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

We are interested in the regulation of the tissue specificity of the megakaryocyte-specific platelet glycoprotein IIb gene. The murine embryonic stem (ES) cells are able to differentiate into erythroid, mast and granulomonocytic cells in appropriate culture conditions. Our goal is to optimize the production of myeloid cells including megakaryocytes (MKs) by ES cells. We have found that coculture with MS-5 stromal cells and the presence of a cocktail of hematopoietic growth factors (HGFs) [stem cell factor, interleukin 3 (IL-3), IL-6, IL-11, G-CSF and erythropoietin] had a high synergistic activity on differentiation of ES cells into pure and MK-containing myeloid colonies from day 12 embryoid bodies. Thrombopoietin increased the number of MKs only when added to the HGF cocktail in the presence of MS-5 cells. Interestingly, many MKs exhibited a "hairy" appearance evocative of pseudopodial proplatelet formation. Expression of genes specific for the megakaryocytic lineage, GPIIb, PF4, mpl and GPIIIa, was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) during differentiation of ES cells, and their relative time course was evaluated. This demonstrates that optimized culture conditions for the differentiation of ES cells into the MK lineage provide a useful tool for the study of the regulation of expression of genes during megakaryocytopoiesis.
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PMID:Hematopoietic differentiation of embryonic stem cells: an in vitro model to study gene regulation during megakaryocytopoiesis. 1101 21

This study examined the expression of the platelet collagen receptor glycoprotein VI (GPVI) in megakaryocyte cell lines and primary megakaryocytes by reverse transcriptase-polymerase chain reaction and by flow cytometry and ligand blotting using the snake venom toxin convulxin. Expression of GPVI is increased in the megakaryoblastic cell lines HEL and CMK on differentiation with the phorbol ester phorbol 12-myristate 13-acetate (PMA), along with the Fc receptor gamma-chain (FcR gamma-chain). The increase in GPVI expression is associated with marked potentiation of tyrosine phosphorylation and Ca(++) elevation in response to convulxin. Syk, linker for activated T cells, and phospholipase C gamma 2 (PLC gamma 2) are among the proteins tyrosine phosphorylated on convulxin stimulation in PMA-differentiated HEL cells. Studies on primary murine megakaryocytes grown in vitro confirmed that GPVI is up-regulated in parallel with functional activation, assessed by measurement of [Ca(++)](i), during differentiation. The results demonstrate that expression of GPVI is up-regulated along with the FcR gamma-chain during differentiation of megakaryocytes. (Blood. 2000;96:2740-2745)
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PMID:Expression of the collagen receptor glycoprotein VI during megakaryocyte differentiation. 1102 7

During megakaryocyte differentiation, the immature megakaryocyte increases its ploidy to a 2(x) DNA content by a process called endomitosis. This leads to the formation of a giant cell, the mature megakaryocyte, which gives rise to platelets. We investigated the role of human-nuc (h-nuc), a gene involved in septum formation in karyokynesis in yeast, during megakaryocytic polyploidization. Nocodazole and 12-O-tetradecanoylphorbol-13-acetate (TPA) were used to induce megakaryocytic differentiation in K562 cell line. The ploidy distribution and CD41 expression of treated K562 cells were evaluated by flow cytometry. Using quantitative reverse transcriptase polymerase chain reaction (RT-PCR), we analyzed the h-nuc mRNA expression on treated K562 cells. Mature megakaryocyte-like polyploid cells were detected at day 5-7 of treatment with nocodazole. TPA also had a similar effect on K562 cells, but it was much weaker than that of nocodazole. The analysis of ploidy of nocodazole-treated K562 cells showed that nocodazole preferentially induced polyploidization of K562 cell line with a pronounced increase of the cells 8N at day 7 of culture. Expression of CD41, a differentiation-related phenotype, was significantly induced by TPA after 7 days of treatment, showing that functional maturation was mainly induced by TPA. In contrast, there was no significant increase in CD41 expression in nocodazole-treated K562 cells, suggesting that polyploidization and functional maturation are separately regulated during megakaryocytopoiesis. RT-PCR analysis indicated that h-nuc mRNA increased after 72 hours in the presence of nocodazole, preceding the induction of polyploidization. Our data indicate that h-nuc might play a role in polyploidization during megakaryocytic differentiation via inhibition of septum formation.
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PMID:The involvement of human-nuc gene in polyploidization of K562 cell line. 1114 65

The granulocyte-derived hemoregulatory peptide pyroGlu-Glu-Asp-Cys-Lys = pEEDCK is known to keep hematopoietic cells quiescent. When oxidized to its dimeric form (pEEDCK)2, it activates growth of hematopoietic progenitors in association with stroma-derived cytokines. (pEEDCK)2 has a Cys-Cys motif which is also a typical feature of the macrophage inflammatory protein (MIP-1alpha). The present study was designed to analyze differences between the response of normal and leukemic progenitor cells to (pEEDCK)2 or MIP-1alpha. When long-term bone marrow cultures (LTBMCs) were incubated with (pEEDCK)2 or MIP-1alpha and/or cytokines, the stimulatory effect on colony-forming units-granulocyte/erythroid/macrophage/megakaryocyte of LTBMC from chronic myeloid leukemia (CML) patients was less than 50% compared to LTBMC from healthy humans. No difference in oncogene expression could be observed in LTBMC from CML patients regarding reduction of Philadelphia chromosome-associated transcription of the BCR-ABL gene. With respect to the expression of growth and differentiation-associated genes (Galpha16, 5-lipoxygenase, phospholipaseA2, c-kit, and CD34), which were analyzed from LTBMC by semiquantitative reverse transcriptase-polymerase chain reaction, the same transcription rate was observed in CML patients and healthy donors. However, two isoforms of a key enzyme of oxidative metabolism, carnitine palmitoyltransferase (CPT1A and CPT1B), showed 50-fold higher expression rates in LTBMC cells of healthy donors compared to CML patients. It is known that a decrease in oxidative metabolism is associated with an increase in redox equivalents in malignancy. This might result in a reduction of disulphide bonds in (pEEDCK)2 or MIP-1alpha, thus inducing a downregulation of these factors in bone marrow from CML patients.
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PMID:Effect of the hemoregulatory peptide (pEEDCK)2 (pyroGlu-Glu-Asp-Cys-Lys)2 and MIP-1alpha is reduced in bone marrow cultures from patients with chronic myeloid leukemia (CML). 1146 52

One important question in stem cell biology of childhood acute lymphoblastic leukemia (ALL) is whether immature CD34+CD19- cells are part of the leukemic cell clone. CD34+CD19- cells from the bone marrow of 9 children with TEL/AML1-positive ALL were purified by flow sorting and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR), fluorescence in situ hybridization, and methylcellulose cultures. In 3 of 8 patients analyzed by RT-PCR, no TEL/AML1-positive cells could be detected in the CD34+CD19- cell fraction. Altogether, the percentage of TEL/AML1-positive cells was low: 1.6% (n = 8; SD 2.2%) by nested real-time RT-PCR and 2.5% (n = 5; SD 2.6%) by fluorescence in situ hybridization. This correlated with the percentage of contaminating CD19+ leukemic cells in the CD34+CD19- cell fraction in 6 control sorts (mean 4.6%, SD 3.6%), indicating that the low levels of leukemic cells detected in the CD34+CD19- cell fraction could be attributed to sorter errors. Methylcellulose cultures in 3 patients provided further evidence that CD34+CD19- cells represent a candidate normal cell population. The clonogenicity of the CD34+CD19- cell fraction was similar to normal progenitors, including growth of primitive granulocyte, erythroid, macrophage, megakaryocyte colony-forming units. Each of 92 colonies from cultures with CD34+CD19- cells tested negative for TEL/AML1. In conclusion, our data support the hypothesis that the leukemia in TEL/AML1-positive childhood ALL originates in a CD19+ lymphoid progenitor. This has many therapeutic implications, eg, for purging of autologous stem cell products, flow cytometric monitoring of minimal residual disease, and targeting immunotherapy against the leukemic cell clone.
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PMID:Immature CD34+CD19- progenitor/stem cells in TEL/AML1-positive acute lymphoblastic leukemia are genetically and functionally normal. 1209 59

The marrow microenvironment consists of several different interacting cell types, including hematopoietic-derived monocyte/macrophages and nonhematopoietic-derived stromal cells. Gene-expression profiles of stromal cells and monocytes cultured together differ from those of each population alone. Here, we report that CXCL7 gene expression, previously described as limited to the megakaryocyte lineage, is expressed by monocytes cocultured with stromal cells. CXCL7 gene expression was confirmed by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and secretion of protein was detected by enzyme-linked immunosorbent assay (ELISA) and Western blot. At least 2 stromal-derived activities, one yet to be identified, were required for optimal expression of CXCL7 by monocytes. NAP-2, the shortest form of CXCL7 detected in the coculture media, was confirmed to decrease the size and number of CFU-Meg colonies. The propeptide LDGF, previously reported to be mitogenic for fibroblasts, was not secreted by stimulated monocytes. The recombinant form of LDGF produced in a prokaryotic expression system did not have biologic activity in our hands. The monocytic source of CXCL7 was also detected by immunohistochemistry in normal bone marrow biopsies, indicating an in vivo function. We conclude that stromal-stimulated monocytes can serve as an additional source for CXCL7 peptides in the microenvironment and may contribute to the local regulation of megakaryocytopoiesis.
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PMID:Monocyte-derived CXCL7 peptides in the marrow microenvironment. 1639 Oct 12

TPO (thrombopoietin) and SCF (stem-cell factor) are functionally related cytokines with overlapping but distinct haematopoietic effects. In the present study, a novel TPO-SCF fusion protein that combined the complementary biological effects of TPO and SCF into a single molecule was expressed in, and purified from, Sf9 [Spodoptera frugiperda (fall armyworm)] insect cells. The specific activity of rhTPO (recombinant human TPO)-SCF in megakaryoblastic Mo7e cell proliferation assays was 2.90+/-0.35 x 10(7) units/micromol, approx. 1.7 times as high as that of rhTPO. The specific activity of rhTPO-SCF in TF-1 cells proliferation assays was 7.10+/-0.95 x 10(6) units/micromol, approx. 1.2 times as high as that of rhSCF (recombinant human SCF). In a megakaryocyte-colony-forming assay using human peripheral-blood CD34(+) cells, the SCF moiety of rhTPO-SCF worked in a synergistic way to augment the colony number and exhibited a higher potential to stimulate megakaryocyte colony growth. According to the results of EMSA (electrophoretic mobility-shift assay) and semi-quantitative RT (reverse transcriptase)-PCR, the synergistic effects of the SCF moiety were also reflected in increased STAT5 (signal transducer and activator of transcription 5) DNA binding and enhanced up-regulation of p21 expression in Mo7e cells treated by rhTPO-SCF, suggesting that rhTPO-SCF could be more potent in promoting megakaryocyte proliferation and differentiation.
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PMID:A novel thrombopoietin-stem-cell factor fusion protein possesses enhanced potential in stimulating megakaryocyte proliferation and differentiation. 1751 19

In platelets, splicing and translation occur in the absence of a nucleus. However, the integrity and stability of mRNAs derived from megakaryocyte progenitor cells remain poorly quantified on a transcriptome-wide level. As circular RNAs (circRNAs) are resistant to degradation by exonucleases, their abundance relative to linear RNAs can be used as a surrogate marker for mRNA stability in the absence of transcription. Here we show that circRNAs are enriched in human platelets 17- to 188-fold relative to nucleated tissues and 14- to 26-fold relative to samples digested with RNAse R to selectively remove linear RNA. We compare RNAseq read depths inside and outside circRNAs to provide in silico evidence of transcript circularity, show that exons within circRNAs are enriched on average 12.7 times in platelets relative to nucleated tissues and identify 3162 genes significantly enriched for circRNAs, including some where all RNAseq reads appear to be derived from circular molecules. We also confirm that this is a feature of other anucleate cells through transcriptome sequencing of mature erythrocytes, demonstrate that circRNAs are not enriched in cultured megakaryocytes, and demonstrate that linear RNAs decay more rapidly than circRNAs in platelet preparations. Collectively, these results suggest that circulating platelets have lost >90% of their progenitor mRNAs and that translation in platelets occurs against the backdrop of a highly degraded transcriptome. Finally, we find that transcripts previously classified as products of reverse transcriptase template switching are both enriched in platelets and resistant to decay, countering the recent suggestion that up to 50% of rearranged RNAs are artifacts.
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PMID:Circular RNA enrichment in platelets is a signature of transcriptome degradation. 2694 89


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