Chick Cartilage Research Articles

Dietary lipids modify the fatty acid composition of cartilage, isolated chondrocytes and matrix vesicles

The effects of dietary lipids on the fatty acid composition of hyaline cartilage, epiphyseal chondrocytes (EC) and matrix vesicles (MV) were evaluated in chicks. A basal semipurified diet was fed to chicks containing one of the following lipid sources at 70 g/kg: soybean oil, butter+corn oil, margarine+corn oil or menhaden oil+corn oil (MEC). Articular and epiphyseal growth cartilage were isolated from the proximal tibiotarsus; EC and MV were subsequently released by trypsin (EC 3.4.21.4) and collagenase (EC 3.4.24.3) digestion followed by ultracentrifugation. The fatty acid composition of polar lipids in chick epiphyseal cartilage at three and six weeks, as well as articular cartilage, EC and MV at eight weeks of age revealed the presence of high levels of saturated and monounsaturated fatty acids (up to 85.5%) but low levels of n-6 polyunsaturated fatty acids (PUFA) (2.6-10.2%). Mead acid (20:3n-9, > 3%) was also present in cartilage, EC and MV lipids, and was unaffected by the dietary lipid treatments. Total n-3 PUFA concentrations were the highest in cartilage, EC and MV of chicks consuming MEC. Feeding MEC lowered the levels of 20:4n-6 in cartilage, but increased 20:5n-3 levels. The data are consistent with those reported previously which showed that cartilage tissues are low in n-6 PUFA and that they contain 20:3n-9. We furthermore demonstrated that the PUFA composition of cartilage can be modified by dietary lipids.

Roles of the nucleational core complex and collagens (types II and X) in calcification of growth plate cartilage matrix vesicles.

Matrix vesicles (MV) were shown to initiate mineralization in cartilage and other vertebrate tissues. However, the factors that drive this process remain to be fully elucidated. Recent studies have shown that a preformed nucleational core consisting mainly of a Ca(2+)-phosphatidylserine-Pi complex, is necessary for the accumulation of Ca2+ by MV. In addition, the collagens attached to the MV surface were shown to play an important role in stimulating Ca2+ uptake. In this study, we extend this knowledge by showing that both, the nucleational core and the collagens (types II and X), are co-requirements for rapid influx of Ca2+ into intact MV. MV to which collagen fragments were attached were released from hypertrophic chicken cartilage by trypsin and collagenase digestion (trypsin/collagenase-released MV (TCRMV), while "collagen-free" MV were released by hyaluronidase and collagenase digestion (hyaluronidase/collagenase-released MV (HCRMV). In contrast to TCRMV which showed active uptake of Ca2+, HCRMV showed only little uptake. However, binding of native type II collagen to HCRMV stimulated uptake of Ca2+. Sucrose gradients separated TCRMV and HCRMV into three different density fractions: a low density top fraction (SI), an intermediate density middle fraction (SII), and a high density pellet fraction (SIII). The SIII fractions of TCRMV and HCRMV contained significantly higher levels of mineral ions than did the SI and SII fractions. Only the SIII fraction of TCRMV which contained a stable nucleational core and surface-attached collagens, showed active Ca2+ uptake; all other sucrose fractions of TCRMV and HCRMV showed little or no uptake. Detergent treatment to purposely rupture the membrane greatly enhanced Ca2+ uptake by the SIII fraction of HCRMV, presumably by exposing the internal nucleational core. Addition of either native type II or type X collagen to the intact SIII fraction of HCRMV stimulated Ca2+ uptake to a level similar to that of the SIII fraction of TCRMV; however, incubation of the SI and SII fractions of either TCRMV or HCRMV with type II or X collagen did not activate Ca2+ uptake. These findings indicate that both a functional nucleational core and surface-attached collagens need to be present to support active mineralization of MV.

An alternative transcript of the chick type III collagen gene that does not encode type III collagen.

Type III collagen, a ubiquitous protein found in most connective tissues, is not present in hyaline cartilage. However, we have identified an alternative transcript of the type III collagen gene in cultured chondrocytes from several embryonic chick cartilages. This RNA contains exons 24-52, but exons 1-23 are replaced by 70 nucleotides of unique sequence, suggesting that transcription initiates at an alternative promoter. Two of the open reading frames in the alternative transcript are out of frame with the collagen coding sequence; a third open reading frame encodes the carboxyl-terminal two-thirds of the collagen sequence. Thus, this RNA cannot serve as a template for synthesis of normal type III collagen and may encode noncollagenous proteins and/or a truncated collagen. The alternative transcript has been detected as early as 2.5 days of embryogenesis and at later stages is present at low levels in many tissues, including limb mesenchyme and cartilage. These results, together with our previous identification of an alternative transcript of the chick alpha 2(I) collagen gene (Bennett, V. D., and Adams, S. L. (1990) J. Biol. Chem. 265, 2223-2230), suggest that some collagen genes may have alternative functions that are independent of their roles in collagen production.

Effect of magnesium chloride and guanidinium chloride on the extraction of components of extracellular matrix from chicken cartilage.

In order to evaluate the effect of chaotropic agents on proteoglycan and non-collagenous proteins, chicken xiphoid cartilage was treated with guanidine-HCl and MgCl2 in different concentrations (1M to 5M), and different periods of time (12, 24, 48 and 72 hr). The maximum yield of uronic acid was obtained with 3M MgCl2 (73.3%). Concentrations of 4M and 5M of MgCl2 showed that much less uronic acid was removed, 55.3% and 38.1% respectively. Extraction with 3M MgCl2 and 3M guanidine-HCl resulted better efficiency when performed for 48 hr. Analysis by SDS-PAGE of the extracts obtained with guanidine-HCl and MgCl2 in different concentrations pointed out that most components are equally removed with the two solvents, showing that the extraction with MgCl2 is an alternative assay to remove non-collagenous proteins from extracellular matrix.

The zonal expression of chicken cartilage matrix protein gene in the developing skeleton of transgenic mice.

Cartilage matrix protein (CMP) is a major noncollagenous glycoprotein of hyaline cartilage with a molecular mass of about 148 kDa. It has been proposed to be involved in matrix organization by its interactions with proteoglycan and type II collagen. The 54-kDa monomers form homotrimers stabilized by disulfide bonds. The gene for chicken cartilage matrix protein was isolated, and its regulation has been studied recently in transient expression experiments. To learn more about the spatial and temporal expression of the gene during ontogenic development, we created transgenic mice via microinjection of a 21.8-kb genomic fragment, encoding the chicken cartilage matrix protein. None of the founder animals exhibited any abnormal phenotype. The developmental stage-specific expression of the transgene was examined by immunostaining with a chicken CMP specific antiserum at different stages of embryonic development in cartilage from different sources: lower and upper limb, vertebrae, ribs and nasal septum. The level of transgene expression showed marked differences in various zones of cartilage. Briefly, high levels were found in the zones of proliferating chondrocytes, while little if any transgene product was detected in the very early and hypertrophic stage of chondrogenesis. The expression pattern of the transgene correlated with the endogenous mouse CMP and did not cause any morphological changes detectable by microscopic analysis of cartilage. These data indicate that the injected CMP gene with its flanking sequences contained all the information necessary for cell type-specific expression in transgenic mice.

CDNA cloning of chick cartilage chondroitin sulfate (aggrecan) core protein and identification of a stop codon in the aggrecan gene associated with the chondrodystrophy, nanomelia.

We previously reported the cloning and sequencing of a 1.5-kilobase cDNA which encoded a portion of the chondroitin sulfate domain from the chick cartilage proteoglycan core protein and the localization of a species-specific monoclonal antibody epitope. Using polymerase chain reaction amplification and primer extension, cDNA clones which code for the entire proteoglycan core protein have now been obtained from a 10-day chick embryo cDNA library. The composite sequence is 6464 nucleotides long, coding for a protein of 2109 amino acid residues with a calculated M(r) = 223,500. The overall arrangement of globular and carbohydrate-attachment domains is similar to human and rat chondrosarcoma aggrecan, but there are significant differences in detailed homology between chick and mammalian core proteins. Most significantly a highly repetitive region (19 repeat units of 20 residues each), not found in either human or rat, enlarges one of the characteristic serine-glycine containing regions (designated CS-2) while the other serine-glycine containing domain (designated CS-1) is approximately one-fourth the length of the mammalian CS-1. Analysis of a polymerase chain reaction-amplified fragment encoding the chick-specific repeat region revealed a single base mutation at position 4553 (G to T transversion) that converted the codon GAA for glutamate at amino acid 1513 to TAA, a stop codon, in nanomelic chondrocytes. Genomic DNA from nanomelic liver was also digested with restriction enzyme BsaBI to verify the G to T transversion. This single mutation leads to a shortened core protein precursor with a calculated M(r) = 158,300. The resulting phenotype, nanomelia, arises because the truncated core protein is neither processed to a mature proteoglycan, nor secreted from the chondrocyte.

Expression of vigilin in chicken cartilage and bone

The expression of vigilin was followed during chick embryonal development by in situ hybridization. Vigilin mRNA is abundantly expressed in tissues of mesenchymal and ectomesenchymal origin. The mesenchymal primordial cells of cartilage and bone did not show any significant expression of vigilin. As tissue differentiation proceeded, vigilin mRNA levels increased in hyaline cartilage and in both endochondral as well as intramembranous bone. The results suggest that the expression of vigilin mRNA in cartilage- and bone-forming cells, chondrocytes and osteoblasts, is dependent on the stage of development and cellular differentiation, although not a unique process of bone formation. Most striking is the correlation of the maximum vigilin mRNA expression in osteoblasts and hypertrophic chondrocytes to periods when cell-specific genes were highly transcribed and substantially translated, e.g., synthesis of procollagen and formation of extracellular matrix in bone and cartilage.

Radiation effects on the matrix synthesis in non-ossifying embryonic cartilage in vitro: A functional and morphological study

Radiation effects on collagen and glycosaminoglycan (GAG) synthesis were studied in non-ossifying embryonic chick cartilage, in vitro. Fragments of the non-calcifying region of 15-day-old chick sterna were irradiated with 20, 50 and 100 Gy. The counterparts served as controls. Fragments were cultured up to 14 days. Pulse labeling experiments with 3H-proline and 3H-glucosamine started immediately after irradiation and on day 3, 6 and 13 post-irradiation. Fragments for morphological evaluation were fixed on day 1, 4, 7 and 14, simultaneously with the end of the labeling period. The same dose- and time-dependent inhibition was observed for the collagen and GAG synthesis. Radiation doses of 20, 50 and 100 Gy cause respectively and inhibition of about 20, 35 and 60% at the end of the culture period. Morphological alterations were observed after radiation doses of 50 and 100 Gy. Dose- and time-dependent necrosis all over the sternum was observed. A restricted number of cells showed an increased GAG synthesis after irradiation (50 Gy). This could explain the levelling off of the radiation effect on the incorporation of the labeled precursors towards the end of the culture period for radiation doses up to 50 Gy.

Insulin-like growth factor binding protein–4 inhibits both basal and IGF-mediated chick pelvic cartilage growth in vitro

This laboratory has purified a unique insulin-like growth factor binding protein (IGFBP-4) that was previously demonstrated to be inhibitory to bone cell proliferation. In this study, the hypothesis that IGFBP-4 is inhibitory to insulin-like growth factor (IGF) actions on cartilage was tested using the pelvic cartilages of 10-day-old chick embryos as an in vitro model system. Pelvic leaflets were incubated in serum-free medium for 18 h with effectors (BSA, IGF-I, IGF-II, IGFBP-4, or a combination of IGF and IGFBP-4). After the first 8 h, 1.5 microCi [3H]thymidine per well was added. Cartilage growth was assayed by TCA-insoluble [3H]thymidine incorporation into DNA. Additional experiments were conducted under similar conditions to assess the actions of the effectors on cartilage dry weight over a 72 h time period. In separate experiments, serum-free medium conditioned by chick pelvic cartilages for 72 h was assayed for IGF-II by radioreceptorassay, IGF-I by radioimmunoassay, and IGFBP by western ligand analysis. Exogenous IGF addition increased [3H]thymidine incorporation and dry weight of cartilages compared to controls. IGFBP-4 decreased both parameters in basal cartilage growth and also inhibited IGF-mediated cartilage growth. Pelvic cartilages secreted in vitro both IGF-I and IGF-II and a 32-34 kD IGFBP. In conclusion, the IGFs are stimulatory to cartilage growth in vitro and embryonic chick cartilage in vitro produces both IGF-I and II as well as an IGFBP.(ABSTRACT TRUNCATED AT 250 WORDS)

Gallium nitrate inhibits alkaline phosphatase activity in a differentiating mesenchymal cell culture

The effect of gallium nitrate on alkaline phosphatase activity in a differentiating chick limb-bud mesenchymal cell culture was monitored in order to gain insight into the observation that rachitic rats treated with gallium nitrate failed to show the expected increase in serum alkaline phosphatase activity. Cultures maintained in media containing 15 microM gallium nitrate showed drastically decreased alkaline phosphatase activities in the absence of significant alterations in total protein synthesis and DNA content. However, addition of 15 microM gallium nitrate to cultures 18 h before assay for alkaline phosphatase activity had little effect. At the light microscopic and electron microscopic level, gallium-treated cultures differed morphologically from gallium-free cultures: with gallium present, there were fewer hypertrophic chondrocytes and cartilage nodules were flatter and further apart. Because of altered morphology, staining with an antibody against chick cartilage alkaline phosphatase appeared less extensive; however, all nodules stained equivalently relative to gallium-free controls. Histochemical staining for alkaline phosphatase activity was negative in gallium-treated cultures, demonstrating that the alkaline phosphatase protein present was not active. The defective alkaline phosphatase activity in cultures maintained in the presence of gallium was also evidenced when cultures were supplemented with the alkaline phosphatase substrate, beta-glycerophosphate (beta GP). The data presented suggest that gallium inhibits alkaline phosphatase activity in this culture system and that gallium causes alterations in the differentiation of mesenchymal cells into hypertrophic chondrocytes.

FT-IR microscopic mappings of early mineralization in chick limb bud mesenchymal cell cultures.

Chick limb bud mesenchymal cells differentiate into chondrocytes and form a cartilaginous matrix in culture. In this study, the mineral formed in different areas within cultures supplemented with 4 mM inorganic phosphate, or 2.5, 5.0, and 10 mM beta-glycerophosphate (beta GP), was characterized by Fourier-transform infrared (FT-IR) microscopy. The relative mineral-to-matrix ratios, and distribution of crystal sizes at specific locations throughout the matrix were measured from day 14 to day 30. The only mineral phase detected was a poorly crystalline apatite. Cultures receiving 4 mM inorganic phosphate had smaller crystals which were less randomly distributed around the cartilage nodules than those in the beta GP-treated cultures. beta GP-induced mineral consisted of larger, more perfect apatite crystals. In cultures receiving 5 or 10 mM beta GP, the relative mineral-to-matrix ratios (calculated from the integrated intensities of the phosphate and amide I bands, respectively) were higher than in the cultures with 4 mM inorganic phosphate or in the in vivo calcified chick cartilage.

Влияние 1 α-оксивитамина D3 и 24,25-диоксивитамина D3 на коллагены кости, кожи и хряща цыплят

Влияние 1 α-оксивитамина D3 и 24,25-диоксивитамина D3 на коллагены кости, кожи и хряща цыплят

Коллаген хряща цыплят при различной обеспеченности Ca и витамином D3

Коллаген хряща цыплят при различной обеспеченности Ca и витамином D3

Remodelling of collagen types I, II and X and calcification of human fetal cartilage

Evidence from recent studies on type X collagen in hypertrophic chick cartilage suggests that it may be involved in cartilage calcification. Here we compare the distribution of type X collagen with that of calcium mineral deposition in fetal human growth plate cartilages of long bones and ribs. Using a specific antibody we demonstrate the presence of type X collagen in a narrow, sharply defined zone of hypertrophic chondrocytes. Type X collagen was also localized in the calcifying cartilage remaining within spongy bone trabecules. Calcium deposits were, however, detected by alizarine red S only in the lower hypertrophic zone and in bone, confirming the notion that type X collagen is deposited in the hypertrophic cartilage before mineral deposition. By immunofluorescence double staining we demonstrate codistribution of type II and X collagen in the hypertrophic zone, while type I collagen was absent from hypertrophic cartilage matrix; it was detected only in the perichondrium, in vascular cavities, and in osteoid and bone. From these observations we conclude that the sequence of events leading to cartilage mineralization begins with chondrocyte hypertrophy, followed by type X collagen synthesis and finally by deposition of calcium mineral.

Two immunologically and developmentally distinct chondroitin sulfate proteolglycans in embryonic chick brain.

Two different chondroitin sulfate proteoglycans (CSPG) in embryonic chick brain were distinguished by immunoreactivity either with S103L, a rat monoclonal antibody which reacts specifically with an 11-amino-acid region in the chondroitin sulfate domain of the core protein of chick cartilage CSPG (Krueger, R. C., Jr., Fields, T. A., Mensch, J. R., and Schwartz, N. B. (1990) J. Biol. Chem. 265, 12088-12097), or with HNK-1, a mouse monoclonal antibody which reacts with a 3-sulfoglucuronic acid residue on neural glycolipids and glycoproteins (Chou, D. K. H., Ilyas, A., Evans, J. E. Costello, C., Quarles, R. H., and Jungawala, F. B. (1986) J. Biol. Chem. 261, 11717-11725) but not with both antibodies. This specific immunoreactivity was used to separate the two CSPGs for further characterization. The S103L reactive brain proteoglycan had a core protein of similar size to cartilage CSPG (370 kDa) but exhibited a smaller hydrodynamic size (K(av) of 0.308). It was substituted predominantly with chondroitin sulfate chains and virtually no keratan sulfate chains. The HNK-1 reactive CSPG had a smaller core protein (340 kDa), an even smaller hydrodynamic size (K(av) of 0.564), and was substituted with both chondroitin sulfate and keratan sulfate chains. Glycosidase digestion patterns with endo-beta-galactosidase, N-glycosidase F, neuraminidase, and O-glycosidase, and reactivity with an antibody to the hyaluronate binding region also showed significant differences between the two brain CSPGs. Expression of the S103L reactive brain CSPG was developmentally regulated from embryonic day 7 through 19 with a peak in core protein on day 13, and in mRNA expression at day 10. In contrast the HNK-1 reactive brain CSPG was constitutively present from day 7 through hatching. These data suggest that these two distinct core proteins are immunologically and biochemically unique translation products of two different CSPG genes.

Cloning and developmental expression of the alpha 3 chain of chicken type IX collagen.

Fibrous and nonfibrous collagens comprise two major groups within the collagen family and both groups are found in a diverse variety of tissue fabrics. Type IX collagen is in the nonfibrous group; three different subunits of type IX collagen have been identified and the alpha 1 and alpha 2 subunits have been cloned. Using molecular cloning methods we have isolated, from an embryonic chicken cartilage library, cDNA clones which code for the entire alpha 3 chain of chicken type IX collagen. The cDNA clones encompass 2416 base pairs which have a conceptual open reading frame for a protein containing 675 amino acids including 193 Gly-X-Y repeats. These collagen repeats are in three separate domains which are interspersed with four major noncollagen domains. The collagen repeats also have four minor interruptions. This chain organization directly aligns with both the alpha 1 and alpha 2 chains of chicken type IX collagen. Comparison of the deduced amino acid sequence with peptide sequences of type IX collagens shows identity with 95 of the 96 known residues of the chicken alpha 3 chain and 81 of the 98 known residues of the bovine alpha 3 chain. The identical residues match those in five peptide fragments, two from the bovine protein and three from the chicken protein. The chicken and bovine alpha 3 chains have conserved cross-linking sites, separated by 137 residues which span 40 nm, the length of the hole zone in a collagen fibril. The NC3 domain of the chicken alpha 3 chain contains a repeat Cys-Pro motif which is present in both vertebrate and invertebrate nonfibrillar collagens. Northern blot hybridization exhibits a major mRNA of about 3.3 kilobases; this transcript is found in cartilaginous tissues in the embryo, including the developing limb and is not detected in other tissues or in the precondensation stage of limb development. The composite data delineate the primary structure of the alpha 3 chain of chicken type IX collagen, show its close relationship to the alpha 1 and alpha 2 chains, demonstrate its mRNA transcript, and show the appearance of that transcript in tissues of the developing chick embryo.

Glucuronosyl transfer to galactose residues in the biosynthesis of HNK-1 antigens and xylose-containing glycosaminoglycans: One or two transferases?

An early step in the assembly of the xylose→serine-linked proteoglycans is the transfer of glucuronic acid to the C-3 position of a galactose residue in the carbohydrate-protein linkage region. Since a similar reaction occurs in the biosynthesis of HNK-1 antigens, the question arose whether these processes are catalyzed by the same enzyme. In the present study, the proteoglycan-related glucuronosyltransferase activity in embryonic chick brain was found to be firmly membrane-associated, while the majority of the activity towards N-acetyllactosamine — a model substrate for HNK-1 antigen biosynthesis — was readily solubilized. No activity towards N-acetyllactosamine was found in embryonic chick cartilage, which is a rich source of the proteoglycan-related enzyme. Together with the results of mixed substrate experiments, these findings strongly indicate the existence of two separate glucuronosyltransferases catalyzing transfer to galactose residues.

Ultrastructural localization of tartrate-resistant acid phosphatase (purple acid phosphatase) activity in chicken cartilage and bone.

Tartrate-resistant acid adenosine triphosphatase activity at pH 6.5, using a lead-salt method, was localized at light and electron microscopic levels in cartilage and bone matrices, osteoclasts, and chondroclasts. Cartilage matrix staining occurred after vascular invasion of the growth plate. In osteoclasts, activity was present in lysosomes, extracellular ruffled border channels, and the underlying cartilage and bone matrices. Staining artifacts occurred at lower pH levels (pH 5.4, 5.0). Adenosine diphosphate, p-nitrophenylphosphate, thiamine pyrophosphate, and alpha-naphthylphosphate also acted as substrates; but no activity was observed when adenosine monophosphate, adenylate-(beta, gamma-methylene) diphosphate, and beta-glycerophosphate were used. The activity was inhibited by NaF, dithionite, and a high concentration of p-chloromercuribenzoic acid, and activated by simultaneous addition of FeCl2 and ascorbic acid, as has been shown in biochemical studies. These histochemical results support the view that the adenosine triphosphate hydrolyzing activity at pH 6.5 is due to tartrate-resistant acid phosphatase (TRAP). There were some differences in ultrastructural localization between TRAP and tartrate-sensitive acid phosphatase (TSAP) activities in osteoclasts: TSAP activity was more intense in lysosomes and Golgi complexes and TRAP was stronger in the cartilage and bone matrices. It is suggested, therefore, that most of TRAP is in an inactive form in cells and is activated when secreted.

Monoclonal antibodies against bovine type IX collagen (LMW fragment): production, characterization, and use for immunohistochemical localization studies.

Four high-affinity monoclonal antibodies (MAb) which react specifically with the low molecular weight (LMW) fragment of bovine type IX collagen (BIX) have been produced in mice. On the basis of the ability of these MAb to cross-react with type IX collagen purified from human, rat, and chick cartilage and to inhibit one another in a competitive inhibition assay, we conclude that the MAb D1-9, B3-1, and B2-7 recognize unique epitopes, whereas MAb B4-5 recognizes the same epitope as B3-1. None of the MAb reacted with bovine type I, II, and XI collagen. MAb D1-9 and B3-1 were tested for their ability to bind to tissue antigen, using an immunohistochemical assay system. Positive immunoperoxidase reactions were observed in the perichondrocytic regions of human and rat costochondral cartilage. Positive responses were also detected in rat auricular cartilage, as well as in tissue obtained from the middle and inner ears of rats and mice. This report demonstrates the relative ease of producing MAb to heterologous type IX collagen and the utility of these MAb for localizing type IX collagen in cartilage and cartilage-like tissues.

Structural and functional comparison of type IX collagen-proteoglycan from chicken cartilage and vitreous humor.

Type IX collagen-proteoglycan is a major component of hyaline cartilages where it is located on the surface of the collagen fibrils so that a collagenous domain of the molecule (called COL3) and a non-collagenous domain (called NC4) project at periodic distances away from the surface of the fibril. Type IX collagen-proteoglycan is also present on the surface of the collagen fibrils of the adult chicken vitreous but, unlike cartilage, lacks the NC4 domain and possesses a very long chondroitin sulfate chain which provides an extensive coat to the fibril. A monoclonal antibody (called 4D6) is described which will distinguish cartilage from vitreous type IX collagen. To form the epitope for 4D6 two peptides called C2 and C5 derived, respectively, from the alpha 1(IX) and alpha 3(IX) chains are required. Further analysis shows that specificity for 4D6 resides only in the C2 peptide from cartilage and not in C5. These results are entirely consistent with recent evidence that there are two promoters for transcription of the alpha 1(IX) chain which will result in an alpha 1(IX) chain in which the NC4 domain is either present or absent and that expression of these two promoters has tissue specificity (Nishimura, I., Muragaki, Y., and Olsen, B. R. (1989) J. Biol. Chem. 264, 20033-20041). In addition, the function of type IX collagen in cartilage and vitreous may differ with the long chondroitin sulfate chains of vitreous type IX collagen being responsible for the gel-like matrix of this tissue.