AAV8-Mediated Gene Therapy Rescues Retinal Degeneration Phenotype in a Tlcd3b Knockout Mouse Model

PURPOSE: The purpose of this study was to assess the therapeutic efficacy of rAAV8-hGRK1-Tlcd3b in a Tlcd3b(−)(/)(−) mouse model of retinal generation and validate TLCD3B's role as a ceramide synthase in vivo. METHODS: Using Tlcd3b(−)(/)(−) mice as an inherited retinal disease animal model, we performed subretinal injection of rAAV8-hGRK1-Tlcd3b and evaluated the efficacy of gene replacement therapy. Tlcd3b(−)(/)(−) mice were treated at two time points: postnatal day 21 (P21) and postnatal day 120 (P120) with various dosages. RESULTS: Tlcd3b overexpression rescued retinal degeneration in the mutant mice, as indicated by significantly improved photoreceptor function and preservation of photoreceptor cells over the course of 1 year. Although Tlcd3b is expressed in all cell types in the retina, photoreceptor cell-specific expression of Tlcd3b is sufficient to rescue the phenotype, indicating the primary function of TLCD3B is in photoreceptors. Consistent with the idea that TLCD3B is a ceramide synthase, mass spectrometry analyses of the mutant retina indicate the reduction of C16-, C18-, and C20-ceramides in the retina, which are restored with Tlcd3b overexpression. CONCLUSIONS: Our findings demonstrated the therapeutic efficacy of gene therapy in treating Tlcd3b mutant retina, laying the foundation for developing future therapy for TLCD3B retinopathy.