BACKGROUND: Determination of the genetic defect in patients with a congenital disorder of glycosylation (CDG) is challenging because of the wide clinical presentation, the large number of gene products involved, and the occurrence of secondary causes of underglycosylation. Transferrin isoelectric focusing has been the method of choice for CDG screening; however, improved methods are required for the molecular diagnosis of patients with CDG type II. METHODS: Plasma samples with a typical transferrin isofocusing profile were analyzed. N-glycans were released from these samples by PNGase F [peptide-N4-(acetyl-β-glucosaminyl)-asparagine amidase] digestion, permethylated and purified, and measured on a MALDI linear ion trap mass spectrometer. A set of 38 glycans was used for quantitative comparison and to establish reference intervals for such glycan features as the number of antennae, the level of truncation, and fucosylation. Plasma N-glycans from control individuals, patients with known CDG type II defects, and patients with a secondary cause of underglycosylation were analyzed. RESULTS: CDGs due to mannosyl (α-1,6-)-glycoprotein β-1,2-N-acetylglucosaminyltransferase (MGAT2), β-1,4-galactosyltransferase 1 (B4GALT1), and SLC35C1 (a GDP-fucose transporter) defects could be diagnosed directly from the N-glycan profile. CDGs due to defects in proteins involved in Golgi trafficking, such as subunit 7 of the conserved oligomeric Golgi complex (COG7) and subunit V0 a2 of the lysosomal H(+)-transporting ATPase (ATP6V0A2) caused a loss of triantennary N-glycans and an increase of truncated structures. Secondary causes with liver involvement were characterized by increased fucosylation, whereas the presence of plasma sialidase produced isolated undersialylation. CONCLUSIONS: MALDI ion trap analysis of plasma N-glycans documents features that discriminate between primary and secondary causes of underglycosylation and should be applied as the first step in the diagnostic track of all patients with an unsolved CDG type II.
BACKGROUND: Determination of the genetic defect in patients with a congenital disorder of glycosylation (CDG) is challenging because of the wide clinical presentation, the large number of gene products involved, and the occurrence of secondary causes of underglycosylation. Transferrin isoelectric focusing has been the method of choice for CDG screening; however, improved methods are required for the molecular diagnosis of patients with CDG type II. METHODS: Plasma samples with a typical transferrin isofocusing profile were analyzed. N-glycans were released from these samples by PNGase F [peptide-N4-(acetyl-β-glucosaminyl)-asparagine amidase] digestion, permethylated and purified, and measured on a MALDI linear ion trap mass spectrometer. A set of 38 glycans was used for quantitative comparison and to establish reference intervals for such glycan features as the number of antennae, the level of truncation, and fucosylation. Plasma N-glycans from control individuals, patients with known CDG type II defects, and patients with a secondary cause of underglycosylation were analyzed. RESULTS:CDGs due to mannosyl (α-1,6-)-glycoprotein β-1,2-N-acetylglucosaminyltransferase (MGAT2), β-1,4-galactosyltransferase 1 (B4GALT1), and SLC35C1 (a GDP-fucose transporter) defects could be diagnosed directly from the N-glycan profile. CDGs due to defects in proteins involved in Golgi trafficking, such as subunit 7 of the conserved oligomeric Golgi complex (COG7) and subunit V0 a2 of the lysosomal H(+)-transporting ATPase (ATP6V0A2) caused a loss of triantennary N-glycans and an increase of truncated structures. Secondary causes with liver involvement were characterized by increased fucosylation, whereas the presence of plasma sialidase produced isolated undersialylation. CONCLUSIONS: MALDI ion trap analysis of plasma N-glycans documents features that discriminate between primary and secondary causes of underglycosylation and should be applied as the first step in the diagnostic track of all patients with an unsolved CDG type II.
Authors: Petcharat Leoyklang; May Christine Malicdan; Tal Yardeni; Frank Celeste; Carla Ciccone; Xueli Li; Rong Jiang; William A Gahl; Nuria Carrillo-Carrasco; Miao He; Marjan Huizing Journal: Biomark Med Date: 2014 Impact factor: 2.851
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Authors: Nurulamin Abu Bakar; Nicol C Voermans; Thorsten Marquardt; Christian Thiel; Mirian C H Janssen; Hana Hansikova; Ellen Crushell; Jolanta Sykut-Cegielska; Francis Bowling; Lars MØrkrid; John Vissing; Eva Morava; Monique van Scherpenzeel; Dirk J Lefeber Journal: Transl Res Date: 2018-05-10 Impact factor: 7.012
Authors: Jos C Jansen; Sebahattin Cirak; Monique van Scherpenzeel; Sharita Timal; Janine Reunert; Stephan Rust; Belén Pérez; Dorothée Vicogne; Peter Krawitz; Yoshinao Wada; Angel Ashikov; Celia Pérez-Cerdá; Celia Medrano; Andrea Arnoldy; Alexander Hoischen; Karin Huijben; Gerry Steenbergen; Dulce Quelhas; Luisa Diogo; Daisy Rymen; Jaak Jaeken; Nathalie Guffon; David Cheillan; Lambertus P van den Heuvel; Yusuke Maeda; Olaf Kaiser; Ulrike Schara; Patrick Gerner; Marjolein A W van den Boogert; Adriaan G Holleboom; Marie-Cécile Nassogne; Etienne Sokal; Jody Salomon; Geert van den Bogaart; Joost P H Drenth; Martijn A Huynen; Joris A Veltman; Ron A Wevers; Eva Morava; Gert Matthijs; François Foulquier; Thorsten Marquardt; Dirk J Lefeber Journal: Am J Hum Genet Date: 2016-01-28 Impact factor: 11.025