate that AAV-based Ascl1 augmentation can enhance retinal stress resilience following acute photo-oxidative injury, motivating further evaluation in chronic, age-associated models with dose/safety optimization and pathway-level validation.