Previously, our laboratory generated a Gaa knockout (KO) (Gaa−/−) mouse model that has a complete GAA deficiency, resulting in tissue pathology and symptoms indicative of classic infantile Pompe disease.56, 57, 58 Using this mouse model, we demonstrated that HSPC-mediated lentiviral gene therapy with human GAA resulted in increased GAA enzyme activity in host tissues, reduction of glycogen accumulation, and improved cardiac and motor function.59 The gene discussed is GAA; the disease is glycogen storage disease II.