Disorder Of Glycosylation Type Ia Research Articles

Gastrointestinal and other clinical manifestations in 17 children with congenital disorders of glycosylation type Ia, Ib, and Ic.

The typical signs and symptoms of congenital disorders of glycosylation (CDG) include dysmorphy, failure to thrive, and neurologic abnormalities. However, more and more children diagnosed at a young age are not dysmorphic and do not have neurologic involvement. The authors studied the gastrointestinal and other clinical manifestations of CDG type Ia, Ib, and Ic. As of January 2003, 17 children were identified with CDG at the authors' institution. The medical records of the patients were reviewed. Five children had CDG Ia, three children CDG Ib, and nine children CDG Ic. Age at diagnosis ranged from 2 months to 15 years. Failure to thrive was present in 80% of patients with CDG Ia, in 66% of those with CDG Ib, and in 11% of those with CDG Ic. Five children had protein-losing enteropathy (two CDG Ia, two CDG Ib, and one CDG Ic). Hepatomegaly was present in 40% of patients with CDG Ia, in 66% of those with CDG Ib, and in 11% of those with CDG Ic. In CDG Ic, hepatomegaly was transient. In CDG Ia, histologic analysis of the liver showed swollen hepatocytes, steatosis, and fibrosis. In CDG Ib, hamartomatous collections of bile ducts were seen. In one patient with CDG Ib, the clinical picture was restricted to congenital hepatic fibrosis for more than a decade. The study confirms the heterogeneity of the clinical picture in children with CDG type Ia, Ib, and Ic. Children with protein-losing enteropathy should be tested for CDG. Protein-losing enteropathy can be caused, not only by CDG Ia and Ib, but also by type Ic. Children with congenital hepatic fibrosis should be tested for CDG, even in the absence of other symptoms. In CDG Ib, histologic analysis of the liver showed hamartomatous collections of bile ducts (Meyenburg complex).

Gastrointestinal and Other Clinical Manifestations in 17 Children With Congenital Disorders of Glycosylation Type Ia, Ib, and Ic

ABSTRACTObjectivesThe typical signs and symptoms of congenital disorders of glycosylation (CDG) include dysmorphy, failure to thrive, and neurologic abnormalities. However, more and more children diagnosed at a young age are not dysmorphic and do not have neurologic involvement. The authors studied the gastrointestinal and other clinical manifestations of CDG type Ia, Ib, and Ic.MethodsAs of January 2003, 17 children were identified with CDG at the authors' institution. The medical records of the patients were reviewed.ResultsFive children had CDG Ia, three children CDG Ib, and nine children CDG Ic. Age at diagnosis ranged from 2 months to 15 years. Failure to thrive was present in 80% of patients with CDG Ia, in 66% of those with CDG Ib, and in 11% of those with CDG Ic. Five children had protein‐losing enteropathy (two CDG Ia, two CDG Ib, and one CDG Ic). Hepatomegaly was present in 40% of patients with CDG Ia, in 66% of those with CDG Ib, and in 11% of those with CDG Ic. In CDG Ic, hepatomegaly was transient. In CDG Ia, histologic analysis of the liver showed swollen hepatocytes, steatosis, and fibrosis. In CDG Ib, hamartomatous collections of bile ducts were seen. In one patient with CDG Ib, the clinical picture was restricted to congenital hepatic fibrosis for more than a decade.ConclusionsThe study confirms the heterogeneity of the clinical picture in children with CDG type Ia, Ib, and Ic. Children with protein‐losing enteropathy should be tested for CDG. Protein‐losing enteropathy can be caused, not only by CDG Ia and Ib, but also by type Ic. Children with congenital hepatic fibrosis should be tested for CDG, even in the absence of other symptoms. In CDG Ib, histologic analysis of the liver showed hamartomatous collections of bile ducts (Meyenburg complex).

CycloSaligenyl‐mannose‐1‐monophosphates as a New Strategy in CDG‐Ia Therapy: Hydrolysis, Mechanistic Insights and Biological Activity

AbstractPhosphomannomutase 2 (PMM‐2) deficiency leads to an inefficient intracellular formation of mannose‐1‐phosphate (1), which causes an inherited metabolic disease with multisystemic abnormalities (Congenital Disorder of Glycosylation type Ia, CDG‐Ia). In order to circumvent this metabolic deficiency, the cycloSal approach was applied for the intracellular delivery of mannose‐1‐monophosphate (1). cycloSaligenyl‐pyranose‐1‐monophosphates 6−11 were obtained by a phosphitylation/oxidation procedure starting from appropriately protected D‐pyranoses. The chemical hydrolysis data and the involved hydrolysis mechanisms of cyclosaligenyl‐mannose‐1‐monophosphates 6−9 and their epimeric glucose analogues 10, 11 are reported. Furthermore, the biological activity of cycloSal‐mannose‐1‐phosphates 6−9 was tested in vitro in PMM‐2‐deficient fibroblasts. 3‐Methyl‐cycloSal‐2,3,4,6‐tetra‐O‐acetyl‐α‐D‐mannopyranose‐1‐monophosphate (8) showed a total correction of the phenotype, thus proving the delivery of mannose‐1‐phosphate. This may offer a suitable possibility for a therapy of CDG‐Ia. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Novel nonsense mutation (R194X) in the PMM2 gene in a Japanese patient with congenital disorder of glycosylation type Ia

A Japanese boy had clinical features of congenital disorder of glycosylation type Ia (CDG Ia, also known as carbohydrate-deficient-glycoprotein syndrome, previously), and enzymatic and molecular assay of phosphomannomutase confirmed this diagnosis. During infancy, the patient showed delayed mental and motor development, hypotonia, ataxia, hepatomegaly, liver dysfunction, abnormal coagulation system and cerebellar hypoplasia. At present, though he is 3 years and 8 months old, he cannot utter meaningful words or sit by himself. These findings suggested that he had one of the severe phenotypes of Japanese CDG Ia. Mutational analysis demonstrated heterozygosity for the missense mutation in exon 4 (P113L) and a novel nonsense mutation in exon 7 (R194X). We report his clinical course and the results of molecular assay, and discuss correlation between clinical severity and genotype.

Phosphomannomutase activity in congenital disorders of glycosylation type Ia determined by direct analysis of the interconversion of mannose-1-phosphate to mannose-6-phosphate by high-pH anion-exchange chromatography with pulsed amperometric detection

Congenital disorders of glycosylation (CDG) are a group of multisystemic disorders resulting from defects in the synthesis and processing of N-linked oligosaccharides. The most common form, CDG type Ia (CDG-Ia), results from a deficiency of the enzyme phosphomannomutase (PMM). PMM converts mannose 6-phosphate (man-6-P) to mannose-1-phosphate (man-1-P), which is required for the synthesis of GDP-mannose, a substrate for dolichol-linked oligosaccharide synthesis. The traditional assay for PMM, a coupled enzyme system based on the reduction of NADP + to NADPH using man-1-P as a substrate, has limitations in accuracy and reproducibility. Therefore, a more sensitive, direct test for PMM activity, based on the detection of the conversion of man-1-P to man-6-P by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), was developed. Using this assay, the activity of PMM was markedly deficient in fibroblasts and lymphoblasts from 23 patients with CDG-Ia (range 0–15.3% of control, average 4.9±4.7%) and also decreased in seven obligate heterozygotes (range 33.0–72.0% of control, average 52.2±14.7%). Unlike the spectrophotometric method, there was no overlap in PMM activity among patients, obligate heterozygotes, or controls. Thus, the PMM assay based on HPAEC-PAD has increased utility in the clinical setting, and can be used, together with transferrin isoelectric focusing, to diagnose patients with CDG-Ia and to identify heterozygotes when clinically indicated.

Biochemical and molecular studies in 26 Spanish patients with congenital disorder of glycosylation type Ia.

We present our experience with the diagnosis of 26 patients (19 families) with congenital disorders of glycosylation classified as type Ia due to PMM deficiency. In all but one of these CDG Ia families the patients are compound heterozygous for mutations in PMM2. Eighteen different mutations were detected. In contrast to other series in which R141H represents 43-50% of the alleles, only 9/36 (25%) alleles have this mutation. Two mutations (R123Q and T237M) have been found on three disease chromosomes, four (V44A, Y64C, P113L and F207S) on two disease chromosomes and 12 mutations (D65Y, Y76C, IVS3+2C>T, E93A, R123X, V129M, I153T, F157S, E197A, N216I, T226S, C241S) only on one disease chromosome. V44A and D65Y probably originated in the Iberian peninsula, as they have only been reported in Portuguese and Latin-American patients; Y64C, Y76C, R123X and F207S have not been detected in other patients. R123X is the only stop codon mutation so far described in PMM2. The common European F119L mutation has not been found in our patients, although it is very frequent in other populations (43% allele frequency in Danish patients). Probably because of this genetic heterogeneity, Spanish patients show very diverse phenotypes that are, in general, milder than in other series. This points to the necessity of widening the criteria for CDG in the routine screening for inborn metabolic diseases.

Neurological Presentation in Pediatric Patients with Congenital Disorders of Glycosylation Type Ia

Congenital disorders of glycosylation (CDG), formerly called carbohydrate-deficient glycoprotein syndromes, constitute a newly identified group of multisystem disorders characterized by defective glycosylation of N-glycosylated proteins. The objective of this work was to describe precisely neurological findings in patients with type Ia CDG (CDG-Ia) and to compare our results with the literature. We retrospectively reviewed neurological and neurodevelopmental, neuroimaging, and genetic features in ten patients with CDG-Ia who mainly presented with neurological abnormalities during childhood and therefore were referred to a neuropediatrician or a neurogeneticist. Neurological manifestations had a static clinical course, dominated by mental retardation and cerebellar dysfunction, and acute episodes: stroke-like episodes and seizures. However, microcephaly, retinopathy, and polyneuropathy were progressive. All patients had severe global neurodevelopmental delay: only one was able to walk alone at ten years of age and only one could read. Marked heterogeneity in manifestations and delay of diagnosis was noted across the patients. Cerebellar hypoplasia was found by magnetic resonance imaging in all ten patients and olivopontocerebellar hypoplasia in four patients. As in the literature, there was no clear phenotype-mutation correlation. Our findings confirm the importance of a precise and complete description of the neurological and neuroradiological phenotype delineating the phenotype of CDG-Ia to increase the likelihood of diagnosing the disease.

Mass spectrometric analysis of human transferrin in different body fluids.

In this study, we present a versatile new procedure for the analysis of transferrin and its isoforms isolated from human body fluids such as serum, plasma, and cerebrospinal fluid. This method is based on a three-step procedure: (i) isolation of transferrins using anion-exchange chromatography with UV detection; (ii) concentration of the transferrin fraction; (iii) detection of the transferrins with liquid chromatography-electrospray mass spectrometry. Pre-analytical sample procedures can be omitted and no immunoaffinity columns or transferrin-specific immunoassays were used. Anticoagulants such as heparin, EDTA, citrate, and oxalate do not interfere with our analysis. According to their respective molecular masses, up to ten different isoforms of transferrin could be identified in a serum sample from a patient with a congenital disorder of glycosylation type Ia (CDG-Ia). The method was successfully applied to different pathological samples from patients with CDG-Ia, CDG-Ib, CDG-Ic, CDG-Ie, CDG-If, and CDG-IIa. Additionally, samples from alcohol consumers that were found with turbidimetric immunoassay to contain increased levels of carbohydrate-deficient transferrin were analyzed.

Ophthalmic manifestations of congenital disorder of glycosylation type 1a

Purpose: To present the ophthalmic manifestations of patients with congenital disorder of glycosylation type Ia (CDG-Ia) due to the frequent R141H/F119L PMM2 genotype. Methods: Ophthalmic records of 23 patients (age: 10 months to 20 years) were evaluated. They had had at least one ophthalmic reexamination. Results: Measurements of refractive error showed that 18 patients were myopic, two were hypermetropic, and three could not be measured. Serial measurements in 12 patients indicated a progression towards myopia of 0.80 diopters (D) per year. Congenital esotropia and delayed visual maturation (DVM) were consistent findings. Two children developed good visual acuity (VA), 16 had low vision, and five were legally blind. Pallor of the optic disc was noted in five patients. Electroretinography (ERG) performed in nine patients showed reduced rod responses, while cone responses were only slightly reduced. Conclusions: The present study illustrates the difficulties in examining severely disabled children. Consistent ophthalmic manifestations of CDG-Ia patients due to the R141H/F119L genotype were congenital esotropia, DVM, and a reduced rod response in ERG-examined patients.The vast majority of patients had reduced VA and developed myopia.We speculate that there is a relationship between the glycosylation defect in CDGIa and the development of myopia. We recommend that CDG-Ia patients be followed annually by an ophthalmologist.

Membrane-Permeant derivatives of mannose-1-phosphate

For treatment of congenital disorder of glycosylation type Ia (CDG-Ia) membrane-permeant derivatives of mannose-1-phosphate are required. Employing biologically cleavable phosphate protecting groups advantageous precursor derivatives could be synthesized following a facile approach. Their enzymatic cleavages using esterase from porcine liver (E.C. 3.1.1.1) were investigated.

Prepubertal growth in congenital disorder of glycosylation type Ia (CDG-Ia)

Aims: To delineate the pattern of growth in prepubertal children with congenital disorder of glycosylation type Ia (CDG-Ia) in order to identify critical period(s) and possible cause(s) of growth failure....

Identification of α1-Antitrypsin Variants in Plasma with the Use of Proteomic Technology

Proteomic technology permits the investigation of genetic metabolic diseases at the level of protein expression. Changes in the expression, polypeptide structure, and posttranslational modification of individual proteins can be detected in complex mixtures of proteins. We used high-resolution two-dimensional polyacrylamide gel electrophoresis to separate isoforms of plasma proteins and detect abnormalities of mass and/or charge. We confirmed the identity of the separated proteins by in-gel digestion with proteases and N-glycanases and then analyzed the released peptides and glycans by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry. Complete characterization of the polypeptide sequences and glycosylation of alpha(1)-antitrypsin isoforms was achieved in plasma from controls and from patients with three different known alpha(1)-antitrypsin deficiencies and congenital disorder of glycosylation type Ia. This study shows that proteomic techniques are a powerful and sensitive means of detecting changes in the amino acid sequence and abnormal posttranslational modifications of specific proteins in a complex biologic matrix.

Congenital disorder of glycosylation type Ia (CDG-Ia): phenotypic spectrum of the R141H/F119L genotype

AIMSTo delineate common and variable features and outcome of children with congenital disorder of glycosylation type Ia (CDG-Ia) caused by the frequent R141H/F119LPMM2 genotype.METHODSClinical data on 25 patients (mean age...

Congenital disorders of glycosylation type Ia and IIa are associated with different primary haemostatic complications.

Congenital disorders of glycosylation (CDG) type I are mostly due to a deficient phosphomannomutase activity, called CDG Ia. CDG IIa (mutations in the MGAT2 gene) results from a deficient activity of the Golgi enzyme N-acetylglucosaminyltransferase II. CDG Ia patients predominantly have a thrombotic tendency, whereas our CDG IIa patient has an increased bleeding tendency, despite similar coagulation factor abnormalities in both types. We have investigated whether abnormally glycosylated platelet membrane glycoproteins are involved in the haemostatic complications of both CDG groups. In flow cytometry, the binding of Ricinus communis lectin (reactive with beta-galactose primarily) to control platelets increased after neuraminidase treatment: this increase was smaller (p < 0.01) in CDG Ia patients (3.1 +/- 0.08 times) than in control platelets (8.5 +/- 1.8 times) and did not occur in the CDG IIa patient. Platelet-rich plasma from CDG Ia patients, but not a CDG IIa patient. aggregated spontaneously and gel-filtered platelets from CDG Ia patients agglutinated at very low concentrations of ristocetin, independently of von Willebrand factor (vWF). Accordingly, in stirred whole blood, the rate of single platelet disappearance of CDG Ia patients was twice that of control platelets. In contrast, perfusion of whole anticoagulated blood of the CDG IIa patient over collagen yielded markedly decreased platelet adherence to collagen at shear rates involving glycoprotein (GP) Ib-vWF interactions. Thus, abnormal glycosylation of platelet glycoproteins in CDG Ia enhances nonspecific platelet interactions, in agreement with a thrombotic tendency. The reduced GP Ib-mediated platelet reactivity with vessel wall components in the CDG IIa patient under flow conditions provides a basis for his bleeding tendency.

Neurologic Course of Congenital Disorders of Glycosylation

Congenital disorders of glycosylation, formerly called carbohydrate-deficient glycoprotein syndrome, may present in infancy with slowly progressive neurologic deficits including cognitive impairment, ataxia, pigmentary retinal degeneration, and neuropathy. The metabolic defect is in N-linked oligosaccharide synthesis, and diagnosis is made by a serum transferrin isoelectric focusing. We reviewed the neurologic course of 10 children with congenital disorders of glycosylation (ages 13 months to 7 years). All had severe developmental delay and ataxia; none walked unassisted, and the highest level of communication was simple sign language in one patient. Five of 10 children had seizures (absence, complex partial, tonic clonic). Only one patient has had strokelike episodes, despite reports that they are common in this population. The underlying basis of these episodes has been hypothesized to be coagulopathy due to dysfunctional, incorrectly glycosylated coagulation factors. This 5-year-old patient with congenital disorders of glycosylation type Ia had two strokelike episodes, with evolving hemiparesis over 5 to 6 days' duration, followed by focal tonic-clonic seizures. Coagulation studies were normal. Electroencephalography showed transient hemispheric polymorphous delta-range slowing and suppression. Magnetic resonance imaging revealed corresponding cortical swelling. Magnetic resonance angiography was normal. Magnetic resonance spectroscopy revealed a decrease in the N-acetylaspartate peak, suggesting neuronal loss, with normal lactate peak. The neuroradiologic data do not support a thrombotic, embolic, or hemorrhagic basis for strokelike episodes in carbohydrate-deficient glycoprotein syndrome; other mechanisms must be considered.

Scandinavian CDG-Ia patients: genotype/phenotype correlation and geographic origin of founder mutations.

Congenital disorders of glycosylation type Ia, (previous name carbohydrate-deficient glycoprotein syndrome type Ia; CDG-Ia) is an inherited disorder of the glycosylation of certain glycoproteins. The defect is caused by mutations in the phosphomannomutase 2 (PMM2) gene located in chromosome region 16p13. The purpose of this study was twofold: (1) to investigate the possible correlation between certain genotypes and the phenotype of the patients and their PMM activity, and (2) to study further the founder origin of the Scandinavian mutations. Sixty-four CDG-Ia patients were studied. Regardless of mutation combination, the patients showed the basic neurological symptoms associated with CDG-Ia. However, patients carrying the mutation 548T-->C had less severe disease, e.g., no pericardial effusions, malnutrition, or clinical coagulation disturbances. Liver dysfunction and peripheral neuropathy were milder. In contrast, patients carrying mutation 691G-->A showed a high incidence of severe malnutrition and hepatopathy, and they had the highest mortality including affected siblings. Heterozygotes for the two most common mutations (422G-->A and 357C-->A) displayed a phenotype of variable severity sometimes leading to early death. PMM activity showed no correlation with either genotype or phenotype but was reduced in most patients. There was a pronounced geographic clustering for some of the Scandinavian mutations. For example, 548T-->C was almost exclusively found in patients stemming from southeastern parts of Sweden, whereas 26G-->A was found to cluster in a region in the most southern parts of Sweden, suggesting that these mutations originated in these two regions separately as founder mutations. The most frequent mutation (422G-->A) did not show a specific geographic focus. The widespread 422G-->A mutation is probably an older mutation, although haplotype data from intragenic polymorphisms indicate that this mutation also arose only once. The detailed information of the origin of mutations and their respective associated phenotypic pattern should enable improvements to be made regarding tools for genetic counseling and for prenatal diagnoses in CDG-Ia families.

Increased α3-fucosylation of α 1-acid glycoprotein in patients with congenital disorder of glycosylation type IA (CDG-Ia)

Increased fucosylation of the type (sialyl) Lewis x was detected on the acute-phase plasma protein α 1-acid glycoprotein (AGP) in patients with the congenital disorder of glycosylation type IA. This is remarkable, because in these patients the biosynthesis of guanosine 5′-diphosphate (GDP)- D-mannose is strongly decreased, and GDP- D-mannose is the direct precursor for GDP- L-fucose, the substrate for fucosyltransferases. The concomitantly occurring increased branching of the glycans of AGP and the increased fucosyltransferase activity in plasma suggest that a chronic hepatic inflammatory reaction has induced the increase in fucosylation.

Band 3 glycoprotein and glycophorin A from erythrocytes of children with congenital disorder of glycosylation type-Ia are underglycosylated

Band 3 glycoprotein and glycophorin A from erythrocytes of children with congenital disorder of glycosylation type-Ia are underglycosylated

Band 3 glycoprotein and glycophorin A from erythrocytes of children with congenital disorder of glycosylation type-Ia are underglycosylated.

Band 3 and PAS-1 (a dimer of glycophorin A) from erythrocyte membranes of three children with congenital disorder of glycosylation, type Ia (CDG-Ia), aged 1 month, 3 years and 10 years respectively, were examined by a new technique that allowed determination of carbohydrate molar composition of glycoproteins separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In CDG children a single N-glycan of band 3 glycoprotein was hypoglycosylated and its mannose content was normal or elevated. Glycophorin A which is the major carrier of erythrocyte sialic acid, was deficient in N-acetylgalactosamine, and sialic acid residues. This finding indicated a partial unglycosylation of O-glycans in glycophorin A. In keeping with the results of PAS-1 analysis, total sialic acid in erythrocyte membranes from CDG children was reduced to 40-56% of normal values. A possible molecular mechanism of hypo- and unglycosylation of band 3 and glycophorin A, respectively, in CDG is discussed.