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Clin Epigenetics. 2018 Jun 4;10:75. doi: 10.1186/s13148-018-0507-y. eCollection 2018.

Promoter methylation of the MGAT3 and BACH2 genes correlates with the composition of the immunoglobulin G glycome in inflammatory bowel disease.

Author information

1
1Department of Biology, Division of Molecular Biology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
2
2Gastrointestinal Unit, Centre for Genomics and Molecular Medicine, University of Edinburgh, Edinburgh, EH4 6XU UK.
3
Genos Glycoscience Research Laboratory, Borongajska cesta 83h, 10000 Zagreb, Croatia.
4
5IBD Pharmacogenetics, University of Exeter, Exeter, UK.
5
10Translational Gastroenterology Unit, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
6
6Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Porto, Portugal.
7
7Department of Medical and Surgical Sciences, Division of Gastroenterology, University Hospital Careggi, Florence, Italy.
8
Department of Medical Sciences, Division of Gastroenterology, IRCCS-CSS Hospital, Viale Cappuccini, Rotondo, Italy.
9
9Gastrointestinal Unit, University of Padua, Padua, Italy.
10
4Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia.
#
Contributed equally

Abstract

Background:

Many genome- and epigenome-wide association studies (GWAS and EWAS) and studies of promoter methylation of candidate genes for inflammatory bowel disease (IBD) have demonstrated significant associations between genetic and epigenetic changes and IBD. Independent GWA studies have identified genetic variants in the BACH2, IL6ST, LAMB1, IKZF1, and MGAT3 loci to be associated with both IBD and immunoglobulin G (IgG) glycosylation.

Methods:

Using bisulfite pyrosequencing, we analyzed CpG methylation in promoter regions of these five genes from peripheral blood of several hundred IBD patients and healthy controls (HCs) from two independent cohorts, respectively.

Results:

We found significant differences in the methylation levels in the MGAT3 and BACH2 genes between both Crohn's disease and ulcerative colitis when compared to HC. The same pattern of methylation changes was identified for both genes in CD19+ B cells isolated from the whole blood of a subset of the IBD patients. A correlation analysis was performed between the MGAT3 and BACH2 promoter methylation and individual IgG glycans, measured in the same individuals of the two large cohorts. MGAT3 promoter methylation correlated significantly with galactosylation, sialylation, and bisecting GlcNAc on IgG of the same patients, suggesting that activity of the GnT-III enzyme, encoded by this gene, might be altered in IBD. The correlations between the BACH2 promoter methylation and IgG glycans were less obvious, since BACH2 is not a glycosyltransferase and therefore may affect IgG glycosylation only indirectly.

Conclusions:

Our results suggest that epigenetic deregulation of key glycosylation genes might lead to an increase in pro-inflammatory properties of IgG in IBD through a decrease in galactosylation and sialylation and an increase of bisecting GlcNAc on digalactosylated glycan structures. Finally, we showed that CpG methylation in the promoter of the MGAT3 gene is altered in CD3+ T cells isolated from inflamed mucosa of patients with ulcerative colitis from a third smaller cohort, for which biopsies were available, suggesting a functional role of this glyco-gene in IBD pathogenesis.

PMID:
29991969
PMCID:
PMC5987481
DOI:
10.1186/s13148-018-0507-y
[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

For the Edinburgh and Florence cohorts, ethical approvals were obtained from Tayside Committee on Medical Ethics B, and all patients and controls provided written, informed consent (LREC 06/S1101/16, LREC 2000/4/192). For the patients from Portugal, all clinical procedures and research protocols were approved by the ethics committee of CHP/HSA, Portugal (233/12(179-DEFI/177-CES); all participants gave their informed consent.The authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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