title: Classical galactosaemia: novel insights in IgG N-glycosylation and N-glycan biosynthesis.
abstract: Classical galactosaemia (OMIM #230400), a rare disorder of carbohydrate metabolism, is caused by a deficient activity of galactose-1-phosphate uridyltransferase (EC 2.7.7.12). The pathophysiology of the long-term complications, mainly cognitive, neurological and female fertility problems remains poorly understood. The lack of validated biomarkers to determine prognosis, monitor disease progression and responses to new therapies, pose a huge challenge. We report the detailed analysis of an automated robotic hydrophilic interaction ultra-performance liquid chromatography N-glycan analytical method of high glycan peak resolution applied to serum IgG. This has revealed specific N-glycan processing defects observed in 40 adult galactosaemia patients (adults and adolescents), in comparison with 81 matched healthy controls. We have identified a significant increase in core fucosylated neutral glycans (P<0.0001) and a significant decrease in core fucosylated (P<0.001), non-fucosylated (P<0.0001) bisected glycans and, of specific note, decreased N-linked mannose-5 glycans (P<0.0001), in galactosaemia patients. We also report the abnormal expression of a number of related relevant N-glycan biosynthesis genes in peripheral blood mononuclear cells from 32 adult galactosaemia patients. We have noted significant dysregulation of two key N-glycan biosynthesis genes: ALG9 upregulated (P<0.001) and MGAT1 downregulated (P<0.01) in galactosaemia patients, which may contribute to its ongoing pathophysiology. Our data suggest that the use of IgG N-glycosylation analysis with matched N-glycan biosynthesis gene profiles may provide useful biomarkers for monitoring response to therapy and interventions. They also indicate potential gene modifying steps in this N-glycan biosynthesis pathway, of relevance to galactosaemia and related N-glycan biosynthesis disorders.
authors.affiliation: National Centre for Inherited Metabolic Disorders, Children's University Hospital, Dublin, Ireland.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Maratha
authors.affiliation: Glycoscience Group, National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin University College, Dublin, Ireland.
authors.forename: Henning
authors.initials: H
authors.lastname: Stockmann
authors.affiliation: Department of Infectious Diseases, King's College London, Faculty of Life Sciences and Medicine, Guy's Hospital, London, UK.
authors.forename: Karen P
authors.initials: KP
authors.lastname: Coss
authors.affiliation: Department of Paediatrics and Laboratory of Genetic Metabolic Diseases, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Estela Rubio-Gozalbo
authors.affiliation: National Centre for Inherited Metabolic Disorders, Children's University Hospital, Dublin, Ireland.
authors.forename: Ina
authors.initials: I
authors.lastname: Knerr
authors.affiliation: National Centre for Inherited Metabolic Diseases, Misericordiae University Hospital, Dublin, Ireland.
authors.forename: Maria
authors.initials: M
authors.lastname: Fitzgibbon
authors.affiliation: National Centre for Inherited Metabolic Diseases, Misericordiae University Hospital, Dublin, Ireland.
authors.forename: Terri P
authors.initials: TP
authors.lastname: McVeigh
authors.affiliation: National Centre for Inherited Metabolic Disorders, Children's University Hospital, Dublin, Ireland.
authors.forename: Patricia
authors.initials: P
authors.lastname: Foley
authors.affiliation: Core Genomics Facility, Conway Institute, University College, Dublin, Ireland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Moss
authors.affiliation: Department of Paediatrics, Trinity College, Dublin, Ireland.
authors.forename: Hugh-Owen
authors.initials: HO
authors.lastname: Colhoun
authors.affiliation: Department of Paediatrics and Laboratory of Genetic Metabolic Diseases, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Britt
authors.initials: B
authors.lastname: van Erven
authors.affiliation: University College Dublin Clinical Research Centre, Dublin Academic Medical Centre, Dublin, Ireland.
authors.forename: Kelly
authors.initials: K
authors.lastname: Stephens
authors.affiliation: University College Dublin Clinical Research Centre, Dublin Academic Medical Centre, Dublin, Ireland.
authors.forename: Peter
authors.initials: P
authors.lastname: Doran
authors.affiliation: Glycoscience Group, National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin University College, Dublin, Ireland.
authors.forename: Pauline
authors.initials: P
authors.lastname: Rudd
authors.affiliation: National Centre for Inherited Metabolic Disorders, Children's University Hospital, Dublin, Ireland.|National Centre for Inherited Metabolic Diseases, Misericordiae University Hospital, Dublin, Ireland.|Department of Paediatrics, Trinity College, Dublin, Ireland.|University College Dublin Clinical Research Centre, Dublin Academic Medical Centre, Dublin, Ireland.
authors.forename: Eileen
authors.initials: E
authors.lastname: Treacy
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D005260:Female; D005693:Galactosemias / Q000097:blood / Q000235:genetics* / Q000473:pathology; D006031:Glycosylation; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000378:metabolism*; D008297:Male; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000096:biosynthesis*; D011499:Protein Processing, Post-Translational
chemical_list: D015415:Biomarkers; D007074:Immunoglobulin G; D008565:Membrane Proteins; D011134:Polysaccharides; C469962:ALG9 protein, human; C561128:MGAT1 protein, human; D008364:Mannosyltransferases; D017351:N-Acetylglucosaminyltransferases