title: Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy.
abstract: Hypoglycosylation and reduced laminin-binding activity of alpha-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 alpha-dystroglycan; however, no signs of muscular dystrophy were observed. More sensitive methods detected minor levels of intact alpha-dystroglycan, and solid-phase assays determined laminin binding levels to be approximately 50% of normal. In contrast, intact alpha-dystroglycan is undetectable in the dystrophic Large(myd) mouse, and laminin-binding activity is markedly reduced. These data indicate that a small amount of intact alpha-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 alpha-dystroglycan. In addition, transfer of LARGE produced laminin-binding forms of alpha-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 alpha-dystroglycan glycosylation and laminin-binding activity by replacing or augmenting glycosylation-related genes might effectively deter dystroglycanopathy progression and thus provide therapeutic benefits.
authors.affiliation: Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Motoi
authors.initials: M
authors.lastname: Kanagawa
authors.forename: Akemi
authors.initials: A
authors.lastname: Nishimoto
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Chiyonobu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takeda
authors.forename: Yuko
authors.initials: Y
authors.lastname: Miyagoe-Suzuki
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Fujikake
authors.forename: Mariko
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Zhongpeng
authors.initials: Z
authors.lastname: Lu
authors.forename: Masaji
authors.initials: M
authors.lastname: Tachikawa
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nagai
authors.forename: Fumi
authors.initials: F
authors.lastname: Tashiro
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Youichi
authors.initials: Y
authors.lastname: Tajima
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Takeda
authors.forename: Tamao
authors.initials: T
authors.lastname: Endo
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Campbell
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Toda
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D049030:Dystroglycans / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D006031:Glycosylation; D006801:Humans; D007797:Laminin / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000378:metabolism; D009136:Muscular Dystrophies / Q000235:genetics / Q000378:metabolism* / Q000628:therapy; D016254:Mutagenesis, Insertional; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D014166:Transferases
chemical_list: D007797:Laminin; D011506:Proteins; D049030:Dystroglycans; C491879:Fcmd protein, mouse; D014166:Transferases; C502747:Large1 protein, mouse; D017351:N-Acetylglucosaminyltransferases