A Zebrafish Model Of PMM2-CDG Reveals Altered Neurogenesis And A Substrate-Accumulation Mechanism For N-Linked Glycosylation Deficiency

Cline, A., Gao, N., Flanagan-Steet, H., Sharma, V., Rosa, S., Sonon, R., Azadi, P., Sadler, K.C., Freeze, H.H., Lehrman, M.A., and Steet, R.
Molecular biology of the cell   23(21): 4175-4187 (Journal)
Registered Authors
Flanagan-Steet, Heather, Rosa, Sabrina, Sadler Edepli, Kirsten C., Steet, Richard
MeSH Terms
  • Animals
  • Cartilage/drug effects
  • Cartilage/embryology
  • Cartilage/pathology
  • Cell Shape/drug effects
  • Chondrocytes/drug effects
  • Chondrocytes/metabolism
  • Chondrocytes/pathology
  • Congenital Disorders of Glycosylation/enzymology*
  • Congenital Disorders of Glycosylation/genetics
  • Congenital Disorders of Glycosylation/pathology*
  • Craniofacial Abnormalities/embryology
  • Craniofacial Abnormalities/pathology
  • Disease Models, Animal
  • Embryo, Nonmammalian/abnormalities
  • Embryo, Nonmammalian/drug effects
  • Embryo, Nonmammalian/enzymology
  • Gene Expression Regulation, Developmental/drug effects
  • Glycosylation/drug effects
  • Lipopolysaccharides/metabolism
  • Mannose-6-Phosphate Isomerase/metabolism
  • Mannosephosphates/metabolism
  • Morpholinos/pharmacology
  • Motor Neurons/drug effects
  • Motor Neurons/pathology
  • Movement/drug effects
  • Neurogenesis*/drug effects
  • Phosphotransferases (Phosphomutases)/deficiency
  • Phosphotransferases (Phosphomutases)/genetics
  • Phosphotransferases (Phosphomutases)/metabolism*
  • Skull/abnormalities
  • Skull/drug effects
  • Skull/embryology
  • Spinal Cord/drug effects
  • Spinal Cord/embryology
  • Spinal Cord/pathology
  • Substrate Specificity/drug effects
  • Zebrafish/embryology
  • Zebrafish/genetics
  • Zebrafish/metabolism*
  • Zebrafish Proteins/deficiency
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
22956764 Full text @ Mol. Biol. Cell

Congenital Disorder of Glycosylation PMM2-CDG results from mutations in PMM2, which encodes the phosphomannomutase that converts mannose-6-P to mannose-1-P. Patients have wide-spectrum clinical abnormalities associated with impaired protein N-glycosylation. Though widely proposed that PMM2 deficiency depletes mannose-1-P, a precursor of GDP-mannose, and consequently suppresses lipid-linked oligosaccharide (LLO) levels needed for N-glycosylation, these deficiencies have not been demonstrated in patients or any animal model. Here, we report a morpholino-based PMM2-CDG model in zebrafish. Morphant embryos had developmental abnormalities consistent with PMM2-CDG patients, including craniofacial defects and impaired motility associated with altered motor neurogenesis within the spinal cord. Significantly, global N-linked glycosylation and LLO levels were reduced in pmm2 morphants. While mannose-1-P and GDP-mannose were below reliable detection/quantification limits, Pmm2 depletion unexpectedly caused accumulation of mannose-6-P, shown earlier to promote LLO cleavage in vitro. In pmm2 morphants, the free glycan by-products of LLO cleavage increased nearly twofold. Suppression of the mannose-6-P synthesizing enzyme, mannose phosphate isomerase, within the pmm2 background normalized mannose-6-P levels and certain aspects of the craniofacial phenotype, and abrogated pmm2-dependent LLO cleavage. In summary, we report the first zebrafish model of PMM2-CDG and uncover novel cellular insights not possible with other systems, including a mannose-6-P accumulation mechanism for under-glycosylation.

Genes / Markers
Mutation and Transgenics
Human Disease / Model Data
Sequence Targeting Reagents
Engineered Foreign Genes
Errata and Notes