Glycosaminoglycan chain analysis and characterization (glycosylation/epimerization)

Switching mechanism from AR to EGFR signaling via 3-O-sulfated heparan sulfate in castration-resistant prostate cancer

Androgen deprivation therapy is given to suppress prostate cancer growth; however, some cells continue to grow hormone-independently as castration-resistant prostate cancer (CRPC). Sulfated glycosaminoglycans promote ligand binding to receptors as co-receptors, but their role in CRPC remains unknown. Using the human prostate cancer cell line C4-2, which can proliferate in hormone-dependent and hormone-independent conditions, we found that epidermal growth factor (EGF)-activated EGFR-ERK1/2 signaling via 3-O-sulfated heparan sulfate (HS) produced by HS 3-O-sulfotransferase 1 (HS3ST1) is activated in C4-2 cells under hormone depletion. Knockdown of HS3ST1 in C4-2 cells suppressed hormone-independent growth, and inhibited both EGF binding to the cell surface and activation of EGFR-ERK1/2 signaling. Gefitinib, an EGFR inhibitor, significantly suppressed C4-2 cell proliferation and growth of a xenografted C4-2 tumor in castrated mouse. Collectively, our study has revealed a mechanism by which cancer cells switch to hormone-independent growth and identified the key regulator as 3-O-sulfated HS.

Mice lacking nucleotide sugar transporter SLC35A3 exhibit lethal chondrodysplasia with vertebral anomalies and impaired glycosaminoglycan biosynthesis

SLC35A3 is considered an uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) transporter in mammals and regulates the branching of N-glycans. A missense mutation in SLC35A3 causes complex vertebral malformation (CVM) in cattle. However, the biological functions of SLC35A3 have not been fully clarified. To address these issues, we have established Slc35a3-/-mice using CRISPR/Cas9 genome editing system. The generated mutant mice were perinatal lethal and exhibited chondrodysplasia recapitulating CVM-like vertebral anomalies. During embryogenesis, Slc35a3 mRNA was expressed in the presomitic mesoderm of wild-type mice, suggesting that SLC35A3 transports UDP-GlcNAc used for the sugar modification that is essential for somite formation. In the growth plate cartilage of Slc35a3-/-embryos, extracellular space was drastically reduced, and many flat proliferative chondrocytes were reshaped. Proliferation, apoptosis and differentiation were not affected in the chondrocytes of Slc35a3-/-mice, suggesting that the chondrodysplasia phenotypes were mainly caused by the abnormal extracellular matrix quality. Because these histological abnormalities were similar to those observed in several mutant mice accompanying the impaired glycosaminoglycan (GAG) biosynthesis, GAG levels were measured in the spine and limbs of Slc35a3-/-mice using disaccharide composition analysis. Compared with control mice, the amounts of heparan sulfate, keratan sulfate, and chondroitin sulfate/dermatan sulfate, were significantly decreased in Slc35a3-/-mice. These findings suggest that SLC35A3 regulates GAG biosynthesis and the chondrodysplasia phenotypes were partially caused by the decreased GAG synthesis. Hence, Slc35a3-/- mice would be a useful model for investigating the in vivo roles of SLC35A3 and the pathological mechanisms of SLC35A3-associated diseases.

Enzymatic comparison of two homologous enzymes reveals N-terminal domain of chondroitinase ABC I regulates substrate selection and product generation

Chondroitinase ABC-type I (CSase ABC I), which can digest both chondroitin sulfate (CS) and dermatan sulfate (DS) in an endolytic manner, is an essential tool in structural and functional studies of CS/DS. Although a few CSase ABC I have been identified from bacteria, the substrate-degrading pattern and regulatory mechanisms of them have rarely been investigated. Herein, two CSase ABC I, IM3796 and IM1634, were identified from the intestinal metagenome of CS-fed mice. They show high sequence homology (query coverage: 88.00%, percent identity: 90.10%) except for an extra peptide (Met¹-His¹⁰⁹) at the N-terminus in IM1634, but their enzymatic properties are very different. IM3796 prefers to degrade 6-O-sulfated GalNAc residue-enriched CS into tetra- and disaccharides. In contrast, IM1634 exhibits nearly a thousand times more activity than IM3796, and can completely digest CS/DS with various sulfation patterns to produce disaccharides, unlike most CSase ABC I. Structure modeling showed that IM3796 did not contain an N-terminal domain composed of two β-sheets, which is found in IM1634 and other CSase ABC I. Furthermore, deletion of the N-terminal domain (Met¹-His¹⁰⁹) from IM1634 caused the enzymatic properties of the variant IM1634-T109 to be similar to those of IM3796, and conversely, grafting this domain to IM3796 increased the similarity of the variant IM3796-A109 to IM1634. In conclusion, the comparative study of the new CSase ABC I provides two unique tools for CS/DS-related studies and applications and, more importantly, reveals the critical role of the N-terminal domain in regulating the substrate binding and degradation of these enzymes.

The Interplay of Glycosaminoglycans and Cysteine Cathepsins in Mucopolysaccharidosis

Mucopolysaccharidosis (MPS) consists of a group of inherited lysosomal storage disorders that are caused by a defect of certain enzymes that participate in the metabolism of glycosaminoglycans (GAGs). The abnormal accumulation of GAGs leads to progressive dysfunctions in various tissues and organs during childhood, contributing to premature death. As the current therapies are limited and inefficient, exploring the molecular mechanisms of the pathology is thus required to address the unmet needs of MPS patients to improve their quality of life. Lysosomal cysteine cathepsins are a family of proteases that play key roles in numerous physiological processes. Dysregulation of cysteine cathepsins expression and activity can be frequently observed in many human diseases, including MPS. This review summarizes the basic knowledge on MPS disorders and their current management and focuses on GAGs and cysteine cathepsins expression in MPS, as well their interplay, which may lead to the development of MPS-associated disorders.

A Concise Review of Extraction and Characterization of Chondroitin Sulphate from Fish and Fish Wastes for Pharmacological Application

Chondroitin sulphate (CS) is one of the most predominant glycosaminoglycans (GAGs) available in the extracellular matrix of tissues. It has many health benefits, including relief from osteoarthritis, antiviral properties, tissue engineering applications, and use in skin care, which have increased its commercial demand in recent years. The quest for CS sources exponentially increased due to several shortcomings of porcine, bovine, and other animal sources. Fish and fish wastes (i.e., fins, scales, skeleton, bone, and cartilage) are suitable sources of CS as they are low cost, easy to handle, and readily available. However, the lack of a standard isolation and characterization technique makes CS production challenging, particularly concerning the yield of pure GAGs. Many studies imply that enzyme-based extraction is more effective than chemical extraction. Critical evaluation of the existing extraction, isolation, and characterization techniques is crucial for establishing an optimized protocol of CS production from fish sources. The current techniques depend on tissue hydrolysis, protein removal, and purification. Therefore, this study critically evaluated and discussed the extraction, isolation, and characterization methods of CS from fish or fish wastes. Biosynthesis and pharmacological applications of CS were also critically reviewed and discussed. Our assessment suggests that CS could be a potential drug candidate; however, clinical studies should be conducted to warrant its effectiveness.

A new mouse model of Ehlers-Danlos syndrome generated using CRISPR/Cas9-mediated genomic editing

Musculocontractural Ehlers-Danlos syndrome (mcEDS) is caused by generalized depletion of dermatan sulfate (DS) due to biallelic pathogenic variants in CHST14 encoding dermatan 4-O-sulfotransferase 1 (D4ST1) (mcEDS-CHST14). Here, we generated mouse models for mcEDS-CHST14 carrying homozygous mutations (1 bp deletion or 6 bp insertion/10 bp deletion) in Chst14 through CRISPR/Cas9 genome engineering to overcome perinatal lethality in conventional Chst14-deleted knockout mice. DS depletion was detected in the skeletal muscle of these genome-edited mutant mice, consistent with loss of D4ST1 activity. The mutant mice showed common pathophysiological features, regardless of the variant, including growth impairment and skin fragility. Notably, we identified myopathy-related phenotypes. Muscle histopathology showed variation in fiber size and spread of the muscle interstitium. Decorin localized diffusely in the spread endomysium and perimysium of skeletal muscle, unlike in wild-type mice. The mutant mice showed lower grip strength and decreased exercise capacity compared to wild type, and morphometric evaluation demonstrated thoracic kyphosis in mutant mice. The established CRISPR/Cas9-engineered Chst14 mutant mice could be a useful model to further our understanding of mcEDS pathophysiology and aid in the development of novel treatment strategies.

Summary: CRISPR/Cas9 genome-engineered Chst14^−/− mouse models of musculocontractural Ehlers-Danlos syndrome (mcEDS) display similar myopathic features (particularly those caused by the loss of D4ST1) to mcEDS patients and may facilitate further understanding of mcEDS.

Myopathy Associated With Dermatan Sulfate-Deficient Decorin and Myostatin in Musculocontractural Ehlers-Danlos Syndrome: A Mouse Model Investigation

Carbohydrate sulfotransferase 14 (CHST14) encodes dermatan 4-O-sulfotransferase 1, a critical enzyme for dermatan sulfate (DS) biosynthesis. Musculocontractural Ehlers-Danlos syndrome (mcEDS) is associated with biallelic pathogenic variants of CHST14 and is characterized by malformations and manifestations related to progressive connective tissue fragility. We identified myopathy phenotypes in Chst14-deficient mice using an mcEDS model. Decorin is a proteoglycan harboring a single glycosaminoglycan chain containing mainly DS, which are replaced with chondroitin sulfate (CS) in mcEDS patients with CHST14 deficiency. We studied the function of decorin in the skeletal muscle of Chst14-deficient mice because decorin is important for collagen-fibril assembly and has a myokine role in promoting muscle growth. Although decorin was present in the muscle perimysium of wild-type (Chst14+/+ ) mice, decorin was distributed in the muscle perimysium as well as in the endomysium of Chst14-/- mice. Chst14-/- mice had small muscle fibers within the spread interstitium; however, histopathological findings indicated milder myopathy in Chst14-/- mice. Myostatin, a negative regulator of protein synthesis in the muscle, was upregulated in Chst14-/- mice. In the muscle of Chst14-/- mice, decorin was downregulated compared to that in Chst14+/+ mice. Chst14-/- mice showed altered cytokine/chemokine balance and increased fibrosis, suggesting low myogenic activity in DS-deficient muscle. Therefore, DS deficiency in mcEDS causes pathological localization and functional abnormalities of decorin, which causes disturbances in skeletal muscle myogenesis.

Dermatan sulphate promotes neuronal differentiation in mouse and human stem cells

Dermatan sulphate (DS), a glycosaminoglycan, is present in the extracellular matrix and on the cell surface. Previously, we showed that heparan sulphate plays a key role in the maintenance of the undifferentiated state in mouse embryonic stem cells (mESCs) and in the regulation of their differentiation. Chondroitin sulphate has also been to be important for pluripotency and differentiation of mESCs. Keratan sulphate is a marker of human pluripotent stem cells. To date, however, the function of DS in mESCs has not been clarified. Dermatan 4 sulfotransferase 1, which transfers sulphate to the C-4 hydroxyl group of N-acetylgalactosamine of DS, contributes to neuronal differentiation of mouse neural progenitor cells. Therefore, we anticipated that neuronal differentiation would be induced in mESCs in culture by the addition of DS. To test this expectation, we investigated neuronal differentiation in mESCs and human neural stem cells (hNSCs) cultures containing DS. In mESCs, DS promoted neuronal differentiation by activation of extracellular signal-regulated kinase 1/2 and also accelerated neurite outgrowth. In hNSCs, DS promoted neuronal differentiation and neuronal migration, but not neurite outgrowth. Thus, DS promotes neuronal differentiation in both mouse and human stem cells, suggesting that it offers a novel method for efficiently inducing neuronal differentiation.

b3galt6 Knock-Out Zebrafish Recapitulate β3GalT6-Deficiency Disorders in Human and Reveal a Trisaccharide Proteoglycan Linkage Region

Proteoglycans are structurally and functionally diverse biomacromolecules found abundantly on cell membranes and in the extracellular matrix. They consist of a core protein linked to glycosaminoglycan chains via a tetrasaccharide linkage region. Here, we show that CRISPR/Cas9-mediated b3galt6 knock-out zebrafish, lacking galactosyltransferase II, which adds the third sugar in the linkage region, largely recapitulate the phenotypic abnormalities seen in human β3GalT6-deficiency disorders. These comprise craniofacial dysmorphism, generalized skeletal dysplasia, skin involvement and indications for muscle hypotonia. In-depth TEM analysis revealed disturbed collagen fibril organization as the most consistent ultrastructural characteristic throughout different affected tissues. Strikingly, despite a strong reduction in glycosaminoglycan content, as demonstrated by anion-exchange HPLC, subsequent LC-MS/MS analysis revealed a small amount of proteoglycans containing a unique linkage region consisting of only three sugars. This implies that formation of glycosaminoglycans with an immature linkage region is possible in a pathogenic context. Our study, therefore unveils a novel rescue mechanism for proteoglycan production in the absence of galactosyltransferase II, hereby opening new avenues for therapeutic intervention.

Hyaluronan degradation and release of a hyaluronan-aggrecan complex from perineuronal nets in the aged mouse brain

BACKGROUND

Perineuronal nets (PNNs) are insoluble aggregates of extracellular matrix molecules in the brain that consist of hyaluronan (HA) and chondroitin sulfate proteoglycans (CSPGs). PNNs promote the acquisition and storage of memories by stabilizing the formation of synapses in the adult brain. Although the deterioration of PNNs has been suggested to contribute to the age-dependent decline in brain function, the molecular mechanisms underlying age-related changes in PNNs remain unclear.

METHODS

The amount and solubility of PNN components were investigated by sequential extraction followed by a disaccharide analysis and immunoblotting. We examined the interaction between HA and aggrecan, a major HA-binding CSPG, by combining mass spectrometry and pull-down assays.

RESULTS

The solubility and amount of HA increased in the brain with age. Among several CSPGs, the solubility of aggrecan was selectively elevated during aging. In contrast to alternations in biochemical properties, the expression of PNN components at the transcript level was not markedly changed by aging. The increased solubility of aggrecan was not due to the loss of HA-binding properties. Our results indicated that the degradation of high-molecular-mass HA induced the release of the HA-aggrecan complex from PNNs in the aged brain.

CONCLUSION

The present study revealed a novel mechanism underlying the age-related deterioration of PNNs in the brain.

Systematic investigation of the skin in Chst14-/- mice: A model for skin fragility in musculocontractural Ehlers-Danlos syndrome caused by CHST14 variants (mcEDS-CHST14)

Loss-of-function variants in CHST14 cause a dermatan 4-O-sulfotransferase deficiency named musculocontractural Ehlers-Danlos syndrome-CHST14 (mcEDS-CHST14), resulting in complete depletion of the dermatan sulfate moiety of decorin glycosaminoglycan (GAG) chains, which is replaced by chondroitin sulfate. Recently, we uncovered structural alteration of GAG chains in the skin of patients with mcEDS-CHST14. Here, we conducted the first systematic investigation of Chst14 gene-deleted homozygote (Chst14-/-) mice. We used skin samples of wild-type (Chst14+/+) and Chst14-/- mice. Mechanical fragility of the skin was measured with a tensile test. Pathology was observed using light microscopy, decorin immunohistochemistry and electron microscopy (EM) including cupromeronic blue (CB) staining. Quantification of chondroitin sulfate and dermatan sulfate was performed using enzymatic digestion followed by anion-exchange HPLC. In Chst14-/- mice, skin tensile strength was significantly decreased compared with that in Chst14+/+ mice. EM showed that collagen fibrils were oriented in various directions to form disorganized collagen fibers in the reticular layer. Through EM-based CB staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside of the fibrils, in contrast to them being round and wrapping the collagen fibrils in Chst14+/+ mice. A very low level of dermatan sulfate disaccharides was detected in the skin of Chst14-/- mice by anion-exchange chromatography. Chst14-/- mice, exhibiting similar abnormalities in the GAG structure of decorin and collagen networks in the skin, could be a reasonable model for skin fragility of patients with mcEDS-CHST14, shedding light on the role of dermatan sulfate in maintaining skin strength.

Hyaluronidase-4 is produced by mast cells and can cleave serglycin chondroitin sulfate chains into lower molecular weight forms

Mast cells represent a heterogeneous cell population that is well-known for the production of heparin and the release of histamine upon activation. Serglycin is a proteoglycan that within mast cell α-granules is predominantly decorated with the glycosaminoglycans heparin or chondroitin sulfate (CS) and has a known role in granule homeostasis. Heparanase is a heparin-degrading enzyme, is present within the α-granules, and contributes to granule homeostasis, but an equivalent CS-degrading enzyme has not been reported previously. In this study, using several approaches, including epitope-specific antibodies, immunohistochemistry, and EM analyses, we demonstrate that human HMC-1 mast cells produce the CS-degrading enzymes hyaluronidase-1 (HYAL1) and HYAL4. We observed that treating the two model CS proteoglycans aggrecan and serglycin with HYAL1 and HYAL4 in vitro cleaves the CS chains into lower molecular weight forms with nonreducing end oligosaccharide structures similar to CS stub neoepitopes generated after digestion with the bacterial lyase chondroitinase ABC. We found that these structures are associated with both the CS linkage region and with structures more distal toward the nonreducing end of the CS chain. Furthermore, we noted that HYAL4 cleaves CS chains into lower molecular weight forms that range in length from tetra- to dodecasaccharides. These results provide first evidence that mast cells produce HYAL4 and that this enzyme may play a specific role in maintaining α-granule homeostasis in these cells by cleaving CS glycosaminoglycan chains attached to serglycin.

Compositional analysis of the glycosaminoglycan family in velvet antlers of Sika deer (Cervus nippon) at different growing stages

Glycosaminoglycans (GAG) from the velvet antlers of Sika deer (Cervus nippon) at the different growing stages (Fukurozuno, Anshi, and Santajo) of bred and wild deer were isolated and their concentrations and sulfation patterns were analyzed. GAG were digested with chondroitinase ABC, ACI, heparinase-I and -III, and keratanase-II into the corresponding repeating disaccharides of chondroitin sulfate (CS), dermatan sulfate (DS), hyaluronan, heparan sulfate (HS), and keratan sulfate. Cartilaginous tissues contained CS-DS at high concentrations with an almost equal ratio of 4- and 6-sulfates, while 4-sulfate-type CS-DS predominantly occupied ossified tissues, but at low concentrations. High O- and N-sulfation degrees of HS correspond to high ossification. Dynamic quantitative changes in CS-DS and compositional changes in CS-DS and HS were closely associated with the mineralization of deer antlers.

Vascular abnormalities in the placenta of Chst14-/- fetuses: implications in the pathophysiology of perinatal lethality of the murine model and vascular lesions in human CHST14/D4ST1 deficiency

Collagen is one of the most important components of the extracellular matrix that is involved in the strength of tissues, cell adhesion and cell proliferation. Mutations in several collagen and post-translational modification enzyme genes cause Ehlers-Danlos syndrome (EDS) characterized by joint and skin hyperextensibility as well as fragility of various organs. Carbohydrate sulfotransferase 14/dermatan 4-O-sulfotransferase-1 (CHST14/D4ST1) is a critical enzyme for biosynthesis of dermatan sulfate, a side chain of various proteoglycans including biglycan that regulates collagen fibrils through their interaction. Mutations in CHST14 were found to cause a new form of EDS, named musculocontractural type EDS (mcEDS-CHST14). Large subcutaneous hematomas are one of the most serious complications accompanied by decreased quality of life and potential lethality. In this study, Chst14 gene-deleted mice were expected to be an animal model of the vascular abnormalities of mcEDS-CHST14. However, only limited numbers of adult mice were generated because of perinatal lethality in most Chst14 gene-deleted homozygote (Chst14-/-) mice. Therefore, we investigated the placentas of these fetuses. The placentas of Chst14-/- fetuses showed a reduced weight, alterations in the vascular structure, and ischemic and/or necrotic-like changes. Electron microscopy demonstrated an abnormal structure of the basement membrane of capillaries in the placental villus. These findings suggest that Chst14 is essential for placental vascular development and perinatal survival of fetuses. Furthermore, placentas of Chst14-/- fetuses could be a useful model for vascular manifestations in mcEDS-CHST14, such as the large subcutaneous hematomas.

Roles of two types of heparan sulfate clusters in Wnt distribution and signaling in Xenopus

Wnt proteins direct embryonic patterning, but the regulatory basis of their distribution and signal reception remain unclear. Here, we show that endogenous Wnt8 protein is distributed in a graded manner in Xenopus embryo and accumulated on the cell surface in a punctate manner in association with “N-sulfo-rich heparan sulfate (HS),” not with “N-acetyl-rich HS”. These two types of HS are differentially clustered by attaching to different glypicans as core proteins. N-sulfo-rich HS is frequently internalized and associated with the signaling vesicle, known as the Frizzled/Wnt/LRP6 signalosome, in the presence of Wnt8. Conversely, N-acetyl-rich HS is rarely internalized and accumulates Frzb, a secreted Wnt antagonist. Upon interaction with Frzb, Wnt8 associates with N-acetyl-rich HS, suggesting that N-acetyl-rich HS supports Frzb-mediated antagonism by sequestering Wnt8 from N-sulfo-rich HS. Thus, these two types of HS clusters may constitute a cellular platform for the distribution and signaling of Wnt8.

Wnt proteins mediate embryonic development but how protein localization and patterning is regulated is unclear. Here, the authors show that distinct structures with different heparan sulfate modifications (‘N-sulfo-rich’ and ‘N-acetyl-rich’) regulate cellular localization and signal transduction of Wnt8 in Xenopus.

Defect in dermatan sulfate in urine of patients with Ehlers-Danlos syndrome caused by a CHST14/D4ST1 deficiency

PURPOSE

Dermatan sulfate (DS) plays a number of roles in a wide range of biological activities such as cell signaling and tissue morphogenesis through interactions with various extracellular matrix proteins including collagen. Mutations in the carbohydrate sulfotransferase 14 gene (CHST14) encoding CHST14/dermatan 4-O-sulfotransferase-1 (D4ST1), which is responsible for the biosynthesis of DS, cause a recently delineated form of Ehlers-Danlos syndrome (EDS, musculocontractural type 1), an autosomal recessive connective tissue disorder characterized by congenital malformations (specific craniofacial features, and congenital multiple contractures) and progressive fragility-related complications (skin hyperextensibility, bruisability, and fragility with atrophic scars; recurrent dislocations; progressive talipes or spinal deformities; and large subcutaneous hematomas). In an attempt to develop a diagnostic screening method for this type of EDS, the amount of DS in the urine of patients was analyzed.

METHODS

Urinary DS was quantified by an anion-exchange chromatography after treatment with DS-specific degrading enzyme.

RESULTS

DS was not detected in the urine of patients with homo- or compound heterozygous mutations in CHST14. These results suggest that the quantification of DS in urine is applicable to an initial diagnosis of DS-defective EDS.

CONCLUSIONS

This is the first study to perform a urinary disaccharide compositional analysis of chondroitin sulfate (CS)/DS chains in patients with EDS caused by a CHST14/D4ST1 deficiency, and demonstrated the absence of DS chains. This result suggests systemic DS depletion in this disorder, and also proposes the usefulness of a urinary disaccharide compositional analysis of CS/DS chains as a non-invasive screening method for this disorder.

Pivotal Role of Carbohydrate Sulfotransferase 15 in Fibrosis and Mucosal Healing in Mouse Colitis

Induction of mucosal healing (MH) is an important treatment goal in inflammatory bowel disease (IBD). Although the molecular mechanisms underlying MH in IBD is not fully explored, local fibrosis would contribute to interfere mucosal repair. Carbohydrate sulfotransferase 15 (CHST15), which catalyzes sulfation of chondroitin sulfate to produce rare E-disaccharide units, is a novel mediator to create local fibrosis. Here we have used siRNA-based approach of silencing CHST15 in dextran sulfate sodium (DSS) induced colitis in mice, human colon fibroblasts and cancer cell lines. In a DSS-induced acute colitis model, CHST15 siRNA reduced CHST15 mRNA in the colon, serum IL-6, disease activity index (DAI) and accumulation of F4/80+ macrophages and ER-TR7+ fibroblasts, while increased Ki-67+ epithelial cells. In DSS-induced chronic colitis models, CHST15 siRNA reduced CHST15 mRNA in the colon, DAI, alpha-smooth muscle actin+ fibroblasts and collagen deposition, while enhanced MH as evidenced by reduced histological and endoscopic scores. We also found that endoscopic submucosal injection achieved effective pancolonic delivery of CHST15 siRNA in mice. In human CCD-18 Co cells, CHST15 siRNA inhibited the expression of CHST15 mRNA and selectively reduced E-units, a specific product biosynthesized by CHST15, in the culture supernatant. CHST15 siRNA significantly suppressed vimentin in both TGF-ß-stimulated CCD18-Co cells and HCT116 cells while up-regulated BMP7 and E-cadherin in HCT116 cells. The present study demonstrated that blockade CHST15 represses colonic fibrosis and enhances MH partly though reversing EMT pathway, illustrating a novel therapeutic opportunity to refractory and fibrotic lesions in IBD.

Skeletal dysplasia in a consanguineous clan from the island of Nias/Indonesia is caused by a novel mutation in B3GAT3

We describe a large family with disproportionate short stature and bone dysplasia from Nias in which we observed differences in severity when comparing the phenotypes of affected individuals from two remote branches. We conducted a linkage scan in the more severely affected family branch and determined a critical interval of 4.7 cM on chromosome 11. Sequencing of the primary candidate gene TBX10 did not reveal a disease-causing variant. When performing whole exome sequencing we noticed a homozygous missense variant in B3GAT3, c.419C>T [p.(Pro140Leu)]. B3GAT3 encodes β-1,3-glucuronyltransferase-I (GlcAT-I). GlcAT-I catalyzes an initial step of proteoglycan synthesis and the mutation p. (Pro140Leu) lies within the donor substrate-binding subdomain of the catalytic domain. In contrast to the previously published mutation in B3GAT3, c.830G>A [p.(Arg277Gln)], no heart phenotype could be detected in our family. Functional studies revealed a markedly reduced GlcAT-I activity in lymphoblastoid cells from patients when compared to matched controls. Moreover, relative numbers of glycosaminoglycan (GAG) side chains were decreased in patient cells. We found that Pro140Leu-mutant GlcAT-I cannot efficiently transfer GlcA to the linker region trisaccharide. This failure results in a partial deficiency of both chondroitin sulfate and heparan sulfate chains. Since the phenotype of the Nias patients differs from the Larsen-like syndrome described for patients with mutation p.(Arg277Gln), we suggest mutation B3GAT3:p.(Pro140Leu) to cause a different type of GAG linkeropathy showing no involvement of the heart.

Glycosaminoglycan blotting and detection after electrophoresis separation

Separation of glycosaminoglycans (GAGs) by electrophoresis and their characterization to the microgram level are integral parts of biochemical research. Their blotting on membranes after electrophoresis offers the advantage to perform further analysis on single separated species such as identification with antibodies and/or recovery of single band. A method for the blotting and immobilizing of several nonsulfated and sulfated complex GAGs on membranes made hydrophilic and positively charged by cationic detergent after their separation by conventional agarose-gel electrophoresis is illustrated. This approach to the study of these complex macromolecules utilizes the capacity of agarose-gel electrophoresis to separate single species of polysaccharides from mixtures and the membrane technology for further preparative and analytical uses. Nitrocellulose membranes are derivatized with the cationic detergent cetylpyridinium chloride (CPC) and mixtures of GAGs are capillary blotted after their separation in agarose-gel electrophoresis. Single purified species of variously sulfated polysaccharides are transferred on derivatized membranes with an efficiency of 100 % and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining). This enables a lower amount limit of detection of 0.1 μg. Nonsulfated polyanions, for example hyaluronic acid (HA), may also be transferred to membranes with a limit of detection of approximately 0.1-0.5 μg after irreversible or reversible staining. The membranes may be stained with reversible staining and the same lanes used for immunological detection or other applications.

Receptor protein tyrosine phosphatase σ binds to neurons in the adult mouse brain

The role of type IIA receptor protein tyrosine phosphatases (RPTPs), which includes LAR, RPTPσ and RPTPδ, in the nervous system is becoming increasingly recognized. Evidence supports a significant role for these RPTPs during the development of the nervous system as well as after injury, and mutations in RPTPs are associated with human disease. However, a major open question is the nature of the ligands that interact with type IIA RPTPs in the adult brain. Candidates include several different proteins as well as the glycosaminoglycan chains of proteoglycans. In order to investigate this problem, we used a receptor affinity probe assay with RPTPσ-AP fusion proteins on sections of adult mouse brain and to cultured neurons. Our results demonstrate that the major binding sites for RPTPσ in adult mouse brain are on neurons and are not proteoglycan GAG chains, as RPTPσ binding overlaps with the neuronal marker NeuN and was not significantly altered by treatments which eliminate chondroitin sulfate, heparan sulfate, or both. We also demonstrate no overlap of binding of RPTPσ with perineuronal nets, and a unique modulation of RPTPσ binding to brain by divalent cations. Our data therefore point to neuronal proteins, rather than CSPGs, as being the ligands for RPTPσ in the adult, uninjured brain.

Mutations in B3GALT6, which encodes a glycosaminoglycan linker region enzyme, cause a spectrum of skeletal and connective tissue disorders

Proteoglycans (PGs) are a major component of the extracellular matrix in many tissues and function as structural and regulatory molecules. PGs are composed of core proteins and glycosaminoglycan (GAG) side chains. The biosynthesis of GAGs starts with the linker region that consists of four sugar residues and is followed by repeating disaccharide units. By exome sequencing, we found that B3GALT6 encoding an enzyme involved in the biosynthesis of the GAG linker region is responsible for a severe skeletal dysplasia, spondyloepimetaphyseal dysplasia with joint laxity type 1 (SEMD-JL1). B3GALT6 loss-of-function mutations were found in individuals with SEMD-JL1 from seven families. In a subsequent candidate gene study based on the phenotypic similarity, we found that B3GALT6 is also responsible for a connective tissue disease, Ehlers-Danlos syndrome (progeroid form). Recessive loss-of-function mutations in B3GALT6 result in a spectrum of disorders affecting a broad range of skeletal and connective tissues characterized by lax skin, muscle hypotonia, joint dislocation, and spinal deformity. The pleiotropic phenotypes of the disorders indicate that B3GALT6 plays a critical role in a wide range of biological processes in various tissues, including skin, bone, cartilage, tendon, and ligament.

Loss of dermatan sulfate epimerase (DSE) function results in musculocontractural Ehlers-Danlos syndrome

The sulfated polysaccharide dermatan sulfate (DS) forms proteoglycans with a number of distinct core proteins. Iduronic acid-containing domains in DS have a key role in mediating the functions of DS proteoglycans. Two tissue-specific DS epimerases, encoded by DSE and DSEL, and a GalNAc-4-O-sulfotransferase encoded by CHST14 are necessary for the formation of these domains. CHST14 mutations were previously identified for patients with the musculocontractural type of Ehlers-Danlos syndrome (MCEDS). We now identified a homozygous DSE missense mutation (c.803C>T, p.S268L) by the positional candidate approach in a male child with MCEDS, who was born to consanguineous parents. Heterologous expression of mutant full-length and soluble recombinant DSE proteins showed a loss of activity towards partially desulfated DS. Patient-derived fibroblasts also showed a significant reduction in epimerase activity. The amount of DS disaccharides was markedly decreased in the conditioned medium and the cell fraction from cultured fibroblasts of the patient when compared with a healthy control subject, whereas no apparent difference was observed in the chondroitin sulfate (CS) chains from the conditioned media. However, the total amount of CS disaccharides in the cell fraction from the patient was increased ∼1.5-fold, indicating an increased synthesis or a reduced conversion of CS chains in the cell fraction. Stable transfection of patient fibroblasts with a DSE expression vector increased the amount of secreted DS disaccharides. DSE deficiency represents a specific defect of DS biosynthesis. We demonstrate locus heterogeneity in MCEDS and provide evidence for the importance of DS in human development and extracellular matrix maintenance.

Biological functions of iduronic acid in chondroitin/dermatan sulfate

The presence of iduronic acid in chondroitin/dermatan sulfate changes the properties of the polysaccharides because it generates a more flexible chain with increased binding potentials. Iduronic acid in chondroitin/dermatan sulfate influences multiple cellular properties, such as migration, proliferation, differentiation, angiogenesis and the regulation of cytokine/growth factor activities. Under pathological conditions such as wound healing, inflammation and cancer, iduronic acid has diverse regulatory functions. Iduronic acid is formed by two epimerases (i.e. dermatan sulfate epimerase 1 and 2) that have different tissue distribution and properties. The role of iduronic acid in chondroitin/dermatan sulfate is highlighted by the vast changes in connective tissue features in patients with a new type of Ehler–Danlos syndrome: adducted thumb-clubfoot syndrome. Future research aims to understand the roles of the two epimerases and their interplay with the sulfotransferases involved in chondroitin sulfate/dermatan sulfate biosynthesis. Furthermore, a better definition of chondroitin/dermatan sulfate functions using different knockout models is needed. In this review, we focus on the two enzymes responsible for iduronic acid formation, as well as the role of iduronic acid in health and disease.

Expression of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase involved in chondroitin sulfate synthesis is responsible for pulmonary metastasis

Chondroitin sulfate (CS) containing E-disaccharide units, glucuronic acid-N-acetylgalactosamine(4, 6-O-disulfate), at surfaces of tumor cells plays a key role in tumor metastasis. However, the molecular mechanism of the metastasis involving the CS chain-containing E-units is not fully understood. In this study, to clarify the role of E-units in the metastasis and to search for potential molecular targets for anticancer drugs, the isolation and characterization of Lewis lung carcinoma (LLC) cells stably downregulated by the knockdown for the gene encoding N-acetylgalactosamine 4-O-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), which is responsible for the formation of E-units in CS chains, were performed. Knockdown of GalNAc4S-6ST in LLC cells resulted in a reduction in the proportion of E-units, in adhesiveness to extracellular matrix adhesion molecules and in proliferation in vitro. Furthermore, the stable downregulation of GalNAc4S-6ST expression in LLC cells markedly inhibited the colonization of the lungs by inoculated LLC cells and invasive capacity of LLC cells. These results provide clear evidence that CS chain-containing E-units and/or GalNAc4S-6ST play a crucial role in pulmonary metastasis at least through the increased adhesion and the invasive capacity of LLC cells and also provides insights into future drug targets for anticancer treatment.

Highly sulfated hexasaccharide sequences isolated from chondroitin sulfate of shark fin cartilage: insights into the sugar sequences with bioactivities

Chondroitin sulfate (CS) chains regulate the development of the central nervous system in vertebrates and are linear polysaccharides consisting of variously sulfated repeating disaccharides, [-4GlcUAβ1-3GalNAcβ1-](n), where GlcUA and GalNAc represent D-glucuronic acid and N-acetyl-D-galactosamine, respectively. CS chains containing D-disaccharide units [GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate)] are involved in the development of cerebellar Purkinje cells and neurite outgrowth-promoting activity through interaction with a neurotrophic factor, pleiotrophin, resulting in the regulation of signaling. In this study, to obtain further structural information on the CS chains containing d-disaccharide units involved in brain development, oligosaccharides containing D-units were isolated from a shark fin cartilage. Seven novel hexasaccharide sequences, ΔO-D-D, ΔA-D-D, ΔC-D-D, ΔE-A-D, ΔD-D-C, ΔE-D-D and ΔA-B-D, in addition to three previously reported sequences, ΔC-A-D, ΔC-D-C and ΔA-D-A, were isolated from a CS preparation of shark fin cartilage after exhaustive digestion with chondroitinase AC-I, which cannot act on the galactosaminidic linkages bound to D-units. The symbol Δ stands for a 4,5-unsaturated bond of uronic acids, whereas A, B, C, D, E and O represent [GlcUA-GalNAc(4-O-sulfate)], [GlcUA(2-O-sulfate)-GalNAc(4-O-sulfate)], [GlcUA-GalNAc(6-O-sulfate)], [GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate)], [GlcUA-GalNAc(4-O-, 6-O-sulfate)] and [GlcUA-GalNAc], respectively. In binding studies using an anti-CS monoclonal antibody, MO-225, the epitopes of which are involved in cerebellar development in mammals, novel epitope structures, ΔA-D-A, ΔA-D-D and ΔA-B-D, were revealed. Hexasaccharides containing two consecutive D-units or a B-unit will be useful for the structural and functional analyses of CS chains particularly in the neuroglycobiological fields.