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PubMed1990

An immunohistochemical study of the distribution of matrical proteins in the mandibular condyle of neonatal mice. I. Collagens.

This study provides new information concerning the distribution of cartilage collagens in neonatal mammalian condylar cartilage. It became apparent that young cartilage cells contain pro-Type I collagen as well as pro-Type II collagen. The mature molecule of Type I collagen appears only in the extracellular matrix of the mineralisation zone close to the ossification front. Type II collagen, on the other hand, is apparent throughout the extracellular matrix as soon as the chondroprogenitor cells have differentiated into chondroblasts. In addition, Type II collagen is noticed in the core of the newly formed bone trabeculae within the primary spongiosa. Type IX collagen was found to be co-distributed with Type II collagen in cartilage and bone. Hypertrophic chondrocytes within the mineralisation zone, but in no other zone, demonstrate an intense reactivity for Type X collagen. Mild reactivity throughout the condylar process is encountered with regard to Type VI collagen. Perichondrium but not cartilage reacts positively for Type III collagen.

Animals↗
PubMed1992

Thyroid hormone, insulin, and glucocorticoids are sufficient to support chondrocyte differentiation to hypertrophy: a serum-free analysis.

Chondrocytes from chicken embryo tibia can be maintained in culture as adherent cells in Coon's modified Ham's F-12 medium supplemented with 10% FCS. In this condition, they dedifferentiate, losing type II collagen expression in favor of type I collagen synthesis. Their differentiation to hypertrophy can be obtained by transferring them to suspension culture. Differentiation is evidenced by the shift from type I to type II and type IX collagen synthesis and the following predominant expression of type X collagen, all markers of specific stages of the differentiation process. To identify the factors required for differentiation, we developed a serum-free culture system where only the addition of triiodothyronine (T3; 10(-11) M), insulin (60 ng/ml), and dexamethasone (10(-9) M) to the F-12 medium was sufficient to obtain hypertrophic chondrocytes. In this hormonal context, chondrocytes display the same changes in the pattern of protein synthesis as described above. For proper and complete cell maturation, T3 and insulin concentrations cannot be modified. Insulin cannot be substituted by insulin-like growth factor-I, but dexamethasone concentration can be decreased to 10(-12) M without chondrogenesis being impaired. In the latter case, the expression of type X collagen and its mRNA are inversely proportional to dexamethasone concentration. When ascorbic acid is added to the hormone-supplemented medium, differentiating chondrocytes organize their matrix leading to a cartilage-like structure with hypertrophic chondrocytes embedded in lacunae. However, this structure does not present detectable calcification, at variance with control cultures maintained in FCS. Accordingly, in the presence of the hormone mixture, the differentiating chondrocytes have low levels of alkaline phosphatase activity. This report indicates that T3 and insulin are primary factors involved in the onset and progression of chondrogenesis, while dexamethasone supports cell viability and modulates some differentiated functions.

Alkaline Phosphatase↗
PubMed2002

Clinical phenotype and molecular diagnosis of multiple epiphyseal dysplasia with relative hip sparing during childhood (EDM2).

We report on a family of 19 individuals over four generations in which 12 members are affected with a variant of multiple epiphyseal dysplasia. Beginning in childhood, the disease leads to pain and stiffness of knees, ankles, elbows and finger joints. Some adult patients repeatedly suffer from free articular bodies resulting in locking of the joint. Finally, affected individuals are prone to the development of early degenerative joint disease. Mutation screening of candidate regions revealed a novel point mutation at position -1 in the COL9A2 exon 3/intron 3 splicing region. This G --> C substitution most probably induces an alteration of the splicing process. Family screening was carried out by both automated sequencing and by digestion of amplicons with BsaWI. We confirmed the nucleotide substitution in eight clinically affected family members as well as in three presymptomatic young children. Electron microscopy showed that the diameter of collagen fibrils from arthroscopically removed free articular bodies of two patients was not obviously different from that of normal articular cartilage. Together with previous reports our results indicate that mutations leading to skipping of exon 3 within the COL3 domain of the alpha2-chain of collagen type IX may be relatively common in patients with a special subtype of multiple epiphyseal dysplasia (MED) in which the hips are not markedly affected at early age (EDM2). In these patients and their families, mutation screening of the candidate regions may help to confirm the diagnosis, lead to appropriate advice for lifestyle and well based genetic counseling.

Adult↗
PubMed2001

Calreticulin, PDI, Grp94 and BiP chaperone proteins are associated with retained COMP in pseudoachondroplasia chondrocytes.

Cartilage oligomeric matrix protein (COMP), a large pentameric glycoprotein and member of the thrombospondin (TSP) group of extracellular proteins, is found in the territorial matrix surrounding chondrocytes. More than 50 unique COMP mutations have been identified as causing two skeletal dysplasias: pseudoachondroplasia (PSACH); and multiple epiphyseal dysplasia (EDM1). Recent studies suggest that calcium-binding and calcium-induced protein folding differ between wild type and mutant proteins, and abnormal processing of the mutant COMP protein contributes to the characteristic enlarged lamellar appearing rER cisternae in PSACH and EDMI chondrocytes in vivo and in vitro. Towards the goal of delineating the pathogenesis of PSACH and EDM1, in-vivo PSACH growth plate and in-vitro PSACH chondrocytes cultured in alginate beads were examined to identify and localize the chaperone proteins participating in the processing of the retained extracellular matrix proteins in the PSACH rER. Aggrecan was localized to both the rER cisternae and matrix while COMP and type IX collagen were only found in the rER. Type II collagen was solely found in the ECM suggesting that it is processed and transported differently from other retained ECM proteins. Five chaperone proteins: BiP (Grp78); calreticulin (CRT); protein disulfide (PDI); ERp72; and Grp94, demonstrated immunoreactivity in the enlarged PSACH cisternae and the short rER channels of chondrocytes from both in-vivo and in-vitro samples. The chaperone proteins cluster around the electron dense material within the enlarged rER cisternae. CRT, PDI and GRP94 AB-gold particles appear to be closely associated with COMP. Immunoprecipitation and Western blot, and Fluorescence Resonance Energy Transfer (FRET) analyses indicate that CRT, PDI and GRP94 are in close proximity to normal and mutant COMP and BiP to mutant COMP. These results suggest that these proteins play a role in the processing and transport of wild type COMP in normal chondrocytes and in the retention of mutant COMP in PSACH chondrocytes.

Achondroplasia↗
PubMed2005

Mutation analysis of COL9A3, a gene highly expressed in the cochlea, in hearing loss patients.

cDNA microarray analysis indicated that COL9A3 is one of the highly expressed genes in the cochlea. This suggests that collagen type IX has a crucial functional role in the inner ear and may be a candidate gene for hearing loss. Mutation analysis was carried out to find possible disease-causing mutations in this gene. The direct-sequencing method was applied to the COL9A3 gene in 159 non-syndromic sensorineural deafness patients and 150 normal controls. Two possible disease-causing mutations were identified: an in-frame deletion of three amino acid residues (G181-P183 del) and a missense mutation (D617E). The patients with the mutations showed a moderate progressive bilateral sensorineural hearing impairment in all frequencies. The present data indicate that mutations of COL9A3 may cause non-syndromic hearing impairment.

Amino Acid Sequence↗
PubMed2003

Sequence variations in the collagen IX and XI genes are associated with degenerative lumbar spinal stenosis.

BACKGROUND: Degenerative lumbar spinal stenosis (LSS) is usually caused by disc herniation or degeneration. Several genetic factors have been implicated in disc disease. Tryptophan alleles in COL9A2 and COL9A3 have been shown to be associated with lumbar disc disease in the Finnish population, and polymorphisms in the vitamin D receptor gene (VDR) (FokI and TaqI), the matrix metalloproteinase-3 gene (MMP-3) and an aggrecan gene (AGC1) VNTR have been reported to be associated with disc degeneration. In addition, an IVS6-4 a>t polymorphism in COL11A2 has been found in connection with stenosis caused by ossification of the posterior longitudinal ligament in the Japanese population. OBJECTIVE: To study the role of genetic factors in LSS. METHODS: 29 Finnish probands were analysed for mutations in the genes coding for intervertebral disc matrix proteins, COL1A1, COL1A2, COL2A1, COL9A1, COL9A2, COL9A3, COL11A1, COL11A2, and AGC1. VDR and MMP-3 polymorphisms were also analysed. Sequence variations were tested in 56 Finnish controls. RESULTS: Several disease associated alleles were identified. A splice site mutation in COL9A2 leading to a premature translation termination codon and the generation of a truncated protein was identified in one proband, another had the Trp2 allele, and four others the Trp3 allele. The frequency of the COL11A2 IVS6(-4) t allele was 93.1% in the probands and 72.3% in controls (p = 0.0016). The differences in genotype frequencies for this site were less significant (p = 0.0043). CONCLUSIONS: Genetic factors have an important role in the pathogenesis of LSS.

Adult↗
PubMed2002

The assembly and remodeling of the extracellular matrix in the growth plate in relationship to mineral deposition and cellular hypertrophy: an in situ study of collagens II and IX and proteoglycan.

The recent development of new specific immunoassays has provided an opportunity to study the assembly and resorption of type II and IX collagens of the extracellular matrix in relationship to endochondral calcification in situ. Here, we describe how in the bovine fetal physis prehypertrophic chondrocytes deposit an extensive extracellular matrix that, initially, is rich in both type II and type IX collagens and proteoglycan (PG; principally, aggrecan). The majority of the alpha1(IX)-chains lack the NC4 domain consistent with our previous studies with cultured chondrocytes. During assembly, the molar ratio of type II/COL2 domain of the alpha1(IX)-chain varied from 8:1 to 25:1. An increase in the content of Ca2+ and inorganic phosphate (Pi) was initiated in the prehypertrophic zone when the NC4 domain was removed selectively from the alpha1(IX)-chain. This was followed by the progressive loss of the alpha1(IX) COL2 domain and type II collagen. In the hypertrophic zone, the Ca2+/Pi molar ratio ranged from 1.56 to a maximum of 1.74, closely corresponding to that of mature hydroxyapatite (1.67). The prehypertrophic zone had an average ratio Ca2+/Pi ranging from 0.25 to 1, suggesting a phase transformation. At hypertrophy, when mineral content was maximal, type II collagen was reduced maximally in content coincident with a peak of cleavage of this molecule by collagenase when matrix metalloproteinase 13 (MMP-13) expression was maximal. In contrast, PG (principally aggrecan) was retained when hydroxyapatite was formed consistent with the view that this PG does not inhibit and might promote calcification in vivo. Taken together with earlier studies, these findings show that matrix remodeling after assembly is linked closely to initial changes in Ca2+ and Pi to subsequent cellular hypertrophy and mineralization. These changes involve a progressive and selective removal of types II and IX collagens with the retention of the PG aggrecan.

Animals↗
PubMed1990

T cell regulation of collagen-induced arthritis in mice. I. Isolation of Type II collagen-reactive T cell hybridomas with specific cytotoxic function.

After immunization with native type II collagen (CII), susceptible strains of mice (H-2q) develop a polyarthritis that mimics rheumatoid arthritis. Although the underlying mechanisms are still undefined, T cells and particularly CD4+ lymphocytes seem to play a crucial role in the initiation of collagen-induced arthritis. To investigate whether CD8+ cells may participate in the pathogenesis of the disease, we have generated lines and clones of cytotoxic T cell hybridomas reactive to CII by fusion of lymph node and spleen cells from bovine native CII-primed C3H.Q (H-2q) mice and the AKR-derived thymoma cell line BW 5147. Clones were selected for their ability to lyse syngeneic macrophages pulsed with bovine native CII in an Ag-dependent manner. The two hybrid clones that were characterized, exhibited cell surface phenotypes of cytotoxic cells and reacted with CII purified from various species. However, each of them recognized different determinants on the CII molecule. P3G8 clone was specific for an epitope shared by CII and type XI collagen, whereas P2D9 clone reacted with CII and type IX collagen. Both hybridomas recognized CII-pulsed targets in association with H-2Kq molecules. These data indicate that the two CII-specific cytotoxic clones recognize different epitopes that are shared by other articular collagens and will allow us to test their influence on the development of arthritis in vivo.

Animals↗
PubMed1996

[Immunohistochemical localization of Type I, II and IX collagens in pleomorphic adenoma of human salivary glands].

The expression patterns of type I, II and IX collagens in chondromyxoid tissue of salivary pleomorphic adenomas were examined by immunohistochemistry. In the early stage of cartilage development, type IX collagen was detected intracytoplasmically, mainly in the proliferating myoepithelial cells and not in the extracellular matrix. Proliferating myoepithelial cells did not show chondrocytic characteristics at this stage. Type I and II collagens were co-distributed in the extracellular matrix of myxoid tissue. In the chondroid tissue, variable immunostaining patterns of type I and II collagens were also observed. Some proliferating myoepithelial cells in myxoid and chondroid tissue were immunostained with anti-alpha-smooth muscle actin antibody indicating their myoepithelial origin. These results suggested that proliferating myoepithelial cells may be the origin of the chondroid tissue and the expression of type IX collagen in cartilaginous tissue precedes the expression of type I and II collagens.

Adenoma, Pleomorphic↗
PubMed1992

Electron-microscopic localization of type II, IX, and V collagen in the organ of Corti of the gerbil.

The presence of types II, IX and V collagen was probed in the organ of Corti of the adult gerbil cochlea by use of immunocytochemistry at the light- and electron-microscopic levels. Type II collagen is found in the connective tissues of the osseous spiral lamina and spiral limbus. In the region of the sensory hair cells it is present in the tectorial membrane and antibodies bind to the thick unbranched radial fibers. Type IX collagen co-localizes with type II collagen in the tectorial membrane, where antibodies bind to the thick unbranched radial fibers. Type V collagen is present in the connective tissue of the spiral limbus, the osseous spiral lamina, the eighth nerve, and the tectorial membrane. In the tectorial membrane, the staining with antibodies to type V collagen is more diffuse than that seen for types II and IX collagen and antibodies to type V bind to the thin, highly branched fibers in which the thick fibers are embedded. The results indicate that collagens characteristic of cartilage are localized in the organ of Corti. Within the tectorial membrane, types II and IX collagen form heterotypic thick fibers embedded in a reticular network of type V collagen fibers. These collagens form a highly structured matrix which contributes to the rigidity of the tectorial membrane and allow it to withstand the physical stresses associated with transmission of the stimuli necessary for sensory transduction.

Animals↗
PubMed1995

Collagen types in the middle ear mucosa.

The distribution of various collagen types--in particular that of type II as the major collagen in cartilage--in normal auricular structures is discussed with reference to a 1994 report by Ovesen describing the presence of collagen type II in normal middle ear mucosa. In contrast to this report, no collagen type II is normally found in the normal mucosa of the middle ear, while multiple structures of the normal middle and inner ear (which mostly consist of cartilage or have at least a cartilaginous origin) contain this unique collagen type. This indicates that the collagen type II staining previously observed in the normal middle ear mucosa is most likely an artifact. Of the at least 18 collagen types now known, interstitial and ubiquitously present types I, III and V can be found in the normal middle ear. The minor cartilage collagen types IX and XI have been found in cartilage of the middle (and inner) ear. The basement membrane collagen type IV is normally present in different microanatomical settings, particularly in the epithelial and endothelial basement membranes. In general, an exclusive morphometric estimation of area changes for collagens, particularly for collagen type IV, regardless of any tissue localization seems to be of minor value, since no attribution can be drawn to any of the histoanatomical structures present in the ear. The presence of further collagen types has not yet been tested in normal auricular structures.

Basement Membrane↗
PubMed1986

Biosynthetic expression of type X collagen in embryonic chick sternum cartilage during development.

To investigate the temporal and topographic changes in the expression of various collagens during the process of endochondral bone formation, qualitative and quantitative analysis of the collagens synthesized by organ cultures from the separated presumptive calcification and permanent cartilaginous regions of embryonic chick sternum at various stages of development was performed. Special emphasis was placed on the study of Type X collagen, a recently described species that may play a role in tissue calcification. We found that Type X collagen is biosynthesized exclusively by cartilage from the zone of presumptive calcification and that its biosynthetic expression is acquired at stage 43 (day 17) of sternal development. Quantitative analysis indicated that Type X was the biosynthetic product which showed the most dramatic changes increasing markedly with increased sternal age. While no Type X collagen could be detected at stage 40, it represented about 12% of the total collagen synthesized at stage 43, further increasing to 45% at stage 46 of sternal development. The increase in Type X collagen in the presumptive calcification region was accompanied by a relative decrease in the proportion of 1 alpha, 2 alpha, 3 alpha, alpha 1(II), and Type IX collagens. In contrast, the permanent hyaline cartilage did not display detectable synthesis of Type X collagen at any sternal age. The strict topographic distribution and the temporal expression of Type X collagen biosynthesis coincident with the development of sternal calcification, confirm the notion that this collagen may play an important role in the extracellular matrix remodeling associated with the initiation and progression of tissue calcification.

Animals↗
PubMed1997

Analysis of types I, II, III, IX and XI collagens synthesized by fetal bovine chondrocytes in high-density culture.

OBJECTIVE: This study was undertaken in order to determine phenotypic modulation of the chondrocytes more closely in high-density culture conditions and to clarify the role of ascorbate. Levels of five collagen types were analyzed qualitatively and quantitatively, and their distribution was observed in the cell layer and the culture medium. DESIGN: Types I, II, III, IX and XI collagens, synthesized by fetal bovine chondrocytes in high-density culture, were analyzed qualitatively and quantitatively by direct measurement of radiolabeled collagens separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and by specific radioimmunoassays. RESULTS: Under the experimental conditions used in this study (0.6 x 10(6) cells/cm2), chondrocytes did not proliferate in the absence of ascorbate, whereas a twofold increase in cell number was observed in the presence of ascorbate at day 14. Cartilage-specific collagens (types II, IX and XI) were synthesized throughout the culture period (up to 47 days), as was type III collagen, which appeared as early as day 1 and was essentially present in the culture medium. Partial dedifferentiation of chondrocytes was demonstrated by the synthesis of type I collagen, which was detected by day 2 in culture medium containing ascorbate, and by day 6 without ascorbate. After 33 days of culture, a threefold increase in type I collagen synthesis was observed in culture medium with ascorbate, reaching 66% of the type II collagen content of the cell layer. One month of culture marked the onset of a progressive decrease in the synthesis of all collagen types. CONCLUSIONS: Under these high-density culture conditions, fetal bovine chondrocytes undergo a time and ascorbate-dependent program of partial dedifferentiation. This system provides a simple model for studying the initial mechanisms of chondrocytes dedifferentiation.

Animals↗
PubMed2000

Structural macromolecules and supramolecular organisation of the vitreous gel.

The vitreous gel is a transparent extracellular matrix that fills the cavity behind the lens of the eye and is surrounded by and attached to the retina. This gel liquefies during ageing and in 25-30% of the oppulation the residual gel structure eventually collapses away from the posterior retina in a process called posterior retina in a process called posterior vitreous detachment. This process plays a pivotal role in a number of common blinding conditions including rhegmatogenous retinal detachment, proliferative diabetic retinopathy and macular hole formation. In order to understand the molecular events underlying vitreous liquefaction and posterior vitreous detachment and to develop new therapies it is important to understand the molecular basis of normal vitreous gel structure and how this is altered during ageing. It has previously been established that a dilute dispersion of thin (heterotypic) collagen fibrils is essential to the gel structure and that age-related vitreous liquefaction is intimately related to a process whereby these collagen fibrils aggregate. Collagen fibrils have a natural tendency to aggregate so a key question that has to be addressed is: what normally maintains the spacing of the collagen fibrils? In mammalian vitreous a network of hyaluronan normally fills the spaces between these collagen fibrils. This hyaluronan network can be removed without destroying the gel structure, so the hyaluronan is not essential for maintaining the spacing of the collagen fibrils although it probably does increase the mechanical resilience of the gel. The thin heterotypic collagen fibrils have a coating of non-covalently bound macromolecules which, along with the surface features of the collagen fibrils themselves, probably play a fundamental role in maintaining gel stability. They are likely to both maintain the short-range spacing of vitreous collagen fibrils and to link the fibrils together to form a contiguous network. A collagen fibril-associated macromolecule that may contribute to the maintenance of short-range spacing is opticin, a newly discovered extracellular matrix leucine-rich repeat protein. In addition, surface features of the collagen fibrils such as the chondroitin sulphate glycosaminoglycan chains of type IX collagen proteoglycan may also play an important role in maintaining fibril spacing. Furthering our knowledge of these and other components related to the surface of the heterotypic collagen fibrils will allow us to make important strides in understanding the macromolecular organisation of this unique and fascinating tissue. In addition, it will open up new therapeutic opportunities as it will allow the development of therapeutic reagents that can be used to modulate vitreous gel structure and thus treat a number of common, potentially blinding, ocular conditions.

Aging↗
PubMed1990

Extracellular matrix production by embryonic epithelium cultured on type IV collagen. Deposition of a primary corneal stroma-like structure containing large irregular type I fibrils without type II collagen.

The corneal stroma of the chick embryo is deposited in two steps. The primary stroma is laid down by the corneal epithelium and it contains type I, type II and type IX collagens. Its formation is subsequent to the presumptive epithelial cells' migration onto the lens capsule (which is rich in type IV collagen). The secondary, ultimate stroma is synthesized by fibroblasts which, on day 5 of development, invade the swollen primary stroma. It is composed of a matrix of thin (25 nm), regular fibrils containing type I and type V collagens. We found that a chick corneal epithelium isolated from either a 6-day or a 14-day embryo was able to produce, in vitro, stroma-containing type I collagen fibrils. However, the amount of collagen deposited and its organization were highly dependent on the substratum used. Plastic or purified bovine type I collagen substrata led to the release of very few fibrils. Purified human type IV collagen induced the production of an abundant matrix made of large irregular collagen fibrils. When compared to native corneal stroma, there were two aspects in which this matrix differed: (1) it contained only type I collagen, as shown by indirect immunofluorescence, and (2) there were numerous large, irregular fibrils of about 100 to 130 nm in diameter. In conclusion, it is suggested that purified type IV collagen substitutes, in part, for the basement membrane and allows the production of a corneal stroma-like matrix by an embryonic corneal epithelium in culture. This production is possible even with a 14-day epithelium which, in vivo, is no more involved in the synthesis of the stroma collagens. Moreover, the regulatory effect of type II collagen, previously suggested by in vivo observations, may be confirmed in this in vitro system by the appearance of large fibrils in the newly deposited stroma that are made only by type I collagen.

Animals↗
PubMed1994

Synthesis of a phenotypically abnormal type XI: type II collagen ratio by chondrocytes from canine osteoarthritic cartilage.

Collagen synthesis by osteoarthritic cartilage from dogs that had undergone anterior cruciate ligament transection was measured in short-term organ cultures and chondrocyte suspension cultures. Slices of osteoarthritic cartilage from unstable knees 2, 6 or 12 weeks after anterior cruciate ligament transection converted approximately 10% of the total incorporated 14C-proline to 14C-hydroxyproline, while the value for cartilage from the contralateral knee or from knees of normal control dogs was generally less than 1%. The increase in collagen synthesis in the osteoarthritic cartilage was not related to the duration of knee instability, but was greater in grossly fibrillated cartilage than in the total pooled cartilage from the osteoarthritic joint. The collagen that was synthesized was predominantly type II, although some type XI and/or type V collagen was also synthesized. Chondrocytes isolated from osteoarthritic knee cartilage of dogs 12 weeks after anterior cruciate ligament transection showed changes in collagen synthesis similar to those seen in the cartilage organ cultures. As in the organ culture studies, type II collagen was the predominant species synthesized. When cell-associated collagen was considered, type II collagen accounted for 87+/-7% of the total collagen synthesized and retained by the osteoarthritic chondrocytes. The corresponding value for cells from the contralateral knee was 63+/-10%. Since the collagen fiber in articular cartilage is a heteropolymer of type II, type XI and type IX collagen, it is likely that the newly synthesized collagens in this model of osteoarthritis form fibers that are phenotypically different from those in normal articular cartilage.

Animals↗
PubMed1987

Type XII collagen is expressed in embryonic chick tendons. Isolation of pepsin-derived fragments.

Two new disulfide-bonded collagenous pepsin-derived fragments have been isolated from chick embryo tendons. These fragments represent less than 0.5% of the pepsin-extractable collagen. We purified 10- and 16-kDa reduced fragments derived, respectively, from 32- and 46-kDa disulfide-bonded fragments. Unique tryptic peptide maps were obtained for each fragment. Although these collagenous fragments differ from all the known collagens in their electrophoretic behaviors, tryptic peptides and amino acid compositions, they present some striking similarities with the pepsin-derived fragments from cartilage type IX collagen. Unique sequences from the amino terminus and from a tryptic peptide were obtained for the 10-kDa reduced fragment, demonstrating that this fragment is derived from type XII collagen, whose existence had only been inferred so far from a cDNA encoding it.

Amino Acid Sequence↗
PubMed1994

Achondrogenesis type IB (Fraccaro): study of collagen in the tissue and in chondrocytes cultured in agarose.

A lethal chondrodysplasia characterized by extreme micromelia was diagnosed by ultrasound examination in two sibs whose nonconsanguineous parents were healthy. Radiographic and histopathologic data indicated that the two foetuses (18 and 21 weeks old) had achondrogenesis type IB (Fraccaro). Quantitation of total collagen extractable from dried cartilage samples demonstrated a 50% decrease when compared to an age-related control. This decrease was essentially related to type II collagen. Nevertheless, the alpha chains and the CB peptides of type II collagen had a normal electrophoretic mobility. A significant amount of collagen type I was also detected. The electrophoretic pattern of collagens type IX and XI did not differ significantly from control sample. The extracellular matrix elaborated by patient chondrocytes cultured in agarose for 10-12 days, contained less collagen type II than normal cells. Labelling with 14C-proline of cultured cells showed the presence of procollagen and type II collagen chains with a normal electrophoretic mobility, but an alpha 2(I) chain was detectable in the patient material, indicating the presence of collagen type I which supported the tissue findings. The significance of the type II collagen reduction in the patient's cartilage is unclear but it is unlikely to be the primary defect in achondrogenesis type I.

Blotting, Western↗