Olga Gornik

Bio: Olga Gornik is an academic researcher from University of Zagreb. The author has contributed to research in topics: Glycosylation & Glycome. The author has an hindex of 34, co-authored 79 publications receiving 4042 citations. Previous affiliations of Olga Gornik include University of Edinburgh.

Loci Associated with N-Glycosylation of Human Immunoglobulin G Show Pleiotropy with Autoimmune Diseases and Haematological Cancers

Abstract: Glycosylation of immunoglobulin G (IgG) influences IgG effector function by modulating binding to Fc receptors. To identify genetic loci associated with IgG glycosylation, we quantitated N-linked IgG glycans using two approaches. After isolating IgG from human plasma, we performed 77 quantitative measurements of N-glycosylation using ultra-performance liquid chromatography (UPLC) in 2,247 individuals from four European discovery populations. In parallel, we measured IgG N-glycans using MALDI-TOF mass spectrometry (MS) in a replication cohort of 1,848 Europeans. Meta-analysis of genome-wide association study (GWAS) results identified 9 genome-wide significant loci (P,2.27610 29 ) in the discovery analysis and two of the same loci (B4GALT1 and MGAT3 )i n the replication cohort. Four loci contained genes encoding glycosyltransferases (ST6GAL1, B4GALT1, FUT8 ,a ndMGAT3), while the remaining 5 contained genes that have not been previously implicated in protein glycosylation (IKZF1, IL6ST-ANKRD55, ABCF2SMARCD3, SUV420H1 ,a ndSMARCB1-DERL3). However, most of them have been strongly associated with autoimmune and inflammatory conditions (e.g., systemic lupus erythematosus, rheumatoid arthritis, ulcerative colitis, Crohn’s disease, diabetes type 1, multiple sclerosis, Graves’ disease, celiac disease, nodular sclerosis) and/or haematological cancers (acute lymphoblastic leukaemia, Hodgkin lymphoma, and multiple myeloma). Follow-up functional experiments in haplodeficient Ikzf1 knock-out mice showed the same general pattern of changes in IgG glycosylation as identified in the meta-analysis. As IKZF1 was associated with multiple IgG Nglycan traits, we explored biomarker potential of affected N-glycans in 101 cases with SLE and 183 matched controls and demonstrated substantial discriminative power in a ROC-curve analysis (area under the curve = 0.842). Our study shows that it is possible to identify new loci that control glycosylation of a single plasma protein using GWAS. The results may also provide an explanation for the reported pleiotropy and antagonistic effects of loci involved in autoimmune diseases and haematological cancer.

Glycans Are a Novel Biomarker of Chronological and Biological Ages

Abstract: Aging is a complex process of accumulation of molecular, cellular, and organ damage, leading to loss of function and increased vulnerability to disease and finally to death (1). It is well known that lifestyle choices such as smoking and physical activity can hasten or delay the aging process (2). Such observations have led to the search for molecular markers of age that can be used to predict, monitor, and provide insight into age-associated physiological decline and disease. Protein structure is defined by the sequence of nucleotides in the corresponding genes, thus the polypeptide sequence of a protein cannot change with age. However, an important structural and functional element of the majority of proteins are the glycans that participate in virtually all physiological processes (3). Glycans are product of a complex pathway that involves hundreds of different proteins and are encoded in a complex dynamic network of hundreds of genes (4). Epigenetic regulation of gene expression is expected to affect protein glycosylation and several publications recently reported this effect (5–8). Changes in glycosylation with age have been shown over 20 years ago (9) and have also replicated in recent large population studies (10–13). Immunoglobulin G (IgG) is an excellent model glycoprotein because its glycosylation has been well defined (Figure 1), and many important functional effects of alternative IgG glycosylation have been described (14). For example, glycosylation acts as a switch between pro- and anti-inflammatory IgG functionality. Most of the IgG molecules are not sialylated and are proinflammatory. Terminal α2,6-sialylation of IgG glycans decreases the ability of IgG to bind to activating FcγRs and promotes recognition by DC-SIGN, which increases expression of inhibitory FcγRIIB and is anti-inflammatory (15). Another fascinating example is the role of core fucose in the modulation of antibody-dependent cellular cytotoxicity: IgG-containing glycans that lack core fucose have 100-fold increased affinity for FcγRIIIA and are therefore much more efficient in activating antibody-dependent cellular cytotoxicity than fucosylated glycoforms of the same molecule (16). On average, 95% of the IgG population is core fucosylated (12); thus, most of the immunoglobulins have a “safety switch,” which prevents them from activating antibody-dependent cellular cytotoxicity. Malfunction of this system appears to be associated with autoimmune diseases as indicated by both pleiotropic effects of genes that associate with IgG glycosylation on different inflammatory and autoimmune diseases, and the observed alterations in IgG glycosylation in systemic lupus erythematous (17) and many inflammatory diseases (18). Figure 1. UPLC analysis of immunoglobulin G (IgG) glycosylation. Each IgG contains one conserved N-glycosylation site on Asn197 of its heavy chain. Different glycans can be attached to this site and the process seems to be highly regulated. UPLC analysis can reveal ... Interindividual variability of IgG glycosylation in a population is large (12) and it appears to be affected by both variation in DNA sequence (19) and environmental factors (11). Most of the studies that investigated glycosylation changes with age were either of limited size or were performed on the total plasma glycome; thus, in addition to changes in glycosylation, the observed differences reflected changes in the concentration of individual plasma proteins. In this study, we focused on glycosylation of IgG and analyzed more than 5,000 individuals from four different European populations to provide definitive data about changes in IgG glycosylation through the lifetime.

Genomics meets glycomics-the first GWAS study of human N-Glycome identifies HNF1α as a master regulator of plasma protein fucosylation.

Abstract: Over half of all proteins are glycosylated, and alterations in glycosylation have been observed in numerous physiological and pathological processes. Attached glycans significantly affect protein function; but, contrary to polypeptides, they are not directly encoded by genes, and the complex processes that regulate their assembly are poorly understood. A novel approach combining genome-wide association and high-throughput glycomics analysis of 2,705 individuals in three population cohorts showed that common variants in the Hepatocyte Nuclear Factor 1α (HNF1α) and fucosyltransferase genes FUT6 and FUT8 influence N-glycan levels in human plasma. We show that HNF1α and its downstream target HNF4α regulate the expression of key fucosyltransferase and fucose biosynthesis genes. Moreover, we show that HNF1α is both necessary and sufficient to drive the expression of these genes in hepatic cells. These results reveal a new role for HNF1α as a master transcriptional regulator of multiple stages in the fucosylation process. This mechanism has implications for the regulation of immunity, embryonic development, and protein folding, as well as for our understanding of the molecular mechanisms underlying cancer, coronary heart disease, and metabolic and inflammatory disorders.

Glycosylation of serum proteins in inflammatory diseases.

Abstract: Inflammatory diseases are accompanied by numerous changes at the site of inflammation as well as many systemic physiological and biochemical changes In the past two decades more and more attention is being paid to changes in glycosylation and in this review we describe some of the changes found on main serum proteins (α1-acid glycoprotein, immunoglobulin G, immunoglobulin A, transferrin, haptoglobin, α2-macroglobulin, C-reactive protein, and others) Molecular background and physiological importance of most of these changes are yet to be discovered, but it is evident that glycosylation plays an important role in the inflammatory response Maybe the greatest value of these changes currently lays in their potential diagnostic and prognostic usage, either in combination with current diagnostic markers or on their own However, determining glycan structures is still technically too complex for most clinical laboratories and further efforts have to be made to develop simple analytical tools to study changes in glycosylation

Glycosylation in cancer: mechanisms and clinical implications

Abstract: Despite recent progress in understanding the cancer genome, there is still a relative delay in understanding the full aspects of the glycome and glycoproteome of cancer. Glycobiology has been instrumental in relevant discoveries in various biological and medical fields, and has contributed to the deciphering of several human diseases. Glycans are involved in fundamental molecular and cell biology processes occurring in cancer, such as cell signalling and communication, tumour cell dissociation and invasion, cell-matrix interactions, tumour angiogenesis, immune modulation and metastasis formation. The roles of glycans in cancer have been highlighted by the fact that alterations in glycosylation regulate the development and progression of cancer, serving as important biomarkers and providing a set of specific targets for therapeutic intervention. This Review discusses the role of glycans in fundamental mechanisms controlling cancer development and progression, and their applications in oncology.

IgG subclasses and allotypes: from structure to effector functions.

Abstract: Of the five immunoglobulin isotypes, Immunoglobulin G (IgG) is most abundant in human serum. The four subclasses, IgG1, IgG2, IgG3 and IgG4 which are highly conserved, differ in their constant region, particularly in their hinges and upper CH2 domains. These regions are involved in binding to both IgG-Fc receptor (FcγR) and C1q. As a result, the different subclasses have different effector functions, both in terms of triggering FcγR-expressing cells, resulting in phagocytosis or Antibody-dependent cell-mediated cytotoxicity (ADCC), and activating complement. The Fc-regions also contain a binding epitope for the neonatal Fc-receptor (FcRn), responsible for the extended half-life, placental transport, and bidirectional transport of IgG to mucosal surfaces. However, FcRn is also expressed in myeloid cells, where it participates in both phagocytosis and antigen presentation together with classical FcγR and complement. How these properties, IgG-polymorphisms and post-translational modification of the antibodies in the form of glycosylation, affect IgG-function, will be the focus of the current review.

Inflammaging: a new immune–metabolic viewpoint for age-related diseases

Abstract: Ageing and age-related diseases share some basic mechanistic pillars that largely converge on inflammation. During ageing, chronic, sterile, low-grade inflammation - called inflammaging - develops, which contributes to the pathogenesis of age-related diseases. From an evolutionary perspective, a variety of stimuli sustain inflammaging, including pathogens (non-self), endogenous cell debris and misplaced molecules (self) and nutrients and gut microbiota (quasi-self). A limited number of receptors, whose degeneracy allows them to recognize many signals and to activate the innate immune responses, sense these stimuli. In this situation, metaflammation (the metabolic inflammation accompanying metabolic diseases) is thought to be the form of chronic inflammation that is driven by nutrient excess or overnutrition; metaflammation is characterized by the same mechanisms underpinning inflammaging. The gut microbiota has a central role in both metaflammation and inflammaging owing to its ability to release inflammatory products, contribute to circadian rhythms and crosstalk with other organs and systems. We argue that chronic diseases are not only the result of ageing and inflammaging; these diseases also accelerate the ageing process and can be considered a manifestation of accelerated ageing. Finally, we propose the use of new biomarkers (DNA methylation, glycomics, metabolomics and lipidomics) that are capable of assessing biological versus chronological age in metabolic diseases.

Methodology for Genetic Studies of Twins and Families

Abstract: The saimie paper suggests how susceptible individuals could reduce their total intake of aluminium. In presenting the cpidemiological evidence for a link betveen aluminium and Alzheimcr's, Nart'n suggests that although definite proof is still lacking, there is more than enough positixe evidence to fuel further epidemiological investigation. It states that such investigations might specificallx address the issue of the confounding cffect of silicon and an assessment of exposure to spccific