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Biomedical subjects

M Martins-Green

Publications and source records attributed to M Martins-Green.

At least 19 recordsLinked to original sources
PubMed2001

The chicken Chemotactic and Angiogenic Factor (cCAF), a CXC chemokine.

The chemokine cCAF (&cmacr;hicken &Cmacr;hemotactic and Angiogenic &Fmacr;actor), is the product of the 9E3/CEF4 gene. Its name reflects the biological properties of the protein: chemotactic and angiogenic. This CXC chemokine is highly homologous to human IL-8, both at the protein and gene level. Molecular modeling based on the known structure of IL-8 shows that the structure of cCAF is very similar to that of other CXC chemokines. Regulation of expression occurs both at the transcriptional and post-transcriptional levels. The cCAF protein is secreted very rapidly as a 9kDa molecule and can be cleaved in the N-terminus after secretion to produce a smaller form ( approximately 7kDa) that binds to ECM molecules. Plasmin, an enzyme present in the early stages of wound healing and in tumor stroma, cleaves the 9kDa to the 7kDa form. The biological properties of this chemokine and its patterns of expression in vivo strongly suggest that cCAF plays important roles in traumatic and pathological conditions.

Animals↗
PubMed2001

Cloning, mRNA distribution, and functional expression of an avian counterpart of the chemokine receptor/HIV coreceptor CXCR4.

The chemokine signaling system, which coordinates the basal and emergency trafficking of leukocytes, presumably coevolved with the hematopoietic system. To study its phylogenetic origins, we used the open reading frame (ORF) of the human chemokine receptor CXCR4 as a genomic probe, since in mammals it is the most highly conserved chemokine receptor known. CXCR4 cross-hybridized to genomic DNA from mouse and chicken, but not zebrafish, Drosophila, or Caenorhabditis elegans. Accordingly, we cloned the corresponding chicken cDNA. The ORF is 359 codons long versus 352 for human CXCR4, and encodes a protein 82% identical to human CXCR4. In a calcium flux assay of receptor function, CHO-K1 cells stably transfected with the chicken cDNA responded specifically to human SDF-1, the specific ligand for CXCR4, but not to a panel of other chemokines tested at 100 nM. SDF-1 activated the cells in a dose-dependent manner (EC50 approximately 5 nM), whereas parental CHO-K1 cells did not respond. The CHO-K1 cell transfectants also bound 125I-SDF-1 specifically. Leukocytes from chicken peripheral blood expressed chCXCR4 mRNA and responded to human SDF-1 in a calcium flux assay with an EC50 similar to that for chCXCR4-transfected CHO cells, suggesting that this response is mediated by native chCXCR4. Analysis of chicken genomic DNA with the chicken cDNA as probe revealed a pattern consistent with a single copy gene, and the absence of any closely related genes. mRNA was detected in brain, bursa, liver, small and large intestine, embryonal fibroblasts, and blood leukocytes, but not in stomach or pancreas. These results, which identify the first functional non-viral, non-mammalian chemokine receptor, suggest that the origins of a functional chemokine system extend at least to birds and suggest that, as in mammals, CXCR4 functions in many avian tissues.

Amino Acid Sequence↗
PubMed2000

Novel nuclear target for thrombin: activation of the Elk1 transcription factor leads to chemokine gene expression.

Thrombin is primarily known for its role in homeostasis and thrombosis. However, this enzyme also plays important roles in wound healing and pathologic situations such as inflammation and tumorigenesis. Among the molecules stimulated by thrombin in these latter processes are the stress response proteins, chemokines. Chemokines are also known for their roles in inflammatory responses and tumor development. These correlative observations strongly suggest that chemokines may be mediators of some of thrombin's functions in these processes. Elucidation of the molecular mechanisms of stimulation of chemokines by thrombin may help to unravel the ways in which their expression can be modulated. Up-regulation of the chemokine 9E3/cCAF by thrombin occurs via its proteolytically activated receptor with subsequent transactivation of the epidermal growth factor receptor tyrosine kinase. This study shows that stimulation by thrombin very rapidly activates this chemokine at the transcriptional level, that 2 Elk1 binding elements located between -534 and -483 bp of the promoter are major thrombin response elements, that activation occurs via the Elk1 transcription factor, and that the latter is directly activated by MEK1/ERK2. The common occurrence of Elk1 binding domains in the promoters of immediate early response genes suggests that it may be characteristically involved in gene activation by stress-inducing agents. (Blood. 2000;96:3696-3706)

Animals↗
PubMed2000

Isolation and characterization of a new chemokine receptor gene, the putative chicken CXCR1.

This study delineates the isolation and characterization of a novel chemokine receptor gene, the putative chicken CXC receptor 1 (cCXCR1). Using a human CXCR1 probe, we isolated several positive clones from a chicken genomic library. One of the clones contained a fragment of approximately 5000bp that hybridized strongly with the hCXCR1 probe. This fragment was sequenced and subjected to a variety of computer analyses. The open reading frame for this gene predicts a seven transmembrane domain protein with all the characteristics of a chemokine receptor and with 67% sequence homology to hCXCR1, 65% to hCXCR2 and also with considerable sequence homology to other human chemokine receptors such as hCXCR4 (50%), hCCR2 (49%) and hCCR1 (49%). However, the homology to a previously isolated potential G-protein-coupled receptor for chickens (AvCRL1) is only 47%. Using 5' RACE, two transcription initiation sites were identified suggesting the potential for the expression of two protein isoforms (I and II) in vivo. The promoter for the putative cCXCR1 contains a variety of consensus transcription factor binding elements that can potentially be involved in the expression of this chicken receptor upon stimulation by stress-inducing agents. RT-PCR analysis was used to determine the pattern of expression of the larger isoform (I) of this receptor in a variety of tissues. This form of the receptor is expressed primarily in the organs of the gastrointestinal tract, tissues that are frequently exposed to stress-inducing agents, but not in the central nervous system, tissues that are protected from insult by the blood barrier. Using the same RT-PCR approach we show that stress-inducing agents, such as 'first-hand' and 'second-hand' cigarette smoke components, tumor promoters and thrombin, differentially stimulate the expression of the isoform I in primary fibroblasts. Thrombin is an enzyme that plays many important roles in thrombosis, angiogenesis and wound healing and exposure to both cigarette smokes and/or to tumor promoters can lead to tumorigenesis. Therefore, upregulation of chemokines and their receptors by stress-inducing agents can confer highly regulated modulation of cellular responses to traumatic and pathological situations.

Amino Acid Sequence↗
PubMed2000

Normal patterns of angiogenesis and extracellular matrix deposition in chick chorioallantoic membranes are disrupted by mainstream and sidestream cigarette smoke.

The adverse effects of cigarette smoke on mature blood vessels are well established, whereas little is known about the influence of smoke on blood vessel development. To determine if cigarette smoke alters angiogenesis, chick chorioallantoic membranes (CAMs) were exposed for 4 days to culture medium (control) or to mainstream (MS) or sidestream (SS) smoke solution, and then blood vessel patterns were compared in blind tests. In contrast to the normal tree-like branching of control blood vessels, smoke-treated CAMs often had vessels that ran parallel to each other without much branching. A significant increase in the number of fibroblasts was observed in histological sections of treated CAMs, and this increase correlated with alterations in extracellular matrix components. Many more matrix fibrils were observed in treated CAMs than in controls using scanning electron microscopy. Immunohistochemistry showed that type III collagen was distributed in a tight band adjacent to the endoderm in controls but was distributed throughout the mesoderm in both treatment groups. Western blots confirmed that both type I and type III collagen were more abundant in treated CAMs than in controls. Fibronectin, which was localized immunohistochemically in the basal laminae and mesodermal matrix of controls, increased in abundance in CAMs treated with SS smoke solutions. Hyaluronic acid, which was present in a dense band subjacent to the capillary plexus of control CAMs, was greatly reduced in MS-treated CAMs and was absent in SS-treated CAMs. These observations demonstrate that both MS and SS cigarette smoke solutions caused abnormal pattern formation of CAM blood vessels and altered the composition of the extracellular matrix in the CAM mesoderm.

Allantois↗
PubMed2000

Tissue specific expression of Yrk kinase: implications for differentiation and inflammation.

The Src family of proto-oncogenes is a highly conserved group of non-receptor tyrosine kinases with very similar, but not identical, tissue distributions and functions. Yrk is a recently discovered new member of this family. Here we report the patterns of expression of this kinase in a variety of chicken tissues during development and after hatching, and experiments that correlate some of the observed patterns of expression with potential functions. The results show that the Yrk protein is primarily found in neuronal and epithelial cells and in monocyte/macrophages. In neuronal tissues of hatched chicks, Yrk is expressed in Purkinje cells, in the gigantocellularis of the brain-stem, and in retinal ganglion cells. In addition, staining for this kinase is also seen as thread-like and punctate patterns suggesting staining in neurites and growth cones. Epithelial cells express Yrk in the stomach during late developmental stages and after hatching but, in other epithelia such as in the peridermis, intestine and kidney, expression is high during development but low (skin) or undetectable (intestine and kidney) after hatching. These results suggest that Yrk may have several functional roles, specifically in cell migration and or differentiation during neuronal and epithelial cell development and in maintenance of the differentiated phenotype. In this study we also show that significant levels of Yrk are detected in monocytes of the blood and in tissue macrophages. Analysis of chicken hematopoietic cell lines confirmed the expression of Yrk in cells of monocyte/macrophage lineage and show for the first time in experimentally-induced inflammation that Yrk kinase activity is high during the period of monocyte infiltration, raising the possibility that this kinase plays a role in inflammation and/or response to injury.

Animals↗
PubMed1999

Activation of the 9E3/cCAF chemokine by phorbol esters occurs via multiple signal transduction pathways that converge to MEK1/ERK2 and activate the Elk1 transcription factor.

Using primary fibroblasts in culture, we have investigated the signal transduction mechanisms by which phorbol esters, a class of tumor promoters, activate the 9E3 gene and its chemokine product the chicken chemotactic and angiogenic factor. This gene is highly stimulated by phorbol 12,13-dibutyrate (PDBu) via three pathways: (i) a small contribution through protein kinase C (the commonly recognized pathway for these tumor promoters), (ii) a contribution involving tyrosine kinases, and (iii) a larger contribution via pathways that can be interrupted by dexamethasone. All three of these pathways converge into the mitogen-activated protein kinases, MEK1/ERK2. Using a luciferase reporter system, we show that although both the AP-1 and PDRIIkB (a NFkappaB-like factor in chickens) response elements are capable of activation in these normal cells, regions of the 9E3 promoter containing them are unresponsive to PDBu stimulation. In contrast, we show for the first time that activation by PDBu occurs through a segment of the promoter containing Elk1 response elements; deletion and mutation of these elements abrogates 9E3/chicken chemotactic and angiogenic factor expression. Electrophoretic mobility shift assays and functional studies using PathDetect systems show that stimulation of the cells by phorbol esters leads to activation of the Elk1 transcription factor, which binds to its element in the 9E3 promoter.

Animals↗
PubMed1998

Thrombin aivation of the 9E3/CEF4 chemokine involves tyrosine kinases including c-src and the epidermal growth factor receptor.

The 9E3/CEF4 gene codes for a chemokine that is highly homologous to human interleukin-8 and melanoma growth-stimulating activity/groalpha. These chemokines belong to a family of molecular mediators that are importantly involved in inflammation, wound healing, tumor development, and viral entry into cells. On the chorioallantoic membrane the 9E3 protein is chemotactic for monocyte/macrophages and lymphocytes and is angiogenic. In cultured chicken embryo fibroblasts, which have many of the properties of wound fibroblasts, the gene is stimulated by a variety of agents including oncogenes, growth factors, phorbol esters, and thrombin. The strong stimulation of 9E3 by thrombin in culture correlates well with the observation that in young chicks this gene is stimulated to very high levels in fibroblasts upon wounding and remains high throughout wound repair. Activation of 9E3 by thrombin: (i) occurs very rapidly, one minute exposure to thrombin is sufficient to initiate the signals necessary for gene activation; (ii) is independent of mitogenesis; (iii) operates through the proteolytically activated receptor for thrombin; (iv) is mediated by tyrosine kinases, including c-src and the epidermal growth factor (EGF) receptor, rather than Ser/Thr kinases such as protein kinase C and protein kinase A. Inhibition of either c-src or the EGF receptor tyrosine kinase inhibits the stimulation of 9E3 by thrombin. We show here for the first time that activation of the EGF receptor through a cell-surface receptor that does not have tyrosine kinase activity can lead to expression of an immediate early response gene which encodes for a secreted protein, a chemokine. This rapidly activated tyrosine kinase pathway may be a general stress response by which in vivo a localized cell population reacts to emergency situations such as viral infection, wounding, or tumor growth.

Animals↗
PubMed1998

The 9E3/CEF4 gene product is a chemotactic and angiogenic factor that can initiate the wound-healing cascade in vivo.

The chicken gene 9E3/CEF4 codes for a 9-kDa protein that belongs to the C-X-C family of chemokines. This gene is stimulated to high levels by thrombin, and is overexpressed in the granulation tissue of wounds, especially in areas of neovascularization, suggesting that it is importantly involved in wound healing. The authors used the Chorioallantoic Membrane (CAM) assay to examine experimentally the functions of the 9E3 chemokine in vivo. It was shown that at lower doses this protein is chemotactic for monocyte/macrophages and lymphocytes (but not heterophils), and directly or indirectly stimulates the growth of blood vessels towards the pellet containing the protein, causes hyperproliferation of the ectoderm of the CAM, and formation of a tissue that resembles the granulation tissue of wounds. At higher doses, however, it does not stimulate chemotaxis of leukocytes but instead causes the blood vessels of the CAM to undergo sprouting. It was also shown that this protein is found in the endothelial cells of developing blood vessels but not in those of mature blood vessels and that, in the latter, expression can be stimulated by application of agents that cause inflammation or are known to be angiogenic. Because the product of the 9E3 gene has chemotactic and angiogenic properties, it is proposed that it be called the chicken Chemotactic and Angiogenic Factor (cCAF). These observations show that in the absence of wounding, cCAF, by itself, can initiate a complex series of events that strongly resemble those involved in the immune response and granulation tissue formation, suggesting an important role for this and related chemokines in wound healing. Although this chemokine belongs to the C-X-C family it can perform functions of both the C-C (chemotaxis for monocyte/macrophages and lymphocytes) and C-X-C (angiogenesis) families, suggesting that this could be the first of a functionally broader family of chemokines which would be generated as a response to emergency situations.

Allantois↗
PubMed1998

The chicken chemotactic and angiogenic factor (9E3 gene product): its angiogenic properties reside in the C-terminus of the molecule.

Chicken chemotactic and angiogenic factor (cCAF) is a 9 kDa protein that belongs to the C-X-C family of chemokines and shows high homology to IL-8 and MGSA/groalpha. It is produced abundantly shortly after wounding and in the granulation tissues of wounds, especially in areas of neovascularization, suggesting that it is important in angiogenesis. In the chorioallantoic membrane (CAM) in vivo assay system, cCAF is chemotactic for monocyte/macrophages and lymphocytes, is angiogenic, and can by itself trigger the formation of granulation-like tissue. We have further investigated the angiogenic properties of this protein to determine what part of the molecule is responsible for this function. Through pellet-release studies in the CAM we show that low doses of the C-terminal 28-aa peptide stimulate oriented blood vessel growth in the CAM without attracting leukocytes. At higher doses the peptide stimulated extensive tortuosity and sprouting of the tertiary blood vessels. Deposition of the peptide under the skin of the wings of newly-hatched chicks resulted in an increase of the number of microvessels in the tissue in the area of application without the presence of leukocytes. Therefore, the C-terminal peptide recapitulates all of the angiogenic properties of the full cCAF molecule, but does not have the chemotactic properties for leukocytes, and it does not cause development of granulation-like tissue. These results coupled with our earlier work in wounded chicks suggest that cCAF directly participates in angiogenesis and that the C-terminal portion of the molecule can perform this function.

Angiogenesis Inducing Agents↗
PubMed1997

The 9E3/CEF4 gene and its product the chicken chemotactic and angiogenic factor (cCAF): potential roles in wound healing and tumor development.

The 9E3/CEF4 gene was one of the first inducible chemokine genes to be discovered. Its product, the chicken chemotactic and angiogenic factor (cCAF), is highly homologous to IL-8. It is expressed at low levels in tissues of mesenchymal origin but is highly expressed shortly after wounding and persists throughout the period of granulation tissue formation. It also is highly expressed around Rous sarcoma virus-induced tumors. The most potent natural stimulator of this gene is thrombin and in vivo cCAF is chemotactic for monocytes and lymphocytes and is angiogenic. The chemotactic properties can be potentially important in the inflammatory response and in the deterrence of tumors, whereas the angiogenic properties could be important in wound repair and tumor growth. The very rapid stimulation of 9E3 by thrombin and fast synthesis and secretion of cCAF suggest that this is a new type of stress response protein whose rapid production is designed to protect tissues rather than individual cells.

Angiogenesis Inducing Agents↗
PubMed1996

The 9E3/CEF4 cytokine: kinetics of secretion, processing by plasmin, and interaction with extracellular matrix.

The chicken gene, 9E3/CEF4, is a small inducible cytokine highly homologous to human IL-8 and gro alpha. It is overexpressed during wound healing and in the tissues around tumours induced by Rous sarcoma virus. More is known about the expression of 9E3 in vivo than any other of the small cytokines, yet little is known about its biochemical characteristics and functions. Here we report on some of the biochemical properties of the 9E3 gene product, the kinetics of protein secretion, the post-secretory processing of the protein, and on its association with ECM molecules. The protein: (1) is synthesized and secreted in < 10 min; (2) is not glycosylated and does not bind heparin with high affinity; (3) is secreted as a 9 kDa form and is processed to a 6-7 kDa form by plasmin, an enzyme released at wound sites and produced in association with tumours; (4) the small form binds to interstitial collagen, laminin and to a lesser extent to proteoglycan, and does not bind to collagen IV or fibronectin. This is the most rapidly secreted protein yet described in eukaryotic cells and is the first of the small inducible cytokines to be found to associate with ECM molecules other than glycosaminoglycans. Our results suggest that, given the appropriate stimulus, the level of the 9E3 cytokine could be elevated very rapidly, resulting in similarly rapid biological responses. The different modes of availability of the two forms of the molecule suggest that the two isoforms may play different roles in vivo.

Animals↗
PubMed1996

Characterization of chicken protein tyrosine phosphatase alpha and its expression in the central nervous system.

Protein tyrosine phosphorylation and dephosphorylation are important in cell proliferation, differentiation and functioning of the central nervous system. We have identified a cDNA clone encoding a new transmembrane protein tyrosine phosphatase from a chicken brain cDNA library. The predicted amino acid sequence contains two phosphatase tandem repeats in the intracellular domain and multiple glycosylation sites in the extracellular domain. Since its intracellular domain shares 94% identity with human PTP alpha, we call it chicken PTP alpha (ChPTP alpha). Antibodies specific to ChPTP alpha recognize two major protein bands at 130 and 85 kDa in immunoblot and immunoprecipitation. ChPTP alpha transcript and protein are found in many tissues, but they are particularly abundant in brain. To gain insight into the function of PTP alpha s, we investigated the cell-type specific localization of ChPTP alpha in cerebellum by in situ hybridization and immunostaining. Throughout development, the level of ChPTP alpha remains similar from embryonic day 7 to post-hatching day 14, but the abundance and distribution of cells expressing this protein vary systematically through this period. During development, ChPTP alpha appears in pre-migratory and migrating granule cells, and in Bergmann glia and their radial processes. By 2-weeks after hatching, ChPTP alpha disappears from all cells of the cerebellum except Bergmann glia. Our data, which show for the first time the temporal and spacial distribution of a PTP alpha, suggest that these transmembrane phosphatases are important in the differentiation and function of Bergmann glia and in the migration of granule cells, and thereby play a role in development of the cerebellum.

Amino Acid Sequence↗
PubMed1994

Inflammation is responsible for the development of wound-induced tumors in chickens infected with Rous sarcoma virus.

When newly hatched chicks are given injections of Rous sarcoma virus, a tumor develops at the site of injection. In spite of the presence of the virus in the blood, no other tumors are found distant from the site of inoculation during the life span of the animal (4-6 weeks). However, if a wound is made away from the primary tumor, a tumor develops at the site of wounding. Work in our laboratory showed previously that these wound tumors do not develop as a result of metastasis, therefore, factors released upon wounding must contribute to the development of the wound tumors. In particular, we showed that transforming growth factor (TGF) beta, a growth factor implicated in wound healing, can replace wounding in tumor development. However, we also showed that epidermal growth factor and TGF-alpha, growth factors that also have roles in wound healing, do not induce tumors. To identify the critical event(s) and to determine the mechanism involved in wound tumor development, we have continued these studies. Here we show that: (a) wound tumor development correlates with the presence of circulating virus and inflammation; (b) the virus is present in serum and in heterophils of the peripheral blood; (c) cell division at the site of wounding precedes the expression of viral proteins; (d) in addition to TGF-beta, acidic and basic fibroblast growth factors can also replace wounding in tumor development; (e) these three factors (TGF-beta, acidic fibroblast growth factor, basic fibroblast growth factor) which promote tumors also induce inflammation, whereas epidermal growth factor and TGF-alpha do not; and (f) during the inflammatory response, blood vessel leakage occurs as tested by the release of fibrinogen into the tissues. To test the possibility that inflammation is the key element in the development of these wound tumors, we used beta-methylprednisolone, an antiinflammatory drug that inhibits inflammation (including blood vessel leakage), to determine if wound tumor development could be prevented. We found that when inflammation was inhibited, tumors were also inhibited; when inflammation could not be stopped, tumors developed as before. These results indicate that the effect of wounding on the development of wound tumors in Rous sarcoma virus-infected chicks is accomplished through the cytokines released by the inflammatory cells at the site of wounding. These inflammatory mediators play a critical role in providing the conducive environment for oncogene integration and activation, and subsequent development of tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

The 9E3 protein: immunolocalization in vivo and evidence for multiple forms in culture.

The avian gene 9E3/CEF4 belongs to a group of genes whose products are highly conserved and are homologous to inflammatory mediators. These genes, sometimes referred to as the gro family, are also expressed upon wounding or serum-stimulation of quiescent cells, suggesting that they may be important in aspects of growth and/or wound healing. We have used an antibody to the product of the 9E3 gene to show for the first time the distribution in vivo of the protein of one of these genes. The polyclonal antibody was produced against a synthetic peptide, [Cys76], 9E3, (77-103), located at the carboxy end of the molecule. The specificity of the antibody was determined by transfection of the 9E3 cDNA into Cos 7 cells, which do not express this gene. Moreover, despite the high homology between 9E3 and IL-8, the antibody did not crossreact with this molecule. The antibody was used to immuno-precipitate the protein from cultured normal and RSV-transformed chick embryo fibroblasts (CEFs) and to determine its distribution in tissues of newly hatched chicks. The staining was abundant in the cells and extracellular matrix (ECM) of connective tissue and other tissues of mesenchymal origin, such as bone and tendon. Most cells in the granulation tissue of wounds stained, some more intensely than others; the ECM also stained, especially in areas of scar tissue where collagen is abundant. In RSV-induced tumors, the protein was absent except in necrotic areas where a few cells--potentially macrophages--stained. In general, as expected, the protein was present in the cells and tissues that expressed the mRNA, but there were exceptions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Wound-factor-induced and cell cycle phase-dependent expression of 9E3/CEF4, the avian gro gene.

The gro genes encode for secreted proteins with sequence homologies to inflammatory mediators. Little is known about the function of these proteins or their regulation. The chicken gro (9E3/CEF4) is expressed abundantly in the cells of proliferating cultures but at very low levels in confluent cultures. In vivo, this gene is expressed in connective tissue and overexpressed at sites of injury, especially in areas of neovascularization. Here we provide a bridge between these observations by examining in culture the effect on 9E3 expression and DNA synthesis induced by cell damage and by addition of factors known to be released on wounding. We mimicked wounding by scraping swaths across confluent cultures of embryonic fibroblasts and determined the time dependence of expression of 9E3 mRNA and incorporation of 3H-thymidine. We find that 9E3 is (1) transiently expressed after "wounding" or serum-stimulation; (2) expressed in a cell cycle phase-dependent manner; it is triggered during the G0-G1 transition or early in G1 and subsides during S-phase; and (3) stimulated to high levels by a-fibroblast growth factor (aFGF), bFGF, transforming growth factor alpha (TGF alpha), and TGF beta, to intermediate levels by platelet-derived growth factor and not stimulated by epidermal growth factor. We also find that cells that are constantly cycling do not express 9E3, indicating that they skip either the portion of the cell cycle where 9E3 is induced or that they constitutively express a repressor of transcription or an RNA-degrading enzyme. Taken together, these observations suggest that the product of this gene could play more than one role in vivo. For example, in normal tissues the 9E3 protein could be involved in the exit of cells from the resting stage, whereas during wound healing the secreted protein or its cleavage products also could play a role in angiogenesis.

Animals↗
PubMed1990

Localization of 9E3/CEF-4 in avian tissues: expression is absent in Rous sarcoma virus-induced tumors but is stimulated by injury.

The avian gene 9E3/CEF-4, a member of the superfamily of genes that includes KC and gro, is expressed abundantly in exponentially growing cultures of chick embryo fibroblasts (CEFs) and at high levels in CEFs transformed with Rous sarcoma virus (RSV). The product of this gene is a secreted protein that has homologies and structural similarities to inflammatory mediators. The function of 9E3 is obscure and its expression in vivo has not yet been investigated. We studied by in situ hybridization and RNA blots the pattern of 9E3 mRNA distribution in the wings of normal, wounded, and RSV-infected newly hatched chicks. We found that the message for 9E3 is high in specific tissues in normal wings; whereas connective tissue, tendon, and bone express the gene, muscle fibers, endothelium, epidermis, and bone marrow do not. The distribution coincides with that of interstitial collagen. Wounding results in marked elevation of the mRNA within the granulation tissue formed during healing and in adjacent tissues, especially those showing neovascularization. Similar elevation of mRNA occurs immediately adjacent to RSV tumors but, surprisingly, the tumor tissue itself shows no detectable levels of this message. Cells explanted from the tumors and grown in culture also show no expression of 9E3, in marked contrast to the very high level found in similarly cultured RSV-transformed CEFs. These results show that there are intrinsic differences between transformed embryonic cells in tissue culture and RSV target cells in the hatched chick. However, the expression of the gene in the periphery of tumors leaves open the possibility that 9E3 may still be involved in RSV carcinogenesis. The abundant expression of 9E3 in normal tissues indicates that the product of this gene plays a normal physiological role in tissues growing by cell division, perhaps as a growth regulator. The elevated expression of 9E3 in areas of neovascularization, makes it possible that the product of this gene could act as an angiogenic factor. Finally, expression in conjunction with high collagen levels and in wounded tissues may point to a role in wound response and/or repair, possibly via alteration of extracellular matrix.

Animals↗