Human genetic disorders caused by mutations in genes encoding biosynthetic enzymes for sulfated glycosaminoglycans

Chondroitin sulfate synthase 1 expression is associated with malignant potential of soft tissue sarcomas with myxoid substance

The glycosyltransferases chondroitin sulfate synthase 1 (CHSY1) and exostoses-like 3 (EXTL3) specifically function in biosynthesis of the glycans chondroitin sulfate and heparan sulfate, respectively. Although these glycans play important roles in pathogenesis of various tumors, their significance in soft tissue sarcoma remains unknown. Here, we asked whether CHSY1 or EXTL3 expression correlates with malignant potential of soft tissue sarcomas with myxoid substance. To do so, we examined 40 samples representing specific types, including 12 cases of myxoid liposarcoma, 14 of myxofibrosarcoma, 12 of malignant peripheral nerve sheath tumor, and 2 of low-grade fibromyxoid sarcoma. We performed immunohistochemistry with anti-CHSY1 and anti-EXTL3 antibodies and compared enzyme expression levels with tumor histologic grade as assessed by the Fédération Nationale des Centres de Lutte Contre le Cancer classification and with patient 5-year survival rate. CHSY1 and EXTL3 were expressed in 72.5% and 32.5% of all tumors, respectively. Notably, CHSY1 was strongly expressed in myxofibrosarcoma and malignant peripheral nerve sheath tumor compared with other tumors and significantly associated with higher- rather than lower-grade tumors (P < .01). High expression of CHSY1 was also significantly associated with poorer patient outcomes (P = .031) and higher stages assessed by American Joint Committee on Cancer staging system (P = .004). By contrast, EXTL3 expression was not correlated with histologic grade or patient prognosis. We conclude that CHSY1 expression is closely associated with malignant potential of soft tissue sarcomas with myxoid substance.

Mutations in Biosynthetic Enzymes for the Protein Linker Region of Chondroitin/Dermatan/Heparan Sulfate Cause Skeletal and Skin Dysplasias

Glycosaminoglycans, including chondroitin, dermatan, and heparan sulfate, have various roles in a wide range of biological events such as cell signaling, cell proliferation, tissue morphogenesis, and interactions with various growth factors. Their polysaccharides covalently attach to the serine residues on specific core proteins through the common linker region tetrasaccharide, -xylose-galactose-galactose-glucuronic acid, which is produced through the stepwise addition of respective monosaccharides by four distinct glycosyltransferases. Mutations in the human genes encoding the glycosyltransferases responsible for the biosynthesis of the linker region tetrasaccharide cause a number of genetic disorders, called glycosaminoglycan linkeropathies, including Desbuquois dysplasia type 2, spondyloepimetaphyseal dysplasia, Ehlers-Danlos syndrome, and Larsen syndrome. This review focused on recent studies on genetic diseases caused by defects in the biosynthesis of the common linker region tetrasaccharide.

Chemistry of xylopyranosides

Xylose is one of the few monosaccharidic building blocks that are used by mammalian cells. In comparison with other monosaccharides, xylose is rather unusual and, so far, only found in two different mammalian structures, i.e. in the Notch receptor and as the linker between protein and glycosaminoglycan (GAG) chains in proteoglycans. Interestingly, simple soluble xylopyranosides can not only initiate the biosynthesis of soluble GAG chains but also function as inhibitors of important enzymes in the biosynthesis of proteoglycans. Furthermore, xylose is a major constituent of hemicellulosic xylans and thus one of the most abundant carbohydrates on Earth. Altogether, this has spurred a strong interest in xylose chemistry. The scope of this review is to describe synthesis of xylopyranosyl donors, as well as protective group chemistry, modifications, and conformational analysis of xylose.

Heparan sulfate proteoglycans undergo differential expression alterations in right sided colorectal cancer, depending on their metastatic character

Background

Heparan sulfate proteoglycans (HSPGs) are complex molecules involved in the growth, invasion and metastatic properties of cancerous cells. This study analyses the alterations in the expression patterns of these molecules in right sided colorectal cancer (CRC), both metastatic and non-metastatic.

Methods

Twenty right sided CRCs were studied. A transcriptomic approach was used, employing qPCR to analyze both the expression of the enzymes involved in heparan sulfate (HS) chains biosynthesis, as well as the proteoglycan core proteins. Since some of these proteoglycans can also carry chondroitin sulfate (CS) chains, we include the study of the genes involved in the biosynthesis of these glycosaminoglycans. Immunohistochemical techniques were also used to analyze tissue expression of particular genes showing significant expression differences, of potential interest.

Results

Changes in proteoglycan core proteins differ depending on their location; those located intracellularly or in the extracellular matrix show very similar alteration patterns, while those located on the cell surface vary greatly depending on the nature of the tumor: glypicans 1, 3, 6 and betaglycan are affected in the non-metastatic tumors, whereas in the metastatic, only glypican-1 and syndecan-1 are modified, the latter showing opposing alterations in levels of RNA and of protein, suggesting post-transcriptional regulation in these tumors. Furthermore, in non-metastatic tumors, polymerization of glycosaminoglycan chains is modified, particularly affecting the synthesis of the tetrasaccharide linker and the initiation and elongation of CS chains, HS chains being less affected. Regarding the enzymes responsible for the modificaton of the HS chains, alterations were only found in non-metastatic tumors, affecting N-sulfation and the isoforms HS6ST1, HS3ST3B and HS3ST5. In contrast, synthesis of the CS chains suggests changes in epimerization and sulfation of the C4 and C2 in both types of tumor.

Conclusions

Right sided CRCs show alterations in the expression of HSPGs, including the expression of the cell surface core proteins, many glycosiltransferases and some enzymes that modify the HS chains depending on the metastatic nature of the tumor, resulting more affected in non-metastatic ones. However, matrix proteoglycans and enzymes involved in CS fine structure synthesis are extensively modified independetly of the presence of lymph node metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1724-9) contains supplementary material, which is available to authorized users.

The Regulation of Steroid Action by Sulfation and Desulfation

Steroid sulfation and desulfation are fundamental pathways vital for a functional vertebrate endocrine system. After biosynthesis, hydrophobic steroids are sulfated to expedite circulatory transit. Target cells express transmembrane organic anion-transporting polypeptides that facilitate cellular uptake of sulfated steroids. Once intracellular, sulfatases hydrolyze these steroid sulfate esters to their unconjugated, and usually active, forms. Because most steroids can be sulfated, including cholesterol, pregnenolone, dehydroepiandrosterone, and estrone, understanding the function, tissue distribution, and regulation of sulfation and desulfation processes provides significant insights into normal endocrine function. Not surprisingly, dysregulation of these pathways is associated with numerous pathologies, including steroid-dependent cancers, polycystic ovary syndrome, and X-linked ichthyosis. Here we provide a comprehensive examination of our current knowledge of endocrine-related sulfation and desulfation pathways. We describe the interplay between sulfatases and sulfotransferases, showing how their expression and regulation influences steroid action. Furthermore, we address the role that organic anion-transporting polypeptides play in regulating intracellular steroid concentrations and how their expression patterns influence many pathologies, especially cancer. Finally, the recent advances in pharmacologically targeting steroidogenic pathways will be examined.

The phenotype of the musculocontractural type of Ehlers-Danlos syndrome due to CHST14 mutations

The musculocontractural type of Ehlers-Danlos syndrome (MC-EDS) has been recently recognized as a clinical entity. MC-EDS represents a differential diagnosis within the congenital neuromuscular and connective tissue disorders spectrum. Thirty-one and three patients have been reported with MC-EDS so far with bi-allelic mutations identified in CHST14 and DSE, respectively, encoding two enzymes necessary for dermatan sulfate (DS) biosynthesis. We report seven additional patients with MC-EDS from four unrelated families, including the follow-up of a sib-pair originally reported with the kyphoscoliotic type of EDS in 1975. Brachycephaly, a characteristic facial appearance, an asthenic build, hyperextensible and bruisable skin, tapering fingers, instability of large joints, and recurrent formation of large subcutaneous hematomas are always present. Three of seven patients had mildly elevated serum creatine kinase. The oldest patient was blind due to retinal detachment at 45 years and died at 59 years from intracranial bleeding; her affected brother died at 28 years from fulminant endocarditis. All patients in this series harbored homozygous, predicted loss-of-function CHST14 mutations. Indeed, DS was not detectable in fibroblasts from two unrelated patients with homozygous mutations. Patient fibroblasts produced higher amounts of chondroitin sulfate, showed intracellular retention of collagen types I and III, and lacked decorin and thrombospondin fibrils compared with control. A great proportion of collagen fibrils were not integrated into fibers, and fiber bundles were dispersed into the ground substance in one patient, all of which is likely to contribute to the clinical phenotype. This report should increase awareness for MC-EDS.

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.

Congenital disorders of glycosylation: a concise chart of glycocalyx dysfunction

Glycosylation is a ubiquitous modification of lipids and proteins. Despite the essential contribution of glycoconjugates to the viability of all living organisms, diseases of glycosylation in humans have only been identified over the past few decades. The recent development of next-generation DNA sequencing techniques has accelerated the pace of discovery of novel glycosylation defects. The description of multiple mutations across glycosylation pathways not only revealed tremendous diversity in functional impairments, but also pointed to phenotypic similarities, emphasizing the interconnected flow of substrates underlying glycan assembly. The current list of 100 known glycosylation disorders provides an overview of the significance of glycosylation in human development and physiology.

Proteoglycans and neuronal migration in the cerebral cortex during development and disease

Chondroitin sulfate proteoglycans and heparan sulfate proteoglycans are major constituents of the extracellular matrix and the cell surface in the brain. Proteoglycans bind with many proteins including growth factors, chemokines, axon guidance molecules, and cell adhesion molecules through both the glycosaminoglycan and the core protein portions. The functions of proteoglycans are flexibly regulated due to the structural variability of glycosaminoglycans, which are generated by multiple glycosaminoglycan synthesis and modifying enzymes. Neuronal cell surface proteoglycans such as PTPζ, neuroglycan C and syndecan-3 function as direct receptors for heparin-binding growth factors that induce neuronal migration. The lectican family, secreted chondroitin sulfate proteoglycans, forms large aggregates with hyaluronic acid and tenascins, in which many signaling molecules and enzymes including matrix proteases are preserved. In the developing cerebrum, secreted chondroitin sulfate proteoglycans such as neurocan, versican and phosphacan are richly expressed in the areas that are strategically important for neuronal migration such as the striatum, marginal zone, subplate and subventricular zone in the neocortex. These proteoglycans may anchor various attractive and/or repulsive cues, regulating the migration routes of inhibitory neurons. Recent studies demonstrated that the genes encoding proteoglycan core proteins and glycosaminoglycan synthesis and modifying enzymes are associated with various psychiatric and intellectual disorders, which may be related to the defects of neuronal migration.

Chondroitin / dermatan sulfate modification enzymes in zebrafish development

Chondroitin/dermatan sulfate (CS/DS) proteoglycans consist of unbranched sulfated polysaccharide chains of repeating GalNAc-GlcA/IdoA disaccharide units, attached to serine residues on specific proteins. The CS/DS proteoglycans are abundant in the extracellular matrix where they have essential functions in tissue development and homeostasis. In this report a phylogenetic analysis of vertebrate genes coding for the enzymes that modify CS/DS is presented. We identify single orthologous genes in the zebrafish genome for the sulfotransferases chst7, chst11, chst13, chst14, chst15 and ust and the epimerase dse. In contrast, two copies were found for mammalian sulfotransferases CHST3 and CHST12 and the epimerase DSEL, named chst3a and chst3b, chst12a and chst12b, dsela and dselb, respectively. Expression of CS/DS modification enzymes is spatially and temporally regulated with a large variation between different genes. We found that CS/DS 4-O-sulfotransferases and 6-O-sulfotransferases as well as CS/DS epimerases show a strong and partly overlapping expression, whereas the expression is restricted for enzymes with ability to synthesize di-sulfated disaccharides. A structural analysis further showed that CS/DS sulfation increases during embryonic development mainly due to synthesis of 4-O-sulfated GalNAc while the proportion of 6-O-sulfated GalNAc increases in later developmental stages. Di-sulfated GalNAc synthesized by Chst15 and 2-O-sulfated GlcA/IdoA synthesized by Ust are rare, in accordance with the restricted expression of these enzymes. We also compared CS/DS composition with that of heparan sulfate (HS). Notably, CS/DS biosynthesis in early zebrafish development is more dynamic than HS biosynthesis. Furthermore, HS contains disaccharides with more than one sulfate group, which are virtually absent in CS/DS.

Role for chondroitin sulfate glycosaminoglycan in NEDD9-mediated breast cancer cell growth

There are lines of evidence demonstrating that NEDD9 (Cas-L, HEF-1) plays a key role in the development, progression, and metastasis of breast cancer cells. We previously reported that NEDD9 plays a critical role for promoting migration and growth of MDA-MB-231. In order to further characterize the mechanisms of NEDD9-mediated cancer migration and growth, stable cells overexpressing NEDD9 were generated using HCC38 as a parental cell line which expresses low level of endogenous NEDD9. Microarray studies demonstrated that core proteins of CD44 and Serglycin were markedly upregulated in HCC38(NEDD9) cells compared to HCC38(Vector) cells, while those of Syndecan-1, Syndecan-2, and Versican were downregulated in HCC38(NEDD9). Importantly, enzymes generating chondroitin sulfate glycosaminoglycans (CS) such as CHST11, CHST15, and CSGALNACT1 were upregulated in HCC38(NEDD9) compared to HCC38(Vector). Immunofluorescence studies using specific antibody, GD3G7, confirmed the enhanced expression of CS-E subunit in HCC38(NEDD9). Immunoprecipitation and western blotting analysis demonstrated that CS-E was attached to CD44 core protein. We demonstrated that removing CS by chondroitinase ABC significantly inhibited anchorage-independent colony formation of HCC38(NEDD9) in methylcellulose. Importantly, the fact that GD3G7 significantly inhibited colony formation of HCC38(NEDD9) cells suggests that CS-E subunit plays a key role in this process. Furthermore, treatment of HCC38(NEDD9) cells with chondroitinase ABC or GD3G7 significantly inhibited mammosphere formation. Exogenous addition of CS-E enhanced colony formation and mammosphere formation of HCC38 parental and HCC38(Vector) cells. These results suggest that NEDD9 regulates the synthesis and expression of tumor associated glycocalyx structures including CS-E, which plays a key role in promoting and regulating breast cancer progression and metastasis and possibly stem cell phenotypes.

Sulfation patterns of exogenous chondroitin sulfate affect chondrogenic differentiation of ATDC5 cells

BACKGROUND

Chondroitin sulfate (CS) has been used in cartilage tissue engineering techniques as a positive modulator of scaffolds. CS is a linear polysaccharide consisting of variously sulfated repeating disaccharides. The sulfation patterns of CS are closely related to their biological functions, but only monosulfated CS has been applied to scaffolds. In this study, we investigated the effects of various sulfation patterns of CS on chondrogenic differentiation using ATDC5 chondroprogenitor cells.

METHODS

Disaccharide composition analysis of CS produced by ATDC5 cells at various differentiation steps was performed using high-performance liquid chromatography. ATDC5 cells were cultured with exogenously added, variously sulfated CS. Cell proliferation was analyzed by the 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt (WST-8) assay. Extracellular matrix production was evaluated by Alcian blue staining. Alkaline phosphatase (ALP) activity was evaluated using an ALP assay kit. Expression of chondrogenic markers was evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR) or an enzyme-linked immunosorbent assay (ELISA) using a Type II Collagen Detection kit.

RESULTS

The major components of CS produced by ATDC5 cells were 4-O-monosulfated disaccharides throughout chondrogenic differentiation. Low proportions of 4,6-O-disulfated disaccharides were also detected. Compared to the control group, which did not contain GAGs, the WST-8 assay indicated fewer viable cells when treated with CS-E, which are rich in 4,6-O-disulfated disaccharides. CS-E significantly enhanced Alcian blue staining in a dose-dependent manner and decreased ALP activity after 21 days of culture. Real-time RT-PCR showed that CS-E significantly enhanced all chondrogenic markers, col2a1, aggrecan, and sox9, either at day 4 or day 14 of culture. The results of ELISA analysis confirmed that CS-E significantly enhanced the production of type II collagen.

CONCLUSIONS

ATDC5 cells produced four different monosulfated or disulfated disaccharides in their extracellular matrices. The sulfation patterns of exogenously added CS affected chondrogenic differentiation of ATDC5 cells. In particular, CS-E rich in disulfated disaccharides significantly promoted chondrogenic differentiation of ATDC5 cells. Thus, CS containing this disulfated structure may be a useful scaffold component for enhancing chondrogenesis in cartilage tissue engineering.

Identification of chondroitin sulfate linkage region glycopeptides reveals prohormones as a novel class of proteoglycans

Vertebrates produce various chondroitin sulfate proteoglycans (CSPGs) that are important structural components of cartilage and other connective tissues. CSPGs also contribute to the regulation of more specialized processes such as neurogenesis and angiogenesis. Although many aspects of CSPGs have been studied extensively, little is known of where the CS chains are attached on the core proteins and so far, only a limited number of CSPGs have been identified. Obtaining global information on glycan structures and attachment sites would contribute to our understanding of the complex proteoglycan structures and may also assist in assigning CSPG specific functions. In the present work, we have developed a glycoproteomics approach that characterizes CS linkage regions, attachment sites, and identities of core proteins. CSPGs were enriched from human urine and cerebrospinal fluid samples by strong-anion-exchange chromatography, digested with chondroitinase ABC, a specific CS-lyase used to reduce the CS chain lengths and subsequently analyzed by nLC-MS/MS with a novel glycopeptide search algorithm. The protocol enabled the identification of 13 novel CSPGs, in addition to 13 previously established CSPGs, demonstrating that this approach can be routinely used to characterize CSPGs in complex human samples. Surprisingly, five of the identified CSPGs are traditionally defined as prohormones (cholecystokinin, chromogranin A, neuropeptide W, secretogranin-1, and secretogranin-3), typically stored and secreted from granules of endocrine cells. We hypothesized that the CS side chain may influence the assembly and structural organization of secretory granules and applied surface plasmon resonance spectroscopy to show that CS actually promotes the assembly of chromogranin A core proteins in vitro. This activity required mild acidic pH and suggests that the CS-side chains may also influence the self-assembly of chromogranin A in vivo giving a possible explanation to previous observations that chromogranin A has an inherent property to assemble in the acidic milieu of secretory granules.

OASIS regulates chondroitin 6-O-sulfotransferase 1 gene transcription in the injured adult mouse cerebral cortex

Old astrocyte specifically induced substance (OASIS), a basic leucine zipper transcription factor of the cAMP response element binding/Activating transcription factor family, is induced in reactive astrocytes in vivo and has important roles in quality control of protein synthesis at the endoplasmic reticulum. Reactive astrocytes produce a non-permissive environment for regenerating axons by up-regulating chondroitin sulfate proteoglycans (CSPGs). In this study, we focus on the potential role of OASIS in CSPG production in the adult mouse cerebral cortex. CS-C immunoreactivity, which represents chondroitin sulfate moieties, was significantly attenuated in the stab-injured cortices of OASIS knockout mice compared to those of wild-type mice. We next examined expression of the CSPG-synthesizing enzymes and core proteins of CSPGs in the stab-injured cortices of OASIS knockout and wild-type mice. The levels of chondroitin 6-O-sulfotransferase 1 (C6ST1, one of the major enzymes involved in sulfation of CSPGs) mRNA and protein increased after cortical stab injury of wild-type, but not of OASIS knockout, mice. A C-terminal deletion mutant OASIS over-expressed in rat C6 glioma cells increased C6ST1 transcription by interacting with the first intron region. Neurite outgrowth of cultured hippocampal neurons was inhibited on culture dishes coated with membrane fractions of epidermal growth factor-treated astrocytes derived from wild type but not from OASIS knockout mice. These results suggest that OASIS regulates the transcription of C6ST1 and thereby promotes CSPG sulfation in astrocytes. Through these mechanisms, OASIS may modulate axonal regeneration in the injured cerebral cortex. OASIS, an ER stress-responsive CREB/ATF family member, is up-regulated in the reactive astrocytes of the injured brain. We found that the up-regulated OASIS is involved in the transcriptional regulation of C6ST1 gene, which promotes chondroitin sulfate proteoglycan (CSPG) sulfation. We conclude that OASIS functions as an anti-regenerative transcription factor by establishing a non-permissive microenvironment to regenerating axons.

A novel eliminase from a marine bacterium that degrades hyaluronan and chondroitin sulfate

Lyases cleave glycosaminoglycans (GAGs) in an eliminative mechanism and are important tools for the structural analysis and oligosaccharide preparation of GAGs. Various GAG lyases have been identified from terrestrial but not marine organisms even though marine animals are rich in GAGs with unique structures and functions. Herein we isolated a novel GAG lyase for the first time from the marine bacterium Vibrio sp. FC509 and then recombinantly expressed and characterized it. It showed strong lyase activity toward hyaluronan (HA) and chondroitin sulfate (CS) and was designated as HA and CS lyase (HCLase). It exhibited the highest activities to both substrates at pH 8.0 and 0.5 m NaCl at 30 °C. Its activity toward HA was less sensitive to pH than its CS lyase activity. As with most other marine enzymes, HCLase is a halophilic enzyme and very stable at temperatures from 0 to 40 °C for up to 24 h, but its activity is independent of divalent metal ions. The specific activity of HCLase against HA and CS reached a markedly high level of hundreds of thousands units/mg of protein under optimum conditions. The HCLase-resistant tetrasaccharide Δ(4,5)HexUAα1-3GalNAc(6-O-sulfate)β1-4GlcUA(2-O-sulfate)β1-3GalNAc(6-O-sulfate) was isolated from CS-D, the structure of which indicated that HCLase could not cleave the galactosaminidic linkage bound to 2-O-sulfated d-glucuronic acid (GlcUA) in CS chains. Site-directed mutagenesis indicated that HCLase may work via a catalytic mechanism in which Tyr-His acts as the Brønsted base and acid. Thus, the identification of HCLase provides a useful tool for HA- and CS-related research and applications.

Human genetic disorders and knockout mice deficient in glycosaminoglycan

Glycosaminoglycans (GAGs) are constructed through the stepwise addition of respective monosaccharides by various glycosyltransferases and maturated by epimerases and sulfotransferases. The structural diversity of GAG polysaccharides, including their sulfation patterns and sequential arrangements, is essential for a wide range of biological activities such as cell signaling, cell proliferation, tissue morphogenesis, and interactions with various growth factors. Studies using knockout mice of enzymes responsible for the biosynthesis of the GAG side chains of proteoglycans have revealed their physiological functions. Furthermore, mutations in the human genes encoding glycosyltransferases, sulfotransferases, and related enzymes responsible for the biosynthesis of GAGs cause a number of genetic disorders including chondrodysplasia, spondyloepiphyseal dysplasia, and Ehlers-Danlos syndromes. This review focused on the increasing number of glycobiological studies on knockout mice and genetic diseases caused by disturbances in the biosynthetic enzymes for GAGs.

Chondroitin sulphate N-acetylgalactosaminyl-transferase-1 inhibits recovery from neural injury

Extracellular factors that inhibit axon growth and intrinsic factors that promote it affect neural regeneration. Therapies targeting any single gene have not yet simultaneously optimized both types of factors. Chondroitin sulphate (CS), a glycosaminoglycan, is the most abundant extracellular inhibitor of axon growth. Here we show that mice carrying a gene knockout for CS N-acetylgalactosaminyltransferase-1 (T1), a key enzyme in CS biosynthesis, recover more completely from spinal cord injury than wild-type mice and even chondroitinase ABC-treated mice. Notably, synthesis of heparan sulphate (HS), a glycosaminoglycan promoting axonal growth, is also upregulated in TI knockout mice because HS-synthesis enzymes are induced in the mutant neurons. Moreover, chondroitinase ABC treatment never induces HS upregulation. Taken together, our results indicate that regulation of a single gene, T1, mediates excellent recovery from spinal cord injury by optimizing counteracting effectors of axon regeneration—an extracellular inhibitor of CS and intrinsic promoters, namely, HS-synthesis enzymes.

The glycosaminoglycan chondroitin sulphate inhibits axon growth. Here the authors show that mice deficient in chondroitin sulphate biosynthesis have increased levels of heparan sulphate, which is more efficient than chondroitinase in supporting recovery from spinal cord injury.

An automated mass spectrometry-based screening method for analysis of sulfated glycosaminoglycans

Glycosaminoglycans (GAGs) are linear polysaccharides, consisting of repeated disaccharide units, attached to core proteins in all multicellular organisms. Chondroitin sulfate (CS) and dermatan sulfate (DS) constitute a subgroup of sulfated GAGs for which the degree of sulfation varies between species and tissues. One major goal in GAG characterization is to correlate structure to function. A common approach is to exhaustively degrade the GAG chains and thereafter determine the amount of component disaccharide units. In large-scale studies, there is a need for high-throughput screening methods since existing methods are either very time- or samples consuming. Here, we present a new strategy applying MALDI-TOF MS in positive ion mode for semi-qualitative and quantitative analysis of CS/DS derived disaccharide units. Only a few picomoles of sample are required per analysis and 10 samples can be analyzed in 25 min, which makes this approach an attractive alternative to many established assay methods. The total CS/DS concentration in 19 samples derived from Caenorhabditis elegans and mammalian tissues and cells was determined. The obtained results were well in accordance with concentrations determined by a standard liquid chromatography-based method, demonstrating the applicability of the method for samples from various biological matrices containing CS/DS of different sulfation degrees.

Effects of sesamin on the biosynthesis of chondroitin sulfate proteoglycans in human articular chondrocytes in primary culture

Osteoarthritis (OA) is a degenerative joint disease that progressively causes a loss of joint functions and the impaired quality of life. The most significant event in OA is a high degree of degradation of articular cartilage accompanied by the loss of chondroitin sulfate-proteoglycans (CS-PGs). Recently, the chondroprotective effects of sesamin, the naturally occurring substance found in sesame seeds, have been proved in a rat model of papain-induced osteoarthritis. We hypothesized that sesamin may be associated with possible promotion of the biosynthesis of CS-PGs in human articular chondrocytes. The aim of the study was to investigate the effects of sesamin on the major CS-PG biosynthesis in primary human chondrocyte. The effects of sesamin on the gene expression of the PG core and the CS biosynthetic enzymes as well as on the secretion of glycosaminoglycans (GAGs) in monolayer and pellet culture systems of articular chondrocytes. Sesamin significantly increased the GAGs content both in culture medium and pellet matrix. Real-time-quantitative PCR showed that sesamin promoted the expression of the genes encoding the core protein (ACAN) of the major CS-PG aggrecan and the biosynthetic enzymes (XYLT1, XYLT2, CHSY1 and CHPF) required for the synthesis of CS-GAG side chains. Safranin-O staining of sesamin treated chondrocyte pellet section confirmed the high degree of GAG accumulation. These results were correlated with an increased level of secreted GAGs in the media of cultured articular chondrocytes in both culture systems. Thus, sesamin would provide a potential therapeutic strategy for treating OA patients.

Skeletal dysplasia, global developmental delay, and multiple congenital anomalies in a 5-year-old boy-report of the second family with B3GAT3 mutation and expansion of the phenotype

As a major component of the extracellular matrix, proteoglycans influence the mechanical properties of connective tissue and play an important role in cell-cell and cell-matrix interactions. Genetic defects of proteoglycan biosynthesis lead to multi-system disorders, often most prominently affecting the skeletal system and skin. Specific deficiencies in the enzymes involved in the biosynthesis of the linkage region between the core of the proteoglycan protein and its glycosaminoglycan side chains are known as linkeropathies. We report on a patient from a second family with a homozygous c.830G>A (p.Arg277Gln) mutation in the B3GAT3 gene. The clinical features expand the previously reported phenotype of B3GAT3 mutations and of linkeropathies in general. This patient has short stature, facial dysmorphisms, skeletal findings, joint laxity, and cardiac manifestations similar to those previously associated with B3GAT3 mutations. However, he also has developmental delay, a refractive errors, dental defects, pectus carinatum, and skin abnormalities that have only been associated with linkeropathies caused by mutations in B4GALT6 and B4GALT7. He has bilateral inguinal hernias and atlanto-axial as well as atlanto-occipital instability that have not been previously associated with B3GAT3 mutations. We provide a detailed clinical report and a comparative overview of the phenotypic features of the linkeropathies caused by mutations in B3GAT3, B4GALT6, and B4GALT7.

Molecular and bioenergetic differences between cells with African versus European inherited mitochondrial DNA haplogroups: implications for population susceptibility to diseases

The geographic origins of populations can be identified by their maternally inherited mitochondrial DNA (mtDNA) haplogroups. This study compared human cybrids (cytoplasmic hybrids), which are cell lines with identical nuclei but mitochondria from different individuals with mtDNA from either the H haplogroup or L haplogroup backgrounds. The most common European haplogroup is H while individuals of maternal African origin are of the L haplogroup. Despite lower mtDNA copy numbers, L cybrids had higher expression levels for nine mtDNA-encoded respiratory complex genes, decreased ATP (adenosine triphosphate) turnover rates and lower levels of reactive oxygen species production, parameters which are consistent with more efficient oxidative phosphorylation. Surprisingly, GeneChip arrays showed that the L and H cybrids had major differences in expression of genes of the canonical complement system (5 genes), dermatan/chondroitin sulfate biosynthesis (5 genes) and CCR3 (chemokine, CC motif, receptor 3) signaling (9 genes). Quantitative nuclear gene expression studies confirmed that L cybrids had (a) lower expression levels of complement pathway and innate immunity genes and (b) increased levels of inflammation-related signaling genes, which are critical in human diseases. Our data support the hypothesis that mtDNA haplogroups representing populations from different geographic origins may play a role in differential susceptibilities to diseases.

Validation of Urinary Glycosaminoglycans in Iranian patients with Mucopolysaccharidase type I: The effect of urine sedimentation characteristics

OBJECTIVE

The first line-screening test for mucopolysaccharidosis is based on measurement of urinary glycosaminoglycans. The most reliable test for measurement of urine glycosaminoglycans is the 1,9-dimethyleneblue colorimetric assay. Biological markers are affected by ethnical factors, for this reason, the World Health Organization recommends that the diagnostic test characteristics should be used to determine results for different populations. This study determines the diagnostic value of 1,9-dimethyleneblue tests for diagnosis of mucopolysaccharidosis type I patients in Iran.

MATERIALS & METHODS

In addition to routine urine analysis, the qualitative and quantitative measurements of urine glucosaminoglycans were performed with the Berry spot test and 1,9-dimethyleneblue assay. Diagnostic values of the tests were determined using the ROC curve.

RESULTS

Urine total glycosaminoglycans were significantly higher in male subjects than in female subjects. Glycosaminoglycan concentration was markedly decreased in specimens with elevated white blood cell and epithelial cells count. Using a cut-off level of 10.37 mg/g creatinine, sensitivity, and specificity were 100% and 97.22%, respectively, for a 1,9-dimethyleneblue colorimetric assay.

CONCLUSION

Urine glycosaminoglycans concentration significantly differs in our studied population. In addition to determine diagnostic validity of the 1,9-dimethyleneblue test, our results demonstrate the usefulness of measuring glycosaminoglycans for early screening of mucopolysaccharidosis type I Iran.

Clinical and radiographic features of the autosomal recessive form of brachyolmia caused by PAPSS2 mutations

Brachyolmia is a heterogeneous skeletal dysplasia characterized by generalized platyspondyly without significant long-bone abnormalities. Based on the mode of inheritance and radiographic features, at least three types of brachyolmia have been postulated. We recently identified an autosomal recessive form of brachyolmia that is caused by loss-of-function mutations of PAPSS2, the gene encoding PAPS (3'-phosphoadenosine 5'-phosphosulfate) synthase 2. To understand brachyolmia caused by PAPSS2 mutations (PAPSS2-brachyolmia), we extended our PAPSS2 mutation analysis to 13 patients from 10 families and identified homozygous or compound heterozygous mutations in all. Nine different mutations were found: three splice donor-site mutations, three missense mutations, and three insertion or deletion mutations within coding regions. In vitro enzyme assays showed that the missense mutations were also loss-of-function mutations. Phenotypic characteristics of PAPSS2-brachyolmia include short-trunk short stature, normal intelligence and facies, spinal deformity, and broad proximal interphalangeal joints. Radiographic features include platyspondyly with rectangular vertebral bodies and irregular end plates, broad ilia, metaphyseal changes of the proximal femur, including short femoral neck and striation, and dysplasia of the short tubular bones. PAPSS2-brachyolmia includes phenotypes of the conventional clinical concept of brachyolmia, the Hobaek and Toledo types, and is associated with abnormal androgen metabolism.

Expression analysis of a family of developmentally-regulated cytosolic sulfotransferases (SULTs) in Drosophila

We have compared the amino acid sequence of all four cytosolic sulfotransferases (SULTs) in Drosophila and analyzed their spatial expression patterns during development. Three out of four SULTs show distinct expression activity during embryogenesis, while the 4th SULT shows expression only post-embryonically. st1, st3 and st4 are expressed in non-overlapping expression domains mainly confined to organs of the alimentary canal such as esophagus, malphigian tubules, hindgut, as well as in the tracheal system. All these organs are surrounded by the hemolymph suggesting that Drosophila SULTs exert their function in detoxification of substances upon influx from the hemolymph.