Glycogen reduction in myotubes of late-onset Pompe disease patients using antisense technology

Glycogen storage disease type II (GSDII) is a lysosomal disorder caused by the deficient activity of acid alpha-glucosidase (GAA) enzyme leading to the accumulation of glycogen within the lysosomes. The disease has been classified in infantile and late-onset forms. Interestingly, most late-onset patients share a splicing mutation c.-32-13T>G in intron 1 of the GAA gene that prevents efficient recognition of exon 2 by the spliceosome. In this study, we have mapped the splicing silencers of GAA exon 2 and developed Antisense Morpholino Oligonucleotides (AMOs) to inhibit those regions and rescue normal splicing in the presence of the c.-32-13T>G mutation. Using a minigene approach and patients fibroblasts we successfully increased inclusion of exon 2 in the mRNA and GAA enzyme production by targeting a specific silencer with a combination of AMOs. Most importantly, the use of these AMOs in patient myotubes results in a decreased accumulation of glycogen. To our knowledge, this is the only therapeutic approach resulting in a decrease of glycogen accumulation in patient tissues beside enzyme replacement therapy (ERT) and TFEB overexpression. As a result, it may represent a highly novel and promising therapeutic line for GSDII.