Apolipoprotein C-III isofocusing in the diagnosis of genetic defects in O-glycan biosynthesis.

Abstract

BACKGROUND:

Defects in the biosynthesis of N-glycans may be found by isoelectric focusing (IEF) of plasma transferrin. No test is available to demonstrate O-glycan biosynthesis defects.

METHODS:

We used isoforms of apolipoprotein C-III (apoC-III) as a marker for the biosynthesis of core 1 mucin type O-glycans. Plasma samples from patients with primary defects and secondary alterations in N-glycan biosynthesis were studied by apoC-III isofocusing.

RESULTS:

Age-related reference values for apoC-III were determined. Plasma samples from patients with the primary congenital disorders of glycosylation (CDG) types Ia-Ic, Ie, If, IIa, and IId all showed a normal apoC-III isofocusing profile. Plasma from two patients with CDG type IIx were tested: one showed a normal apoC-III distribution, whereas the other showed a hypoglycosylation profile. In plasma from patients with hemolytic uremic syndrome (HUS), a hypoglycosylation profile was obtained.

CONCLUSIONS:

IEF of apoC-III is a rapid and simple technique that may be used as a screening assay for abnormalities in core 1 mucin type O-glycans. Evidence that a patient in this study has a primary genetic defect affecting both N- and O-glycosylation provides the first example of an inborn error of metabolism affecting the biosynthesis of core 1 mucin type O-glycans. Our data narrow the options for the position of the primary defect in this patient down to a step in the biosynthesis, activation, or transfer of galactose or N-acetylneuraminic acid to both N- and O-glycans. Circulating neuraminidase excreted by Streptococcus pneumoniae caused the high percentage of asialo apoC-III in two HUS patients.

• Authors: Suzan Wopereis, Stephanie Grünewald, Eva Morava, Johannes M Penzien, Paz Briones, M Teresa García-Silva, Pierre N M Demacker, Karin M L C Huijben, Ron A Wevers
• Journal: Clinical chemistry (Clin Chem) Vol. 49 Issue 11 Pg. 1839-45 (Nov 2003) ISSN: 0009-9147 [Print] England
• PMID: 14578315 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Apolipoprotein C-III
• Apolipoproteins C
• Polysaccharides
• Protein Isoforms

Topics

• Adolescent
• Age Factors
• Apolipoprotein C-III
• Apolipoproteins C (genetics)
• Carbohydrate Metabolism, Inborn Errors (diagnosis)
• Child
• Child, Preschool
• Glycosylation
• Humans
• Infant
• Infant, Newborn
• Isoelectric Focusing
• Polysaccharides (biosynthesis)
• Protein Isoforms (genetics)
• Reference Values