Abstract
Summary: Muscle cultures from a patient with I-cell disease showed the characteristic morphologic and biochemical abnormalities previously observed in cultured fibroblasts. At early stages of myoblast growth, there were numerous inclusions. Biochemically, the intra-cellular activities of β-galactosidase, β-hexosaminidase, and α-mannosidase were reduced to 1,14, and 5%, respectively, of control values, and this was accompanied by elevated levels of β-hexosaminidase and α-mannosidase in the culture medium. Cultures from the patient did not fuse as well as controls; however, when well-developed myotubes possessing distinct cross-striations were present, these no longer had inclusions. In the muscle biopsy from this patient, only β-galactosidase was decreased to approximately 50% of the mean control value whereas β;-hexosaminidase and α-mannosidase activities were increased as compared to controls. These data suggest that the I-cell mutation is expressed during early myogenesis but not in well-differentiated myotubes or mature muscle fibers.
Speculation: The expression of the I-cell mutation in cultured fibroblasts as compared to immature versus mature muscle suggests that the intracellular localization of acid hydrolases into lysosomes may occur via different pathways in different tissues and may also differ at various stages in development.
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Shanske, S., Miranda, A., Penn, A. et al. Mucolipidosis II (I-Cell Disease): Studies of Muscle Biopsy and Muscle Cultures. Pediatr Res 15, 1334–1339 (1981). https://doi.org/10.1203/00006450-198110000-00006
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DOI: https://doi.org/10.1203/00006450-198110000-00006
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