Cytodifferentiation and proteoglycan biosynthesis

Effect of Molecular Sizes of Chondroitin Sulfate on Interaction with L-Selectin

Chondroitin sulfate (CS) is a glycosaminoglycan (GAG) side chain of proteoglycans (PGs) which are widely distributed in the extracellular matrix and at cell surface. CS shows a highly structural diversity in not only molecular weight (MW) but sulfonation pattern. CS has been reported to exert anti-inflammatory activity by having effects on cytokine production by helper T cells. In this study, we focused on the structures of CS chains, especially MW of CS, and investigated effect of the different MW of CS on binding affinity with L-selectin and cytokine production by murine splenocytes. Firstly, we fractionated CS by employing gel　filtration chromatography and obtained several CS fractions with different MW. Then the interaction between fractionated CS and L-selectin was analyzed by surface plasmon resonance (SPR). Finally, the influence of MW of CS on cytokine production by murine splenocytes was investigated in vitro. The results showed that interferon-gamma production was significantly increased by mouse splenocytes cocultivated with CS. On the contrary, CS inhibited interleukin 5 production by murine splenocytes depending on MW of the cocultivated CS. These results strongly indicate the existence of the optimal molecular size for an anti-inflammatory effect of CS through cytokine production by murine splenocytes.

Chondroitin sulfate intake inhibits the IgE-mediated allergic response by down-regulating Th2 responses in mice

Chondroitin sulfate (CS) was administered orally to BALB/c mice immunized intraperitoneally with ovalbumin (OVA) and/or dinitrophenylated OVA. The titers of antigen-specific IgE and IgG1 in mouse sera were determined. The antigen-specific IgE production by mice fed ad libitum with CS was significantly inhibited. We also examined the effect of feeding CS on immediate-type hypersensitivity. One hour after antigen stimulation, the ears of mice fed with CS swelled less than those of the control mice. Furthermore, the rise in serum histamine in the mice fed with CS under active systemic anaphylaxis was significantly lower than that in the controls. We next examined the pattern of cytokine production by splenocytes from mice followed by re-stimulation with OVA in vitro. The splenocytes from the mice fed with CS produced less interleukin (IL)-5, IL-10, and IL-13 than those from the control group. In contrast, the production of interferon-gamma and IL-2 by the splenocytes of mice fed with CS was not significantly different from those in the control mice. In addition, the production of transforming growth factor-beta from the splenocytes of mice fed with CS was significantly higher than that of the control mice. Furthermore, we showed that the percentages of CD4(+) cells, CD8(+) cells, and CD4(+)CD25(+) cells in the splenocytes of mice fed with CS are significantly higher than those of the control. These findings suggest that oral intake of CS inhibits the specific IgE production and antigen-induced anaphylactic response by up-regulating regulatory T-cell differentiation, followed by down-regulating the Th2 response.

Chondroitin sulphate structure affects its immunological activities on murine splenocytes sensitized with ovalbumin

Chondroitin sulphate (CS) is a glycosaminoglycan widely distributed in animal tissues, which has anti-inflammatory and chondroprotective properties. We reported previously that chondroitin 4-sulphate (CS-A) up-regulates the antigen-specific Th1 immune response of murine splenocytes sensitized with ovalbumin in vitro, and that CS suppresses the antigen-specific IgE responses. We now demonstrate that a specific sulphation pattern of the CS polysaccharide is required for the Th1-promoted activity, as other polysaccharides such as dextran and dextran sulphate do not significantly induce this activity. While the presence of some O-sulpho groups appear to be essential for activity, CS-A, and synthetically prepared, partially O-sulphonated CS, induce higher Th1-promoted activity than synthetically prepared, fully O-sulphonated CS. CS-A induces an activity greater than chondroitin sulphate B (CS-B) or chondroitin 6-sulphate (CS-C). In addition, chondroitin sulphate E (CS-E) induces greater activity than CS-A or CS-D. These results suggest that the GlcA(beta1-3)GalNAc(4,6-O-disulpho) sequence in CS-E is important for Th1-promoted activity. Furthermore, rat anti-mouse CD62L antibody, an antibody to L-selectin, inhibits the Th1-promoting activity of CS. These results suggest that the Th1-promoted activity could be associated with L-selectin on lymphocytes. These findings describe a new mechanism for the anti-inflammatory and chondroprotective properties of CS that may be useful in designing new therapeutic applications for CS used in the treatment of immediate-type hypersensitivity.

Loss of chondroitin 6-O-sulfotransferase-1 function results in severe human chondrodysplasia with progressive spinal involvement

We studied two large consanguineous families from Oman with a distinct form of spondyloepiphyseal dysplasia (SED Omani type). By using a genome-wide linkage approach, we were able to map the underlying gene to a 4.5-centimorgan interval on chromosome 10q23. We sequenced candidate genes from the region and identified a missense mutation in the chondroitin 6-O-sulfotransferase (C6ST-1) gene (CHST3) changing an arginine into a glutamine (R304Q) in the well conserved 3'-phosphoadenosine 5'-phosphosulfate binding site. C6ST-1 catalyzes the modifying step of chondroitin sulfate (CS) synthesis by transferring sulfate to the C-6 position of the N-acetylgalactosamine of chondroitin. From the crystal structures of other sulfotransferases, it could be inferred that Arg-304 is essential for the structure of the cosubstrate binding site. We used recombinant C6ST-1 to show that the identified missense mutation completely abolishes C6ST-1 activity. Disaccharide composition analysis of CS chains by anion-exchange HPLC shows that both Delta HexA-GalNAc(6S) and Delta HexA(2S)-GalNAc(6S) were significantly reduced in the patient's cells and that Delta HexA-GalNAc(4S,6S), undetectable in controls, was elevated. Analysis of the patient's urine shows marked undersulfation of CS, in particular reduction in 6-O-sulfated disaccharide and an increase in the nonsulfated unit. Our results indicate that the mutation in CHST3 described here causes a specific but generalized defect of CS chain sulfation resulting in chondrodysplasia with major involvement of the spine.

Chondroitin sulfate synthase-3. Molecular cloning and characterization

Recently, it has become evident that chondroitin sulfate (CS) glycosyltransferases, which transfer glucuronic acid and/or N-acetylgalactosamine residues from each UDP-sugar to the nonreducing terminus of the CS chain, form a gene family. We report here a novel human gene (GenBank trade mark accession number AB086062) that possesses a sequence homologous with the human chondroitin sulfate synthase-1 (CSS1) gene, formerly known as chondroitin synthase. The full-length open reading frame consists of 882 amino acids and encodes a typical type II membrane protein. This enzyme contains a beta 3-glycosyltransferase motif and a beta 4-glycosyltransferase motif similar to that found in CSS1. Both the enzymes were expressed in COS-7 cells as soluble proteins, and their enzymatic natures were characterized. Both glucuronyltransferase and N-acetylgalactosaminyltransferase activities were observed when chondroitin, CS polymer, and their corresponding oligosaccharides were used as the acceptor substrates, but no polymerization reaction was observed as in the case of CSS1. The new enzyme was thus designated chondroitin sulfate synthase-3 (CSS3). However, the specific activity of CSS3 was much lower than that of CSS1. The reaction products were shown to have a GlcUA beta 1-3GalNAc linkage and a GalNAc beta 1-4GlcUA linkage in the nonreducing terminus of chondroitin resulting from glucuronyltransferase activity and N-acetylgalactosaminyltransferase activity, respectively. Quantitative real time PCR analysis revealed that the transcript level of CSS3 was much lower than that of CSS1, although it was ubiquitously expressed in various human tissues. These results indicate that CSS3 is a glycosyltransferase having both glucuronyltransferase and N-acetylgalactosaminyltransferase activities. It may make a contribution to CS biosynthesis that differs from that of CSS1.

Chondroitin sulfate synthase-2. Molecular cloning and characterization of a novel human glycosyltransferase homologous to chondroitin sulfate glucuronyltransferase, which has dual enzymatic activities

Chondroitin sulfate is found in a variety of tissues as proteoglycans and consists of repeating disaccharide units of N-acetylgalactosamine and glucuronic acid residues with sulfate residues at various places. We found a novel human gene (GenBank accession number AB086063) that possesses a sequence homologous with the human chondroitin sulfate glucuronyltransferase gene which we recently cloned and characterized. The full-length open reading frame encodes a typical type II membrane protein comprising 775 amino acids. The protein had a domain containing beta 3-glycosyltransferase motif but lacked a typical beta 4-glycosyltransferase motif, which is the same as chondroitin sulfate glucuronyltransferase, whereas chondroitin synthase had both domains. The putative catalytic domain was expressed in COS-7 cells as a soluble enzyme. Surprisingly, both glucuronyltransferase and N-acetylgalactosaminyltransferase activities were observed when chondroitin, chondroitin sulfate, and their oligosaccharides were used as the acceptor substrates. The reaction products were identified to have the linkage of GlcUA beta 1-3GalNAc and GalNAc beta 1-4GlcUA at the non-reducing terminus of chondroitin for glucuronyltransferase activity and N-acetylgalactosaminyltransferase activity, respectively. Quantitative real time PCR analysis revealed that the transcripts were ubiquitously expressed in various human tissues but highly expressed in the pancreas, ovary, placenta, small intestine, and stomach. These results indicate that this enzyme could synthesize chondroitin sulfate chains as a chondroitin sulfate synthase that has both glucuronyltransferase and N-acetylgalactosaminyltransferase activities. Sequence analysis based on three-dimensional structure revealed the presence of not typical but significant beta 4-glycosyltransferase architecture.

Effect of chondroitin sulfate on murine splenocytes sensitized with ovalbumin

Chondroitin sulfate (CS) is a glycosaminoglycan that is widely present in animals organisms, and it has anti-inflammatory and chondroprotective properties. To examine the effects of CS on the immune system, splenocytes obtained from ovalbumin (OVA)-sensitized BALB/c mice were challenged with OVA in the presence of CS, and cytokine levels in the medium of the cultured cells were measured. CS induced secretion of Th1-type cytokines (IFN-gamma, IL-2, and IL-12) by OVA-sensitized splenocytes but suppressed secretion of Th2-type cytokines (IL-5 and IL-10). Flow cytometric assay showed a significantly higher percentage of helper T cells (CD4(+)CD8(-) cells) among the splenocytes cultured with OVA and CS than with OVA alone. Analysis of the IFN-gamma mRNA level of the splenocytes by the real-time quantitative RT-PCR technique revealed higher levels in the splenocytes cultured with OVA and CS than in the splenocytes cultured with OVA alone. This is the first demonstration that CS inhibits antigen-induced IgE production through induction of cytokine secretion by Th1 cells, and this finding suggests a potential use of CS in preventing IgE-mediated allergy.

(1)H nuclear magnetic resonance spectroscopic analysis for determination of glucuronic and iduronic acids in dermatan sulfate, heparin, and heparan sulfate

(1)H NMR spectroscopy has been established for the determination of uronate residues in glycosaminoglycans (GAGs) such as dermatan sulfate (DS), heparin (HP), and heparan sulfate (HS). Because of variation in the sulfonation positions in DS, HP, or HS, interpretation of spectra is difficult. Solvolysis was applied to remove O-sulfo groups from these GAG chains in dimethyl sulfoxide containing 10% methanol at 80 degrees C for 5 h. In the cases of HP and HS, N-sulfo groups on glucosamine residues were also removed under the same conditions. The resulting unsubstituted amino groups in HP and HS chains were re-N-acetylated using acetic anhydride to obtain homogeneous core structure with the exception of the variation of uronate residues. The contents of glucuronate and iduronate residues in the chemically modified DS, HP, and HS samples were analyzed by 600-MHz (1)H NMR spectroscopy. These methods were applied to compositional analysis of uronate residues in GAGs isolated from various sources.

Human glycosaminoglycan glucuronyltransferase I gene and a related processed pseudogene: genomic structure, chromosomal mapping and characterization

Here we describe the characterization of the human glycosaminoglycan glucuronyltransferase I gene (GlcAT-I) and a related pseudogene. The GlcAT-I gene was localized to human chromosome 11q12-q13 by in situ hybridization of metaphase chromosomes. GlcAT-I spanned 7 kb of human genomic DNA and was divided into five exons. Northern blot analysis showed that GlcAT-I exhibited ubiquitous but markedly different expressions in the human tissues examined. The GlcAT-I promoter was approx. 3-fold more active in a melanoma cell line than in a hepatoma cell line, providing evidence for the differential regulation of the gene's expression. Stepwise 5' deletions of the promoter identified a strong enhancer element between -303 and -153 bp that included binding motifs for Ets, CREB (cAMP-response-element-binding protein) and STAT (signal transducers and activators of transcription). Screening of a human genomic library identified one additional distinct genomic clone containing an approx. 1.4 kb sequence region that shared an overall 95.3% nucleotide identity with exons 1-5 of GlcAT-I. However, a lack of intron sequences, as well as the presence of several nucleotide mutations, insertions and deletions that disrupted the potential GlcAT-I reading frame, suggested that the clone contained a processed pseudogene. The pseudogene was localized to chromosome 3. The human genome therefore contains two related GlcAT-I genes that are located on separate chromosomes.

Characterization of oligosaccharides from the chondroitin sulfates. (1)H-NMR and (13)C-NMR studies of reduced disaccharides and tetrasaccharides

Chondroitin sulfates were fragmented using the enzymes chondroitin sulfate ABC endolyase and chondroitin ACII lyase; both disaccharide and tetrasaccharide fragments were isolated after reduction to the corresponding 2-deoxy-2-N-acetylamino-D-galactitol (GalNAc-ol) form. These have the structures: Delta UA(beta 1--3)GalNAc4S-ol, Delta UA(beta 1--3)GalNAc6S-ol, Delta UA2S(beta 1--3)GalNAc6S-ol, Delta UA(beta 1--3)GalNAc4S(beta 1--4)L-IdoA(alpha 1--3)GalNAc4S-ol, Delta UA(beta 1--3)GalNAc4S(beta 1--4)GlcA(beta 1--3)GalNAc4S-ol, Delta UA(beta 1--3)GalNAc6S(beta 1--4)GlcA(beta 1--3)GalNAc4S-ol, Delta UA(beta 1--3)GalNAc6S(beta 1--4)GlcA(beta 1--3)GalNAc6S-ol, Delta UA2S(beta 1--3)GalNAc6S(beta 1--4)GlcA(beta 1--3)GalNAc4S-ol and Delta UA2S(beta 1--3)GalNAc6S(beta 1--4)GlcA(beta 1--3)GalNAc6S-ol, where Delta UA represents a 4,5-unsaturated hexuronic acid (4-deoxy-alpha-Lthreo-hex-4-enepyranosyluronic acid) and 6S/4S/2S represent O-ester sulfate groups at C6/C4/C2 sites. Complete (1)H-NMR and (13)C-NMR data are derived for these species, which may help to alleviate some of the significant difficulties resulting from signal complexity that are currently hindering the characterization and assignment of major and minor structural components within chondroitin sulfate and dermatan sulfate polymers.

Molecular cloning and expression of a novel chondroitin 6-O-sulfotransferase

A novel human chondroitin 6-O-sulfotransferase, designated C6ST-2, was identified by BLAST analysis of expressed sequence tag using the sequence of a previously described human chondroitin 6-O-sulfotransferase (C6ST-1) as a probe. The new cDNA sequence revealed an open reading frame coding for a protein of 486 amino acids with a type II transmembrane protein topology. The amino acid sequence displayed 24% identity to the human C6ST-1, and the highest sequence identity was found in the COOH-terminal catalytic domain. The expression of a soluble recombinant form of the protein in COS-1 cells produced an active sulfotransferase with marked specificity for polymer chondroitin. In contrast, keratan sulfate and oligosaccharides containing the Galbeta1-4GlcNAc sequence, which are good acceptor substrates for the C6ST-1, hardly served as acceptors. The identification of the reaction product indicated that the enzyme is a novel chondroitin 6-O-sulfotransferase (C6ST-2) that mainly transfers sulfate to N-acetylgalactosamine. The coding region of C6ST-2 was contained in a single exon and localized to chromosome Xp11. Northern blot analysis of human brain poly(A)(+) RNA revealed a single transcript of 2.4 kilobase pairs. Reverse transcription-polymerase chain reaction analysis showed that C6ST-2 is developmentally regulated in various tissues with expression persisting through adulthood in the spleen. Thus, we demonstrated the redundancy in chondroitin 6-O-sulfotransferases capable of forming chondroitin 6-sulfate, which is important for understanding the mechanisms leading to specific changes in the sulfation profile of chondroitin sulfate chains in various tissues during development and malignant transformation.

Effect of 6-O-sulfonate hexosamine residue on anticoagulant activity of fully O-sulfonated glycosaminoglycans

Intact and fully O-sulfonated glycosaminoglycans (GAGs) including chondroitin sulfate, dermatan sulfate, hyaluronan, heparan sulfate and heparin were chemically de-O-sulfonated on their hexosamine C-6 position (6-O-desulfonation) using N,O-bis(trimethylsilyl) acetamide. 1H NMR spectroscopy and chemical compositional analysis showed that the chemical de-O-sulfonation at C-6 position of hexosamine residues in both intact and fully O-sulfonated GAGs was completely achieved. Since GAGs and their derivatives are often used as anticoagulant agents, their anti-amidolytic activities were determined. While most of anticoagulant activity of fully O-sulfonated GAGs (FGAGs) and heparin disappeared following chemical 6-O-desulfonation, the activity of 6-O-desulfonated fully O-sulfonated dermatan sulfate (De6FDS) remained. This observation suggests the importance of the position of O-sulfonate groups for anti-coagulant activity.

Molecular cloning and expression of chondroitin 4-sulfotransferase

Chondroitin 4-sulfotransferase (C4ST) catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 4 of N-acetylgalactosamine residue of chondroitin. The enzyme has been previously purified to apparent homogeneity from the serum-free culture medium of rat chondrosarcoma cells (Yamauchi, A., Hirahara, Y., Usui, H., Takeda, Y., Hoshino, M., Fukuta, M., Kimura, J. H., and Habuchi, O. (1999) J. Biol. Chem. 274, 2456-2463). The purified enzyme also catalyzed the sulfation of partially desulfated dermatan sulfate. We have now cloned the cDNA of the mouse C4ST on the basis of the amino acid sequences of peptides obtained from the purified enzyme by protease digestion. This cDNA contains a single open reading frame that predicts a protein composed of 352 amino acid residues. The protein predicts a Type II transmembrane topology. The predicted sequence of the protein contains all of the known amino acid sequence and four potential sites for N-glycosylation, which corresponds to the observation that the purified C4ST is an N-linked glycoprotein. The amino acid sequence of mouse C4ST showed significant sequence homology to HNK-1 sulfotransferase. Comparison of the sequence of mouse C4ST with human HNK-1 sulfotransferase revealed approximately 29% identity and approximately 48% similarity at the amino acid level. When the cDNA was introduced in a eukaryotic expression vector and transfected in COS-7 cells, the sulfotransferase activity that catalyzes the transfer of sulfate to position 4 of GalNAc residue of both chondroitin and desulfated dermatan sulfate was overexpressed. Northern blot analysis showed that, among various mouse adult tissues, 5.7-kilobase message of C4ST was mainly expressed in the brain and kidney.

Preparation and anticoagulant activity of fully O-sulphonated glycosaminoglycans

Glycosaminoglycans including dermatan sulphate, hyaluronan, heparan sulphate and heparin were chemically modified by O-sulphonation. By altering the reaction conditions, products having a different degree of O-sulphonation could be obtained. Glycosaminoglycan derivatives were prepared having no free hydroxyl groups, with sulphoester group/disaccharide unit ratios of 4.0 for dermatan sulphate and hyaluronan, and sulphoester and sulphamide group/disaccharide unit ratios of 4.22 and 4.88 for heparan sulphate and heparin, respectively. 1H NMR spectroscopy showed that the fully O-sulphonated hyaluronan derivative had a glucuronate residue with an altered conformation. Since glycosaminiglycans and their derivatives are often used as anticoagulant/antithrombotic agents, their anti-amidolytic activities were determined. The anti-factor IIa activity of fully O-sulphonated dermatan sulphate, hyaluronan and heparan sulphate ranged from 40 to 80 units/mg, while no anti-factor Xa activity of the fully O-sulphonated glycosaminoglycans was detected. These values are lower than those reported for low-molecular-weight heparins and are consistent with the requirement of an antithrombin III pentasaccharide binding site for anti-factor Xa activity. Interestingly, the anti-factor Xa of heparin is lost by chemical O-sulphonation.

Demonstration of glycosaminoglycans in Caenorhabditis elegans

A considerable amount (approximately 1.6 microg from 1 mg of dried nematode) of non-sulfated chondroitin, two orders of magnitude less yet an appreciable amount of heparan sulfate, and no hyaluronate were found in Caenorhabditis elegans nematodes. The chondroitin chains were heterogeneous in size, being shorter than that of whale cartilage chondroitin sulfate. The disaccharide composition analysis of heparan sulfate revealed diverse sulfation including glucosamine 2-N-sulfation, glucosamine 6-O-sulfation and uronate 2-O-sulfation. These results imply that chondroitin and heparan sulfate are involved in fundamental biological processes.

Characterization of recombinant human glucuronyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans

We characterized the recombinant glucuronyltransferase I (GlcAT-I) involved in the glycosaminoglycan-protein linkage region biosynthesis. The enzyme showed strict specificity for Galbeta1-3Galbeta1-4Xyl, exhibiting negligible incorporation into other galactoside substrates including Galbeta1-3Galbeta1-O-benzyl, Galbeta1-4GlcNAc and Galbeta1-4Glc. A comparison of the GlcAT-I with another beta1,3-glucuronyltransferase involved in the HNK-1 epitope biosynthesis revealed that the two beta1,3-glucuronyltransferases exhibited distinct and no overlapping acceptor substrate specificities in vitro. Nevertheless, the transfection of the GlcAT-I cDNA into COS-1 cells induced the significant expression of the HNK-1 epitope. These results suggested that the high expression of the GlcAT-I gene rendered the cells capable of synthesizing the HNK-1 epitope.

Purification and characterization of chondroitin 4-sulfotransferase from the culture medium of a rat chondrosarcoma cell line

Chondroitin 4-sulfotransferase, which transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 4 of N-acetylgalactosamine in chondroitin, was purified 1900-fold to apparent homogeneity with 6.1% yield from the serum-free culture medium of rat chondrosarcoma cells by affinity chromatography on heparin-Sepharose CL-6B, Matrex gel red A-agarose, 3',5'-ADP-agarose, and the second heparin-Sepharose CL-6B. SDS-polyacrylamide gel electrophoresis of the purified enzyme showed two protein bands. Molecular masses of these protein were 60 and 64 kDa under reducing conditions and 50 and 54 kDa under nonreducing conditions. Both the protein bands coeluted with chondroitin 4-sulfotransferase activity from Toyopearl HW-55 around the position of 50 kDa, indicating that the active form of chondroitin 4-sulfotransferase is a monomer. Dithiothreitol activated the purified chondroitin 4-sulfotransferase. The purified enzyme transferred sulfate to chondroitin and desulfated dermatan sulfate. Chondroitin sulfate A and chondroitin sulfate C were poor acceptors. Chondroitin sulfate E from squid cartilage, dermatan sulfate, heparan sulfate, and completely desulfated N-resulfated heparin hardly served as acceptors of the sulfotransferase. The transfer of sulfate to the desulfated dermatan sulfate occurred preferentially at position 4 of the N-acetylgalactosamine residues flanked with glucuronic acid residues on both reducing and nonreducing sides.

Functional expression and genomic structure of human chondroitin 6-sulfotransferase

The cDNA and gene encoding human chondroitin 6-sulfotransferase (C6ST) have been cloned. The expression of a soluble recombinant form of the protein in COS-1 cells produced an active sulfotransferase, which used as acceptor substrates polymer chondroitin, various chondroitin sulfate isoforms and chondroitin sulfate tetrasaccharides. The identification of the reaction products demonstrated that the enzyme transferred sulfate to position 6 of GalNAc in the GlcAbeta1-3GalNAc but not the IdoAalpha1-3GalNAc nor the GlcAbeta1-3GalNAc(4-O-sulfate) sequences. The human C6ST gene spans more than 20 kb and consists of three exons. The protein-coding domain of the C6ST gene is divided into two discrete exons.

Molecular cloning and expression of glucuronyltransferase I involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans

We isolated a cDNA encoding a novel glucuronyltransferase from human placenta cDNA with the use of the degenerate reverse transcriptase-polymerase chain reaction method. Degenerate primers were designed based upon the amino acid sequence alignment of rat glucuronyltransferase (GlcAT-P) involved in the biosynthesis of the carbohydrate epitope HNK-1 with putative proteins in Caenorhabditis elegans and Schistosoma mansoni. The new cDNA sequence revealed an open reading frame coding for a protein of 335 amino acids with a type II transmembrane protein topology. The amino acid sequence displayed 43% identity to the rat GlcAT-P, and the highest sequence identity was found in the COOH-terminal catalytic domain. The expression of a soluble recombinant form of the protein in COS-1 cells produced an active glucuronyltransferase with marked specificity for a glycoserine Galbeta1-3Galbeta1-4Xylbeta1-O-Ser. In contrast, asialoorosomucoid, which contains the Galbeta1-4GlcNAc sequence and is a good acceptor substrate for the GlcAT-P, did not serve as an acceptor. The reaction product was sensitive to beta-glucuronidase digestion and co-chromatographed with authentic GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser in high-performance liquid chromatography, suggesting that the enzyme is a beta1, 3-glucuronyltransferase. These results indicate that this new member of the glucuronyltransferase gene family is the enzyme previously described as glucuronyltransferase I that forms the glycosaminoglycan-protein linkage region, GlcAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser, of proteoglycans.

Role of chondroitin sulfate-hyaluronan interactions in the viscoelastic properties of extracellular matrices and fluids

The purpose of this study was to investigate the role of chondroitin sulfate-hyaluronan interactions in the viscoelastic properties of tissues and fluids, using capillary and cone-on-plate viscometers. Chondroitin sulfate markedly increased the viscosity of hyaluronan solutions at a wide range of hyaluronan mass (50-1900 kDa) under physiological conditions of pH, temperature, ionic strength and glycosaminoglycan concentration (0.5-40 mg/ml), although the viscosity of the chondroitin sulfate solutions themselves was very low. In the assay using a cone-on-plate viscometer, chondroitin sulfate increased the viscosity of hyaluronan solutions at various shear rates. At low shear rates, the viscosity of a chondroitin sulfate (5 mg/ml)-hyaluronan (0.5 mg/ml) mixture was about 40% of that of an aggrecan (5 mg/ml)-hyaluronan (0.5 mg/ml) mixture, and at 2.8-fold higher concentrations, chondroitin sulfate elicited the same effect on the viscosity of hyaluronan solutions (5 mg/ml) as an aggrecan monomer. In the presence of oscillatory motion, the addition of aggrecan increased the elasticity (storage) modulus G' and the viscosity (loss) modulus G" of hyaluronan solutions and markedly decreased the loss tangent G"/G' at frequencies corresponding to normal joint movements. In contrast, chondroitin sulfate had only a marginal effect on the loss tangent G"/G', although it increased G' and G". These findings demonstrated that chondroitin sulfate, as well as aggrecan, increases the viscosity of hyaluronan solutions, although chondroitin sulfate has less effect on the elasticity of hyaluronan solutions than that of aggrecan, and suggest that chondroitin sulfate may play an important physiological role in determining the viscoelastic properties of extracellular matrices and fluids.

Conformational changes and anticoagulant activity of chondroitin sulfate following its O-sulfonation

Chondroitin sulfate from bovine tracheal cartilage, with the basic structure (4-O-sulfo-D-GalpNAc beta-1-->4-D-GlcpA)n, was chemically modified by O-sulfonation. Depending on the reaction conditions, the products showed a different degree of O-sulfonation. A fully O-sulfonated chondroitin sulfate, having no free hydroxyl groups, and a sulfo ester group:disaccharide unit ratio of 4.0 was prepared. This chondroitin sulfate derivative was shown by 1H NMR spectroscopy to have a uronate residue with an altered conformation. Usually, the uronate residue in chondroitin sulfate resides in the 4C1 form. Fully O-sulfonated chondroitin sulfate had an uronate residue in the 1C4 form at 30 degrees C, similar to the preferred conformation of the 2-O-sulfo-iduronate residue most commonly found in heparin. The 2S0 form of the uronate residue was also found in fully O-sulfonated chondroitin sulfate at 60 degrees C. The anti-factor IIa activity of fully O-sulfonated chondroitin sulfate was 40 units/mg. This value is similar to the activities reported for various low-molecular-weight heparins, and substantially higher than those previously reported for partially O-sulfonated chondroitin sulfates having an average sulfate group/disaccharide unit of 2.5 to 3.3. The anti-factor Xa activity of the fully O-sulfonated chondroitin sulfate was 12 units/mg. This value is considerably lower than the activities reported for various low-molecular-weight heparins, consistent with the critical importance of an antithrombin III pentasaccharide binding site for anti-factor Xa activity. These findings suggest that the conformational change of glucuronic acid residue in chondroitin sulfate resulting from its full O-sulfonation can result in enhanced anticoagulant activity, particularly as measured by anti-factor IIa assay.

Developmental regulation of the sulfation profile of chondroitin sulfate chains in the chicken embryo brain

Developmentally regulated and cell type-specific expression of distinct sulfated glycosaminoglycan structures on cell surface proteoglycans is increasingly recognized as providing information relevant to cell-cell interactions and differentiation in developing organisms. In this report, developmental regulation of both the sulfation profile of chondroitin sulfate chains and activities of chondroitin 4-sulfotransferase (C4ST) and chondroitin 6-sulfotransferase (C6ST) were evaluated in embryonic chicken brain. The results revealed that the sulfation profile and the sulfotransferase activities changed markedly with development, and these alterations were precisely coordinated. Specifically, the proportions of both chondroitin 6-sulfate to 4-sulfate and C6ST to C4ST activities progressively decreased with development. In addition, the total amounts of both chondroitin sulfate chains and the sulfotransferase activities were highest during early embryonic stages and decreased sharply as the development reached completion. The developmental expression of the C6ST gene was also found to parallel the developmental down-regulation of both the C6ST activity and the chondroitin 6-sulfate structure. These findings suggest that the developmentally regulated expression of the sulfotransferases is a predominant factor for stage-specific regulation of chondroitin sulfate structures.

Two distinct chondroitin sulfate ABC lyases. An endoeliminase yielding tetrasaccharides and an exoeliminase preferentially acting on oligosaccharides

Crude enzyme obtained from chondroitin sulfate-induced Proteus vulgaris NCTC 4636 has been fractionated into 1) an endoeliminase capable of depolymerizing chondroitin sulfate and related polysaccharides to produce, as end products, a mixture of Delta4-unsaturated tetra- and disaccharides and 2) an exoeliminase preferentially acting on chondroitin sulfate tetra- and hexasaccharides to yield the respective disaccharides. Isolation of the two enzymes was achieved by a simple two-step procedure: extracting the enzymes from intact P. vulgaris cells with a buffer solution of nonionic surfactant and then treating the extract by cation-exchange chromatography. Each of the enzymes thus prepared was apparently homogeneous as assessed by SDS-polyacrylamide gel electrophoresis and readily crystallized from polyethylene glycol solutions. Both enzymes acted on various substrates such as chondroitin sulfate, chondroitin sulfate proteoglycan, and dermatan sulfate at high, but significantly different, initial rates. They also attacked hyaluronan but at far lower rates and were inactive to keratan sulfate, heparan sulfate, and heparin. Our results show that the known ability of the conventional enzyme called "chondroitinase ABC" to catalyze the complete depolymerization of chondroitin sulfates to unsaturated disaccharides may actually result from the combination reactions by endoeliminase (chondroitin sulfate ABC endolyase) and exoeliminase (chondroitin sulfate ABC exolyase).

Developmental changes in serum UDP-GlcA:chondroitin glucuronyltransferase activity

Bovine, rat, and chicken UDP-GlcA:chondroitin glucuronyltransferase activities in sera during prenatal and postnatal development were systematically measured with polymeric chondroitin as an exogenous acceptor and with UDP-[14C]GlcA as a donor. The results indicated that the activity changed markedly with development in all species examined. Specifically, the activity was the highest at the middle prenatal stage in the bovine and chicken sera and at the late prenatal stage in the rat serum, and it decreased sharply thereafter in all three species. Although the origin of the serum enzyme has not yet been determined, these changes may reflect developmentally regulated biosynthesis of chondroitin sulfate and also suggest that the glucuronyltransferase could be a regulatory enzyme controlling the expression of chondroitin sulfate.

Molecular cloning and expression of chick chondrocyte chondroitin 6-sulfotransferase

Chondroitin 6-sulfotransferase (C6ST) catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate to position 6 of the N-acetylgalactosamine residue of chondroitin. The enzyme has been purified previously to apparent homogeneity from the serum-free culture medium of chick chondrocytes. The purified enzyme also catalyzed the sulfation of keratan sulfate. We have now cloned the cDNA of the enzyme. This cDNA contains a single open reading frame that predicts a protein composed of 458 amino acid residues. The protein predicts a Type II transmembrane topology similar to other glycosyltransferases and heparin/heparan sulfate N-sulfotransferase/N-deacetylases. Evidence that the predicted protein corresponds to the previously purified C6ST was the following: (a) the predicted sequence of the protein contains all of the known amino acid sequence, (b) when the cDNA was introduced in a eukaryotic expression vector and transfected in COS-7 cells, both the C6ST activity and the keratan sulfate sulfotransferase activity were overexpressed, (c) a polyclonal antibody raised against a fusion peptide, which was expressed from a cDNA containing the sequence coding for 150 amino acid residues of the predicted protein, cross-reacted to the purified C6ST, and (d) the predicted protein contained six potential sites for N-glycosylation, which corresponds to the observation that the purified C6ST is an N-linked glycoprotein. The amino-terminal amino acid sequence of the purified protein was found in the transmembrane domain, suggesting that the purified protein might be released from the chondrocytes after proteolytic cleavage in the transmembrane domain.

Tandem mass spectrometry for characterization of unsaturated disaccharides from chondroitin sulfate, dermatan sulfate and hyaluronan

Fast atom bombardment tandem mass spectrometry has been used in the characterization of non-, mono-, di- and trisulfated disaccharides from chondroitin sulfate, dermatan sulfate and hyaluronan. The positional isomers of the sulfate group of mono- and disulfated disaccharides were distinguished from each other by both positive- and negative-ion fast atom bombardment tandem mass spectra, which gave sufficient information characteristic of the isomers. The anomeric isomers of nonsulfated disaccharides were characterized by the technique in the positive-ion mode. This fast atom bombardment collision induced dissociation mass spectrometry/mass spectrometry technique was also applied successfully to the characterization of trisulfated disaccharide.

A chondroitin sulfate epitope in mammalian dental pulp and its developmental expression in mouse dental papilla

The molecular specificity of the dental papilla of a bell-stage tooth was studied by production of dental-papilla-reactive monoclonal antibodies (Mabs). One of the Mabs, designated 7C5, recognized an epitope present in glycosaminoglycan. Several lines of evidence suggested that the 7C5-epitope consists of chondroitin 6-sulfate. The Mab did not react with mouse dental epithelium, but reacted uniformly with mesenchymal tissue in the mandibular process and accumulated in the dental sac and in the papilla of bell-stage tooth germs. The 7C5-staining was lost from the differentiating odontoblasts, while the staining in the molar tooth papilla was accumulated in the subodontoblastic layer. In the developing mouse incisor, the 7C5-epitope was restricted to the lingual-posterior area. The 7C5-epitope was also present in pulpal tissue and predentin of different types of teeth of various mammalian species, including man, sheep, swine, and rat. Collagenase pre-treatment of tissue sections abolished the bulk of the 7C5-reactivity in peridental mesenchyme during embryonic stages while leaving the staining of the dental papilla intact. In newborn and adult teeth, collagenase also impaired the reactivity in the pulp except for the subodontoblastic layer. This suggests the existence of different subpopulations of the 7C5-epitope containing proteoglycans in dental papilla and pulp. A high-molecular-weight proteoglycan, sensitive to chondroitinase ABC but not to heparinase or heparitinase, was immunoprecipitated by 7C5 from extracts of bell-stage mouse tooth germs. We suggest that the evolutionary conservation of chondroitin 6-sulfate in the dental pulp reflects its properties as non-terminally differentiated tissue and perhaps the retention of a potential to differentiate to odontoblasts.

Structural domains in chondroitin sulfate identified by anti-chondroitin sulfate monoclonal antibodies. Immunosequencing of chondroitin sulfates

Monoclonal antibodies have been developed that recognize epitopes in native chondroitin sulfate chains. One of these antibodies, CS-56, reportedly recognizes chondroitin 4- and 6-sulfates. However, this antibody, and four other anti-chondroitin sulfate antibodies, 4C3, 4D3, 6C3 and 7D4, do not recognize epitopes in chondroitin sulfate chains from Swarm rat chondrosarcoma proteoglycan, an indication that native chondroitin sulfate epitopes are more structurally complex than the standard 0-, 4-, and 6-sulfated disaccharide repeats that constitute the backbone of chondroitin sulfate chains. A series of limited chondroitinase digestions was performed on the large aggregating proteoglycan monomer extracted from embryonic chick chondrocyte cultures to identify the digestion parameters required to release the different native chondroitin sulfate epitopes. Some epitopes were more accessible to enzymatic digestion than other epitopes. The approximate location of epitopes was determined by measuring the size of undigested oligosaccharides retained on the core protein following a limited digestion, and correlating this with the level of immunoreactivity for the different antibodies. These analyses identified the locations of three different antigenic domains. Domain 1 resides at the linkage region and contains epitopes for two of the five antibodies, and a portion of the epitopes for a third antibody. Domain 2 lies in the interior of the chain and contains epitopes for three of the five antibodies. Domain 3 resides at the non-reducing terminus and does not contain epitopes for any of the anti-chondroitin sulfate antibodies used in this study. These results indicate that specific native chondroitin sulfate epitopes are non-randomly distributed within the linear framework of chondroitin sulfate chains.

Effects of detergents on the sulfation of chondroitin sulfate by sulfotransferase from chicken embryo epiphyseal cartilage

Homogenates of chicken embryo epiphyseal cartilage were prepared in buffered saline. The bulk of the sulfotransferase was found in the supernatant. However, small amounts of sulfotransferase were consistently found in the particulate fraction. Detergents (Triton X-100 and C12E8) added to the incubation mixture activated the sulfation of exogenous sulfate acceptor by the particulate fraction, whereas detergent treatment during homogenization increased sulfotransferase activity in the supernatant at the expense of that in the particulate fraction. Since sulfotransferase activities of the supernatant and particulate fractions had similar properties concerning specificity, affinity for chondroitin with different degrees of sulfation, thermal stability and activation by protamine, we conclude that the same enzyme is present in both fractions and that detergent activates indirectly, by releasing it to the medium.

Chondroitin sulfates in developing mouse tooth germs. An immunohistochemical study with monoclonal antibodies against chondroitin-4 and chondroitin-6 sulfates

The role of glycosaminoglycans and proteoglycans during ontogenesis is not known. The developing tooth offers a potentially important model for studies of structure-function relationships. In this study, we have analysed the temproal and spatial expression of chondroitins of differing sulfation patterns in embryonic molars and incisors. For this purpose, we have used monoclonal antibodies (Mabs) specific for unsulfated, 4-sulfated, and 6-sulfated forms of chondroitin in conjunction with indirect immunofluorescence or immunoperoxidase labeling. Unsulfated chondroitin was not detected in embryonic teeth. Chondroitin 4- and chondroitin 6-sulfates were present in the stellate reticulum but otherwise they were confined to the dental mesenchyme. The 3B3 and MC21C-epitope, which are markers of 6-sulfated chondroitin, were uniformly distributed in the dental mesenchyme during the bud stage; they disappeared from the dental papilla of the cusps and of the anterior region of the incisor as development proceeded. These epitopes were absent from the basement membrane and from the predentin. In the odontoblastic cell lineage, the 3B3 and MC21C-epitopes were detected only between preodontoblasts at an early stage of differentiation. The monoclonal antibody 2B6 served as a probe to localize chondroitin 4-sulfate. This glycosaminoglycan was detected as early as the dental lamina stage but its expression was restricted to the basement membrane of the teeth until the late bell stage. After the onset of cusp formation, strong staining was also observed over the occlusal region of the dental papilla while the cervical region of the dental papilla remained 2B6-negative. Incisors at the bell stage exhibited a decreasing gradient of immunostaining by 2B6 from their anterior region to their posterior end. The extracellular matrix surrounding preodontoblasts reacted with 2B6 and the predentin, produced by the odontoblasts, was also intensely labeled with this antibody. Comparison between immunostaining with 3B3 and 2B6, on consecutive sections revealed a mutually exclusive pattern of distribution of the corresponding epitopes during odontogenesis. Furthermore, in the continuously growing incisor, a striking positive correlation was found between the immunostaining patterns produced by 3B3 and MC21C and the mitotic indices along the anterior-posterior axis of the tooth. Hence, sulfation of chondroitin seems developmentally regulated. We postulate that changes in the sulfation pattern of chondroitin might play a role in ontogenesis by locally altering the functional properties of the extracellular matrix.

Transient expression of a chondroitin sulfate-related epitope during cartilage histomorphogenesis in the axial skeleton of fetal rats

A monoclonal antibody (MC21C), raised in mouse in response to a mixture of bone proteins, was found to exhibit a unique reactivity toward native chondroitin sulfate chains. Indirect immunofluorescence and immunoperoxidase assays were performed on tissue sections at different stages of fetal rat development, in order to investigate the distribution of the MC21C epitope during cartilage morphogenesis and differentiation. This extracellular marker was present in the sclerotome and its distribution subsequently followed the segmentation pattern of the precartilaginous vertebral column. In addition, changes in the MC21C-immunostaining pattern strongly correlated with the initial growth of the vertebrae. In the axial skeleton (spinal column, basis cranii), the immunostaining by MC21C was maximum in precartilaginous condensations and then rapidly disappeared during the process of chondrification. Also, the perinotochordal matrix was intensely immunostained.

Developmental changes in glycosaminoglycan sulfotransferase activities in animal sera

Glycosaminoglycan sulfotransferase activities in sera during the prenatal and postnatal development of the ox, rat, and chicken were systematically measured with chemically desulfated cartilage chondroitin 4-sulfate, cornea keratan sulfate, and kidney heparan sulfate as exogenous sulfate acceptors and with [35S]sulfate-labeled 3'-phosphoadenosine 5'-phosphosulfate as a sulfate donor. The results of specificity studies and product analyses indicated that these enzymes introduce sulfates at position 6 of the internal N-acetylgalactosamine units of chondroitin, position 6 of the galactose units of keratan sulfate, and position 2 (an amino group) of the glucosamine units of heparan sulfate, respectively. The results of the enzyme assays indicated that (1) the three activities change in a development-associated manner in each animal species, (2) generally, the activities of the former two enzymes decrease with embryonic development and aging after birth, although in chicken serum they increase transiently at the late prenatal stage and decrease thereafter, and (3) the pattern of the changes in heparan sulfate sulfotransferase activity is species-dependent: the activity increases in the rat, decreases in the ox, and does not significantly change in the chicken during prenatal or postnatal development. These alterations may reflect development-associated biosynthesis of the corresponding glycosaminoglycans or maturation of the proteoglycans in some tissues.

A distinct terminal structure in newly synthesized chondroitin sulphate chains

A method was developed for the analysis of non-reducing terminal structure of radiolabelled chondroitin sulphate chains with the aid of N-acetylgalactosamine 4-sulphatase ('terminal 4-sulphatase'), N-acetylgalactosamine 6-sulphatase ('terminal 6-sulphatase'), beta-glucuronidase and beta-N-acetylhexosaminidase. Studies with this method on the non-reducing terminal structure of [35S]sulphate- and [3H]glucose-labelled chondroitin sulphate chains from rat and chick-embryo cartilages showed that the presence of a high proportion of 4-sulphated hexosamine residues is a common feature of the termini of newly synthesized chondroitin sulphate chains. Of the non-reducing terminal 4-sulphated hexosamine residues, about 14% (chick embryo) or 46% (rat) contained an additional sulphate group at position 6. The internal portion of the chondroitin sulphate chains, in contrast, contained little or no 4,6-bis-sulphated hexosamine residue, suggesting that 4,6-bis-sulphated structure may play a role in biosynthetic control at the level of chain termination.

Separation and characterization of chondroitin 6-sulfotransferase and chondroitin 4-sulfotransferase from chick embryo cartilage

Two distinct sulfotransferases (chondroitin 6-sulfotransferase and chondroitin 4-sulfotransferase), which catalyzed transfer of sulfate to position 6 and position 4 of acetylgalactosamine residues of chondroitin, were extracted from epiphyseal cartilage of 14-day-old chick embryos and separated by gel chromatography on Sephacryl S-200 in the presence of 3 M guanidine-HCl. When the enzyme solutions containing 3 M guanidine-HCl were dialyzed against 0.02 M Tris-HCl, pH 7.2, containing 10% glycerol, chondroitin 4-sulfotransferase became almost insoluble, whereas chondroitin 6-sulfotransferase remained soluble. Endogenous acceptors for sulfate transfer were completely removed from both enzyme preparations. Addition of basic proteins and polyamines as well as Mn2+ to the incubation medium caused a stimulation of both sulfotransferases; the stimulation of chondroitin 6-sulfotransferase with these cations was higher than that of chondroitin 4-sulfotransferase. The Km values for 3'-phosphoadenylyl sulfate of both enzymes were much smaller in the presence of protamine or spermine than in the presence of Mn2+. The two sulfotransferases differed in the requirement for sulfhydryl compounds; in the absence of sulfhydryl compounds, the activity of chondroitin 4-sulfotransferase was very low, whereas the activity of chondroitin 6-sulfotransferase was essentially unaffected. These observations indicate that at least two sulfotransferases are involved in the biosynthesis of chondroitin sulfate, and suggest that the production of the isomers of chondroitin sulfate in chondrocytes is affected by various factors such as the intracellular concentration of sulfhydryl compounds and basic substances.

Comparative study on glycosaminoglycan-sulfotransferases in rat costal cartilage and chick embryo cartilage

1. The comparative features of glycosaminoglycan-sulfotransferase system in rat costal cartilage and chick-embryo cartilage were examined. Some different properties of glycosaminoglycan-sulfotransferases in the cartilage of both the animals have been observed. 2. This study shows that rat costal cartilage contains more 4-sulfotransferase than 6-sulfotransferase and that that reverse situation pertains to chick-embryo cartilage, although both the rat and chick-embryo cartilage contain two sulfotransferase species. 3. Our preliminary experiments by use of rat sulfotransferases and chick endogenous acceptor or of chick sulfotransferases and rat sulfotransferases and chick endogenous acceptor or of chick sulfotransferases and rat endogenous acceptor suggest that sulfotransferases in a given tissue play a central role in determining which sites of the N-acetylgalactosamine moiety of chondroitin sulfates occurring in the tissue are sulfated.

Stimulation of glycosaminoglycan sulfotransferase from chick embryo cartilage by basic proteins and polyamines

A soluble glycosaminoglycan sulfotransferase (3'-phosphoadenylylsulfate:chondroitin 4'-sulfotransferase, EC 2.8.2.5) from chick embryo cartilage has been prepared free from endogenous acceptor. The reaction with this enzyme preparation was stimulated by basic proteins and polyamines, the degree of stimulation being dependent on the chemical nature of both basic compounds and acceptor glycosaminoglycans. A maximum stimulation was obtained when protamine (basic compound) and chondroitin (acceptor) were involved in the reaction mixture at a molar ratio of protamine to repeating disaccharide units of chondroitin, 1:100. The stimulation of sulfotransferase activity by basic substances was much higher than that by Mn2+. However, increasing the Mn2+ concentration immediately reduced the stimulation by basic substances. The Km value for 3'-phosphoadenosine 5'-phosphosulfate of the sulfotransferase, when chondroitin was used as acceptor, was 1 . 10(-6) M in the presence of 25 microgram/ml protamine, compared to 2 . 10(-5) M in the absence of protamine. These observations indicate that the basic proteins and polyamines may interact with acceptor polysaccharide, thereby causing an increase in the affinity of the enzyme toward 3'-phosphoadenosine 5'-phosphosulfate.

Human cartilage proteoglycans isolated from normally ossifying and congenitally malformed leg bones

Proteoglycans were extracted with 4 M guanidine HCl solution containing protease inhibitors from various zones of human epiphyseal cartilages of the normally ossifying fibula and cartilaginous rudiment of the tibia of a 12-month-old boy with congenital absence of the tibia, when the knee disarticulation was performed. All the proteoglycan preparations from the epiphyseal cartilages were separated with a sucrose density gradient centrifugation into two components: a heavy, major component and a light one. The molecular size and the proportion of isomeric chondroitin sulfates of polysaccharides of the heavy component differed from those of the light one. The relative amounts of isomeric chondroitin sulfates in the polysacharide moieties of the components also varied among these zones. The glycosaminoglycan content in the rudimentary tibia was equal to that of the epiphyseal cartilage of the fibula. However, proteoglycan preparations showed neither the normal sedimentation profile with two peaks nor the zonal differences as to the proportion of isomeric chondroitin sulfates. These results suggest that the alterations in proteoglycan metabolism might be involved in the pathogenetic mechanisms producing the congenital limb defect.

Recessively inherited, late onset spondylar dysplasia and peripheral corneal opacity with anomalies in urinary mucopolysaccharides: a possible error of chondroitin-6-sulfate synthesis

Two male and two female sibs with an unusual form of spondyloepiphyseal dysplasia were reported. The main clinical features were low stature, moderate shortness of trunk and neck, abnormal span: height ratio, low-normal UBS: LBS ratio, and peripheral corneal punctate opacities only seen by the slitlamp. Normal mental status was present. Typical metachromatic granules were not seen either in bone-marrow cells or in peripheral blood cells. The X-ray picture showed spondylar and pelvic dysplasia. Qualitative rather than quantitative anomalies were shown in the urinary mucopolysaccharides, mostly involving chondroitin-6-sulfate. The genetic data are consistent with autosomal recessive inheritance.