Reduced proliferative activity of primary POMGnT1-null myoblasts in vitro

Protein O-linked mannose beta1,2-N-acetylglucosaminyltransferase 1 (POMGnT1) is an enzyme that transfers N-acetylglucosamine to O-mannose of glycoproteins. Mutations of the POMGnT1 gene cause muscle-eye-brain (MEB) disease. To obtain a better understanding of the pathogenesis of MEB disease, we mutated the POMGnT1 gene in mice using a targeting technique. The mutant muscle showed aberrant glycosylation of alpha-DG, and alpha-DG from mutant muscle failed to bind laminin in a binding assay. POMGnT1(-/-) muscle showed minimal pathological changes with very low-serum creatine kinase levels, and had normally formed muscle basal lamina, but showed reduced muscle mass, reduced numbers of muscle fibers, and impaired muscle regeneration. Importantly, POMGnT1(-/-) satellite cells proliferated slowly, but efficiently differentiated into multinuclear myotubes in vitro. Transfer of a retrovirus vector-mediated POMGnT1 gene into POMGnT1(-/-) myoblasts completely restored the glycosylation of alpha-DG, but proliferation of the cells was not improved. Our results suggest that proper glycosylation of alpha-DG is important for maintenance of the proliferative activity of satellite cells in vivo.