Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Shp-1 and Shp-2 are cytoplasmic protein tyrosine phosphatases that contain two Src homology 2 (SH2) domains. A negative regulatory role of Shp-1 in hematopoiesis has been strongly implicated by the phenotype of motheaten mice with a mutation in the Shp-1 locus, which is characterized by leukocyte hypersensitivity, deregulated mast cell function, and excessive erythropoiesis. A targeted deletion of 65 amino acids in the N-terminal SH2 (SH2-N) domain of Shp-2 leads to an embryonic lethality at midgestation in homozygous mutant mice. To further dissect the Shp-2 function in hematopoietic development, we have isolated homozygous Shp-2 mutant embryonic stem (ES) cells. Significantly reduced hematopoietic activity was observed when the mutant ES cells were allowed to differentiate into embryoid bodies (EBs), compared to the wild-type and heterozygous ES cells. Further analysis of ES cell differentiation in vitro showed that mutation in the Shp-2 locus severely suppressed the development of primitive and definitive erythroid progenitors and completely blocked the production of progenitor cells for granulocytes-macrophages and mast cells. Reverse transcriptase PCR analysis of the mutant EBs revealed reduced expression of several specific marker genes that are induced during blood cell differentiation. Stem cell factor induction of mitogen-activated protein kinase activity was also blocked in Shp-2 mutant cells. Taken together, these results indicate that Shp-2 is an essential component and primarily plays a positive role in signaling pathways that mediate hematopoiesis in mammals. Furthermore, stimulation of its catalytic activity is not sufficient, while interaction via the SH2 domains with the targets or regulators is necessary for its biological functions in cells. The in vitro ES cell differentiation assay can be used as a biological tool in dissecting cytoplasmic signaling pathways.
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PMID:A deletion mutation in the SH2-N domain of Shp-2 severely suppresses hematopoietic cell development. 927 25

The distribution of myeloid lineage-associated cytokine receptors and lysosomal proteins was analyzed in human CD34+ cord blood cell (CB) subsets at different stages of myeloid commitment by reverse-transcriptase polymerase chain reaction (RT-PCR). The highly specific granulomonocyte-associated lysosomal proteins myeloperoxidase (MPO) and lysozyme (LZ), as well as the transcription factor PU.1, were already detectable in the most immature CD34+Thy-1+ subset. Messenger RNA (mRNA) levels for the granulocyte-colony stimulating factor (G-CSF) receptor, granulocyte-macrophage (GM)-CSF receptor alpha subunit and tumor necrosis factor (TNF) receptors I (p55) and II (p75) were also detected in this subset in addition to c-kit and flt-3, receptors known to be expressed on progenitor cells. By contrast, the monocyte-macrophage colony stimulating factor (M-CSF) receptor was largely absent at this stage and in the CD34+Thy-1-CD45RA- subsets. The M-CSF receptor was first detectable in the myeloid-committed CD34+Thy-l-CD45RA+ subset. All other molecules studied were found to be expressed at this stage of differentiation. Different cocktails of the identified ligands were added to sorted CD34+Thy-1+ single cells. Low proliferative capacity was observed after 1 week in culture in the presence of stem cell factor (SCF) + Flt-3 ligand (FL) + G-CSF. Addition of GM-CSF to this basic cocktail consistently increased the clonogenic capacity of single CD34+Thy-1+ cells, and this effect was further enhanced (up to 72.3 +/- 4.3% on day 7) by the inclusion of TNF-alpha. In conclusion, the presence of myeloid-associated growth factor receptor transcripts in CD34+ CB subsets does not discriminate the various stages of differentiation, with the exception of the M-CSF receptor. In addition, we show that TNF-alpha is a potent costimulatory factor of the very immature CD34+Thy-1+ CB subset.
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PMID:Analysis of myeloid-associated genes in human hematopoietic progenitor cells. 932 52

Activated macrophage-conditioned medium (M-CM) induces megakaryocytic differentiation of HIMeg-1 cells. The megakaryocytic differentiation activity (MDA) is proteinaceous since it is susceptible to treatments by proteinases, heat, and reducing agents. MDA is not thrombopoietin (TPO) since (1) TPO alone or in conjunction with several other recombinant cytokines fails to induce any degree of HIMeg-1 cell differentiation; and (2) a neutralizing antibody against TPO or an antibody against the extracellular domain of c-mpl is unable to abolish M-CM-induced CD41 expression on HIMeg-1 cells. Reverse transcriptase-mediated polymerase chain reaction shows that HIMeg-1 cells express c-mpl but not TPO. Additional neutralizing antibody studies suggest that MDA is not one of the cytokines known to induce some degree of megakaryopoiesis in vitro or in vivo including interleukin 3 (IL-3), IL-6, IL-11, granulocyte-macrophage colony-stimulating factor, erythropoietin, or stem cell factor. On the other hand, MDA appears to be a combination of interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha), since neutralizing antibodies against these two cytokines completely abolish MDA-induced CD41 expression. In addition, either recombinant human IFN-gamma or TNF-alpha alone is capable of inducing CD41 and CD42 expression on HIMeg-1 cells. In combination, IFN-gamma and TNF-alpha induce a maximal level of CD41 and CD42 expression which is also accompanied by an increase in cell size and DNA ploidy level. Thus, our studies indicate that IFN-gamma/TNF-alpha is capable of inducing megakaryocytic differentiation of the HIMeg-1 cell line and that HIMeg-1 is a good system for studying the molecular mechanism mediating megakaryocytic differentiation.
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PMID:Megakaryocytic differentiation of HIMeg-1 cells induced by interferon gamma and tumour necrosis factor alpha but not by thrombopoietin. 987 25

The receptor for the gene product of the obesity gene, leptin, was recently reported to be expressed on murine and human hematopoietic progenitor cells. Therefore, we studied the expression of the leptin receptor, OB-R, in normal myeloid precursors, human leukemia cell lines, and primary leukemic cells using reverse-transcriptase polymerase chain reaction. In normal hematopoiesis, OB-R was expressed in CD34(+) cells. Normal promyelocytes (CD34(-)33(+) and CD34(-)13(+)) expressed only very low levels of the short, presumably nonsignaling isoform. Both the long and short isoforms of OB-R were expressed in 10 of 22 samples from patients with newly diagnosed primary or secondary acute myeloid leukemia (AML), with a higher incidence of the long isoform in primary AML (87.6% v 28.6%; P =.01). The incidence of OB-R expression was higher in recurrent than in newly diagnosed AML (P <.001), and samples from four patients with refractory AML showed strong expression of both isoforms. Both OB-R isoforms were also expressed in newly diagnosed and recurrent acute promyelocytic leukemia cells but were essentially absent in samples of chronic or acute lymphocytic leukemia. In vitro growth of myeloid leukemic cell lines and of blasts from 14 primary AMLs demonstrated that recombinant human leptin alone induced low level proliferation, significantly (P <.05) increased proliferation induced by recombinant human granulocyte colony-stimulating factor, interleukin 3, and stem cell factor in a subset of AML and increased colony formation (P <.005). Also, leptin reduced apoptosis induced by cytokine withdrawal in MO7E and TF-1 cells. Serum leptin levels correlated only with body mass index (P <. 001) and gender (P =.03). Results confirm the reported expression of leptin receptor in normal CD34(+) cells and demonstrate the frequent expression of leptin receptors in AML blasts. While normal promyelocytes lack receptor expression, leukemic promyelocytes express both isoforms. We also demonstrate proliferative effects of leptin alone and in combination with other physiologic cytokines, and anti-apoptotic properties of leptin. These findings could have implications for the pathophysiology of AML.
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PMID:Expression and function of leptin receptor isoforms in myeloid leukemia and myelodysplastic syndromes: proliferative and anti-apoptotic activities. 1002 96

Philadelphia (Ph) or BCR/ABL-negative cells with immature phenotype (CD34-positive, DR-negative) can be recovered from patients with chronic myeloid leukemia (CML) in chronic phase. We used the technique described by Berardi et al (Science 1995; 267: 104-108) to select stem cells from marrow or blood of CML patients at diagnosis or during treatment with alpha-interferon. Mononuclear cells (MNC), and in some experiments CD34+ cells, were maintained for 7 days in the presence of 5-fluorouracil (5-FU), stem cell factor and interleukin-3. The number of viable cells recovered after culture was between 7.4 and 70.2 for 10(6) cells plated. These cells exhibited the following phenotype: CD34+, CD117+, CD38-, lineage-, and were able to generate cobblestone areas and secondary colonies in long-term culture (LTC), with a frequency similar to that of cells selected from normal marrow. Study by fluorescence in situ hybridization of LTC cells or secondary colonies showed no evidence of BCR/ABL rearrangement. Reverse transcriptase polymerase chain reaction studies on pooled LTC cells or secondary colonies were also negative. By contrast, LTC cells or secondary colonies obtained from CML CD34+ cells without culture in the presence of 5-FU were always positive for BCR/ABL rearrangement. Finally, 5-FU selected cells were able to engraft NOD/SCID mouse, as human cells were detected in blood and marrow 10 weeks post transplantation, which were BCR/ABL negative by RT-PCR. This method of culture makes it possible to select constantly BCR/ABL-negative cells with capacities of development in LTC assay and of NOD/SCID mouse engraftment.
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PMID:Selection of BCR/ABL-negative stem cells from marrow or blood of patients with chronic myeloid leukemia. 1040 Apr 13

The tyrosine kinase receptor c-kit and its ligand [kit ligand (KL) or stem cell factor (SCF)] exert a broad range of biological activities during organogenesis and normal cell development. Recent studies have revealed that altered c-kit levels occur in a variety of malignancies and cancer cell lines. KL has also been shown to stimulate the growth of malignant cells, as well as to promote chemotaxis. We had previously reported expression of KL in stroma cells of normal human prostate. The present study was undertaken in order to analyze the patterns of expression of c-kit and KL in a well characterized set of prostatic tissues, including normal prostate (n=4), benign prostatic hyperplasia (BPH) (n=53) and adenocarcinoma (n=46) samples. The distribution of c-kit and KL proteins was studied by immunohistochemical analyses, while transcript levels were determined by in situ hybridization with specific RNA probes on a subset of the benign and malignant tissues referred above. In addition, reverse-transcriptase polymerase chain reaction (RT-PCR) was performed to determine levels of c-kit and KL expression in cultures of epithelial and stroma cells, as well as in the prostate cancer cell lines LNCaP, DU145 and PC3. c-kit protein in normal prostate was exclusively detected in mast cells by immunohistochemistry and in situ hybridization. However, c-kit transcripts, but not c-kit protein, were detected in low levels and with an heterogeneous pattern in basal epithelial cells of ducts and acini. c-kit in BPH was detected in epithelial cells in 9 of 53 (17%) specimens. c-kit protein expression in malignant epithelial cells was identified in 1 of 46 (2%) tumors. However, c-kit transcripts were detected in low levels by in situ hybridization in most of the tumors analyzed. KL protein and transcripts in normal prostate were detected in high levels in stroma cells. However, epithelial cells were unreactive for anti-KL antibody, but showed low levels of KL transcripts mainly in cells of the basal layer. Basal epithelial cells in hyperplastic glands showed KL expression in 13 of 53 (24%) specimens. KL protein in tumor cells was noted in 18 of 46 (39%) cases. c-kit transcripts were not found in normal prostate and in the 3 cancer cell lines analyzed by RT-PCR, however, it was present in cultured epithelial cells of BPH, and in cultures of stroma cells from both normal and BPH. The majority of cultured cell lines of epithelial and stromal origin displayed considerable levels of KL. In addition all prostate cell lines studied showed significant levels of KL transcripts. In summary, co-expression of c-kit and KL in a subset of BPH cases may suggest an autocrine mode of signaling. Data from this study reveals that altered patterns of c-kit and KL expression are associated with BPH and adenocarcinoma of prostate. It appears that KL induces mast cells proliferation and maturation and enhances their release of protease. This could explain the accumulation of mast cells at tumor sites, a phenomenon that was not observed in normal prostate or BPH samples.
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PMID:Expression of c-kit and kit-ligand in benign and malignant prostatic tissues. 1080 54

The interaction between stem cell factor (SCF), a ligand produced by Sertoli cells, and its c-kit receptor on germ cells is necessary for successful spermatogenesis in animal models. SCF can be alternatively spliced into soluble and transmembrane forms, and it is the transmembrane form that is required for spermatogenesis in rodents. c-Kit receptors are also present on Leydig cells, and soluble SCF has been implicated in the regulation of testosterone production. This study had two goals: To test the hypothesis that the extent of germ cell production in human males is correlated with the expression of transmembrane SCF, and to examine the relationship between testosterone production and the expression of soluble SCF in humans. Reverse transcriptase polymerase chain reaction was used to determine the ratio of transmembrane-to-soluble SCF in testicular tissue. Clinical analysis, hormonal measurements, and histological methods were used to evaluate the causes of infertility and to seek correlations with the pattern of SCF expression. SCF was preferentially expressed as the transmembrane type in all testicular samples, regardless of the state of germ cell production. Furthermore, the percent of transmembrane SCF expression was independent of clinical and histopathological diagnosis (r(s) = 0.111, n = 28) and unrelated to the extent of spermatogenesis. This contrasts with rat models of testicular injury that exhibit a decreased proportion of transmembrane SCF with atrophy. A significant correlation (r(s) = 0.665, P < .02, n = 16) was found between testosterone levels and percent soluble SCF, which suggests that, in humans, there may be a regulatory interaction between soluble SCF and testosterone.
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PMID:Transmembrane versus soluble stem cell factor expression in human testis. 1090 44

The stability of titanium dental implants is determined by osseointegration. Bone is a dynamic tissue continuously remodeled through resorption and formation, processes controlled by local cytokine production. This study investigated osseotropic cytokine expression in gingival mucosa, in the intraforamina and inferior first molar zones, during rehabilitation with implant-retained overdentures. Specimens were taken from six patients prior to placement of implants in the intraforamina bone; at connection of healing abutments; and 4, 8, and 12 months after prosthetic anchorage. Through semi-quantitative reverse-transcriptase polymerase chain-reaction, the following constitutively expressed cytokines were found at first surgical stage: interleukin-1, -6, and -8; small amounts of interleukin-11; stem cell factor; and transforming growth factor-beta1, -beta2, and -beta3. From the connection of healing abutments to 12 months after prosthetic anchorage, transforming growth factor-beta1, -beta2, and -beta3 were markedly higher than initial values. Expression of interleukin-6 and -8 decreased 8 months after prosthetic anchorage, while that of interleukin-1 increased at 12 months. In cultured gingival fibroblasts, modulation of cytokine secretion was also time-dependent. Cell culture supernatants influenced osteoclast-like multinucleated cell formation in long-term human marrow culture or osteoblast function, depending on the cytokine profile produced. These results are consistent with functional contributions of cytokines to osseointegration and minimization of posterior edentulous zone bone resorption.
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PMID:Cytokine production and bone remodeling in patients wearing overdentures on oral implants. 1102 63

Sertoli cells isolated from 6-day postpartum mouse testes were conditionally immortalized with the simian virus 40 large tumor antigen gene (SV40-LTAg) under the control of a promoter inducible with ponasterone A, an analog of ecdysone. This strategy produced 2 cell lines, which exhibited mixed phenotypes. We first tested the conditional expression of the LTAg gene in the presence or absence of ponasterone A. The results showed that both cell lines expressed LTAg when the inducer was present in the culture media. When ponasterone A was removed, the majority of the cells died. After 60 generations, however, the continued expression of LTAg in the absence of the hormone indicated that unknown changes may have occurred in the genome of the cells. One of the cell lines was further subcloned, resulting in 7 new lines exhibiting a morphology resembling that of Sertoli cells in tissue culture. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed on RNA collected from each cell line in order to determine which cells were phenotypically similar to Sertoli cells in vivo. All cell lines expressed the products of the Sertoli cell-specific genes stem cell factor (SCF) and sulfated glycoprotein-2 (SGP-2), in addition to alpha-inhibin, GATA-1, and steroidogenic factor-1. Further, the lines express growth and differentiation factors known to act upon germ cells in vivo and in vitro such as leukemia inhibitory factor (LIF), transforming growth factor beta (TGF-beta), and basic fibroblast growth factor (bFGF). Moreover, when used as feeder layers in cocultures, at least 2 of these lines are able to maintain the viability of type A spermatogonia for at least 7 days and to support the first steps of spermatogonial differentiation.
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PMID:Establishment and characterization of neonatal mouse sertoli cell lines. 1251 93

Vascular endothelial growth factor (VEGF) and stem cell factor (SCF) act as growth factors for the hemangioblast, an embryonic progenitor of the hematopoietic and endothelial lineages. Because thrombopoietin (TPO) and its receptor, c-Mpl, regulate primitive hematopoietic populations, including bone marrow hematopoietic stem cells, we investigated whether TPO acts on the hemangioblasts that derive from differentiation of embryonic stem cells in vitro. Reverse transcriptase polymerase chain reaction analysis detected expression of c-Mpl beginning on day 3 of embryoid body differentiation when the hemangioblast first arises. In assays of the hemangioblast colony-forming cell (BL-CFC), TPO alone supported BL-CFC formation and nearly doubled the number of BL-CFC when added together with VEGF and SCF. When replated under the appropriate conditions, TPO-stimulated BL-CFC gave rise to secondary hematopoietic colonies, as well as endothelial cells, confirming their nature as hemangioblasts. Addition of a neutralizing anti-VEGF antibody did not block TPO enhancement of BL-CFC formation, suggesting that TPO acts independently of VEGF. These results establish that Mpl signaling plays a role in the earliest stages of hematopoietic development and that TPO represents a third growth factor influencing hemangioblast formation.
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PMID:A role for thrombopoietin in hemangioblast development. 1274 22


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