Biomedical subjects

C Hagios

Publications and source records attributed to C Hagios.

13 recordsLinked to original sources

PubMed2001

Tenascin-Y is concentrated in adult nerve roots and has barrier properties in vitro.

Several molecules have been identified as potential sources of the barriers to glial cell mixing and sensory regeneration that exist at the boundary between the peripheral and central nervous systems, including tenascin-C, tenascin-R, chondroitin sulfate proteoglycans, and NG2. Here we show that tenascin-Y, the avian homologue of tenascin-X, is concentrated in the proximal portions of peripheral nerves in the chicken. In vitro analyses of cultures enriched for Schwann cells demonstrate that recombinant tenascin-Y has dose-dependent effects on glial cell attachment, spreading, and migration. In addition, nanomolar concentrations of tenascin-Y cause the rapid collapse of sensory growth cones cultured on fibronectin, and regenerating sensory neurites preferentially migrate on fibronectin and avoid tenascin-Y in microstripe assays. We conclude that the expression pattern of tenascin-Y and its properties in vitro are consistent with a role as an inhibitor of glial cell migration and sensory regeneration in nerve roots.

Animals↗

PubMed2001

Tumors are unique organs defined by abnormal signaling and context.

Many cancer investigations have focussed on the eradication of the cancer cell itself and in doing so, overlook the inherent complexity and heterogeneity of solid tumors. Here, we argue that, in many cases, it is the altered communication within the tumor, rather than mutations per se, that is the defining characteristic of cancer. As a result, tumorigenesis can be indirectly initiated by environmental or inherited factors that affect the stromal cells. We propose that anticancer research might be more effective if aimed at eradicating the cause of abnormality rather than just treating the end result.

Animals↗

PubMed1999

Tenascin-Y, a component of distinctive connective tissues, supports muscle cell growth.

Chicken tenascin-Y is an extracellular matrix protein most closely related to the mammalian tenascin-X. It is highly expressed in the connective tissue of skeletal muscle (C. Hagios, M. Koch, J. Spring, M. Chiquet, and R. Chiquet-Ehrismann, 1996, J. Cell Biol. 134, 1499-1512). Here we demonstrate the presence of tenascin-Y in specific areas of the connective tissues in developing lung, kidney, and skin. In skin tenascin-Y shows a complementary expression pattern to tenascin-C, whereas in the lung and kidney the sites of expression are partly overlapping. Tenascin-Y is also present in embryonic skeletal muscle where it is expressed in the developing connective tissue in between the muscle fibers. This connective tissue is also the major site of alpha5 integrin expression. We purified recombinantly expressed tenascin-Y and tested its effect on cell adhesion and its influence on muscle cell growth and differentiation. C2C12 myoblasts were able to adhere to tenascin-Y and showed extensive formation of actin-rich processes without generation of stress fibers. Furthermore, we found that tenascin-Y influenced cell morphology of chick embryo fibroblasts over prolonged times in culture and that it supports primary muscle cell growth and restricts muscle cell differentiation.

Animals↗

PubMed1999

Thrombospondin-1 and neural crest cell migration.

Using a monoclonal antibody raised against human platelet thrombospondin, we found anti-thrombospondin immunoreactivity in the extracellular matrix of avian embryos, coincident with the ventral pathways followed by trunk neural crest cells. To confirm that the antibody recognized thrombospondin-1 and to determine the tissue of origin of the thrombospondin matrix, a thrombospondin-1 cRNA probe was used for whole mount in situ hybridization. This probe revealed thrombospondin-1 mRNAs in the developing myotome before and during neural crest cell migration. The effect of thrombospondin-1 on neural crest cell migration, morphology, and adhesion was assayed in vitro. Quail trunk neural crest cells cultured on 4 microg/ml of thrombospondin-1 migrate at 1.14 +/- 0.54 microm/min, which is significantly greater than the rate of cell migration on tissue culture plastic. Using a shaker-based adhesion assay, a significantly greater number of neural crest cells remain attached to dishes coated with 4 microg/ml of thrombospondin-1 than to tissue culture plastic alone. The number of neural crest cells that remain attached to 4 microg/ml of thrombospondin-1 is similar to the number that remain attached to dishes coated with 10 microg/ml of fibronectin. These observations indicate that neural crest cells migrate through a thrombospondin-filled extracellular matrix, and that thrombospondin-1 promotes neural crest cell migration and adhesion. Thus, thrombospondin-1 is the first somite-derived extracellular matrix molecule with properties consistent with a role in the promotion of migration into the anterior somite, as opposed to the repulsion of neural crest cells from the posterior half of the somite.

Animals↗

PubMed1999

Tenascin-Y in the developing and adult avian nervous system.

The glycoproteins tenascin-C and tenascin-R are abundant in the developing and adult nervous system, respectively. We have used a polyclonal antiserum to determine if tenascin-Y, a novel member of the tenascin family previously identified in the extracellular matrix of muscle, is also expressed in the avian nervous system. Beginning at embryonic day 3 tenascin-Y immunoreactivity is associated with bottle-shaped ependymal cells in the roof plate and floor plate of the spinal cord and brain. These cells resemble the secretory cells that synthesize the ventricular extracellular matrix, including Reissner's fiber. Tenascin-Y immunoreactivity is also seen in pia mater and blood vessels in the developing and adult central nervous system. Anti-tenascin-Y stains the connective tissue sheath of peripheral nerves and the dorsal roots beginning around embryonic day 20. In vitro, sensory neurites fail to form lamellipodia when cultured in the presence of recombinant tenascin-Y, suggesting that tenascin-Y may play a role in inhibiting sensory neurite regeneration into the spinal cord. There is little overlap in the expression patterns of tenascin-Y and tenascin-C during development and between tenascin-Y and tenascin-R in the adult central nervous system, which is further evidence of distinctive mechanisms of gene regulation by the different members of the tenascin family.

Animals↗

PubMed1998

Tissue architecture: the ultimate regulator of epithelial function?

The architecture of a tissue is defined by the nature and the integrity of its cellular and extracellular compartments, and is based on proper adhesive cell-cell and cell-extracellular matrix interactions. Cadherins and integrins are major adhesion-mediators that assemble epithelial cells together laterally and attach them basally to a subepithelial basement membrane, respectively. Because cell adhesion complexes are linked to the cytoskeleton and to the cellular signalling pathways, they represent checkpoints for regulation of cell shape and gene expression and thus are instructive for cell behaviour and function. This organization allows a reciprocal flow of mechanical and biochemical information between the cell and its microenvironment, and necessitates that cells actively maintain a state of homeostasis within a given tissue context. The loss of the ability of tumour cells to establish correct adhesive interactions with their microenvironment results in disruption of tissue architecture with often fatal consequences for the host organism. This review discusses the role of cell adhesion in the maintenance of tissue structure and analyses how tissue structure regulates epithelial function.

Animals↗

PubMed1997

In situ localization of thrombospondin-1 and thrombospondin-3 transcripts in the avian embryo.

Two novel cDNA probes to chicken thrombospondin-1 (TSP-1) and TSP-3 were used to determine by in situ hybridization the origins of these extracellular matrix proteins during embryogenesis. Both TSP-1 and TSP-3 are expressed in embryonic cartilage. TSP-1 expression is limited to early chondrocytes, in contrast to TSP-3 mRNAs that are found in older proliferative and hypertrophic chondrocytes. TSP-1 and TSP-3 are expressed consecutively during neurogenesis as well, with the TSP-1 probe hybridizing in proliferating neuroblasts, and TSP-3 expressed by neurons as they are actively extending processes. A TSP-1 hybridization signal reappears in subpopulations of neurons in the spinal cord and brain after the periods of active neurite extension and programmed cell death are complete. TSP-1 is also expressed in the spinal cord floor plate, in mesenchyme surrounding the developing paramesonephric duct, at the tips of growing lung bronchioles, in lens, and in corneal endothelium. These observations indicate that there is little overlap in the expression patterns of TSP-1 and TSP-3 and that they are expressed consecutively during the development of cartilage and neurons. The pattern of TSP-1 expression in avascular tissues and in the floor plate is consistent with possible roles for this glycoprotein in regulating angiogenesis and establishing morphogenetic gradients.

Animals↗

PubMed1996

Tenascin-Y: a protein of novel domain structure is secreted by differentiated fibroblasts of muscle connective tissue.

Tenascin-Y was identified in chicken as a novel member of the tenascin (TN) family of ECM proteins. Like TN-C, TN-R, and TN-X, TN-Y is a multidomain protein consisting of heptad repeats, epidermal growth factor-like repeats, fibronectin type III-like (FNIII) domains and a domain homologous to fibrinogen. In contrast to all other known TNs, the series of FNIII domains is interrupted by a novel domain, rich in serines (S) and prolines (P) that occur as repeated S-P-X-motifs, where X stands for any amino acid. Interestingly, the TN-Y-type FNIII domains are 70-100% identical with respect to their DNA sequence. Different TN-Y variants are created by alternative splicing of FNIII domains. Although, based on sequence comparisons TN-Y is most similar to mammalian TN-X, these molecules are not species homologues. TN-Y is predominantly expressed in embryonic and adult chicken heart and skeletal muscle and, to a lower extent, also in several non-muscular tissues. Two major transcripts of approximately 6.5 and 9.5 kb are differentially expressed during heart and skeletal muscle development and are also present in the adult. Anti-TN-Y antibodies recognize a approximately 400-kD double band and a approximately 300-kD form of TN-Y on immunoblots of chicken heart extracts. In situ hybridization and immunofluorescence analysis of aortic smooth muscle, heart, and skeletal muscle revealed that TN-Y is mainly expressed and secreted by cells within muscle-associated connective tissue. Cultured primary muscle fibroblasts released a approximately 220-kD doublet and a approximately 170-kD single TN-Y variant only when cultured in 10% horse serum but not in medium containing 10% fetal calf serum. All TN-Y variants isolated bind to heparin under physiologically relevant conditions that may indicate an important function retained in all tenascins.

Age Factors↗

PubMed1995

The complexity in regulating the expression of tenascins.

The tenascins are a growing family of extracellular matrix proteins of typical multidomain structure. The prototype to be discovered was tenascin-C. It shows a highly regulated expression pattern during embryonic development and is often transiently associated with morphogenetic tissue interactions during organogenesis. In the adult organism reexpression of tenascin-C occurs in tumors and many other pathological conditions. Tenascin-C expression can be regulated by many different growth factors and hormones. Furthermore, mechanical strain exerted by fibroblasts seems to induce the expression of tenascin-C. This could represent a mechanism of translating mechanical forces into protein patterns, a step of potential relevance in the organization of embryogenesis. Tenascin-C as well as tenascin-R are believed to counteract the cell adhesion and spreading activity of fibronectin, thereby facilitating cell movement.

Animals↗

PubMed1995

Large and small splice variants of collagen XII: differential expression and ligand binding.

Collagen XII has a short collagenous tail and a very large, three-armed NC3 domains consisting primarily of fibronectin type III repeats. Differential splicing within this domain gives rise to a large (320 kD) and a small (220 kD) subunit; the large but not the small can carry glycosaminoglycan. To investigate whether collagen XII variants have distinct expression patterns and functions, we generated antibody and cDNA probes specific for the alternatively spliced domain. We report here that the large variant has a more restricted expression in embryonic tissue than the small. For example, whereas the small variant is widespread in the dermis, the large is limited to the base of feather buds. Distinct proportions of mRNA for the two variants were detected depending on the tissue. Monoclonal antibodies allowed us to separate collagen XII variants, and to show that homo- and heterotrimers exist. Collagen XII variants differ in ligand binding. Small subunits interact weakly with heparin via their COOH-terminal domain. Large subunits have additional, stronger heparin-binding site(s) in their NH2-terminal extra domain. In vivo, both large and small collagen XII are associated with interstitial collagen. Here we show biochemically and ultrastructurally that collagen XII can be incorporated into collagen I fibrils when it is present during, but not after, fibril formation. Removal of the collagenous domain of collagen XII reduces its coprecipitation with collagen I. Our results indicate that collagen XII is specifically associated with fibrillar collagen, and that the large variant has binding sites for extracellular ligands not present in the small variant.

Alternative Splicing↗

PubMed1994

Tenm, a Drosophila gene related to tenascin, is a new pair-rule gene.

We describe the molecular characterization of the Drosophila gene tenm, a large transcription unit spanning > 110 kb of DNA. tenm encodes a large extracellular protein of 2515 amino acids related to the extracellular matrix molecule tenascin. The Tenm protein is found in seven stripes during the blastoderm stage, and each stripe overlaps with the even-skipped stripes. tenm mutants show a phenotype resembling that of odd-paired (opa), a member of the pair-rule class of segmentation genes. Thus, Tenm is the first example of a pair-rule gene product acting from outside the cell. While the Tenm protein is under the control of fushi tarazu and even-skipped, but not of opa, at least two pair-rule genes, paired (prd) and sloppy paired (slp), and all segment-polarity genes analysed to date are under the control of tenm. Our data suggest that Tenm initiates a signal transduction cascade which acts, via or in concert with opa, on downstream targets such as prd, slp, gooseberry, engrailed and wingless, leading to an opa-like phenotype.

Amino Acid Sequence↗

PubMed1994

Novel tenascin variants with a distinctive pattern of expression in the avian embryo.

Previous studies have shown that several forms of the glycoprotein tenascin are present in the embryonic extracellular matrix. These forms are the result of alternative splicing, which generates tenascin variants with different numbers of fibronectin type III repeats. We have used degenerate primers and PCR to isolate a novel tenascin exon from an avian genomic library. Genomic clones contained a sequence encoding a fibronectin type III repeat that corresponds to repeat 'C' from the variable domain of human tenascin. To demonstrate that tenascin containing repeat 'C' is actually synthesized by avian cells, a monospecific antiserum was raised against a repeat 'C' fusion protein. This antiserum recognized a novel high-molecular-weight variant on immunoblots of tenascin isolated from chicken embryo fibroblast-conditioned medium, and stained tendons on frozen sections of chicken embryos. A cDNA probe specific for mRNA encoding repeat 'C' was used for in situ hybridization. This probe hybridized in a subset of the embryonic tissues labelled with a universal tenascin probe, including tendons, ligaments and mesenchyme at sites of epithelial-mesenchymal interactions. Finally, we provide evidence that additional fibronectin type III repeats, one corresponding to a recently discovered human repeat as well as one entirely novel sequence, also exists in chicken tenascin mRNA. These data indicate that tenascin is present in the embryonic matrix in a multitude of forms and that these forms have distinctive distributions that may reflect more than one function for tenascin in development.

Amino Acid Sequence↗

PubMed1994

The tenascin gene family.

Tenascin is believed to be an important extracellular matrix protein involved in regulating numerous developmental processes, such as morphogenetic cell migration and organogenesis. This function was implied by its tissue distribution and regulated expression during embryogenesis. However, such an important function was questioned recently, since mice lacking a functional tenascin gene apparently developed normally. To us, this is not conclusive evidence that tenascin has no function, for we believe that the loss of tenascin could be compensated for. Since in several other cases compensation occurs by other members of a gene family, we started to investigate the family of tenascin-like genes and we review in this article the structures of the original tenascin/cytotactin (tenascin-C), restrictin/J-160/180 (tenascin-R), and the tenascin-like gene present in the major histocompatibility complex class III locus (tenascin-X). Furthermore, we present evidence for the likely existence of even more members of this tenascin family.

Animals↗