Multi-allelic origin of congenital disorder of glycosylation (CDG)-Ic

Abstract. Congenital disorders of glycosylation (CDG), formerly known as carbohydrate-deficient glycoprotein syndrome, represent a family of genetic diseases with variable clinical presentations. Common to all types of CDG characterized to date is a defective Asn-linked glycosylation caused by enzymatic defects of N-glycan synthesis. Previously, we have identified a mutation in the ALG6 α1,3 glucosyltransferase gene as the cause of CDG-Ic in four related patients. Here, we present the identification of seven additional cases of CDG-Ic among a group of 35 untyped CDG patients. Analysis of lipid-linked oligosaccharides in fibroblasts confirmed the accumulation of dolichyl pyrophosphate-Man9GlcNAc2 in the CDG-Ic patients. The genomic organization of the human ALG6 gene was determined, revealing 14 exons spread over 55 kb. By polymerase chain reaction amplification and sequencing of ALG6 exons, three mutations, in addition to the previously described A333 V substitution, were detected in CDG-Ic patients. The detrimental effect of these mutations on ALG6 activity was confirmed by complementation of alg6 yeast mutants. Haplotype analysis of CDG-Ic patients revealed a founder effect for the ALG6 allele bearing the A333 V mutation. Although more than 80% of CDG are type Ia, CDG-Ic may be the second most common form of the disease.

[1]  M. Aebi,et al.  The yeast WBP1 is essential for oligosaccharyl transferase activity in vivo and in vitro. , 1992, The EMBO journal.

[2]  H. Freeze,et al.  Dolichol phosphate mannose synthase (DPM1) mutations define congenital disorder of glycosylation Ie (CDG-Ie) , 2000, The Journal of clinical investigation.

[3]  H. G. van Eijk,et al.  Microheterogeneity of human serum transferrin: A biological phenomenon studied by isoelectric focusing in immobilized pH gradients , 1988, Electrophoresis.

[4]  M. Aebi,et al.  The ALG10 locus of Saccharomyces cerevisiae encodes the alpha-1,2 glucosyltransferase of the endoplasmic reticulum: the terminal glucose of the lipid-linked oligosaccharide is required for efficient N-linked glycosylation. , 1998, Glycobiology.

[5]  F. Hanefeld,et al.  Carbohydrate-deficient glycoprotein syndrome type V: deficiency of dolichyl-P-Glc:Man9GlcNAc2-PP-dolichyl glucosyltransferase. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[6]  J. Weissenbach,et al.  A first-generation physical map of the human genome , 1993, Nature.

[7]  A. Myers,et al.  Yeast/E. coli shuttle vectors with multiple unique restriction sites , 1986, Yeast.

[8]  J. Hofsteenge,et al.  Protein C-mannosylation is enzyme-catalysed and uses dolichyl-phosphate-mannose as a precursor. , 1998, Molecular biology of the cell.

[9]  G. Matthijs,et al.  Evidence for genetic heterogeneity in the carbohydrate-deficient glycoprotein syndrome type I (CDG1). , 1996, Genomics.

[10]  M. Aebi,et al.  STT3, a highly conserved protein required for yeast oligosaccharyl transferase activity in vivo. , 1995, The EMBO journal.

[11]  E. Berger,et al.  Deficiency of dolichol-phosphate-mannose synthase-1 causes congenital disorder of glycosylation type Ie. , 2000, The Journal of clinical investigation.

[12]  H. Freeze,et al.  Carbohydrate-deficient glycoprotein syndrome type Ib. Phosphomannose isomerase deficiency and mannose therapy. , 1998, The Journal of clinical investigation.

[13]  W. Gahl,et al.  Carbohydrate-deficient glycoprotein syndrome. , 1997, Advances in pediatrics.

[14]  J. Jaeken,et al.  Mutations in the MGAT2 gene controlling complex N-glycan synthesis cause carbohydrate-deficient glycoprotein syndrome type II, an autosomal recessive disease with defective brain development. , 1996, American journal of human genetics.

[15]  H. Stroink,et al.  Clinical and biochemical characteristics of congenital disorder of glycosylation type Ic, the first recognized endoplasmic reticulum defect in N‐glycan synthesis , 2000, Annals of neurology.

[16]  J. Sambrook,et al.  Molecular Cloning: A Laboratory Manual , 2001 .

[17]  E. Berger,et al.  A mutation in the human ortholog of the Saccharomyces cerevisiae ALG6 gene causes carbohydrate-deficient glycoprotein syndrome type-Ic. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[18]  M. Aebi,et al.  Isolation of the ALG6 locus of Saccharomyces cerevisiae required for glucosylation in the N-linked glycosylation pathway. , 1996, Glycobiology.

[19]  E. Pardon,et al.  Mutations in PMM2, a phosphomannomutase gene on chromosome 16p13 in carbohydrate-deficient glycoprotein type I syndrome (Jaeken syndrome) , 1997, Nature Genetics.

[20]  E. Bertini,et al.  Phosphomannose isomerase deficiency: a carbohydrate-deficient glycoprotein syndrome with hepatic-intestinal presentation. , 1998, American journal of human genetics.

[21]  G. Fink,et al.  Genetic screens and selections for cell and nuclear fusion mutants. , 1991, Methods in enzymology.

[22]  J. Jaeken,et al.  The carbohydrate-deficient glycoprotein syndromes: pre-Golgi and Golgi disorders? , 1993, Glycobiology.

[23]  E. Yeh,et al.  Identification of defects in glycosylphosphatidylinositol anchor biosynthesis in the Thy-1 expression mutants. , 1991, The Journal of biological chemistry.

[24]  P. Robbins,et al.  Two yeast mutations in glucosylation steps of the asparagine glycosylation pathway. , 1984, The Journal of biological chemistry.

[25]  A. Düsterhöft,et al.  Stepwise assembly of the lipid-linked oligosaccharide in the endoplasmic reticulum of Saccharomyces cerevisiae: identification of the ALG9 gene encoding a putative mannosyl transferase. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[26]  J. Scott,et al.  New vectors for construction of recombinant high-copy-number yeast acentric-ring plasmids. , 1985, Gene.

[27]  R. Spiro,et al.  Transfer of glucose to oligosaccharide-lipid intermediates by thyroid microsomal enzymes and its relationship to the N-glycosylation of proteins. , 1981, The Journal of biological chemistry.

[28]  E. Berger,et al.  A novel carbohydrate-deficient glycoprotein syndrome characterized by a deficiency in glucosylation of the dolichol-linked oligosaccharide. , 1998, The Journal of clinical investigation.

[29]  K. Yamashita.  Carbohydrate-deficient glycoprotein syndrome type I. , 1996 .