Novel Insight Into Glycosaminoglycan Biosynthesis Based on Gene Expression Profiles

Genetic variability in proteoglycan biosynthetic genes reveals new facets of heparan sulfate diversity

Heparan sulfate (HS) and chondroitin sulfate (CS) proteoglycans (PG) consist of a core protein to which the glycosaminoglycan (GAG) chains, HS or CS, are attached through a common linker tetrasaccharide. In the extracellular space, they are involved in the regulation of cell communication, assuring development and homeostasis. The HSPG biosynthetic pathway has documented 51 genes, with many diseases associated to defects in some of them. The phenotypic consequences of this genetic variation in humans, and of genetic ablation in mice, and their expression patterns, led to a phenotypically centered HSPG biosynthetic pathway model. In this model, HS sequences produced by ubiquitous NDST1, HS2ST and HS6ST enzymes are essential for normal development and homeostasis, whereas tissue restricted HS sequences produced by the non-ubiquitous NDST2-4, HS6ST2-3, and HS3ST1-6 enzymes are involved in adaptative behaviors, cognition, tissue responsiveness to stimuli, and vulnerability to disease. The model indicates that the flux through the HSPG/CSPG pathways and its diverse branches is regulated by substrate preferences and protein-protein-interactions. This results in a privileged biosynthesis of HSPG over that of CSPGs, explaining the phenotypes of linkeropathies, disease caused by defects in genes involved in the biosynthesis of the common tetrasaccharide linker. Documented feedback loops whereby cells regulate HS sulfation, and hence the interactions of HS with protein partners, may be similarly implemented, e.g., protein tyrosine sulfation and other posttranslational modifications in enzymes of the HSPG pathway. Together, ubiquitous HS, specialized HS, and their biosynthesis model can facilitate research for a better understanding of HSPG roles in physiology and pathology.

Targeting chondroitin sulfate suppresses macropinocytosis of breast cancer cells by modulating syndecan-1 expression

Accumulation of abnormal chondroitin sulfate (CS) chains in breast cancer tissue is correlated with poor prognosis. However, the biological functions of these CS chains in cancer progression remain largely unknown, impeding the development of targeted treatment focused on CS. Previous studies identified chondroitin polymerizing factor (CHPF; also known as chondroitin sulfate synthase 2) is the critical enzyme regulating CS accumulation in breast cancer tissue. We then assessed the association between CHPF-associated proteoglycans (PGs) and signaling pathways in breast cancer datasets. The regulation between CHPF and syndecan 1 (SDC1) was examined at both the protein and RNA levels. Confocal microscopy and image flow cytometry were employed to quantify macropinocytosis. The effects of the 6-O-sulfated CS-binding peptide (C6S-p) on blocking CS functions were tested in vitro and in vivo. Results indicated that the expression of CHPF and SDC1 was tightly associated within primary breast cancer tissue, and high expression of both genes exacerbated patient prognosis. Transforming growth factor beta (TGF-β) signaling was implicated in the regulation of CHPF and SDC1 in breast cancer cells. CHPF supported CS-SDC1 stabilization on the cell surface, modulating macropinocytotic activity in breast cancer cells under nutrient-deprived conditions. Furthermore, C6S-p demonstrated the ability to bind CS-SDC1, increase SDC1 degradation, suppress macropinocytosis of breast cancer cells, and inhibit tumor growth in vivo. Although other PGs may also be involved in CHPF-regulated breast cancer malignancy, this study provides the first evidence that a CS synthase participates in the regulation of macropinocytosis in cancer cells by supporting SDC1 expression on cancer cells.

Glycosaminoglycan microarrays for studying glycosaminoglycan-protein systems

More than 3000 proteins are now known to bind to glycosaminoglycans (GAGs). Yet, GAG-protein systems are rather poorly understood in terms of selectivity of recognition, molecular mechanism of action, and translational promise. High-throughput screening (HTS) technologies are critically needed for studying GAG biology and developing GAG-based therapeutics. Microarrays, developed within the past two decades, have now improved to the point of being the preferred tool in the HTS of biomolecules. GAG microarrays, in which GAG sequences are immobilized on slides, while similar to other microarrays, have their own sets of challenges and considerations. GAG microarrays are rapidly becoming the first choice in studying GAG-protein systems. Here, we review different modalities and applications of GAG microarrays presented to date. We discuss advantages and disadvantages of this technology, explain covalent and non-covalent immobilization strategies using different chemically reactive groups, and present various assay formats for qualitative and quantitative interpretations, including selectivity screening, binding affinity studies, competitive binding studies etc. We also highlight recent advances in implementing this technology, cataloging of data, and project its future promise. Overall, the technology of GAG microarray exhibits enormous potential of evolving into more than a mere screening tool for studying GAG - protein systems.

Complexed amino acid minerals vs. bis-glycinate chelated minerals: Impact on the performance of old laying hens

The present study was to evaluate the effect of trace minerals (Zn, Mn, and Cu) from complexed amino acid minerals (ZMCAA) and bis-glycinate chelated minerals (ZMCGly) in laying hen diets on performance, internal and external egg quality, yolk mineral deposition, intestinal morphometry, and bone characteristics. From 78 to 98 weeks of age, 400 White LSL-Lite strain laying hens were distributed in a randomized design with 4 treatments with 10 replicates per treatment. Treatments were distributed in a 2 × 2 factorial arrangement using either Zn, Mn, and Cu of ZMCAA or ZMCGly source at 2 levels: low (20, 20, and 3.5 mg/kg of Zn, Mn, and Cu, respectively) or high (40, 40, and 7 mg/kg of Zn, Mn, and Cu, respectively). The analysis of variance was performed, and in cases where differences were observed, the means were compared using Tukey's test (P < 0.05). The source and level of trace mineral supplementation had a significant impact on the performance of laying hens. Hens fed ZMCAA had higher egg production (P = 0.01), egg weight (P = 0.02), egg mass (P = 0.01), and lower feed conversion ratio (P = 0.05) compared to those fed ZMCGly. The ZMCAA supplementation showed higher albumen height (P = 0.01), albumen weight (P = 0.01), and eggshell thickness (P < 0.01). The deposition of Zn (P < 0.01), Mn (P < 0.01), and Cu (P < 0.01) in the egg yolk was greater for hens received ZMCAA. Tibia weight (P = 0.04) and bone densitometry (P < 0.01) in the tibia were higher with ZMCAA supplementation. In the small intestine, ZMCAA resulted in longer villi (P = 0.02) and shorter crypt depth (P = 0.01) in the duodenum. Jejunum and ileum measurements were influenced by the level and source of trace minerals (P < 0.05). Laying hens fed ZMCAA exhibited superior performance, egg quality, deposition of trace minerals in the egg yolk, and bone density compared to hens fed ZMCGly. In this study, older laying hens supplemented with ZMCAA at lower levels demonstrated adequate levels of supplementation.

CHST11-modified chondroitin 4-sulfate as a potential therapeutic target for glioblastoma

Aberrant chondroitin sulfate (CS) accumulation in glioblastoma (GBM) tissue has been documented, but the role of excessive CS in GBM progression and whether it can be a druggable target are largely unknown. The aim of this study is to clarify the biological functions of CHST11 in GBM cells, and evaluate therapeutic effects of blocking CHST11-derived chondroitin 4-sulfate (C4S). We investigated the expression of CHST11 in glioma tissue by immunohistochemistry, and analyzed CHST11 associated genes using public RNA sequencing datasets. The effects of CHST11 on aggressive cell behaviors have been studied in vitro and in vivo. We demonstrated that CHST11 is frequently overexpressed in GBM tissue, promoting GBM cell mobility and modulating C4S on GBM cells. We further discovered that CSPG4 is positively correlated with CHST11, and CSPG4 involved in CHST11-mediated cell invasiveness. In addition, GBM patients with high expression of CHST11 and CSPG4 have a significantly shorter survival time. We examined the effects of treating C4S-specific binding peptide (C4Sp) as a therapeutic agent in vitro and in vivo. C4Sp treatment attenuated GBM cell invasiveness and, notably, improved survival rate of orthotopic glioma cell transplant mice. Our results propose a possible mechanism of CHST11 in regulating GBM malignancy and highlight a novel strategy for targeting aberrant chondroitin sulfate in GBM cells.

Genome-wide identification of potential odontogenic genes involved in the dental epithelium-mesenchymal interaction during early odontogenesis

BACKGROUND

Epithelium-mesenchymal interactions are involved in odontogenic processes. Previous studies have focused on the intracellular signalling regulatory network in tooth development, but the functions of extracellular regulatory molecules have remained unclear. This study aims to explore the gene profile of extracellular proteoglycans and their glycosaminoglycan chains potentially involved in dental epithelium-mesenchymal interactions using high-throughput sequencing to provide new understanding of early odontogenesis.

RESULTS

Whole transcriptome profiles of the mouse dental epithelium and mesenchyme were investigated by RNA sequencing (RNA-seq). A total of 1,281 and 1,582 differentially expressed genes were identified between the dental epithelium and mesenchyme at E11.5 and E13.5, respectively. Enrichment analysis showed that extracellular regions and ECM-receptor interactions were significantly enriched at both E11.5 and E13.5. Polymerase chain reaction analysis confirmed that the extracellular proteoglycan family exhibited distinct changes during epithelium-mesenchymal interactions. Most proteoglycans showed higher transcript levels in the dental mesenchyme, whereas only a few were upregulated in the epithelium at both stages. In addition, 9 proteoglycans showed dynamic expression changes between these two tissue compartments. Gpc4, Sdc2, Spock2, Dcn and Lum were expressed at higher levels in the dental epithelium at E11.5, whereas their expression was significantly higher in the dental mesenchyme at E13.5, which coincides with the odontogenic potential shift. Moreover, the glycosaminoglycan biosynthetic enzymes Ext1, Hs3st1/5, Hs6st2/3, Ndst3 and Sulf1 also exhibited early upregulation in the epithelium but showed markedly higher expression in the mesenchyme after the odontogenic potential shift.

CONCLUSION

This study reveals the dynamic expression profile of extracellular proteoglycans and their biosynthetic enzymes during the dental epithelium-mesenchymal interaction. This study offers new insight into the roles of extracellular proteoglycans and their distinct sulfation underlying early odontogenesis.

Transcriptomic analysis of mid-secretory endometrium reveals essential immune factors associated with pregnancy after single euploid blastocyst transfer

PURPOSE

Implantation is a limiting factor for treatment success in assisted reproduction. Both embryonic and endometrial factors contribute to implantation. Embryonic factors have often been ignored in previous studies about the role of endometrium in implantation. In this study, we sought to identify the endometrial genes associated with negative pregnancy outcomes following the transfer of a single euploid blastocyst.

METHODS

Computational analyses of the transcriptomes of mid-secretory endometria from nine pregnant and seven non-pregnant patients in a cycle preceding the transfer of a single euploid blastocyst in a vitrified-warmed cycle were performed.

RESULTS

Principal component analysis of two reported endometrial receptivity gene sets showed close clustering of the pregnant and non-pregnant samples. Differential gene expression analysis and co-expression module analysis identified 131 genes associated with the pregnancy status. The endometrial signatures identified highlight the importance of immune and metabolic regulation in pregnancy outcome. Network analysis identified 20 hub genes that could predict pregnancy outcomes with 88.9% sensitivity and 85.7% specificity. Single-cell gene expression analysis highlighted the regulation of endometrial natural killer (NK) cells, T cells, and macrophages during embryo implantation. Immune cell abundance analysis supported the dysregulation of cytotoxic immune cells in the endometria of non-pregnant women.

CONCLUSIONS

We reported the first endometrial gene signature associated with pregnancy after elimination of embryo aneuploidy and highlighted the importance of the endometrial immune microenvironment and metabolic status in pregnancy outcomes.

Simultaneous production of N-acetylheparosan and recombinant chondroitin using gene-engineered Escherichia coli K5

N-Acetylheparosan and chondroitin are increasingly needed as alternative sources of animal-derived sulfated glycosaminoglycans (GAGs) and as inert substances in medical devices and pharmaceuticals. The N-acetylheparosan productivity of E. coli K5 has achieved levels of industrial applications, whereas E.coli K4 produces a relatively lower amount of fructosylated chondroitin. In this study, the K5 strain was gene-engineered to co-express K4-derived, chondroitin-synthetic genes, namely kfoA and kfoC. The productivities of total GAG and chondroitin in batch culture were 1.2 g/L and 1.0 g/L respectively, which were comparable to the productivity of N-acetylheparosan in the wild K5 strain (0.6-1.2 g/L). The total GAG of the recombinant K5 was partially purified by DEAE-cellulose chromatography and was subjected to degradation tests with specific GAG-degrading enzymes combined with HPLC and 1H NMR analyses. The results indicated that the recombinant K5 simultaneously produced both 100-kDa chondroitin and 45-kDa N-acetylheparosan at a weight ratio of approximately 4:1. The content of chondroitin in total GAG partially purified was 73.2%. The molecular weight of recombinant chondroitin (100 kDa) was 5-10 times higher than that of commercially available chondroitin sulfate. These results indicated that the recombinant K5 strain acquired the chondroitin-producing ability without altering the total GAG productivity of the host.

Fucosyltransferase 8 (FUT8) and core fucose expression in oxidative stress response

GlycoMaple is a new tool to predict glycan structures based on the expression levels of 950 genes encoding glycan biosynthesis-related enzymes and proteins using RNA-seq data. The antioxidant response, protecting cells from oxidative stress, has been focused on because its activation may relieve pathological conditions, such as neurodegenerative diseases. Genes involved in the antioxidant response are defined within the GO:0006979 category, including 441 human genes. Fifteen genes overlap between the glycan biosynthesis-related genes defined by GlycoMaple and the antioxidant response genes defined by GO:0006979, one of which is FUT8. 5-Hydroxy-4-phenyl-butenolide (5H4PB) extracted from Chinese aromatic vinegar induces the expression of a series of antioxidant response genes that protect cells from oxidative stress via activation of the nuclear factor erythroid 2-related factor 2-antioxidant response element pathway. Here, we show that FUT8 is upregulated in both our RNA-seq data set of 5H4PB-treated cells and publicly available RNA-seq data set of cells treated with another antioxidant, sulforaphane. Applying our RNA-seq data set to GlycoMaple led to a prediction of an increase in the core fucose of N-glycan that was confirmed by flow cytometry using a fucose-binding lectin. These results suggest that FUT8 and core fucose expression may increase upon the antioxidant response.

Glycosaminoglycan Analysis: Purification, Structural Profiling, and GAG-Protein Interactions

Glycosaminoglycans (GAGs) are long, linear polysaccharides that are ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These complex carbohydrates are composed of alternating glucosamine and uronic acids that can be heterogeneously N- and O-sulfated. The arrangement and orientation of the sulfated sugar residues specify the location of distinct ligand binding sites on the cell surface, and their capacity to bind ligands impacts cell growth and development, the ability to form tissues and organs, and normal physiology. The heterogeneous nature of GAGs and their inherent structural diversity across different tissues, cell types, and disease states creates challenges to characterizing their structure and function. Here, we describe detailed methods to investigate GAG-protein interactions in vitro and evaluate the structural composition of two classes of sulfated GAGs, heparan sulfate and chondroitin/dermatan sulfate, using liquid chromatography, mass spectrometry, and radiolabeling techniques. Overall, these methods facilitate the evaluation of GAG structure and function to uncover the unique roles these molecules play in cell biology and human disease.

Metastatic phenotype and immunosuppressive tumour microenvironment in pancreatic ductal adenocarcinoma: Key role of the urokinase plasminogen activator (PLAU)

Background

Previous studies have revealed the role of dysregulated urokinase plasminogen activator (encoded by PLAU) expression and activity in several pathways associated with cancer progression. However, systematic investigation into the association of PLAU expression with factors that modulate PDAC (pancreatic ductal adenocarcinoma) progression is lacking, such as those affecting stromal (pancreatic stellate cell, PSC)-cancer cell interactions, tumour immunity, PDAC subtypes and clinical outcomes from potential PLAU inhibition.

Methods

This study used an integrated bioinformatics approach to identify prognostic markers correlated with PLAU expression using different transcriptomics, proteomics, and clinical data sets. We then determined the association of dysregulated PLAU and correlated signatures with oncogenic pathways, metastatic phenotypes, stroma, immunosuppressive tumour microenvironment (TME) and clinical outcome. Finally, using an in vivo orthotopic model of pancreatic cancer, we confirmed the predicted effect of inhibiting PLAU on tumour growth and metastasis.

Results

Our analyses revealed that PLAU upregulation is not only associated with numerous other prognostic markers but also associated with the activation of various oncogenic signalling pathways, aggressive phenotypes relevant to PDAC growth and metastasis, such as proliferation, epithelial-mesenchymal transition (EMT), stemness, hypoxia, extracellular cell matrix (ECM) degradation, upregulation of stromal signatures, and immune suppression in the tumour microenvironment (TME). Moreover, the upregulation of PLAU was directly connected with signalling pathways known to mediate PSC-cancer cell interactions. Furthermore, PLAU upregulation was associated with the aggressive basal/squamous phenotype of PDAC and significantly reduced overall survival, indicating that this subset of patients may benefit from therapeutic interventions to inhibit PLAU activity. Our studies with a clinically relevant orthotopic pancreatic model showed that even short-term PLAU inhibition is sufficient to significantly halt tumour growth and, importantly, eliminate visible metastasis.

Conclusion

Elevated PLAU correlates with increased aggressive phenotypes, stromal score, and immune suppression in PDAC. PLAU upregulation is also closely associated with the basal subtype type of PDAC; patients with this subtype are at high risk of mortality from the disease and may benefit from therapeutic targeting of PLAU.

Bridging Glycomics and Genomics: New Uses of Functional Genetics in the Study of Cellular Glycosylation

All living cells are coated with a diverse collection of carbohydrate molecules called glycans. Glycans are key regulators of cell behavior and important therapeutic targets for human disease. Unlike proteins, glycans are not directly templated by discrete genes. Instead, they are produced through multi-gene pathways that generate a heterogenous array of glycoprotein and glycolipid antigens on the cell surface. This genetic complexity has sometimes made it challenging to understand how glycosylation is regulated and how it becomes altered in disease. Recent years, however, have seen the emergence of powerful new functional genomics technologies that allow high-throughput characterization of genetically complex cellular phenotypes. In this review, we discuss how these techniques are now being applied to achieve a deeper understanding of glyco-genomic regulation. We highlight specifically how methods like ChIP-seq, RNA-seq, CRISPR genomic screening and scRNA-seq are being used to map the genomic basis for various cell-surface glycosylation states in normal and diseased cell types. We also offer a perspective on how emerging functional genomics technologies are likely to create further opportunities for studying cellular glycobiology in the future. Taken together, we hope this review serves as a primer to recent developments at the glycomics-genomics interface.

Spatiotemporal diversity and regulation of glycosaminoglycans in cell homeostasis and human disease

Glycosaminoglycans (GAGs) are long, linear polysaccharides that are ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These complex carbohydrates play important roles in many cellular processes and have been implicated in many disease states, including cancer, inflammation, and genetic disorders. GAGs are among the most complex molecules in biology with enormous information content and extensive structural and functional heterogeneity. GAG biosynthesis is a nontemplate-driven process facilitated by a large group of biosynthetic enzymes that have been extensively characterized over the past few decades. Interestingly, the expression of the enzymes and the consequent structure and function of the polysaccharide chains can vary temporally and spatially during development and under certain pathophysiological conditions, suggesting their assembly is tightly regulated in cells. Due to their many key roles in cell homeostasis and disease, there is much interest in targeting the assembly and function of GAGs as a therapeutic approach. Recent advances in genomics and GAG analytical techniques have pushed the field and generated new perspectives on the regulation of mammalian glycosylation. This review highlights the spatiotemporal diversity of GAGs and the mechanisms guiding their assembly and function in human biology and disease.

Heparan Sulfate, Mucopolysaccharidosis IIIB and Sulfur Metabolism Disorders

Mucopolysaccharidosis, type IIIB (MPS IIIB) is a rare disease caused by mutations in the N-alpha-acetylglucosaminidase (NAGLU) gene resulting in decreased or absent enzyme activity. On the cellular level, the disorder is characterized by the massive lysosomal storage of heparan sulfate (HS)—one species of glycosaminoglycans. HS is a sulfur-rich macromolecule, and its accumulation should affect the turnover of total sulfur in cells; according to the studies presented here, it, indeed, does. The lysosomal degradation of HS in cells produces monosaccharides and inorganic sulfate (SO₄²⁻). Sulfate is a product of L-cysteine metabolism, and any disruption of its levels affects the entire L-cysteine catabolism pathway, which was first reported in 2019. It is known that L-cysteine level is elevated in cells with the Naglu^−/− gene mutation and in selected tissues of individuals with MPS IIIB. The level of glutathione and the Naglu^−/− cells’ antioxidant potential are significantly reduced, as well as the activity of 3-mercaptopyruvate sulfurtransferase (MPST, EC 2.8.1.2) and the level of sulfane sulfur-containing compounds. The direct reason is not yet known. This paper attempts to identify some of cause-and-effect correlations that may lead to this condition and identifies research directions that should be explored.

Deciphering the Molecular Signature of Human Hyalocytes in Relation to Other Innate Immune Cell Populations

Purpose

Hyalocytes are the tissue-resident innate immune cell population of the vitreous body with important functions in health and vitreoretinal disease. The purpose of this study is to gain new insights into the biology and function of human hyalocytes in comparison to other innate immune cells.

Methods

The present study applies fluorescence-activated cell sorting and RNA sequencing to compare the transcriptional profiles of human hyalocytes, retinal microglia (rMG) and classical, intermediate, and non-classical monocytes isolated from the same patients. Immunohistochemistry was applied for morphological characterization of human hyalocytes.

Results

Pairwise analysis indicates distinct differences between hyalocytes and monocytes, whereas a high degree of similarity to rMG is apparent, with comparable expression levels of established microglia markers, such as TREM2, P2RY12, and TMEM119. Among the top expressed genes in hyalocytes, SPP1, CD74, and C3, were significantly upregulated when compared with monocytes. Despite the high level of similarity of hyalocytes and rMG, ten highly expressed genes in hyalocytes compared to microglia were identified, among them FOS, DUSP1, and EGR2.

Conclusions

This study reveals a high degree of similarity between hyalocytes and retinal microglia. Nevertheless, hyalocytes exhibit some expression differences that may adapt them to the specific needs of the vitreous and provide the basis for deciphering the multiple roles of this fascinating cell population in health and vitreoretinal diseases.

An Overview of in vivo Functions of Chondroitin Sulfate and Dermatan Sulfate Revealed by Their Deficient Mice

Chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) are covalently attached to specific core proteins to form proteoglycans in their biosynthetic pathways. They are constructed through the stepwise addition of respective monosaccharides by various glycosyltransferases and maturated by epimerases as well as sulfotransferases. Structural diversities of CS/DS and HS are essential for their various biological activities including cell signaling, cell proliferation, tissue morphogenesis, and interactions with a variety of growth factors as well as cytokines. Studies using mice deficient in enzymes responsible for the biosynthesis of the CS/DS and HS chains of proteoglycans have demonstrated their essential functions. Chondroitin synthase 1-deficient mice are viable, but exhibit chondrodysplasia, progression of the bifurcation of digits, delayed endochondral ossification, and reduced bone density. DS-epimerase 1-deficient mice show thicker collagen fibrils in the dermis and hypodermis, and spina bifida. These observations suggest that CS/DS are essential for skeletal development as well as the assembly of collagen fibrils in the skin, and that their respective knockout mice can be utilized as models for human genetic disorders with mutations in chondroitin synthase 1 and DS-epimerase 1. This review provides a comprehensive overview of mice deficient in CS/DS biosyntheses.