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PubMed1986

Liver fibrosis in alcoholics. Detection by Fab radioimmunoassay of serum procollagen III peptides.

Radioimmunoassays were used to measure serum levels of laminin and of procollagen III peptides, both with the intact antibody and with the Fab fragments, within one week of alcohol withdrawal in 83 alcoholics admitted for detoxification and/or treatment of concomitant medical problems. All patients underwent a diagnostic liver biopsy, which revealed simple fatty liver in 22, perivenular fibrosis in 20, septal fibrosis in 21, and cirrhosis in 20. Although all three serum measurements correlated significantly with the degree of fibrosis, only the Fab radioimmunoassay of procollagen III peptides discriminated between simple fatty liver and perivenular fibrosis in a significant number of subjects.

Adult↗
PubMed1999

Negative modulation of alpha1(I) procollagen gene expression in human skin fibroblasts: transcriptional inhibition by interferon-gamma.

Interferon-gamma (IFN-gamma), a multifunctional cytokine produced by activated Th1 lymphocytes, exerts potent effects on the extracellular matrix by regulating fibroblast function. In this study, we examined the modulation of alpha1(I) procollagen gene (COL1A1) expression by recombinant IFN-gamma. The results showed that IFN-gamma stimulated the rapid accumulation of interferon regulated factor (IRF)-1 mRNA, followed by a delayed and dose-dependent inhibition of alpha1(I) procollagen mRNA expression in skin fibroblasts from several different donors. The inhibitory response was abrogated in fibroblasts stably expressing IRF-1 in the antisense orientation. A marked decrease in the amount of heterogeneous nuclear pre-mRNA preceded the inhibition of COL1A1 mRNA expression. In fibroblasts transiently transfected with COL1A1 promoter-chloramphenicol acetyltransferase reporter gene plasmids, IFN-gamma selectively inhibited promoter activity and abrogated its stimulation induced by TGF-beta. The inhibition by IFN-gamma was not due to downregulation of TGF-beta receptor mRNA expression in the fibroblasts or decreased ligand binding to the receptor. IFN-alpha and IFN-beta by themselves had little effect on promoter activity, but IFN-alpha augmented the inhibitory effect of IFN-gamma. Using a series of 5' deletion constructs, a proximal region of the COL1A1 promoter was shown to function as an IFN-gamma response element. This region of the gene harbors overlapping binding sites for transcription factors Sp1, Sp3, and NF-1 but no homologs of previously characterized IFN-gamma response elements. The putative IFN-gamma response region was sufficient to confer inhibition of reporter gene expression by treatment with IFN-gamma. Gel mobility shift analysis showed that two distinct and specific DNA-protein complexes were formed when fibroblast nuclear extracts were incubated with oligonucleotides spanning the IFN-gamma response region. IFN-gamma did not modify the ability of nuclear proteins to bind to this region. The results indicate that IFN-gamma inhibits COL1A1 expression in fibroblasts principally at the level of gene transcription. Inhibition involves IRF-1 and is mediated through a short proximal promoter segment but without an apparent change in promoter occupancy. The findings provide novel insight into the mechanism of IFN-gamma regulation of fibroblast function.

Adult↗
PubMed1996

Direct sequencing of PCR products derived from cDNAs for the pro alpha 1 and pro alpha 2 chains of type I procollagen as a screening method to detect mutations in patients with osteogenesis imperfecta.

More than 150 mutations in the genes for type I procollagen have been found in unrelated patients with osteogenesis imperfecta (OI), but mutations have been difficult to define in many patients with the mildest forms of the disease. Here, we have used robotically automated sequencing of the cDNAs for type I procollagen to screen for mutations in 12 patients suspected of having nonlethal OI (types I, III, and IV). Single base mutations that changed codons for obligate glycine residues were found in seven of the patients. Altogether, we analyzed 4,379 bp of sequences of both alleles of the pro alpha 1 (I) collagen (8,758 bp of allelic sequences) and 4,200 bp of sequences of both alleles of the pro alpha 2(I) collagen (8,400 bp of allelic) from each patient.

Adult↗
PubMed1999

Stable transfection of human fetal chondrocytes with a type II procollagen minigene: expression of the mutant protein and alterations in the structure of the extracellular matrix in vitro.

OBJECTIVE: To perform stable transfections of human chondrocytes under conditions that allow the maintenance of the chondrocyte-specific phenotype, and to examine the effects of the stable transfection of a mutated type II procollagen gene (COL2A1) on the structure of the cartilaginous extracellular matrix produced in vitro. METHODS: A type II procollagen minigene that lacks exons 16-27 was stably transfected into human fetal epiphyseal chondrocytes in vitro. Expression of the minigene was detected by reverse transcriptase-polymerase chain reaction, and the encoded protein was identified by Western blot with a human type II collagen-specific antibody. The cartilaginous extracellular matrix produced by the cultured transfected chondrocytes was characterized using histochemical staining, polarized light microscopy analysis, and transmission electron microscopy. RESULTS: A shortened type II collagen encoded by the transfected minigene was biosynthesized and produced in the cultures of transfected cells. Histologic analyses demonstrated a more dense, negatively charged cartilaginous matrix in control cultures. In contrast, COL2A1 minigene-transfected cultures were more cellular, were populated with cells of irregular shape and less-chondrocytic appearance, contained abundant intracellular dense granules, and were surrounded by a less-dense matrix. Polarized light microscopy and transmission electron microscopy revealed a well-organized collagen fibrillar matrix in untransfected, control chondrocyte cultures, while the matrix in the transfected cultures was less birefringent and contained numerous truncated collagen fibrils. CONCLUSION: The findings illustrate the feasibility of gene transfer into human fetal chondrocytes under conditions that allow the preservation of their specific phenotype, and also shed light on the function of type II collagen in the maintenance of the structural integrity of articular cartilage matrix.

3T3 Cells↗
PubMed2001

Expression of Sox9 and type IIA procollagen during attempted repair of articular cartilage damage in a transgenic mouse model of osteoarthritis.

OBJECTIVE: To determine the capacity of chondrocytes in aging and degenerating articular cartilage to produce major components of the extracellular matrix and maintain the normal structure of articular cartilage in a transgenic mouse model of osteoarthritis. METHODS: Transcription factor Sox9 was used as an indicator of the activation and maintenance of the articular chondrocyte phenotype. Knee joints of Del1 mice carrying 6 copies of the pro alpha1(II) collagen transgene with a short deletion mutation were analyzed at the age of 10 days and at 2, 3, 4, 6, 9, and 15 months by Northern hybridization, RNase protection assay, quantitative reverse transcription-polymerase chain reaction, and immunohistochemistry. Nontransgenic littermates were used as controls. RESULTS: We demonstrated the presence of Sox9 in articular chondrocytes during development, growth, and aging, with the highest messenger RNA levels during the period of rapid growth. With the appearance of degenerative lesions in articular cartilage, 2 repair processes were observed. Local proliferation and activation of chondrocytes rich in Sox9, surrounded by type IIA procollagen and proteoglycans, was seen in articular cartilage. In contrast, metabolically inactive chondrocytes were observed at the margins of the defects. They were devoid of Sox9 and were surrounded by a proteoglycan-poor matrix. Sometimes, the lesions were filled with repair tissue that contained type III collagen but little proteoglycan or type II collagen. CONCLUSION: The results indicate that chondrocytes in mature articular cartilage are capable of inducing the production of Sox9 and type IIA procollagen, which is typical of early chondrogenesis. Degenerative defects in the knee joints of transgenic Del1 mice are associated with local activation of chondrocytes, which probably contributes to the repair process. In other areas, the repair process produces a noncartilaginous matrix, which is insufficient to maintain the integrity of articular cartilage and which allows degeneration to proceed.

Aggrecans↗
PubMed1984

Studies on the molecular composition and degradation of type IV procollagen.

The effects of trypsin on soluble type IV procollagen from the EHS mouse tumour were studied. The enzyme cleaved the pro alpha 1(IV) and pro alpha 2(IV) chains, causing only a minor decrease in the molecular weight of the pro alpha 1(IV) chain, whereas the pro alpha 2(IV) chain was degraded to at least two smaller peptides. Analyses of the uncleaved and trypsin-digested type IV procollagen by molecular sieving, with and without reduction and denaturation, were consistent with the two chains, pro alpha 1(IV) and pro alpha 2(IV), being in the same molecule, as a heterotrimer with the composition [pro alpha 1(IV)]2pro alpha 2(IV). It was also shown that the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induces the secretion of a type IV collagen-degrading metal protease into media of cultured human skin fibroblasts. This result supports previously reported findings that such an enzyme is associated with malignant transformation of cells.

Cells, Cultured↗
PubMed1986

Serum markers for type IV collagen and type III procollagen in the myelofibrosis-osteomyelosclerosis syndrome and other chronic myeloproliferative disorders.

Myelofibrosis is characterized by excessive deposition of interstitial and basement membrane collagens in the bone marrow. In this study, specific radioimmunoassays for the aminoterminal propeptide of type III procollagen and for the 7S collagen domain of type IV (basement membrane) collagen were used to determine how this accumulation is reflected in serum. Of the 41 patients with chronic myeloproliferative disorders studied, the highest levels of both parameters were found in idiopathic myelofibrosis and in chronic myelogenous leukaemia associated with bone marrow fibrosis. Increasing degrees of bone marrow fibrosis were accompanied by increasing serum concentrations of both markers, except for osteomyelosclerosis, where notably low values were seen. Pathologically high values of one or both parameters were also found in a few patients with polycythaemia vera or a transitional myeloproliferative disorder. The antigens related to type III procollagen and type IV collagen correlated significantly with each other and with the leucocyte count. These parameters should provide noninvasive means for following the accumulation of interstitial and basement membrane collagens in the bone marrow.

Adult↗
PubMed1990

Procollagen type III aminoterminal peptide in serum in idiopathic myelofibrosis and allied conditions: relation to disease activity and effect of chemotherapy.

The serum concentration of the aminoterminal propeptide of type III procollagen (PIIINP) was measured serially in patients with idiopathic myelofibrosis and other myeloproliferative syndromes. Two different assays were applied, the RIA-gnost assay (Hoechst, Frankfurt, FRG) and a new equilibrium RIA for the N-terminal propeptide of human type III procollagen (Farmos Diagnostica, Oulu, Finland). A positive correlation was found between the results obtained by the two RIA's (rho = 0.90, P less than 0.001). The highest propeptide levels were recorded in patients with idiopathic myelofibrosis, particularly in those with active disease. Elevated serum PIIINP levels decreased during treatment with various cytotoxic drugs, including intensive chemotherapy. By contrast, serum PIIINP was unchanged or increased in patients undergoing interferon alpha-2b therapy. Gel filtration of sera on Sephacryl S-300 column (Pharmacia, Sweden) showed that smaller PIIINP related peptides dominated in healthy subjects and in osteomyelosclerosis with stable disease. Conversely, the relative proportion of intact propeptide increased in accelerating disease stages and acute myelofibrosis. In conclusion, the present study implicates serum PIIINP as a useful indicator of disease activity in idiopathic myelofibrosis. The propeptide also appears to be a sensitive sero-marker of chemotherapy effect on fibrogenesis related to clonal myeloproliferation. Finally, the propeptide is suggested as an early predictor of relapse during cytotoxic therapy.

Acute Disease↗
PubMed1994

Connective tissue components in serum in multiple myeloma: analyses of propeptides of type I and type III procollagens, type I collagen telopeptide, and hyaluronan.

The present study was performed to evaluate whether information concerning synthesis and degradation of type I collagen in multiple myeloma (MM) as obtained by serum analyses of C-terminal propeptide of type I procollagen (PICP) and the C-terminal telopeptide of type I collagen (ICTP) may be useful in evaluating the development of osteolytic bone destruction. Serum N-terminal propeptide of type III procollagen (PIIINP) may give information about marrow fibrosis in MM. No data are available about MM and serum hyaluronan, another important component of bone marrow stroma. We examined 15 consecutive patients before treatment and 15 sex- and age-matched controls. We found highly significant elevations in serum ICTP (median 6.2 vs. 2.4 micrograms/L; P < 0.01), PIIINP (median 5.2 vs. 2.9 micrograms/L; P < 0.01) and hyaluronan (median 122 vs. 45 micrograms/L; P < 0.01). ICTP in serum correlated closely to bone morbidity (r = 0.69; P < 0.01). Furthermore, serum ICTP correlated highly significantly to serum PIIINP (P < 0.01) and serum beta 2-microglobulin (P < 0.01), whereas there was no correlation between hyaluronan and any of the collagen-derived peptides or beta 2-microglobulin. The MM group was followed for 9-25 months and analysis of survival data suggested that serum ICTP may be of predictive value (P < 0.05). We conclude that important changes in connective tissue metabolism occur in MM. ICTP in serum seems to be a noninvasive marker of bone morbidity and may be of prognostic value. Furthermore, elevation of hyaluronan in serum is common in MM, the significance of which is unknown.

Aged↗
PubMed1984

Ehlers-Danlos syndrome IV due to a novel defect in type III procollagen.

Ehlers-Danlos syndrome type IV (EDS IV) is characterized by variable changes in the skin, arterial fragility, bowel perforation, minimal joint involvement, and either autosomal recessive or autosomal dominant inheritance. The unifying biochemical abnormality is a deficiency of type III collagen; all patients studied thus far have shown a defect in either synthesis or in secretion of type III procollagen. We report on an adolescent boy who inherited EDS IV from his father and who developed a spontaneous subclavian artery aneurysm. In vitro studies of collagen production in dermal fibroblasts showed normal amounts of pro alpha 1 (III) messenger RNA and synthesis and secretion of nearly equal amounts of normal and of structurally abnormal pro alpha 1 (III) monomers. This patient is biochemically distinct from previous cases of EDS IV and is likely heterozygous for a mutation that results in an aberrant type III procollagen that is particularly susceptible to protease degradation.

Adolescent↗
PubMed1996

Transcriptional activation of the alpha 1(I) procollagen gene in systemic sclerosis dermal fibroblasts. Role of intronic sequences.

OBJECTIVE: To investigate the transcriptional regulation of the alpha 1(I) procollagen gene (COL1A1) in cultured dermal fibroblasts from patients with diffuse systemic sclerosis (SSc) of recent onset and to evaluate the role that intronic sequences may play in the upregulated expression of COL1A1 in SSc dermal fibroblasts. METHODS: Dermal fibroblasts from 6 patients with diffuse SSc of recent onset and from 3 healthy individuals were studied. The steady-state levels of alpha 1(I) procollagen messenger RNA were evaluated by Northern hybridization analysis, and the transcriptional regulation of COL1A1 was examined by transient transfection experiments with deletion constructs containing portions of COL1A1 promoter (with 5' end points at -5.3 kb, -2.3 kb, and -804 bp and 3' end point at +42 bp) ligated to the chloramphenicol acetyltransferase (CAT) reporter gene. To examine the role of intronic sequences, constructs containing, in addition to the COL1A1 promoter, a portion of the first intron (+380 bp to +1,440 bp) cloned in front of the CAT gene were transfected. The efficiency of transfections was normalized relative to the net amount of CAT plasmid actually transfected into recipient cells, determined by a modified Southern hybridization procedure. RESULTS: Maximal CAT activity was observed with constructs extending from -804 bp to +42 bp in both normal and SSc fibroblasts. However, the activity driven by this construct was 80-110% higher in SSc fibroblasts. The CAT activity driven by a construct with a 5' end point at -5.3 kb was only 15-20% higher in SSc cells, and the CAT activity driven by a construct with a 5' end point -2.3 kb was 35-45% higher in SSc fibroblasts. The CAT activity driven by the -804-bp promoter construct was increased up to 4-fold in SSc fibroblasts in comparison with normal cells when the intronic segment spanning +380 bp to +1,440 bp was included in the transfected construct. CONCLUSION: The results directly demonstrate the transcriptional activation of COL1A1 in dermal fibroblasts from SSc patients. The data also indicate that first-intron sequences of COL1A1 are required for maximal transcriptional activity of the collagen gene and may play an important role in the up-regulation of its expression in SSc fibroblasts.

Adult↗
PubMed1997

Major role of collagen IIB in the elevation of total type II procollagen messenger RNA in the hypertrophic phase of experimental osteoarthritis.

OBJECTIVE: To define the relative contributions of procollagen IIA and IIB messenger RNA (mRNA) in the 8-fold elevation of total (IIA + IIB) type II procollagen mRNA in cartilage from joints with early experimental osteoarthritis (OA). METHODS: Unilateral cruciate ligament transection was performed on skeletally mature animals. Total RNA was extracted from articular cartilage from control joints and from joints with experimental OA. Northern blot hybridization with oligoprobes was used to distinguish between types IIA and IIB mRNA. RESULTS: Levels of IIA mRNA were similar in control and experimental cartilage. Type IIB mRNA accounted for the increase in total type II mRNA expression in OA joints. CONCLUSION: Although OA chondrocytes adapt to making immature forms of aggrecan proteoglycan, they do not revert to the prechondrocyte stage characterized by IIA mRNA expression.

Animals↗
PubMedDate not supplied

A radioimmunoassay procedure for type III procollagen: its use in the detection of hepatic fibrosis.

Recent studies suggest that the serum level of Type III procollagen (PC-III) could be a valuable, noninvasive monitor of hepatic fibrogenesis. We have developed a sensitive and specific radioimmunoassay for PC-III procollagen isolated and purified from fetal goat skin which shows high cross-reaction for human PC-III. In a double-blind study, serum samples taken from 8 normal volunteers and 50 patients at the time of liver biopsy were assayed for PC-III. Each biopsy was reviewed without knowledge of the radioimmunoassay results, and old or active fibrosis was graded on a 0 to 3 (none, minimal, moderate, severe) scale. There was a significant difference between serum concentrations of PC-III in normals (mean +/- S.D. = 72 ng per ml +/- 8) as compared to patients with biopsy evidence of active fibrosis (mean +/- S.D. = 153 ng per ml +/- 12; p less than 0.001). The serum concentration of PC-III showed a good correlation (r = 0.58; p less than 0.001) with the histological grade of active lobular fibrosis. Measurement of PC-III is a noninvasive test for detection of active fibrosis in the liver.

Double-Blind Method↗
PubMedDate not supplied

Serum type III procollagen peptide in alcoholic liver disease and idiopathic hemochromatosis: its relationship to hepatic fibrosis, activity of the disease and iron overload.

To assess the value of type III procollagen peptide (sPIIIP) as a marker of hepatic fibrosis, sera from 73 patients with alcohol-related liver disease and 30 patients with idiopathic hemochromatosis (IHC) were studied by a specific radioimmunoassay. sPIIIP was increased in 87% of 30 patients with cirrhosis, in 16% of 32 with steatofibrosis but in none of 11 with steatosis. There was a significant correlation with histologic hepatocellular necroinflammation (r = 0.42, p less than 0.01), but not with hepatic fibrosis. sPIIP was increased in 33% of 30 patients with IHC, whether or not they had cirrhosis or fibrosis, and whatever the level of iron overload or the extent of the hepatic deterioration. IHC patients with increased levels of sPIIIP had a higher prevalence of superimposed hepatic damage than did those with normal procollagen levels (p less than 0.05). Our findings, therefore, weaken the diagnostic value of sPIIIP as an index of connective tissue deposition in the liver, and suggest that, at least in alcohol-related liver disease and IHC, hepatocellular necroinflammation influences the results.

Adult↗
PubMed1992

Detection of sequence variants in the gene for human type II procollagen (COL2A1) by direct sequencing of polymerase chain reaction-amplified genomic DNA.

The direct sequencing of the human type II procollagen (COL2A1) gene from polymerase chain reaction (PCR)-amplified genomic DNA is described. Thirty-two regions of the COL2A1 gene were asymmetrically amplified with intron primers which were specifically chosen to amplify a region spanning 500 to 800 bp of sequence encoding one or more exons and their accompanying intervening sequences. Primers for dideoxynucleotide sequencing of the PCR products were then designed to provide complete exon sequence information and to insure that intron:exon splice junction sequence data would be obtained. Amplification and sequencing reactions were performed on an automated workstation to facilitate the handling of multiple DNA templates. The procedure allowed efficient sequencing of over 25,000 bp of each allele of the COL2A1 gene per diploid genome. We used this method for the comparative analyses of COL2A1 sequences in DNA isolated from the blood of 42 unrelated individuals and we identified 21 neutral sequence variants in the gene. The sequence variations were confirmed by independent assays, including restriction enzyme digestion. The sequence variants described here will be important for identifying haplotypes of the type II procollagen gene that will be useful in defining a genetic etiology for diseases of cartilaginous tissues.

Alleles↗
PubMed1993

Mutations in type 1 procollagen that cause osteogenesis imperfecta: effects of the mutations on the assembly of collagen into fibrils, the basis of phenotypic variations, and potential antisense therapies.

Work by a large number of investigators over the last decade has established that over 90% of patients with osteogenesis imperfecta have mutations in one of the two genes for type I procollagen, that most unrelated probands have different mutations in the genes, and that the mutations found in most of the serious variants of the disease cause synthesis of abnormal pro alpha chains of the protein. The results have demonstrated that synthesis of structurally abnormal but partially functional pro alpha chains can interfere with folding of the central region of the protein into a triple-helical conformation, prevent processing of the N-terminal propeptides of procollagen, or produce subtle alterations in conformation that interfere with the self-assembly of the protein into collagen fibrils. One of the unsolved mysteries about the disease is why some mutations produce severe phenotypes, whereas very similar mutations produce mild phenotypes. Recent studies in transgenic mice suggest that nongenetic factors, such as stochastic events during development, may determine the severity of the disease phenotype produced by a specific mutation. Also, recent results raised the possibility that strategies of antisense gene therapy may be effective in treating the disease some time in the future. Specific inhibition of expression of a mutated collagen gene has been obtained with antisense oligonucleotides in cell culture experiments. However, there is no means of selective delivery of antisense oligonucleotides to the appropriate tissues.

Cells, Cultured↗
PubMed2003

How is Type I procollagen synthesis regulated at the gene level during tissue fibrosis.

In response to tissue injury connective tissue synthesis occurs either normally or abnormally, which is mediated by transforming growth factor-beta (TGF-beta) and other growth factors. This article will be primarily concerned with the response of injured tissues at the gene level of Type I procollagen synthesis in response to TGF-beta. This leads to provisional repair, which in turn may lead to involution, remodeling, regeneration, and ultimately repair. Alternately, continuation of provisional repair may lead to fibrosis and ultimately scarring. Scarring of internal organs such as the liver and the lung leads to loss of function and ultimately death. In the case of scarring of skin, this is a cosmetic problem and can be rectified by surgery. Type I procollagen is synthesized by two genes, proalpha1 (Type I) and proalpha2 (Type I) collagen genes. This article will focus on DNA binding sites on these two genes, which regulate the transcription of the specific gene. This article will also define specific cell signaling pathways for the turning on of the proalpha1 and proalpha2 (Type I) collagen genes. This article will address several questions. First, what is the major cytokine acting extracellularly which stimulates the transcription of the proalpha1 and proalpha2 (Type I) collagen genes during tissue fibrosis? Secondly, how are the signals transmitted by the extracellular profibrotic cytokine TGF-beta from the cellular membrane to the nucleus for transcription of the proalpha1 (Type I) and proalpha2 (Type I) collagen genes? Thirdly, what signaling pathways cross-talk with the signaling pathways resulting in the expression of the Type I collagen genes? Fourthly, how does TGF-beta affect extracellular matrix homeostasis? Fifthly, what are the nuclear factors corresponding to the DNA elements required for the promotion of the proalpha1 (Type I) and proalpha2 (Type I) collagen genes? Finally, how are the proalpha1 (Type I) and proalpha2 (Type I) collagen genes coordinately regulated? Strategies will also be presented for reducing fibrosis, which is the result of overexpression of TGF-beta.

Animals↗
PubMed1985

Intracellular features of type II procollagen and chondroitin sulfate proteoglycan synthesis in chondrocytes.

The intracellular compartments of chondrocytes involved in the synthesis and processing of type II procollagen and chondroitin sulfate proteoglycan (CSPG) monomer were investigated using simultaneous double immunofluorescence and lectin localization reactions. Type II procollagen was distributed in vesicles throughout the cytoplasm, whereas intracellular precursors of CSPG monomer were accumulated in the perinuclear cytoplasm. In this study, cytoplasmic vesicles that stained intensely with antibodies directed against CSPG monomer but did not react with type II collagen antibodies, also were observed. A monoclonal antibody, 5-D-4, that recognizes keratan sulfate determinants was used to identify the Golgi complex (the site of keratan sulfate chain elongation). Staining with 5-D-4 was restricted to the perinuclear cytoplasm. The vesicles outside the perinuclear cytoplasm that stained intensely with antibodies to CSPG monomer did not react with 5-D-4. Fluorescent lectins were used to characterize further subcellular compartments. Concanavalin A, which reacts with mannose-rich oligosaccharides, did not stain the perinuclear region, but it did stain vesicles throughout the rest of the cytoplasm. Because mannose oligosaccharides are added cotranslationally, the stained vesicles throughout the cytoplasm presumably correspond to the rough endoplasmic reticulum. Wheat germ agglutinin, which recognizes N-acetyl-D-glucosamine and sialic acid (carbohydrates added in the Golgi), stained exclusively the perinuclear cytoplasm. By several criteria (staining with the monoclonal antibody 5-D-4 and with wheat germ agglutinin), the perinuclear cytoplasm seems to correspond to the Golgi complex. The cytoplasmic vesicles that react with anti-CSPG monomer and not with anti-type II collagen contain precursors of CSPG monomer not yet modified by Golgi-mediated oligosaccharide additions (because they are not stained with wheat germ agglutinin or with the anti-keratan sulfate antibody); these vesicles may have a unique function in the processing of CSPG.

Animals↗