Maja Pučić

Bio: Maja Pučić is an academic researcher. The author has contributed to research in topics: Glycosylation & Glycome. The author has an hindex of 13, co-authored 15 publications receiving 1511 citations.

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.

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.

Effects of aging, body mass index, plasma lipid profiles, and smoking on human plasma N-glycans.

Abstract: Protein glycosylation affects nearly all molecular interactions at the cell surface and in the intercellular space. Many of the physiological variations which are part of homeostatic mechanisms influence glycosylation. However, a comprehensive overview of changes in glycosylation caused by aging and common lifestyle parameters is still lacking. After analyzing N-glycans in the plasma of 1914 individuals from the Croatian islands of Vis and Korcula, we performed a comprehensive analysis of the dependence of different glycosylation features (position of fucose, level of galactosylation, sialylation and branching) on aging, smoking, body fat and plasma lipid status. A number of statistically significant associations were observed. Glycosylation changes with aging were especially evident in females, mostly in association with the transition from pre-menopausal to post-menopausal age. Levels of core-fucosylated, non-galactosylated, digalactosylated and disialylated biantennary glycans were shown to be mainly age dependent, but the level of branching and higher levels of galactosylation were found to correlate with lipid status. For the majority of glycans which we analyzed, all examined parameters explained up to 5% of the variance. The only notable exception were non-galactosylated glycans where 20% of the variance was explained mostly by age and blood pressure. In general, only a small fraction of the variability in glycan levels observed in a population was explained by age and other measured parameters, indicating that even in the absence of a genetic template, glycan levels are mostly determined by genetic background and/or specific pathophysiological processes.

Stability of N-glycan profiles in human plasma

Abstract: Glycan heterogeneity was shown to be associated with numerous diseases and glycan analysis has a great diagnostic potential. Recently, we reported high biological variability of human plasma N-glycome at the level of population. The observed variations were larger than changes reported to be associated with some diseases; thus, it was of great importance to examine the temporal constancy of human N-glycome before glycosylation changes could be routinely analyzed in diagnostic laboratories. Plasma samples were taken from 12 healthy individuals. The blood was drawn on seven occasions during 5 days. N-Linked glycans, released from plasma proteins, were separated using hydrophilic interaction high-performance liquid chromatography into 16 groups (GP1-GP16) and quantified. The results showed very small variation in all glycan groups, indicating very good temporal stability of N-glycome in a single individual. Coefficients of variation from 1.6% for GP8 to 11.4% for GP1 were observed. The average coefficient of variation was 5.6%. These variations were comparable to those observed when analytical procedure was tested for its precision. Good stability of plasma N-glycome in healthy individuals implies that glycosylation is under significant genetic control. Changes observed in glycan profiles are consequence of environmental influences and physiologic responses and therefore have a significant diagnostic potential.

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.

Vertebrate protein glycosylation: diversity, synthesis and function

Abstract: Protein glycosylation is a ubiquitous post-translational modification found in all domains of life Despite their significant complexity in animal systems, glycan structures have crucial biological and physiological roles, from contributions in protein folding and quality control to involvement in a large number of biological recognition events As a result, they impart an additional level of 'information content' to underlying polypeptide structures Improvements in analytical methodologies for dissecting glycan structural diversity, along with recent developments in biochemical and genetic approaches for studying glycan biosynthesis and catabolism, have provided a greater understanding of the biological contributions of these complex structures in vertebrates

Modulation of genetic associations with serum urate levels by body-mass-index in humans

Abstract: We tested for interactions between body mass index (BMI) and common genetic variants affecting serum urate levels, genome-wide, in up to 42569 participants. Both stratified genome-wide association (GWAS) analyses, in lean, overweight and obese individuals, and regression-type analyses in a non BMI-stratified overall sample were performed. The former did not uncover any novel locus with a major main effect, but supported modulation of effects for some known and potentially new urate loci. The latter highlighted a SNP at RBFOX3 reaching genome-wide significant level (effect size 0.014, 95% CI 0.008-0.02, Pinter= 2.6 x 10-8). Two top loci in interaction term analyses, RBFOX3 and ERO1LB-EDARADD, also displayed suggestive differences in main effect size between the lean and obese strata. All top ranking loci for urate effect differences between BMI categories were novel and most had small magnitude but opposite direction effects between strata. They include the locus RBMS1-TANK (men, Pdifflean-overweight= 4.7 x 10-8), a region that has been associated with several obesity related traits, and TSPYL5 (men, Pdifflean-overweight= 9.1 x 10-8), regulating adipocytes-produced estradiol. The top-ranking known urate loci was ABCG2, the strongest known gout risk locus, with an effect halved in obese compared to lean men (Pdifflean-obese= 2 x 10-4). Finally, pathway analysis suggested a role for N-glycan biosynthesis as a prominent urate-associated pathway in the lean stratum. These results illustrate a potentially powerful way to monitor changes occurring in obesogenic environment.

Glycosylation in health and disease.

Abstract: The glycome describes the complete repertoire of glycoconjugates composed of carbohydrate chains, or glycans, that are covalently linked to lipid or protein molecules. Glycoconjugates are formed through a process called glycosylation and can differ in their glycan sequences, the connections between them and their length. Glycoconjugate synthesis is a dynamic process that depends on the local milieu of enzymes, sugar precursors and organelle structures as well as the cell types involved and cellular signals. Studies of rare genetic disorders that affect glycosylation first highlighted the biological importance of the glycome, and technological advances have improved our understanding of its heterogeneity and complexity. Researchers can now routinely assess how the secreted and cell-surface glycomes reflect overall cellular status in health and disease. In fact, changes in glycosylation can modulate inflammatory responses, enable viral immune escape, promote cancer cell metastasis or regulate apoptosis; the composition of the glycome also affects kidney function in health and disease. New insights into the structure and function of the glycome can now be applied to therapy development and could improve our ability to fine-tune immunological responses and inflammation, optimize the performance of therapeutic antibodies and boost immune responses to cancer. These examples illustrate the potential of the emerging field of ‘glycomedicine’. Glycosylation refers to the addition of carbohydrate chains to proteins and lipids. In this Review, the authors discuss the broad role of glycans in immunity, cancer, xenotransplantation and glomerular filtration and the potential of ‘glycomedicine’.

Genome-wide association analyses identify 18 new loci associated with serum urate concentrations

Abstract: Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SFMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional excretion of urate. Network analyses implicate the inhibins-activins signaling pathways and glucose metabolism in systemic urate control. New candidate genes for serum urate concentration highlight the importance of metabolic control of urate production and excretion, which may have implications for the treatment and prevention of gout.