The use of a canine-specific activin receptor type IIB decoy receptor in dogs did not reverse cardiac cachexia, but reduction of serum myostatin by an insertion of a canine myostatin propeptide gene utilizing an adeno-associated virus serotype 8 vector increased muscle mass in both healthy dogs and golden retrievers with muscular dystrophy [5–7]. The gene discussed is MSTN; the disease is muscular dystrophy.