This technology includes a mouse model of Pompe disease, created by targeted inactivation of the acid alpha-glucosidase gene, to test novel therapies. Pompe disease is a severe muscle disorder that affects people at any age. It is a rare genetic disease caused by a deficiency of a lysosomal enzyme acid alpha-glucosidase. The enzyme degrades glycogen to glucose in the lysosomes. The deficiency leads to accumulation of glycogen in multiple organs, but cardiac and skeletal muscles are most severely affected. This model is used world-wide to test different treatments and to better understand the mechanism of muscle damage in this disorder.