ZFIN ID: ZDB-PUB-130313-10
Mutations in B3GALNT2 Cause Congenital Muscular Dystrophy and Hypoglycosylation of alpha-Dystroglycan
Stevens, E., Carss, K.J., Cirak, S., Foley, A.R., Torelli, S., Willer, T., Tambunan, D.E., Yau, S., Brodd, L., Sewry, C.A., Feng, L., Haliloglu, G., Orhan, D., Dobyns, W.B., Enns, G.M., Manning, M., Krause, A., Salih, M.A., Walsh, C.A., Hurles, M., Campbell, K.P., Manzini, M.C., Stemple, D., Lin, Y.Y., and Muntoni, F.
Date: 2013
Source: American journal of human genetics   92(3): 354-365 (Journal)
Registered Authors: Lin, Yung-Yao, Stemple, Derek L.
Keywords: none
MeSH Terms:
  • Animals
  • Brain/enzymology
  • Brain/metabolism
  • Cell Line
  • Dystroglycans/genetics*
  • Dystroglycans/metabolism
  • Endoplasmic Reticulum/enzymology
  • Endoplasmic Reticulum/genetics
  • Endoplasmic Reticulum/metabolism
  • Female
  • Fibroblasts/enzymology
  • Fibroblasts/metabolism
  • Genetic Predisposition to Disease
  • Glycosylation
  • Humans
  • Infant
  • Male
  • Muscle, Skeletal/enzymology
  • Muscle, Skeletal/metabolism
  • Muscular Dystrophies/enzymology
  • Muscular Dystrophies/genetics*
  • Muscular Dystrophies/metabolism
  • Mutation*
  • N-Acetylgalactosaminyltransferases/genetics*
  • N-Acetylgalactosaminyltransferases/metabolism
  • Zebrafish
PubMed: 23453667 Full text @ Am. J. Hum. Genet.

Mutations in several known or putative glycosyltransferases cause glycosylation defects in α-dystroglycan (α-DG), an integral component of the dystrophin glycoprotein complex. The hypoglycosylation reduces the ability of α-DG to bind laminin and other extracellular matrix ligands and is responsible for the pathogenesis of an inherited subset of muscular dystrophies known as the dystroglycanopathies. By exome and Sanger sequencing we identified two individuals affected by a dystroglycanopathy with mutations in β-1,3-N-acetylgalactosaminyltransferase 2 (B3GALNT2). B3GALNT2 transfers N-acetyl galactosamine (GalNAc) in a β-1,3 linkage to N-acetyl glucosamine (GlcNAc). A subsequent study of a separate cohort of individuals identified recessive mutations in four additional cases that were all affected by dystroglycanopathy with structural brain involvement. We show that functional dystroglycan glycosylation was reduced in the fibroblasts and muscle (when available) of these individuals via flow cytometry, immunoblotting, and immunocytochemistry. B3GALNT2 localized to the endoplasmic reticulum, and this localization was perturbed by some of the missense mutations identified. Moreover, knockdown of b3galnt2 in zebrafish recapitulated the human congenital muscular dystrophy phenotype with reduced motility, brain abnormalities, and disordered muscle fibers with evidence of damage to both the myosepta and the sarcolemma. Functional dystroglycan glycosylation was also reduced in the b3galnt2 knockdown zebrafish embryos. Together these results demonstrate a role for B3GALNT2 in the glycosylation of α-DG and show that B3GALNT2 mutations can cause dystroglycanopathy with muscle and brain involvement.