title: A Novel N-Tetrasaccharide in Patients with Congenital Disorders of Glycosylation, Including Asparagine-Linked Glycosylation Protein 1, Phosphomannomutase 2, and Mannose Phosphate Isomerase Deficiencies.
abstract: BACKGROUND
  Primary deficiencies in mannosylation of N-glycans are seen in a majority of patients with congenital disorders of glycosylation (CDG). We report the discovery of a series of novel N-glycans in sera, plasma, and cultured skin fibroblasts from patients with CDG having deficient mannosylation.
  
  
  METHODS
  We used LC-MS/MS and MALDI-TOF-MS analysis to identify and quantify a novel N-linked tetrasaccharide linked to the protein core, an N-tetrasaccharide (Neu5Acα2,6Galβ1,4-GlcNAcβ1,4GlcNAc) in plasma, serum glycoproteins, and a fibroblast lysate from patients with CDG caused by ALG1 [ALG1 (asparagine-linked glycosylation protein 1), chitobiosyldiphosphodolichol β-mannosyltransferase], PMM2 (phosphomannomutase 2), and MPI (mannose phosphate isomerase).
  
  
  RESULTS
  Glycoproteins in sera, plasma, or cell lysate from ALG1-CDG, PMM2-CDG, and MPI-CDG patients had substantially more N-tetrasaccharide than unaffected controls. We observed a >80% decline in relative concentrations of the N-tetrasaccharide in MPI-CDG plasma after mannose therapy in 1 patient and in ALG1-CDG fibroblasts in vitro supplemented with mannose.
  
  
  CONCLUSIONS
  This novel N-tetrasaccharide could serve as a diagnostic marker of ALG1-, PMM2-, or MPI-CDG for screening of these 3 common CDG subtypes that comprise >70% of CDG type I patients. Its quantification by LC-MS/MS may be useful for monitoring therapeutic efficacy of mannose. The discovery of these small N-glycans also indicates the presence of an alternative pathway in N-glycosylation not recognized previously, but its biological significance remains to be studied.
authors.affiliation: Department of Human Genetics and.
authors.forename: Wenyue
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Division of Genetics, Department of Medicine, Children's Hospital Boston, Boston, MA; Department of Pediatrics, Harvard Medical School, Boston, MA;
authors.forename: Philip M
authors.initials: PM
authors.lastname: James
authors.affiliation: Human Genetics Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA;
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Ng
authors.affiliation: Palmieri Metabolic Disease Laboratory, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Xueli
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Human Genetics and.
authors.forename: Baoyun
authors.initials: B
authors.lastname: Xia
authors.affiliation: Department of Human Genetics and.
authors.forename: Jiang
authors.initials: J
authors.lastname: Rong
authors.affiliation: Department of Human Genetics and.
authors.forename: Ghazia
authors.initials: G
authors.lastname: Asif
authors.affiliation: Mayo Biochemical Genetics Laboratory, Mayo Medical School, Rochester, MN;
authors.forename: Kimiyo
authors.initials: K
authors.lastname: Raymond
authors.affiliation: Department of Human Genetics and.
authors.forename: Melanie A
authors.initials: MA
authors.lastname: Jones
authors.affiliation: Department of Human Genetics and.
authors.forename: Madhuri
authors.initials: M
authors.lastname: Hegde
authors.affiliation: Palmieri Metabolic Disease Laboratory, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Tongzhong
authors.initials: T
authors.lastname: Ju
authors.affiliation: Department of Biochemistry, Emory University, Atlanta, GA;
authors.forename: Richard D
authors.initials: RD
authors.lastname: Cummings
authors.affiliation: Mayo Biochemical Genetics Laboratory, Mayo Medical School, Rochester, MN;
authors.forename: Katie
authors.initials: K
authors.lastname: Clarkson
authors.affiliation: Greenwood Genetics Center, Greenwood, SC;
authors.forename: Tim
authors.initials: T
authors.lastname: Wood
authors.affiliation: Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada;
authors.forename: Cornelius F
authors.initials: CF
authors.lastname: Boerkoel
authors.affiliation: Human Genetics Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA;
authors.forename: Hudson H
authors.initials: HH
authors.lastname: Freeze
authors.affiliation: Palmieri Metabolic Disease Laboratory, Children's Hospital of Philadelphia, Philadelphia, PA; Department of Pathology and Laboratory of Medicine, University of Pennsylvania, Philadelphia, PA. hem@email.chop.edu.
authors.forename: Miao
authors.initials: M
authors.lastname: He
mesh_terms: D002851:Chromatography, High Pressure Liquid; D018981:Congenital Disorders of Glycosylation / Q000175:diagnosis* / Q000378:metabolism; D006801:Humans; D008359:Mannose-6-Phosphate Isomerase / Q000032:analysis* / Q000172:deficiency* / Q000378:metabolism; D008364:Mannosyltransferases / Q000032:analysis* / Q000172:deficiency* / Q000378:metabolism; D009844:Oligosaccharides / Q000032:analysis* / Q000378:metabolism; D017875:Phosphotransferases (Phosphomutases) / Q000032:analysis* / Q000172:deficiency* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D009844:Oligosaccharides; D008364:Mannosyltransferases; C035777:chitobiosyldiphosphodolichol beta-mannosyltransferase; D008359:Mannose-6-Phosphate Isomerase; D017875:Phosphotransferases (Phosphomutases); C519582:phosphomannomutase 2, human