Biomedical subjects

Jaak Jaeken

Publications and source records attributed to Jaak Jaeken.

10 recordsLinked to original sources

PubMed2004

Mutations responsible for 3-phosphoserine phosphatase deficiency.

We report the identification of the mutations in the only known case of L-3-phosphoserine phosphatase deficiency, a recessively inherited condition. The two mutations correspond to the replacement of the semiconserved Asp32 residue by an asparagine and of the extremely conserved Met52 by a threonine. The effects of both mutations were studied on the human recombinant enzyme, expressed in Escherichia coli. Met52Thr almost abolished the enzymatic activity, whereas the Asp32Asn mutation caused a 50% decrease in Vmax. In addition, L-serine, which inhibits the conversion of [(14)C] phosphoserine to serine when catalysed by the wild-type enzyme, had a lesser inhibitory effect on the Asp32Asn mutant, indicating a reduction in the rate of phosphoenzyme hydrolysis. These modifications in the properties of the enzyme are consistent with the modification in the kinetic properties observed in fibroblasts from the patient.

Amino Acid Sequence↗

PubMed2003

Diagnosis of congenital disorders of glycosylation by capillary zone electrophoresis of serum transferrin.

BACKGROUND: Congenital disorders of glycosylation (CDG) are usually diagnosed by isoelectric focusing (IEF) of serum transferrin (Tf). The aim of this study was to evaluate capillary zone electrophoresis (CZE) as a diagnostic alternative to IEF. METHODS: We performed 792 CZE analyses of Tf, using the CEofix(TM)-CDT (carbohydrate-deficient transferrin) assay. Peak identification was based on relative migration times (RMTs) to reduce migration variability. RESULTS: Tf profiles comprised three main groups (A-C). Groups A and B were characterized by one or two dominant tetrasialo-Tf peaks, whereas group C showed a widely variable Tf isoform composition. Group A was composed of four subgroups: a major group with a typical Tf profile (considered as reference group), two minor groups with decreased or moderately increased trisialo-Tf isoform, and a group showing the presence of unknown compounds with RMTs similar to mono- and disialo-Tf. However, these compounds were absent on IEF. Group C contained all profiles from patients with confirmed as well as putative CDG. From the reference group, 99% confidence intervals were calculated for the RMTs of the Tf isoforms, and percentiles representing the Tf isoform distributions were defined. CONCLUSIONS: All patients with abnormal IEF results and confirmed CDG were identified by CZE; thus, this method can be used as a diagnostic alternative to IEF in a manner suitable for automation. Because whole serum is analyzed, it should be kept in mind that CZE profiles can show substances other than Tf.

Adolescent↗

PubMed2003

Detailed glycan analysis of serum glycoproteins of patients with congenital disorders of glycosylation indicates the specific defective glycan processing step and provides an insight into pathogenesis.

The fundamental importance of correct protein glycosylation is abundantly clear in a group of diseases known as congenital disorders of glycosylation (CDGs). In these diseases, many biological functions are compromised, giving rise to a wide range of severe clinical conditions. By performing detailed analyses of the total serum glycoproteins as well as isolated transferrin and IgG, we have directly correlated aberrant glycosylation with a faulty glycosylation processing step. In one patient the complete absence of complex type sugars was consistent with ablation of GlcNAcTase II activity. In another CDG type II patient, the identification of specific hybrid sugars suggested that the defective processing step was cell type-specific and involved the mannosidase III pathway. In each case, complementary serum proteome analyses revealed significant changes in some 31 glycoproteins, including components of the complement system. This biochemical approach to charting diseases that involve alterations in glycan processing provides a rapid indicator of the nature, severity, and cell type specificity of the suboptimal glycan processing steps; allows links to genetic mutations; indicates the expression levels of proteins; and gives insight into the pathways affected in the disease process.

Carbohydrate Metabolism, Inborn Errors↗

PubMed2003

Functional polymorphisms in the paternally expressed XLalphas and its cofactor ALEX decrease their mutual interaction and enhance receptor-mediated cAMP formation.

The paternally expressed extra-large stimulatory G protein gene (XLalphas) is a splice variant of the stimulatory G-protein gene (Gsalpha) consisting of XL-exon1 and exons 2-13 of Gsalpha. A second open reading frame (ORF) in XL-exon1, that completely overlaps the XL-domain ORF, encodes ALEX, which is translated from the XLalphas mRNA and binds the XL-domain of XLalphas. We previously demonstrated that a paternally inherited functional polymorphism in XL-exon1, consisting of a 36 bp insertion and two nucleotide substitutions, is associated with Gs hyperfunction in platelets, leading to an increased trauma-related bleeding tendency and is accompanied by neurological problems and brachydactyly in two families. Here, we describe eight additional patients with brachydactyly, who inherited the same XLalphas polymorphism paternally and who show Gs hyperfunction in their platelets and fibroblasts. All carriers also have an elongated ALEX protein, as a consequence of the paternally inherited insertion. The in vitro interaction between the two elongated XLalphas and ALEX proteins is markedly reduced. Moreover, XLalphas or ALEX can be co-immunoprecipitated with an antibody against either ALEX or XLalphas in platelets from a control but hardly from patients with the XLalphas/ALEX insertion. In contrast to the strong interaction between the two wild-type proteins, we suggest that this defective association results in unimpeded receptor-stimulated activation of XLalphas. The paternally inherited double XLalphas/ALEX functional polymorphism is also associated with elevated platelet membrane Gsalpha protein levels. Both phenomena contribute to increased Gs signaling in patients with platelet hypersensitivity towards Gs-agonists and may be accompanied by neurological problems or growth deficiency.

Blood Platelets↗

PubMed2003

D,L-3-hydroxybutyrate treatment of multiple acyl-CoA dehydrogenase deficiency (MADD).

Cardiomyopathy and leukodystrophy are life-threatening complications of multiple acyl-CoA dehydrogenase deficiency (MADD). A 2-year-old boy with this disorder developed rapidly progressive leukodystrophy resulting in complete paralysis within 4 months. Within a week of starting sodium-D,L-3-hydroxybutyrate he had improved. After 2 years, neurological function returned, including walking independently, with progressive improvement of brain MRI. Two additional infants with MADD developed life-threatening cardiomyopathy unresponsive to conventional treatment. On sodium-D,L-3-hydroxybutyrate treatment their cardiac contractility showed progressive and sustained improvement. D,L-3-hydroxybutyrate is a therapeutic option for cerebral and cardiac complications in severe fatty acid oxidation defects.

3-Hydroxybutyric Acid↗

PubMed2003

Increased fucosylation and reduced branching of serum glycoprotein N-glycans in all known subtypes of congenital disorder of glycosylation I.

The N-glycans present on the total mixture of serum glycoproteins (serum N-glycome) were analyzed in 24 subjects with congenital disorder of glycosylation type I (CDG-I) and 7 healthy, age-matched individuals. No new N-glycan structures were observed in the sera of CDG-I patients as compared with normal sera. However, we observed in all subtypes a significantly increased degree of core alpha-1,6-fucosylation of the biantennary glycans as compared to normal, as well as a significant decrease in the amount of triantennary glycans. These serum N-glycome changes appear to be a milder manifestation of some of the changes observed in adult liver cirrhosis patients, which is compatible with the reported steatosis and fibrosis in CDG-I patients. In the CDG-Ia subgroup, the extent of the serum N-glycome changes correlates with the aberration of the serum transferrin isoelectric focusing pattern, which measures the severity of the lack of entire N-glycan chains (primary consequence of CDG-I) in the liver and is the standard diagnostic test for this category of inherited diseases.

Adult↗

PubMed2003

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.

Body Fluids↗

PubMed2002

Clinical and molecular features of congenital disorder of glycosylation in patients with type 1 sialotransferrin pattern and diverse ethnic origins.

OBJECTIVE: To increase awareness of congenital disorders of glycosylation (CDG), we report the features of patients with a variety of clinical presentations ranging from mild hypotonia and strabismus to severe neurologic impairment. STUDY DESIGN: Nine North American patients with CDG type I and different ethnic origins were studied. RESULTS: All patients had transferrin isoelectric focusing studies with a type 1 sialotransferrin pattern. Molecular analysis showed the previously described R141H, V231M, and T237M PMM2 mutations in four patients as well as 3 rare mutations (DeltaC389, L104V, and IVS1 -1 G-->A) in the PMM2 gene in two Asian patients. CONCLUSIONS: The clinical features of these patients with diverse ethnic backgrounds confirm the variable course of CDG type I. Screening for CDG should be considered in children with relatively mild neurologic impairment, especially if they have suggestive findings such as cerebellar hypoplasia and abnormal fat distribution.

Congenital Disorders of Glycosylation↗

PubMed2002

Congenital disorders of glycosylation: a review.

Congenital disorders of glycosylation (CDGs) are a rapidly growing group of inherited disorders caused by defects in the synthesis and processing of the asparagine(ASN)-linked oligosaccharides of glycoproteins. The first CDG patients were described in 1980. Fifteen years later, a phosphomannomutase deficiency was found as the basis of the most frequent type, CDG-Ia. In recent years several novel types have been identified. The N-glycosylation pathway is highly conserved from yeast to human, and the rapid progress in this field can largely be attributed to the systematic application of the knowledge of yeast mutants. Up to now, eight diseases have been characterized, resulting from enzyme or transport defects in the cytosol, endoplasmic reticulum, or Golgi compartment. CDGs affect all organs and particularly the CNS, except for CDG-Ib, which is mainly a hepatic-intestinal disease.

Animals↗

PubMed2002

Genetic disorders of gamma-aminobutyric acid, glycine, and serine as causes of epilepsy.

Genetic disorders of gamma-aminobutyric acid (GABA), glycine, and serine metabolism and of the GABA and glycine receptors are causes of epilepsy with variable responsiveness to treatment. Pyridoxine-dependent convulsions and the GABA(A) receptor defects are pure epileptic disorders that respond well to treatment. The convulsions associated with 3-phosphoglycerate dehydrogenase deficiency can be completely abolished with amino acid therapy. Epilepsy is a major symptom in succinic semialdehyde dehydrogenase deficiency. The convulsions in these disorders are not responsive or are only partially responsive to treatment.

Amino Acid Metabolism, Inborn Errors↗