Residual laminin-binding activity and enhanced dystroglycan glycosylation by LARGE in novel model mice to dystroglycanopathy.
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.
Kanagawa
Motoi
M
Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Nishimoto
Akemi
A
Chiyonobu
Tomohiro
T
Takeda
Satoshi
S
Miyagoe-Suzuki
Yuko
Y
Wang
Fan
F
Fujikake
Nobuhiro
N
Taniguchi
Mariko
M
Lu
Zhongpeng
Z
Tachikawa
Masaji
M
Nagai
Yoshitaka
Y
Tashiro
Fumi
F
Miyazaki
Jun-Ichi
J
Tajima
Youichi
Y
Takeda
Shin'ichi
S
Endo
Tamao
T
Kobayashi
Kazuhiro
K
Campbell
Kevin P
KP
Toda
Tatsushi
T
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
D007797:Laminin; D011506:Proteins; D049030:Dystroglycans; C491879:Fcmd protein, mouse; D014166:Transferases; C502747:Large1 protein, mouse; D017351:N-Acetylglucosaminyltransferases