Administration of AAV6 Vectors to Mice.

All experiments were conducted in accordance with the relevant code of practice for the care and use of animals for scientific purposes (National Health & Medical Council of Australia, 2016). Vectors carrying transgenes of GDF8 mutants were injected into the right TA muscle of 6- to 8-wk-old male C57BL/6 mice under isoflurane anesthesia at 10¹⁰ vector genomes (vg). As controls, the left TA muscles were injected with AAVs carrying an empty vector at equivalent doses. At the experimental endpoint, mice were humanely killed via cervical dislocation, and TA muscles were excised rapidly and weighed before subsequent processing.