Human Molecular Genetics Advance Access originally published online on November 18, 2008
Human Molecular Genetics 2009 18(4):621-631; doi:10.1093/hmg/ddn387
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Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy
1 Division of Clinical Genetics, Department of Medical Genetics 2 Division of Stem Cell Regulation Research, Department of Molecular Therapeutics, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan 3 Otsuka GEN Research Institute, Otsuka Pharmaceutical Co. Ltd, Tokushima 771-0192, Japan 4 Department of Molecular Therapy, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo 187-8502, Japan 5 Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan 6 Glycobiology Research Group, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan 7 Howard Hughes Medical Institute 8 Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center 9 Department of Molecular Physiology and Biophysics 10 Department of Neurology 11 Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA
* To whom correspondence should be addressed at: Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, 2-2-B9, Yamadaoka, Suita 565-0871, Japan. Tel: +81 668793381; Fax: +81 668793389; Email: toda{at}clgene.med.osaka-u.ac.jp
Received July 21, 2008; Revised November 2, 2008; Accepted November 12, 2008
Hypoglycosylation and reduced laminin-binding activity of 
-dystroglycan are common characteristics of dystroglycanopathy, which is a group of congenital and limb-girdle muscular dystrophies. Fukuyama-type congenital muscular dystrophy (FCMD), caused by a mutation in the fukutin gene, is a severe form of dystroglycanopathy. A retrotransposal insertion in fukutin is seen in almost all cases of FCMD. To better understand the molecular pathogenesis of dystroglycanopathies and to explore therapeutic strategies, we generated knock-in mice carrying the retrotransposal insertion in the mouse fukutin ortholog. Knock-in mice exhibited hypoglycosylated -dystroglycan; however, no signs of muscular dystrophy were observed. More sensitive methods detected minor levels of intact -dystroglycan, and solid-phase assays determined laminin binding levels to be 
50% of normal. In contrast, intact -dystroglycan is undetectable in the dystrophic Largemyd mouse, and laminin-binding activity is markedly reduced. These data indicate that a small amount of intact -dystroglycan is sufficient to maintain muscle cell integrity in knock-in mice, suggesting that the treatment of dystroglycanopathies might not require the full recovery of glycosylation. To examine whether glycosylation defects can be restored in vivo, we performed mouse gene transfer experiments. Transfer of fukutin into knock-in mice restored glycosylation of -dystroglycan. In addition, transfer of LARGE produced laminin-binding forms of -dystroglycan in both knock-in mice and the POMGnT1 mutant mouse, which is another model of dystroglycanopathy. Overall, these data suggest that even partial restoration of -dystroglycan glycosylation and laminin-binding activity by replacing or augmenting glycosylation-related genes might effectively deter dystroglycanopathy progression and thus provide therapeutic benefits.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.