Congenital disorders of glycosylation type Ig is defined by a deficiency in dolichyl-P-mannose:Man7GlcNAc2-PP-dolichyl mannosyltransferase.
Type I congenital disorders of glycosylation (CDG I) are diseases presenting multisystemic lesions including central and peripheral nervous system deficits. The disease is characterized by under-glycosylated serum glycoproteins and is caused by mutations in genes encoding proteins involved in the stepwise assembly of dolichol-oligosaccharide used for protein N-glycosylation. We report that fibroblasts from a type I CDG patient, born of consanguineous parents, are deficient in their capacity to add the eighth mannose residue onto the lipid-linked oligosaccharide precursor. We have characterized cDNA corresponding to the human ortholog of the yeast gene ALG12 that encodes the dolichyl-P-Man:Man(7)GlcNAc(2)-PP-dolichyl alpha6-mannosyltransferase that is thought to accomplish this reaction, and we show that the patient is homozygous for a point mutation (T571G) that causes an amino acid substitution (F142V) in a conserved region of the protein. As the pathological phenotype of the fibroblasts of the patient was largely normalized upon transduction with the wild type gene, we demonstrate that the F142V substitution is the underlying cause of this new CDG, which we suggest be called CDG Ig. Finally, we show that the fibroblasts of the patient are capable of the direct transfer of Man(7)GlcNAc(2) from dolichol onto protein and that this N-linked structure can be glucosylated by UDP-glucose:glycoprotein glucosyltransferase in the endoplasmic reticulum.
Chantret
Isabelle
I
Unité de Glycobiologie et Signalisation Cellulaire, INSERM U504, Bâtiment INSERM, 16 Avenue Paul Vaillant-Couturier, 94807 Villejuif, France.
Dupré
Thierry
T
Delenda
Christophe
C
Bucher
Stéphanie
S
Dancourt
Julia
J
Barnier
Anne
A
Charollais
Aude
A
Heron
Delphine
D
Bader-Meunier
Brigitte
B
Danos
Olivier
O
Seta
Nathalie
N
Durand
Geneviève
G
Oriol
Rafael
R
Codogno
Patrice
P
Moore
Stuart E H
SE
D000595:Amino Acid Sequence; D001483:Base Sequence; D002239:Carbohydrate Metabolism, Inborn Errors / Q000175:diagnosis / Q000201:enzymology* / Q000235:genetics; D002478:Cells, Cultured; D017931:DNA Primers; D020224:Expressed Sequence Tags; D005260:Female; D006031:Glycosylation; D006801:Humans; D007231:Infant, Newborn; D008364:Mannosyltransferases / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D008364:Mannosyltransferases; C066968:dolichyl-P-Man:Man(5)GlcNAc(2)-PP-dolichol alpha-1,3-mannosyltransferase