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

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Wilms tumor suppressor gene (WT1) is mutated in a number of cases of Wilms' tumor as well as in mesothelioma and leukemia. It encodes a transcription factor derived from any one of four alternate transcripts. WT1 has a restricted pattern of expression within the body and within the hemopoietic system its expression is limited to primitive leukemias and a number of leukemic cell lines. Given the overexpression of WT1 in leukemias, we have addressed the question of whether this gene is expressed within the normal hemopoietic system. Mononuclear bone marrow (BM) cells obtained from normal donors were separated by fluorescence-activated cell sorting (FACS) into "primitive" (CD34+) and "mature" (CD34-) cell populations. Total RNA extracted from these cells was subjected to reverse transcriptase polymerase chain reaction (RT-PCR) using primers based on the WT1 sequence, to examine the expression of this gene within the hemopoietic system. Phenotypic purity of cells was guaranteed by performing single-cell sorting followed by RT-PCR to define the precise cellular phenotypes that express WT1. Expression of WT1 was detected in cells bearing the CD34+ phenotype but not in those cells lacking expression of CD34. In addition, single-cell analysis revealed that expression of WT1 occurred in the candidate stem cell-containing population of hemopoietic cells which have the phenotype CD34+ CD38-. Moreover, the single-cell RT-PCR analysis also demonstrated that differential expression of alternate transcripts of WT1 occurs between hemopoietic progenitor cells with the same phenotype. In conclusion, expression of WT1 is limited to early progenitors of the blood system, which suggests that this gene plays a critical role in hemopoietic development.
...
PMID:Expression of the Wilms' tumor gene (WT1) in normal hemopoiesis. 940 89

Dendritic cells are potent antigen-presenting cells involved in the initiation of immune responses. The trafficking of these cells to tissues and lymph nodes is mediated by members of the chemokine family. Recently, a novel CC chemokine known as MIP-3alpha or liver and activation-regulated chemokine has been identified from the EMBL/GenBank/DDBJ expressed sequence tag database. In the present study, we have shown that the messenger RNA for MIP-3alpha is expressed predominantly in inflamed and mucosal tissues. MIP-3alpha produced either synthetically or by human embryonic kidney 293 cells is chemotactic for CD34(+)-derived dendritic cells and T cells, but is inactive on monocytes and neutrophils. MIP-3alpha was unable to displace the binding of specific CC or CXC chemokines to stable cell lines expressing their respective high affinity receptors, namely CCR1-5 and CXCR1 and CXCR2, suggesting that MIP-3alpha acts through a novel CC chemokine receptor. Therefore, we used degenerate oligonucleotide-based reverse transcriptase PCR to identify candidate MIP-3alpha receptors in lung dendritic cells. Our results show that the orphan receptor known as GCY-4, CKRL-3, or STRL-22 is a specific receptor for MIP-3alpha, and that its activation leads to pertussis toxin-sensitive and phospholipase C-dependent intracellular Ca2+ mobilization when it is expressed in HEK 293 cells.
...
PMID:Cloning and characterization of a specific receptor for the novel CC chemokine MIP-3alpha from lung dendritic cells. 929 37

Associations between hematopoietic cells and their microenvironment are central to the development and maintenance of a functional hematopoietic system. It is important, therefore, to identify the surface receptors that mediate adhesive interactions among hematopoietic cells, stromal cells, and extracellular matrix components. In this study, we examined the expression of mRNA transcripts encoding a number of cell adhesion molecules and surface antigens in primitive hematopoietic cells isolated from murine bone marrow and fetal liver. Using a panel of probes, we hybridized a library of globally amplified cDNA prepared by reverse transcriptase-polymerase chain reaction of poly(A)+ mRNA from individual precursors and mature cell populations, representing precisely defined positions within the hematopoietic developmental hierarchy. The panel included probes specific for the CD45, CD34, P-glycoprotein (mdr1), Ly-6A/E (Sca-1), heat stable antigen (CD24), Fc receptor for IgG FcgammaRII (CD32), CD44, CD22, and ICAM-1 (CD54) genes, as well as alphaL (CD11a), alphaM (CD11b), beta2 (CD18), alpha4 (CD49d), alpha5 (CD49e), beta1 (CD29), and beta7 integrin subunit sequences. The data, which revealed stage- and lineage-specific expression patterns, should prove useful in designing future mechanistic studies aimed at elucidating the role played by adhesion receptors in normal and abnormal hematopoiesis.
...
PMID:Expression mapping of adhesion receptor genes during differentiation of individual hematopoietic precursors. 932 54

We have previously characterized stromal progenitor cells contained in fetal bone marrow by fluorescence-activated cell sorting (FACS) using the differential expression of CD34, CD38, and HLA-DR, and found that a small number were contained within the CD34(+) cell fraction. In the present study, the frequency of stromal progenitors in both the CD34+ and CD34- subpopulations from samples of fetal and adult bone marrow was approximately one in 5,000 of the mononuclear cell fraction. Using multiparameter single-cell sorting, one in 20 fetal bone marrow cells with the CD34+, CD38-, HLA-DR-, CDw90+ phenotype were clonogenic stromal progenitors, whereas greater than one in five single cells with the CD34-, CD38-, HLA-DR-, CDw90+ phenotype formed stromal cultures. We found that cultures initiated by hematopoietic and stromal progenitors contained within the CD34+ fraction of bone marrow cells formed mixed hematopoietic/stromal cell cultures that maintained the viability of the hematopoietic progenitor cells for 3 weeks in the absence of added hematopoietic cytokines. We characterized some of the hematopoietic cytokines synthesized by stromal cultures derived from either CD34+ or CD34- bone marrow cells using reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of interleukin-3 (IL-3), stem cell factor (SCF), CD34, Flt3/Flk2 ligand (FL), and thrombopoietin (TPO) mRNA sequences. We found ubiquitous expression of TPO mRNA in greater than 90% of stromal cultures initiated by either CD34+ or CD34- cells, and variable expression of SCF, FL, and CD34 mRNA. In particular, SCF and CD34 mRNA were detected only in stromal cultures initiated by CD34+ bone marrow cells, although the differences between CD34+ and CD34- stromal cells were not statistically significant. IL-3 mRNA was not found in any stromal cultures. An enzyme-linked immunosorbent assay (ELISA) of soluble SCF and TPO present in culture supernatants demonstrated that biologically significant amounts of protein were secreted by some cultured stromal cells: eight of 16 samples of conditioned media from stromal cultures initiated by fetal and adult bone marrow contained more than 32 pg/mL SCF (in the linear range of the ELISA), with a median value of 32 pg/mL (range, 9 to 230), while 13 of 24 samples of conditioned media had more than 16 pg/mL TPO (in the linear range of the ELISA), with a median of 37 pg/mL (range, 16 to 106). Our data indicate that stromal cultures initiated by single bone marrow cells can make FL, SCF, and TPO. Local production of early-acting cytokines and TPO by stromal cells may be relevant to the regulation of hematopoietic stem cell self-renewal and megakaryocytopoiesis in the bone marrow microenvironment.
...
PMID:Thrombopoietin is synthesized by bone marrow stromal cells. 934 28

In humans CD34 is a valid and reliable marker for hematopoletic stem and progenitor cells. In general, solid tumors, with the exception of endothelial cancers, do not express CD34. Accordingly, immunological selection of CD34+ hematopoietic stem/progenitor cells can be used to remove CD34- malignant cells in the setting of autotransplantation. To rule out CD34 expression on tumor cells from small cell lung cancer (SCLC), eleven SCLC cell lines were analyzed by flow cytometry. Interestingly, two of these were positive for CD34 and their expression of full-length CD34 was further confirmed by reverse transcriptase and polymerase chain reaction (RT-PCR). This finding indicates that prior to subjecting SCLC patients to the above treatment modality, preparing CD34+ hematopoietic stem/progenitor cells from SCLC patients for autotransplantation, CD34 expression on their tumor cells should be screened using immunohistochemistry and/or flow cytometry.
...
PMID:Small cell lung cancer can express CD34 antigen. 941 15

Mammalian Polycomb group (Pc-G) genes, constituting some 5 subfamilies based on their identity to the Drosophila genes Pc, Psc, ph, esc, and E(z), appear to play critical roles in maintaining the transcriptional repression state of Hox/HOM-C genes during development. Despite increasing evidence of the important role of Hox genes in both normal hematopoiesis and leukemic transformation, little is known about the expression and possible function played by Pc-G genes in hematopoietic cells. To address this, we first examined the expression of Pc genes in purified CD34(+) human bone marrow cells by reverse transcriptase-polymerase chain reaction (RT-PCR), using degenerate primers that specifically amplify the majority of Pc genes. This analysis showed the expression of 8 different Pc genes in CD34(+) bone marrow cells, including HP1(Hsalpha), HP1(Hsgamma), the heterochromatin p25 protein, the human homologue of the murine M32 gene, and 4 novel members of this family. To assess whether Pc-G mRNA levels change during differentiation of bone marrow cells, a quantitative RT-PCR method was used to amplify the total cDNA originating from three purified subpopulations of CD34(+) bone marrow cells known to differ in their ability to grow in long-term or semisolid cultures. In sharp contrast to Hox gene expression, which is highest in the most primitive bone marrow cells, these studies show that the expression level of 8 of the 9 Pc-G genes studied (ie, HP1(Hsalpha), HP1(Hsgamma), M31, M32, M33, Mel-18, Mph1/Rae-28, and ENX-1) markedly increases with differentiation of bone marrow cells. Interestingly, BMI-1 exhibits a strikingly different pattern of expression, with high expression levels in primitive cells and very little expression in mature CD34(-) cells. Together, these results document for the first time that differentiation of human bone marrow cells is accompanied by profound changes in Pc-G gene expression levels.
...
PMID:Stage-specific expression of polycomb group genes in human bone marrow cells. 945 51

CD44 is a ubiquitous cell-surface glycoprotein that displays many variant isoforms (CD44v) generated by alternative splicing of exons 2v to 10v. The expression of variant isoforms is highly restricted and correlated with specific processes, such as leukocyte activation and malignant transformation. We have herein studied CD44v expression in acute myeloid leukemia (AML) and, for comparison, in normal myelopoiesis. Protein expression of total CD44 and of CD44-3v, -6v, and -9v isoforms has been measured using specific monoclonal antibodies and flow cytometry. The composition of variant exon transcripts has been analyzed by semi-quantitative reverse transcriptase-polymerase chain reaction followed by Southern hybridization with exon-specific probes. Our data show that (1) CD44-6v isoforms are expressed on 12.0% +/- 2.5% of normal CD34(+) cells; this expression is sharply upregulated through monopoiesis and, inversely, downregulated during granulopoiesis. Also, CD44-3v and CD44-9v isoforms are detected on 10% and 14% of normal monocytes, respectively. (2) Sixty-nine from a total of 95 AML patients display a variable proportion (range, 5% to 80%) of CD44-6v+ leukemic cells. (3) A shorter overall survival characterizes the group of AML patients displaying more than 20% of CD44-6v+ leukemic cells (8 months v 18 months, P < .02). These data suggest, for the first time, that the protein expression of CD44-6v containing isoforms may serve as a new prognostic factor in AML.
...
PMID:A strong expression of CD44-6v correlates with shorter survival of patients with acute myeloid leukemia. 955 99

CD34 antigen is present on most, if not all, human hematopoietic stem cells (HSCs). Consistent with this pattern of expression, we recently reported that primitive murine HSCs defined as competitive long-term repopulating units (CRUs) are highly enriched among CD34+ bone marrow (BM) cells (one CRU/2500 cells). However, in agreement with one recent report that some murine HSCs do not express CD34 (Science 273:242), we observed that 15% of phenotypically defined Thy-1lowLin-/lowSca-1+ (TLS) stem cells were CD34- by fluorescence-activated cell sorting. To examine further the nature of CD34 expression on murine hematopoietic cells, we separated TLS cells into CD34+ (0.022% of BM cells) and CD34- (0.005% of BM cells) fractions, confirmed their phenotype by reverse transcriptase-polymerase chain reaction analysis of CD34 transcripts, and evaluated them in a variety of in vitro and in vivo assays. The CD34+ TLS population contained most (93-95%) of the day 12 spleen colony-forming units (CFU-S) and in vitro colony-forming cells (CFCs). Cobblestone area-forming cells (CAFCs) able to proliferate on a murine bone marrow stromal cell line (SyS-1) represented one of every 5 CD34+ TLS and one of every 31 CD34 TLS cells. When lethally irradiated mice were injected with 100 CD34+ TLS cells, all animals survived and began to recover circulating leukocytes, platelets, and erythrocytes by 15 days. In contrast, only 40% of mice injected with 100 CD34- TLS cells were radioprotected, and hematopoietic reconstitution in surviving mice was not apparent until 21 days. The frequency of CRUs in CD34+ and CD34 TLS cells was determined by injecting limiting numbers of cells into lethally irradiated Ly-5 congenic hosts together with 10(5) "compromised" BM cells to provide radioprotection. CRUs able to regenerate and maintain lymphoid and myeloid cells for at least 6 months in primary and 5 months in secondary hosts represented one of every 156 CD34+ TLS and one of every 35 CD34- TLS cells. However, when normalized for the proportion of TLS cells that were CD34+ or CD34-, it was determined that the recovery of CRU among CD34+ and CD34- TLS cells was equivalent (46% and 54%, respectively). These data are consistent with the previous description of repopulating HSCs among CD34-c-kit+Sca-1+Lin- cells (Science 273:242, 1996) and provide additional evidence that TLS cells are functionally heterogeneous and can be further fractionated on the basis of CD34 expression. Overall, approximately 95% of CFCs, CFU-S, and CAFCs in the TLS population were found to be CD34+, whereas more primitive CRU were distributed equally among CD34+ and CD34 TLS cells. These results should enable better characterization of the most primitive stem cells in murine BM.
...
PMID:Equal distribution of competitive long-term repopulating stem cells in the CD34+ and CD34- fractions of Thy-1lowLin-/lowSca-1+ bone marrow cells. 959 Jun 62

CXCR4 is the receptor for the alpha-chemokine stromal cell-derived factor 1 (SDF-1) and has been shown to be expressed on a diversity of leukocytes. In this report, the expression of the CXCR4 receptor in cells of megakaryocytic lineage and the role of SDF-1 in megakaryocytopoiesis were investigated. Using flow cytometry in combination with reverse transcriptase-polymerase chain reaction (RT-PCR), we observed that bone marrow CD34(+), CD61(+) cells, blood platelets, and megakaryocytic leukemia cell lines all expressed the CXCR4 receptor. To examine the expression of the CXCR4 receptor on megakaryocyte progenitors (colony-forming units-megakaryocyte [CFU-Meg]), CXCR4-positive and -negative CD34(+) populations were separated from bone marrow and cultured in a plasma clot culture system. A subpopulation of the CFU-Meg was found in the CXCR4-positive fraction. The functional significance of CXCR4 expression on cells of the megakaryocytic lineage was examined by studying the effects of SDF-1alpha on migration and proliferation of megakaryocyte progenitor cells in vitro. We found that SDF-1alpha potently induced megakaryocyte progenitor migration and significantly enhanced adhesion of mature marrow megakaryocytes to endothelium. No marked effects of SDF-1alpha alone or in combination with thrombopoietin and stem cell factor/kit ligand on megakaryocyte production in vitro were noted. These results demonstrate for the first time that the CXCR4 alpha-chemokine receptor is expressed on cells of the megakaryocytic lineage from progenitors to platelets and that its ligand SDF-1alpha may modulate several aspects of megakaryocytopoiesis.
...
PMID:The alpha-chemokine receptor CXCR4 is expressed on the megakaryocytic lineage from progenitor to platelets and modulates migration and adhesion. 968 Mar 41

Little is known about the mechanisms and the kinetics of the so-called graft-versus-leukemia (GVL) response induced by donor lymphocyte infusions (DLI) in patients with leukemic relapse after allogeneic bone marrow transplantation (BMT). We sought to elucidate this problem by sequentially studying three patients with relapsed chronic myeloid leukemia after sex-mismatched BMT from time before donor leukocyte infusion until achievement of complete molecular remission. Lineage-specific chimerism was assessed longitudinally by a combined fluorescent immunophenotyping and sex chromosome-specific in situ hybridization approach. Results were related to quantitative detection of bcr-abl transcripts by competitive differential reverse transcriptase-polymerase chain reaction (RT-PCR), qualitative bcr-abl RT-PCR, and multiplex PCR-based DNA donor/recipient chimerism. All patients had predominant donor lymphopoiesis at the time of DLI, suggesting a state of tolerance to recipient leukemic and/or normal cells. In contrast, granulopoiesis and erythropoiesis were mainly recipient derived in both patients with hematologic relapse and partly recipient derived in the patient with molecular relapse. Eighty percent, 90%, and 8% of CD34(+) cells, respectively, were found to be of recipient origin at relapse, and few donor stem cells predicted for cytopenia post-DLI. Responses were seen after a time lag of 5 to 13 weeks after DLI and resulted in reversal to full donor chimerism within a critical switch period of 4 to 5 weeks. A sudden decrease in recipient cells was paralleled by a sharp decrease in bcr-abl transcript numbers detectable several weeks before achievement of molecular remission and onset of clinical graft-versus-host disease (GVHD). This response pattern was confirmed by retrospective RT-PCR analysis in an additional five patients. Prospective monitoring of stem cell chimerism and response may enable us to individually tailor adoptive immunotherapy in the future.
...
PMID:Kinetics of the graft-versus-leukemia response after donor leukocyte infusions for relapsed chronic myeloid leukemia after allogeneic bone marrow transplantation. 1023 94


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---