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The Journal of Histochemistry and... Feb 1992We investigated the temporal and spatial distribution of osteonectin during human embryonic and fetal development, using in situ hybridization and immunohistochemistry....
We investigated the temporal and spatial distribution of osteonectin during human embryonic and fetal development, using in situ hybridization and immunohistochemistry. Osteonectin gene expression was generally found in cells exhibiting high rates of matrix production/proliferation. In mineralized tissue, a strong signal was obtained in osteoblasts, odontoblasts, and chondrocytes of the upper hypertrophic and proliferative zones. Chondrocytes of the mineralized zone showed no expression throughout the different stages of development. Strong osteonectin expression was found in odontoblasts of developing teeth. In addition, osteonectin mRNA and protein were detected in several non-mineralized tissues: steroid-producing cells of the adrenal gland and the gonads, kidney (glomeruli), lung (bronchi), skin, megacaryocytes, and large vessels. Histochemistry confirmed the results and detected extracellular osteonectin in bone and in the zone of mineralized cartilage only. The localization of osteonectin in bone, cartilage, and teeth is consistent with a role in the initiation of mineralization. However, the organ-specific distribution in non-mineralized tissues suggests an important multifunction role of this protein during human development.
Topics: Abortion, Spontaneous; Embryo, Mammalian; Embryonic and Fetal Development; Female; Fetus; Gene Expression; Humans; Immunohistochemistry; Organ Specificity; Osteogenesis; Osteonectin; Pregnancy; RNA, Messenger
PubMed: 1552170
DOI: 10.1177/40.2.1552170 -
Cancer Biology & Therapy Jul 2010
Topics: Animals; Humans; Liver Neoplasms; Osteonectin; Osteopontin; Pancreatic Neoplasms; Prognosis
PubMed: 20657168
DOI: 10.4161/cbt.10.1.12452 -
Biomolecules Jul 2023The SPARC gene plays multiple roles in extracellular matrix synthesis and cell shaping, associated with tumor cell migration, invasion, and metastasis. The SPARC gene is... (Review)
Review
The SPARC gene plays multiple roles in extracellular matrix synthesis and cell shaping, associated with tumor cell migration, invasion, and metastasis. The SPARC gene is also involved in the epithelial-mesenchymal transition (EMT) process, which is a critical phenomenon leading to a more aggressive cancer cell phenotype. SPARC gene overexpression has shown to be associated with poor survival in the mesothelioma (MESO) cohort from the TCGA database, indicating that this gene may be a powerful prognostic factor in MESO. Its overexpression is correlated with the immunosuppressive tumor microenvironment. Here, we summarize the omics advances of the SPARC gene, including the summary of SPARC gene expression associated with prognosis in pancancer and MESO, the immunosuppressive microenvironment, and cancer cell stemness. In addition, SPARC might be targeted by microRNAs. Notably, despite the controversial functions on angiogenesis, SPARC may directly or indirectly contribute to tumor angiogenesis in MESO. In conclusion, SPARC is involved in tumor invasion, metastasis, immunosuppression, cancer cell stemness, and tumor angiogenesis, eventually impacting patient survival. Strategies targeting this gene may provide novel therapeutic approaches to the treatment of MESO.
Topics: Humans; Cell Line, Tumor; Mesothelioma; MicroRNAs; Mesothelioma, Malignant; Epithelial-Mesenchymal Transition; Gene Expression Regulation, Neoplastic; Tumor Microenvironment; Osteonectin
PubMed: 37509139
DOI: 10.3390/biom13071103 -
The Journal of Biological Chemistry Jul 2008The 33-kDa matrix protein SPARC (BM-40, osteonectin) binds several collagen types with moderate affinity. The collagen-binding site resides in helix alphaA of the...
The 33-kDa matrix protein SPARC (BM-40, osteonectin) binds several collagen types with moderate affinity. The collagen-binding site resides in helix alphaA of the extracellular calcium-binding domain of SPARC and is partially masked by helix alphaC. Previously, we found that the removal of helix alphaC caused a 10-fold increase in the affinity of SPARC for collagen, and we identified amino acids crucial for binding by site-directed mutagenesis. In this study, we used rotary shadowing, CNBr peptides, and synthetic peptides to map binding sites of SPARC onto collagens I, II, and III. Rotary shadowing and electron microscopy of SPARC-collagen complexes identified a major binding site approximately 180 nm from the C terminus of collagen. SPARC binding was also detected with lower frequency near the matrix metalloproteinase cleavage site. These data fit well with our analysis of SPARC binding to CNBr peptides, denaturation of which abolished binding, indicating triple-helical conformation of collagen to be essential. SPARC binding was substantially decreased in two of seven alpha2(I) mutant procollagen I samples and after N-acetylation of Lys/Hyl side chains in wild-type collagen. Synthetic peptides of collagen III were used to locate the binding sites, and we found SPARC binding activity in a synthetic triple-helical peptide containing the sequence GPOGPSGPRGQOGVMGFOGPKGNDGAO (where O indicates 4-hydroxyproline), with affinity for SPARC comparable with that of procollagen III. This sequence is conserved among alpha chains of collagens I, II, III, and V. In vitro collagen fibrillogenesis was delayed in the presence of SPARC, suggesting that SPARC might modulate collagen fibril assembly in vivo.
Topics: Acetylation; Animals; Binding Sites; Cattle; Fibrillar Collagens; Humans; Hydroxyproline; Mutation; Osteonectin; Peptide Mapping; Peptides; Protein Binding; Protein Structure, Secondary
PubMed: 18487610
DOI: 10.1074/jbc.M710001200 -
Biochemical and Biophysical Research... Apr 1994Osteonectin (OTN) has been implicated in controlling cell adhesivity onto substratum and extracellular matrix (ECM) remodeling. Significant amounts of OTN were...
Osteonectin (OTN) has been implicated in controlling cell adhesivity onto substratum and extracellular matrix (ECM) remodeling. Significant amounts of OTN were synthesized not only by normal fibroblasts and endothelial cells, but also by HT-1080 fibrosarcoma and MG-63 osteosarcoma cells. Levels of secreted OTN were likely to be slightly elevated by the addition of exogenous placental laminin (LN), but not by supplementation of plasma fibronectin (FN). Exogenously supplemented purified bone OTN was not apparently incorporated into the ECM of the adhering cells and had no effect on cell spreading and growth, whereas secretion of type I collagen or FN in the tumor cells was moderately diminished in the presence of soluble OTN. Concentration-dependent down-regulation of cellular LN secretion appeared to be most significant, suggesting that OTN participates in regulating extracellular secretion of ECM components in the cells either with or without the ability to synthesize cellular OTN.
Topics: Amino Acid Sequence; Animals; Blood Platelets; Blotting, Western; Bone Neoplasms; Bone and Bones; Cattle; Cell Line; Chromatography, Ion Exchange; Endothelium, Vascular; Extracellular Matrix Proteins; Female; Fibroblasts; Fibronectins; Fibrosarcoma; Humans; Laminin; Molecular Sequence Data; Osteonectin; Osteosarcoma; Placenta; Pregnancy; Tumor Cells, Cultured
PubMed: 8166715
DOI: 10.1006/bbrc.1994.1466 -
Biochemistry Jul 1989Overlapping human bone osteonectin cDNAs were obtained by screening two independent human SaOS-2 lambda gt11 libraries using antibovine osteonectin monoclonal... (Comparative Study)
Comparative Study
Overlapping human bone osteonectin cDNAs were obtained by screening two independent human SaOS-2 lambda gt11 libraries using antibovine osteonectin monoclonal antibodies. One clone contains a 0.54-kb insert and the other a 1.9-kb insert. Insertion fragments from lambda clones were liberated by restriction digestion and subcloned into pUC19 for sequencing. Digestion of the 1.9-kb insert with EcoRI released 0.4- and 1.5-kb fragments. Sequencing analysis revealed that the 0.54- and 0.4-kb fragments are identical except for 150 nucleotides missing at the 5' region of the 0.4-kb fragment. The composite nucleotide sequence of human osteonectin has a total length of 2091 nucleotides and is comprised of 50 nucleotides of 5'-noncoding sequence, a coding segment for 303 amino acids, a termination codon, and 1114 nucleotides of 3'-noncoding sequence. The primary transcript codes for 286 amino acids of mature protein and a 17-residue amino-terminal hydrophobic signal peptide. Outstanding properties inferred from the primary structure are putative Ca2+ binding domains located in the glutamic acid rich NH2 terminus (residues 1-52) and two "EF"-hand domains in the C-terminal half of the protein (residues 165-176 and 257-286). The mature protein also contains a cysteine-rich, highly hydrophilic region homologous to the ovomucoid serine protease inhibitors (residues 76-132). Overlapping human genomic clones in lambda EMBL3 for osteonectin have been isolated and characterized. Intron/exon junction sequencing of the human osteonectin gene shows the presence of 10 exons and 9 introns. The mature protein is encoded by nine exons separated by eight introns.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Amino Acid Sequence; Animals; Antibodies, Monoclonal; Base Sequence; Bone and Bones; Cattle; Cloning, Molecular; DNA; Genes; Humans; Membrane Glycoproteins; Mice; Molecular Sequence Data; Osteonectin; Restriction Mapping; Sequence Homology, Nucleic Acid
PubMed: 2790009
DOI: 10.1021/bi00441a049 -
Calcified Tissue International Jul 1990Osteonectin is a calcium-binding matrix protein thought to play a role in regulating calcium distribution in a variety of biologic processes. To examine its role in...
Osteonectin is a calcium-binding matrix protein thought to play a role in regulating calcium distribution in a variety of biologic processes. To examine its role in endochondral bone formation, we examined the distribution of the protein during mineralization of the chicken tibial growth cartilage, using immunohistochemistry and immunoelectron microscopy. The synthesis of osteonectin was also determined in chondrocyte populations isolated from premineralizing and mineralizing regions of growth cartilage and assayed in short-term culture. The results show that a very low level of osteonectin is detectable in the resting, proliferating, and early hypertrophic zones of growth cartilage; in these zones, osteonectin is largely cell-associated. In contrast, a large amount of osteonectin is present in the mineralizing zone where it is associated with the matrix. Biosynthetic data from short-term culture experiments indicate, however, that osteonectin is synthesized and secreted by chondrocytes from both premineralizing and mineralizing zones. As indicated by immunoprecipitation, Northern hybridization, in vitro translation of hybrid-selected messenger RNA (mRNA), and electrophoretic analysis, osteonectin synthesized by chondrocytes of the premineralizing zones is not obviously different in structure from that synthesized by chondrocytes of the mineralizing zone. We conclude that osteonectin is a product of chondrocytes in each zone of growth cartilage but accumulates only in the mineralizing zone. The high affinity of the protein for calcium could favor its retention in calcifying matrix.
Topics: Animals; Calcification, Physiologic; Cells, Cultured; Chickens; Growth Plate; Immunohistochemistry; Microscopy, Electron; Minerals; Osteonectin; RNA, Messenger; Tibia
PubMed: 2369692
DOI: 10.1007/BF02555866 -
Molecular Vision Apr 2000We have previously reported increased levels of Osteonectin/SPARC transcript in age-related cataractous compared to normal human lenses. The purpose of the present study...
PURPOSE
We have previously reported increased levels of Osteonectin/SPARC transcript in age-related cataractous compared to normal human lenses. The purpose of the present study was to evaluate the corresponding levels of osteonectin/SPARC protein in age-related cataractous relative to normal lenses and to evaluate the levels of osteonectin/SPARC transcript in specific types of age-related human cataracts. The spatial expression of osteonectin/SPARC was also evaluated in normal human lenses.
METHODS
Specific types of age-related cataracts were collected and graded. Normal human lenses were microdissected into epithelia and fibers. Osteonectin/SPARC protein levels were monitored by Western immunoblotting, and transcript levels were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). Osteonectin/SPARC expression patterns were examined by RT-PCR and by immunostaining.
RESULTS
Higher levels of osteonectin/SPARC protein were detected in age-related cataractous relative to normal human lenses. Increased levels of osteonectin/SPARC transcript were also detected in posterior-subcapsular and nuclear cataractous lenses relative to normal lenses. Osteonectin/SPARC transcripts were detected in the lens epithelium but not fibers. Osteonectin/SPARC protein levels were highest in the peripheral lens epithelium.
CONCLUSIONS
Consistent with our previous studies on osteonectin/SPARC mRNA levels, osteonectin/SPARC protein levels were also elevated in cataractous compared to normal human lenses. Increased levels of osteonectin/SPARC mRNA were also found in nuclear and posterior-subcapsular cataracts relative to normal lenses. Osteonectin/SPARC expression is confined to the lens epithelium, and osteonectin/SPARC levels are highest in the peripheral lens epithelium.
Topics: Adolescent; Aged; Aging; Blotting, Western; Cataract; Female; Humans; Immunohistochemistry; Lens, Crystalline; Middle Aged; Osteonectin; RNA, Messenger; Reverse Transcriptase Polymerase Chain Reaction
PubMed: 10756178
DOI: No ID Found -
Oncogene Aug 2003Deregulated expression of SPARC/osteonectin, a secreted glycoprotein with multiple biological functions, has been associated with the progression of various cancers....
Deregulated expression of SPARC/osteonectin, a secreted glycoprotein with multiple biological functions, has been associated with the progression of various cancers. Using microarrays, we previously identified SPARC as one of the genes induced by treatment with a DNA methylation inhibitor in pancreatic cancer cells. We therefore analysed the expression pattern and methylation status of the SPARC gene in pancreatic cancer. Gene expression profiling by oligonucleotide microarray and reverse transcription-PCR analyses demonstrated that SPARC mRNA was expressed in non-neoplastic pancreatic ductal epithelial cells, but was not expressed in a majority of pancreatic cancer cell lines. The loss of SPARC expression was associated with aberrant hypermethylation of its CpG island. Immunohistochemical labeling revealed that the SPARC protein was overexpressed in the stromal fibroblasts immediately adjacent to the neoplastic epithelium in primary pancreatic cancers, but rarely expressed in the cancers themselves. Primary fibroblasts derived from pancreatic cancer strongly expressed SPARC mRNA and secreted SPARC protein into the conditioned media, and treatment of pancreatic cancer cells with exogenous SPARC resulted in growth suppression. SPARC expression in fibroblasts from noncancerous pancreatic tissue was augmented by coculture with pancreatic cancer cells. These findings suggest that SPARC is a frequent target for aberrant methylation in pancreatic cancer and that SPARC expression in fibroblasts adjacent to pancreatic cancer cells is regulated through tumor-stromal interactions.
Topics: Adenocarcinoma; Animals; Cell Communication; DNA Methylation; Male; Neoplasm Invasiveness; Osteonectin; Pancreatic Neoplasms; Stromal Cells
PubMed: 12902985
DOI: 10.1038/sj.onc.1206807 -
Joint Bone Spine Dec 2007Among the connective tissue diseases, systemic sclerosis is an orphan disease in which diffuse connective tissue alterations lead to multi-organ involvement.... (Review)
Review
Among the connective tissue diseases, systemic sclerosis is an orphan disease in which diffuse connective tissue alterations lead to multi-organ involvement. Environmental factors implicated in triggering this multifactorial disease include crystalline silica, chlorine solvents, welding vapors, and various other solvents. Clustering within families indicates a role for genetic factors. Although concordance for the disease among identical twins is low, concordance for autoantibodies associated with systemic sclerosis and for fibroblast gene expression profiles is higher. Because multiplex families are rare, association and candidate gene strategies are the most appropriate methods for investigating the genetics of systemic sclerosis. The most consistent data relate to the involvement of fibrosis genes, most notably the TGF-beta regulation pathway, secreted protein acid and rich in cysteine (SPARC) genes, and the fibrillin-1 gene (FBN1). Several variants of genes for cytokines or their receptors may be involved. Data on the vasculopathy characteristic of systemic sclerosis are somewhat conflicting. Investigations into the genetics of systemic sclerosis may shed light on the complex pathophysiology of this disease, help to identify factors that predict organ involvement, and suggest new treatment strategies.
Topics: Fibrillin-1; Fibrillins; Genetic Predisposition to Disease; Humans; Microfilament Proteins; Osteonectin; Polymorphism, Genetic; Receptors, Transforming Growth Factor beta; Scleroderma, Systemic
PubMed: 17855142
DOI: 10.1016/j.jbspin.2007.04.005