Retinal gene therapy with a large MYO7A cDNA using adeno-associated virus

Area of Science:

• Ophthalmology
• Genetics
• Molecular Biology

Background:

• Usher syndrome type 1 (USH1) causes profound deafness at birth and progressive retinal degeneration.
• Early identification of USH1 patients allows for potential intervention before vision loss.
• Gene therapy presents a viable strategy to prevent blindness in USH1.

Purpose of the Study:

• To investigate adeno-associated virus (AAV) vector-mediated delivery of the MYO7A gene for Usher 1B.
• To evaluate the efficacy of single and dual AAV vector systems in retinal cells and a mouse model.

Main Methods:

• Cloning of MYO7A cDNA under a smCBA promoter into single AAV2/AAV5 vectors and dual AAV2 vectors.
• Transduction of retinal cells in culture and Myo7a-null mice.
• Assessment of MYO7A protein expression and correction of mutant phenotypes.

Main Results:

• Single AAV2 and AAV5 vectors successfully transduced retinal cells, leading to functional MYO7A protein expression and phenotype correction.
• Dual AAV2 vectors also delivered MYO7A, but with variable protein levels and limited phenotype correction.
• Homologous recombination may explain the functional restoration despite potential gene fragmentation in single vectors.

Conclusions:

• Single AAV2 and AAV5 vectors are efficacious for MYO7A gene therapy in Usher 1B.
• The dual AAV2 vector approach was less effective for delivering functional MYO7A.
• AAV-mediated gene therapy holds potential for treating Usher 1B-related blindness.