Gene replacement using adeno-associated virus (AAV) vectors is a promising therapeutic approach for many diseases^(1,2). However, this therapeutic modality is challenged by the packaging capacity of AAVs (approximately 4.7 kilobases)³, limiting its application for disorders involving large coding sequences, such as Duchenne muscular dystrophy, with a 14 kilobase messenger RNA. Here we developed a new method for expressing large dystrophins by utilizing the protein trans-splicing …