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PubMed2003

Regulated binding of the fibrinogen-like domains of tenascin-R and tenascin-C to the neural EGF family member CALEB.

The neural transmembrane protein CALEB was discovered in a screen for novel molecules implicated in neuronal differentiation processes and was found to bind to two proteins of the extracellular matrix, tenascin-C and tenascin-R. The expression of different isoforms of CALEB in axon- and synapse-rich areas in the nervous system is regulated during development. Here we show that an unusual acidic peptide segment of CALEB is sufficient to mediate the binding of CALEB to the fibrinogen-like globes of both tenascin family members as well as to native tenascin-C. We identify a small sequence element within the acidic peptide segment of CALEB as important for this binding. Interestingly, the interactions of CALEB and tenascin-C and -R seem to be regulated during development. We demonstrate that only CALEB-80, the expression of which is up-regulated in the chicken retina during synaptogenesis, but not CALEB-140, expressed later on in development, can bind to the fibrinogen-like domains of tenascin-R or tenascin-C and to native tenascin-C. While both CALEB-80 and CALEB-140 are expressed in the plexiform layers and the optic fiber layer of embryonic chicken retina, CALEB-140 labeling is more intense in the optic fiber layer in comparison to the inner plexiform layer.

Amino Acid Motifs↗
PubMed1991

Complete primary structure of porcine tenascin. Detection of tenascin transcripts in adult submaxillary glands.

Tenascin is an extracellular matrix protein that is postulated to modulate tissue differentiation and cell migration during development. cDNA clones for tenascin were isolated from a cDNA library of adult porcine submaxillary glands. Three forms of tenascin clones were observed which varied with the number (8-10) of fibronectin type III (FN-III) domains. A major form consists of the N-terminal domain involved in the hexamer formation of tenascin subunits, 14 epidermal-growth-factor-like domains, nine FN-III domains, and the fibrinogen-like domain. A minor form with ten FN-III domains has never been described. Another striking feature is the lack of an RGD sequence that has been implicated to be crucial for cell adhesion, whereas RGD is present in both chicken and human tenascin sequences. In the adult, tenascin is expressed in very restricted tissues such as brain and chicken gizzard. A survey of tenascin transcripts in various adult rat normal tissues, including brain, revealed that the transcripts were detected only in submaxillary glands where tenascin expression has never been reported.

Amino Acid Sequence↗
PubMed1996

Tenascin-C mRNA and tenascin-C protein immunoreactivity increase in astrocytes after activation by bFGF.

Tenascin-C is an extracellular matrix glycoprotein with trophic and repulsive properties, involved in migratory processes in CNS. Previous reports demonstrated that this molecule is produced and secreted by astrocytes. Preliminary data on fibroblasts and astrocytes have suggested that bFGF may modulate tenascin-C expression. bFGF is a mitogenic growth factor, involved in cell differentiation and neovascularization. In the present study, we examined whether bFGF modulates the expression of tenascin-C in hippocampal astrocytes from newborn rats. Our results suggest that bFGF increases the production of tenascin-C by cultured hippocampal astrocytes. We found that both tenascin-C mRNA and protein immunoreactivity were increased after bFGF treatment. Our results also demonstrated that tenascin-C polypeptides were secreted into the extracellular medium. In agreement with previous studies, we suggest that secreted tenascin-C is mainly the high molecular weight form. In addition, our results suggest that a cleavage of the high molecular weight form. In addition, our results suggest that a cleavage of the high molecular weight form may occur in the extracellular medium causing production of proteolytic fragments, that may modify the biological properties of tenascin-C. The present results may be relevant to the understanding of lesion scarring and regeneration process.

Animals↗
PubMed2004

Distribution of tenascin-C and -X and expression of tenascin-C and X mRNA in the postnatal rat tongue.

Different distributions of tenascin-C and -X are found in various organs. However, the role of the tenascin family in the process of formation in the papillae epithelium during development is poorly understood. In order to find more information an tenascin-C and -X distributions during tongue development, immunohistocheminical studies have been carried out to demonstrate these distributions. The number of PCNA positive cells gradually increased from 5- to 15-days, and decreased on 21-days in the intercellular space of the epithelal layer in the postnatal development of rat tongue (150 specimens of Wistar male rats (0-, 5-, 10-, 15-, and 21-days). The reaction of tenascin-C was found mainly in the intercellular space of the epithelial layer on contrast to that of tenascin-X which was mainly found an the epithelial layer under a confocal laser scanning microscope. The level of mRNA of tenascin-C (600bp) and tenascin-X (588bp) gradually decreased from 5-days using RT-PCR methods. The different distribution of these extracellular matrices and weakly-regulated expressions may be related to the replication process of the epithelium in the tongue during development.

Aging↗
PubMed1991

Amino acid sequence of mouse tenascin and differential expression of two tenascin isoforms during embryogenesis.

We have isolated cDNA clones for mouse tenascin and analyzed expression of tenascin mRNAs during embryonic development of the kidney and gut. The deduced amino acid sequence of the mouse tenascin cDNAs shows a modular structure of repeats similar to chicken and human tenascin. In mouse there are 14.5 cysteine-rich repeats with similarity to the EGF repeat, followed by several repeats with similarity to the type III repeat of fibronectin. A longer variant contains 13 fibronectin type III repeats, whereas a shorter splice variant of mouse tenascin lacks the 5 type III repeats that occur directly after the fifth repeat in the longer variant. Contrary to the chicken and human sequences, mouse tenascin does not contain an RGD sequence in the third type III repeat implicated in cell attachment, or in any other positions. In Northern hybridizations to RNA from primary embryonic fibroblasts, the cDNA clone M 20/1 detects two mRNAs with sizes close to 6 and 8 kb. This, and the other data presented here suggest that the two major mouse tenascin polypeptides arise through an alternative RNA splicing. The two major mRNAs are differentially expressed during development. The 8-kb mRNA is more prominent than the 6-kb mRNA throughout prenatal kidney development, but during postnatal development the ratio of the two mRNAs changes. A different expression pattern is seen in the developing gut where the 6-kb mRNA predominates during embryogenesis with the 8-kb mRNA appearing later. The mRNA data of the developing gut correspond with previous protein data, which showed that the shorter Mr 210,000 polypeptide predominates during earlier developmental stages and the larger Mr 260,000 polypeptide appears later in the embryonic gut (Aufderheide, E., and P. Ekblom. 1988. J. Cell Biol. 107:2341-2349).

Amino Acid Sequence↗
PubMed1994

Cloning and characterization of alternatively spliced isoforms of rat tenascin. Platelet-derived growth factor-BB markedly stimulates expression of spliced variants of tenascin mRNA in arterial smooth muscle cells.

To understand the alteration of extracellular matrix composition evoked by chemotactic factors, we have studied the expression of adhesive (fibronectin) and anti-adhesive (tenascin) proteins in response to platelet-derived growth factor-BB (PDGF-BB), a potent chemoattractant for rat aortic smooth muscle cells (ASMC). PDGF-BB markedly induced two major tenascin mRNA transcripts, whereas fibronectin mRNA levels did not change. The results of immunoprecipitation studies paralleled Northern blot data. Since alternative splicing is responsible for the generation of multiple tenascin mRNAs in other cell types, we studied the effect of chemotactic factors on the relative abundance of tenascin isoforms. The alternatively spliced region of ASMC-derived rat tenascin was amplified and the identity of the products confirmed by sequencing. Three major polymerase chain reaction products were detected: a 1727-base pair unspliced form which was maximal at 2 h and 635- and 362-base pair products which were more abundant at 8 h after treatment with PDGF-BB or angiotensin II. Functional studies showed that the unspliced isoform of human tenascin inhibited attachment of both human and rat ASMC to fibronectin. These results suggest that PDGF-BB markedly up-regulates the expression of tenascin variants, which may lead to destabilization of cell-matrix interactions and promotion of cell migration.

Alternative Splicing↗
PubMed1996

Glial cell interactions with tenascin-C: adhesion and repulsion to different tenascin-C domains is cell type related.

The multimodular glycoprotein tenascin-C is transiently expressed, predominantly by glial cells, during the development of the central and peripheral nervous systems. This extracellular matrix glycoprotein is involved in the control of cell adhesion, neuron migration and neurite outgrowth. Distinct functional properties for neuronal cell types have been attributed to separate tenascin-C domains using antibody perturbation studies and in vitro experiments on tenascin-C fragments. In order to study potential roles of tenascin-C for glial cell biology, a library of recombinant tenascin-C domains was used in a bioassay in vitro. Embryonic day 14 astrocytes, various astroglial-derived cell lines (C6, A7 and Neu7) and oligodendroglial-derived cell types (Oli-neu and G26-20) were examined in an adhesion assay and compared to the neuroblastoma cell line N2A. A binding site for most cell types, except for A7 and N2A, could be assigned to the first three fibronectin type III domains. Repulsive properties could be mapped to three different sites the epidermal growth factor-like repeats, fibronectin type III repeats 4 and 5 and to the alternatively spliced region of the molecule. The responses to these repulsive sites varied according to the cell type. These data are consistent with the interpretation that different cell types express distinct sets of tenascin-C receptors which might regulate cellular responses via distinct second messenger pathways.

Animals↗
PubMed2004

Structural basis for interactions between tenascins and lectican C-type lectin domains: evidence for a crosslinking role for tenascins.

The C-terminal G3 domains of lecticans mediate crosslinking to diverse extracellular matrix (ECM) proteins during ECM assembly, through their C-type lectin (CLD) subdomains. The structure of the rat aggrecan CLD in a Ca(2+)-dependent complex with fibronectin type III repeats 3-5 of rat tenascin-R provides detailed support for such crosslinking. The CLD loops bind Ca2+ like other CLDs, but no carbohydrate binding is observed or possible. This is thus the first example of a direct Ca(2+)-dependent protein-protein interaction of a CLD. Surprisingly, tenascin-R does not coordinate the Ca2+ ions directly. Electron microscopy confirms that full-length tenascin-R and tenascin-C crosslink hyaluronan-aggrecan complexes. The results are significant for the binding of all lectican CLDs to tenascin-R and tenascin-C. Comparison of the protein interaction surface with that of P-selectin in complex with the PGSL-1 peptide suggests that direct protein-protein interactions of Ca(2+)-binding CLDs may be more widespread than previously appreciated.

Aggrecans↗
PubMed1993

A novel tenascin type III repeat is part of a complex of tenascin mRNA alternative splices.

Sequence analysis of two human tenascin encoding cDNA clones from a cDNA library of the U251 glioblastoma cell line revealed the presence of a novel 276 bp tenascin type III fibronectin like repeat. This alternatively spliced type III repeat designated AD1 is located between the previously identified repeats 10 and 11 and has sequence homology with human, chicken and mouse tenascin type III repeats. These results show that tenascin has at least 16 consecutive fibronectin like type III repeats. PCR amplification of random primed mRNA with specific type III repeat primers revealed a pattern of multiple alternative splices of AD1 and flanking type III repeats. The alternative splice variants were confirmed by direct sequencing. Differences were observed in the expression of the various alternative splices of tenascin mRNA between tumor and normal cells and may thus indicate differences in tenascin isoform expression and function in normal and tumor cells. PCR and Southern analysis of genomic DNA indicate that AD1 is coded by a single exon present in both human and mouse genome.

Amino Acid Sequence↗
PubMed1998

Zebrafish tenascin-W, a new member of the tenascin family.

A cDNA clone encoding tenascin-W, a novel member of the tenascin family, was isolated from a 20- to 28-h postfertilization (hpf) zebrafish cDNA library on the basis of the conserved epidermal growth factor-like domains represented in all tenascin molecules. An open reading frame of 2796 base pairs encodes a mature protein consisting of heptad repeats, a cysteine-rich amino terminal region, 3.5 epidermal growth factor-like repeats, five fibronectin type III homologous repeats, and a domain homologous to fibrinogen. These domains are the typical modular elements of molecules of the tenascin family. Sequence comparison demonstrated that TN-W shares homologies with the members of the tenascin family but is not a species homolog of any identified tenascin. The expression pattern of tn-w was analyzed by in situ hybridization in 1-day-old embryos, in 3-day-old larvae, and in juvenile zebrafish. At 24-25 hpf, tn-w mRNA was expressed in the lateral plate mesoderm, most conspicuously in the presumptive sclerotome. Migrating cells of sclerotomal and neural crest origins also showed high levels of expression. At 3 days, expression by sclerotomal and neural crest cells continued to be observed while expression in the somitic mesoderm was decreased. In juvenile fish, tn-w was expressed weakly by cells in the myosepta and, more strongly, by presumably nonneuronal cells in the dorsal root ganglia. In these tissues and at the same developmental stages, the expression of tn-w partially overlapped with the distribution of tn-c mRNA. In addition, tn-c was expressed in the central nervous system (CNS) and in the axial mesoderm, neither of which expressed tn-w at any of the age stages examined. The expression pattern of tn-w suggests an involvement in neural crest and sclerotome cell migration and in the formation of the skeleton. Similar and possibly overlapping functions could also be performed by tn-c, which appears to have additional functions during the development of the CNS.

Aging↗
PubMed2002

Tenascin and proteoglycans: the role of tenascin and proteoglycans in canine tumours.

Tenascin is a high molecular weight, extracellular matrix glycoprotein, subject to complex spatial and temporal patterns of expression during embryogenesis, wound healing and neoplastic processes. Proteoglycans are complex macromolecules, containing one or more glycosaminoglycans attached to a core protein, which are involved in cell-cell and cell-matrix interaction. Altered expression of both tenascin and proteoglycans has been found in tumours and expression of these two extracellular matrix proteins seems to be modulated in the same way in human and canine tumours. The quantitative and qualitative changes in tenascin and proteoglycan composition may significantly affect behaviour of tumour cells. While tenascin and proteoglycans have many biological functions likely to influence tumour development and progression, their exact role in regulation of tumour cell-cell interaction, proliferation, invasion and metastasis remains to be established. This review focuses on the role of tenascin and proteoglycans in neoplasia and recent developments in canine tumours.

Animals↗
PubMed2003

Tenascin-N: characterization of a novel member of the tenascin family that mediates neurite repulsion from hippocampal explants.

Tenascin-N, a novel member of the tenascin family, was identified and shown to encode characteristic structural motifs of a cysteine-rich stretch, 3.5 epidermal growth factor-like repeats, 12 fibronectin type III homologous domains, and a fibrinogen-like domain. The third fibronectin type III homologous domain is altered by RNA splicing. Characterization of the expression of tenascin-N by in situ hybridization analysis assigned transcripts to many types of neurons in the central nervous system, to the medullary region in the kidney, and to resident macrophages of the T-cell zone in the splenic white pulp. By immunohistochemistry, tenascin-N expression is detectable in all brain regions, with a characteristic staining pattern in the hippocampus demarcating the CA3 region. Recombinantly expressed protein fragments of the alternatively spliced isoforms were presented in choice assays on patterned substrates to neurites and migrating neurons from hippocampal CA3 region explant cultures. The smaller splice variant inhibited neurite outgrowth or cell migration, whereas the longer splice form did not inhibit these functions. These observations suggest that the novel tenascin family member mediates specific repulsive properties on neurites and neurons by generating splice isoforms.

Alternative Splicing↗
PubMed2000

CALEB binds via its acidic stretch to the fibrinogen-like domain of tenascin-C or tenascin-R and its expression is dynamically regulated after optic nerve lesion.

Recently, we described a novel chick neural transmembrane glycoprotein, which interacts with the extracellular matrix proteins tenascin-C and tenascin-R. This protein, termed CALEB, contains an epidermal growth factor-like domain and appears to be a novel member of the epidermal growth factor family of growth and differentiation factors. Here we analyze the interaction between CALEB and tenascin-C as well as tenascin-R in more detail, and we demonstrate that the central acidic peptide segment of CALEB is necessary to mediate this binding. The fibrinogen-like globe within tenascin-C or -R enables both proteins to bind to CALEB. We show that two isoforms of CALEB in chick and rodents exist that differed in their cytoplasmic segments. To begin to understand the in vivo function of CALEB and since in vitro antibody perturbation experiments indicated that CALEB might be important for neurite formation, we analyzed the expression pattern of the rat homolog of CALEB during development of retinal ganglion cells, after optic nerve lesion and during graft-assisted retinal ganglion cell axon regeneration by in situ hybridization. These investigations demonstrate that CALEB mRNA is dynamically regulated after optic nerve lesion and that this mRNA is expressed in most developing and in one-third of the few regenerating (GAP-43 expressing) retinal ganglion cells.

Amino Acid Sequence↗
PubMed1994

The distribution of tenascin-X is distinct and often reciprocal to that of tenascin-C.

We have isolated a cDNA encoding mouse tenascin-X (TN-X), a new member of the family of tenascin genes. The TN-X gene lies in the major histocompatibility complex (MHC) class III region, as it is the case for its human counterpart. On Northern blots we detected a TN-X mRNA of approximately 13 kb in most tissues analyzed, whereas in various mouse cell lines mRNAs of approximately 11 and 13 kb were detected, suggesting the possibility of alternative splicing of TN-X transcripts. We raised antibodies against mouse TN-X fragments expressed in bacteria and used these antibodies to identify the TN-X protein in heart cell extracts and in the conditioned medium of a renal carcinoma cell line. The subunit molecular size of TN-X is approximately 500 kD, suggesting that the protein may contain up to 40 fibronectin type III repeats, making it the largest tenascin family member known yet. TN-X in conditioned medium, as well as the purified protein bind to heparin, but no binding to tenascin-C (TN-C), fibronectin, laminin or collagens could be detected. Thus the heparin-binding activity may be a common feature of the tenascins. The TN-X mRNA as well as the protein are predominantly expressed in heart and skeletal muscle, but the mRNA is found in most tissues at a low level. Immunostaining showed the protein to be associated with the extracellular matrix of the muscle tissues and with blood vessels in all of the tissues analyzed. Although the TN-X gene lies in the MHC class III locus, it is not expressed in the lymphoid organs analyzed, except for the staining around blood vessels. In skin and tissues of the digestive tract often a reciprocal distribution of TN-X and TN-C was observed.

Amino Acid Sequence↗
PubMed2006

Distribution of tenascin-C and tenascin-X, apoptotic and proliferating cells in postnatal soft-diet rat temporomandibular joint (TMJ).

We immunohistochemically examined the relationship between the distribution of extracellular matrix glycoproteins (tenascin-C and tenascin-X), apoptotic cells, and proliferating cells to determine the effect of a soft diet in the rat temporomandibular joint (TMJ) over a period of 4 weeks from 21 days of age. Using confocal Laser scanning microscopy, strong expression of tenascin-C and tenascin-X was found in the soft-diet group, mainly from the proliferative layer to the cartilage layer of the condyle, and posterior and anterior regions of the disk, in contrast to that of the control group, which was fed a hard diet. The number of proliferating cells in the soft-diet group was lower than that in the control group and was especially low in the calcified zone and proliferative cell layer of the sagittal section of the TMJ. The apoptotic cells were found mainly in the endochondral ossification layer of the condyle. On day 28 in the soft-diet group, they were also highly concentrated in endochondral ossification layer of the anterior condyle beneath the disk. A few apoptotic cells were observed in the synovial membrane and the disk. These distributions reflect the process of replication in the TMJ in accordance with the feeding of a soft diet.

Animal Feed↗
PubMed1997

Differential expression of tenascin-C and tenascin-X in human astrocytomas.

Tenascins (TNs) are a family of extracellular matrix glycoproteins. The first member of this family to be recognized, tenascin-C (TN-C), is known to be expressed in various tumors including human astrocytomas. Tenascin-X (TN-X) is the latest member of the TN family to be reported, and its expression in tumor tissues has not yet been examined. In this study, we found expression of TN-X in glioma cell lines and human astrocytomas by immunoblot analysis using anti-mouse TN-X antibodies. We also examined the expression of TN-C and TN-X immunohistochemically in a series of 32 human astrocytomas and tissue from 5 normal brains. Expression of TN-X was up-regulated to a higher degree in low-grade astrocytomas than in high-grade astrocytomas. TN-X was mainly localized in the perivascular stroma around tumor vessels, and weakly expressed in the intercellular spaces among tumor cells. In contrast, TN-C was more strongly expressed in the intercellular spaces and in tumor vessels in high-grade astrocytomas (anaplastic astrocytomas and glioblastomas) than in low-grade astrocytomas. In the tissues expressing both TNs, the distribution of TN-X was often reciprocal to that of TN-C. These findings indicate that the expression of TN-C and TN-X in astrocytomas is different, and that these glycoproteins could be involved in neovascularization in different manners.

Animals↗
PubMed1998

Structural analysis of mouse tenascin-X: evolutionary aspects of reduplication of FNIII repeats in the tenascin gene family.

Tenascin-X (TNX) is an extracellular matrix glycoprotein involved in both primary structural functions and modulating cellular activities in multicellular organisms. We determined the 67977bp nucleotide sequence of the entire mouse tenascin-X (Tnx) gene, which also includes the last exon of Creb-rp and Cyp21. We compared it with the orthologous human locus. Conservation of both position and orientation of the three functionally unrelated genes at this position was found. Comparison also revealed that introns 1, 4 and 6 of Tnx are highly conserved between species. The sequence showed that mouse Tnx contains 43 exons separated by 42 introns. The deduced amino-acid sequence (4114 residues) revealed that mouse Tnx has a primary structure characteristic of tenascins, which consists of a signal peptide and four heptad repeats followed by 18.5 epidermal growth factor-like (EGF) repeats, 31 fibronectin type III-like (FNIII) repeats, and a region homologous to fibrinogen. cDNA clones generated by alternative splicing of eight consecutive FNIII repeats (M15-M22) as well as a proximal FNIII repeat (M3) were also identified. The FNIII motifs that were subject to alternative splicing were assigned to the group of recently reduplicated FNIII repeats because they have a high level of amino-acid sequence similarity. We also analyzed the evolution of FNIII repeats in TNX.

Amino Acid Sequence↗
PubMed2002

Invasion of melanoma in double knockout mice lacking tenascin-X and tenascin-C.

The roles of extracellular matrix glycoproteins belonging to the tenascin family in the regulation of tumor cell proliferation, invasion, and metastasis are not known. To address this issue, we generated tenascin-X (TNX) and tenascin-C (TNC) double knockout mice and compared findings in these mice with those in single knockout (TNX + / + TNC - / - and TNX - / - TNC + / +) mice. We investigated the proliferation and invasion of B16-BL6 melanoma cells after these cells had been injected into the footpads of mice in each group. The primary tumor size and invasion to the ankle adjacent to the primary tumor site were examined at 35 days after injection of the melanoma cells. The primary tumor size in TNX - / - TNC + / + mice was significantly larger than that in wild-type mice, but those of TNX + / + TNC - / - and double knockout mice were comparable to that in the wild-type mice. On the other hand, invasion to the ankle was obviously promoted in TNX - / - TNC + / + and double knockout mice compared with that in the wild-type mice, but invasion to the ankle in TNX + / + TNC - / - mice was only slightly promoted. Gelatin zymography confirmed increased matrix metalloproteinase (MMP)-9 activity in the dorsal skin of TNX - / - TNC + / +, TNX + / + TNC - / - and double knockout mice. However, the amounts of MMP-9 mRNA in the dorsal skins of all mice were almost the same, indicating that the increased activity of MMP-9 in the single and double knockout mice is regulated at the MMP-9 processing level. These results indicate that MMP-9 is activated in all TN-deficient mice, but that TNX exerts a greater effect on tumor invasion than does TNC.

Animals↗