title: A severe human metabolic disease caused by deficiency of the endoplasmatic mannosyltransferase hALG11 leads to congenital disorder of glycosylation-Ip.
abstract: A new type of congenital disorders of glycosylation, designated CDG-Ip, is caused by the deficiency of GDP-Man:Man3GlcNAc2-PP-dolichol-alpha1,2-mannosyltransferase, encoded by the human ortholog of ALG11 from yeast. The patient presented with a multisystemic disorder characterized by muscular hypotonia, seizures, developmental retardation and death at the age of 2 years. The isoelectric focusing pattern of the patient's serum transferrin showed the partial loss of complete N-glycan side chains, which is a characteristic sign for CDG-I. Analysis of dolichol-linked oligosaccharides in patient-derived fibroblasts revealed an accumulation of Man3GlcNAc2-PP-dolichol and Man4GlcNAc2-PP-dolichol. Determination of mannosyltransferase activities of early steps of lipid-linked oligosaccharide biosynthesis in fibroblasts indicated that the patient was deficient in elongating Man3GlcNAc2-PP-dolichol. These findings gave rise to genetic analysis of the hALG11 cDNA, in which homozygosity for mutation c.T257C (p.L86S) was identified. Verification of the mutation as a primary cause for the genetic defect was proved by retroviral expression of human wild-type and mutated ALG11 cDNA in patient-derived fibroblasts as well as using a yeast alg11 deletion strain as a heterologous expression system for hALG11 variants. Immunofluorescence examinations combined with western blotting showed no differences of intracellular localization or expression of ALG11 between control and patient fibroblasts, respectively, indicating no mislocalization or degradation of the mutated transferase.
authors.affiliation: Center for Child and Adolescent Medicine, Center for Metabolic Diseases Heidelberg, Department I, Im Neuenheimer Feld 153, D-69120 Heidelberg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Rind
authors.forename: Verena
authors.initials: V
authors.lastname: Schmeiser
authors.forename: Christian
authors.initials: C
authors.lastname: Thiel
authors.forename: Birgit
authors.initials: B
authors.lastname: Absmanner
authors.forename: Jürgen
authors.initials: J
authors.lastname: Lübbehusen
authors.forename: Julia
authors.initials: J
authors.lastname: Hocks
authors.forename: Neophytos
authors.initials: N
authors.lastname: Apeshiotis
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Wilichowski
authors.forename: Ludwig
authors.initials: L
authors.lastname: Lehle
authors.forename: Christian
authors.initials: C
authors.lastname: Körner
mesh_terms: D000595:Amino Acid Sequence; D002239:Carbohydrate Metabolism, Inborn Errors / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005936:Glucans / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007223:Infant; D008364:Mannosyltransferases / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics; D008969:Molecular Sequence Data; D021381:Protein Transport; D016415:Sequence Alignment
chemical_list: D005936:Glucans; C552163:ALG11 protein, human; D008364:Mannosyltransferases