title: The values and limits of an in vitro model of Pompe disease: the best laid schemes o' mice an' men...
abstract: In Pompe disease, a lysosomal glycogen storage disorder, cardiac and skeletal muscle abnormalities are responsible for premature death and severe weakness. Swollen glycogen-filled lysosomes, the expected pathology, are accompanied in skeletal muscle by a secondary pathology-massive accumulation of autophagic debris-that appears to contribute greatly to the weakness. We have tried to reproduce these defects in murine, Pompe myotubes derived from either primary myoblasts or myoblasts with extended proliferative capacity. The cells accumulated large lysosomes filled with glycogen, but, to our disappointment, did not have autophagic buildup even though basal autophagy was intact. When we suppressed autophagy by knocking down Atg7, we found that glycogen uptake by lysosomes was not affected, suggesting that macroautophagy is not the major pathway for glycogen delivery to lysosomes. But two apparently incidental observations-a peculiar distribution of both microinjected dextran and of small acidic structures adjacent to the interior membrane of large alkalinized glycogen containing lysosomes-raised the possibility that glycogen traffics to the lysosomes by microautophagy or/and by the engulfment of small lysosomes by large ones. The cultured myotubes, therefore, appear to be a useful model for studying the mechanisms involved in glycogen accumulation in Pompe disease and to test substrate deprivation approaches.
authors: Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD, USA. takikitas@mail.nih.gov
authors: Shoichi
authors: S
authors: Takikita
authors: Rachel
authors: R
authors: Myerowitz
authors: Cynthia
authors: C
authors: Schreiner
authors: Rebecca
authors: R
authors: Baum
authors: Nina
authors: N
authors: Raben
authors: Paul H
authors: PH
authors: Plotz
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006009:Glycogen Storage Disease Type II / Q000473:pathology*; D006801:Humans; D008247:Lysosomes / Q000473:pathology; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000473:pathology