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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The expression of c-myc was analyzed in murine and human erythroblasts throughout their differentiation in vitro into reticulocytes. The murine cells were splenic erythroblasts from animals infected with the anemia strain of Friend virus (FVA cells). In FVA cells cultured without EPO, the c-myc mRNA and protein levels decrease sharply within 3 to 4 h, showing that continual EPO stimulation is required to maintain c-myc expression. When cultured with EPO, the c-myc mRNA level of FVA cells is raised within 30 min of exposure. The c-myc mRNA and protein reach maxima at 1 to 3 h, then decline slowly to very low levels by 18 h. In contrast, c-fos and c-jun mRNA levels are not regulated by EPO in FVA cells. The human cells analyzed were colony-forming units-erythroid, CFU-E, derived in vitro by the culture of peripheral blood burst-forming units-erythroid (BFU-E). When grown in EPO and insulin-like growth factor 1 (IGF-1) these cells differentiate into reticulocytes over 6 days rather than the 2 days required for murine cells, but the c-myc mRNA kinetics and response to EPO parallel those of mouse cells at similar stages of differentiation. Both IGF-1 and c-kit ligand (SCF) cause an additive increase in c-myc mRNA in human CFU-E in conjunction with EPO. These additive effects suggest that EPO, IGF-1, and SCF affect c-myc mRNA accumulation by distinct mechanisms. Addition of an antisense oligonucleotide to c-myc in cultures of human CFU-E specifically inhibited cell proliferation but did not affect erythroid cell differentiation or apoptosis. When human cells were grown in high SCF concentrations, an environment which enhances proliferation and retards differentiation, antisense oligonucleotide to c-myc strongly inhibited proliferation, but such inhibition did not induce differentiation. This latter result indicates that differentiation requires signals other than depression of c-Myc and resultant depression of proliferation.
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PMID:C-myc expression affects proliferation but not terminal differentiation or survival of explanted erythroid progenitor cells. 870 61

A large number of primordial germ cells (PGCs), as well as spermatogonia, undergo programmed cell death or apoptosis in the physiological context. In this process, environmental, cytoplasmic and nuclear factors are involved. Bcl-2 and its related molecules are known as general regulators of cell death, and some are important for survival of PGCs and spermatogonia. Steel factor, a ligand for c-Kit, also supports growth and survival of these cells. In addition, bone morphogenetic protein (BMP)8B and Desert Hedgehog (Dhh), which are secreted proteins, and a nuclear factor, c-Myc, play a role in spermatocyte survival. This suggests that germ cell survival or death at each stage of differentiation is precisely controlled by specific signalling pathways which consist of a number of molecules.
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PMID:Regulation of germ cell death in mammalian gonads. 952 72

Terminal erythroid differentiation is accompanied by decreased expression of c-Kit and decreased proliferation of erythroid progenitor cells. Using a newly established erythroleukemia cell line HB60-5, which proliferates in response to erythropoietin (Epo) and stem cell factor (SCF) and differentiates when stimulated with Epo alone, we characterized several events associated with the cell cycle during erythroid differentiation. Forty-eight h after SCF withdrawal and Epo stimulation, there was strong inhibition of cyclin-dependent kinase (cdk) 4 and cdk6 activities, associated with an increase in the binding of p27 and p15 to cdk6. A significant increase in the binding of p27 to cyclin E- and cyclin A-associated cdk2 correlated with the inhibition of these kinases. In addition, the expression of c-Myc and its downstream transcriptional target Cdc25A were found to be down-regulated during Epo-induced terminal differentiation of HB60-5 cells. The loss of Cdc25A was associated with an increase in the phosphotyrosylation of cyclin E-associated cdk2, which may contribute to cell cycle arrest during differentiation. Although overexpression of p27 in HB60-5 cells caused G1 arrest, it did not promote terminal erythroid differentiation. Thus, the cell cycle arrest that involves p27 is part of a broader molecular program during HB60-5 erythroid differentiation. Moreover, we suggest that SCF stimulation of erythroblasts, in addition to inhibiting erythroid differentiation, activates parallel or sequential signals responsible for maintaining cyclin/cdk activity.
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PMID:Stem cell factor inhibits erythroid differentiation by modulating the activity of G1-cyclin-dependent kinase complexes: a role for p27 in erythroid differentiation coupled G1 arrest. 1084 28

Erythroid homeostasis depends critically upon erythropoietin (Epo) and stem cell factor cosignaling in late progenitor cells. Epo bioresponses are relayed efficiently by minimal receptor forms that retain a single Tyr-343 site for STAT5 binding, while forms that lack all cytoplasmic Tyr(P) sites activate JAK2 and the transcription of c-Myc plus presumed additional target genes. In FDCER cell lines, which express endogenous c-Kit, the signaling capacities of such minimal Epo receptor forms (ER-HY343 and ER-HY343F) have been dissected to reveal: 1) that Epo-dependent mitogenesis, survival, and bcl-x gene expression via ER-HY343 depend upon the intactness of the Tyr-343 STAT5 binding site; 2) that ER-HY343-dependent bcl-x(L) gene transcription is enhanced markedly via c-Kit; 3) that socs-3, plfap, dpp-1, and cacy-bp gene transcription is induced via ER-HY343, whereas dpp-1 and cacy-bp gene expression is also supported by ER-HY343F; 4) that ectopically expressed SOCS-3 suppresses proliferative signaling by not only ER-HY343 but also c-Kit; and 5) that in FDCER and primary erythroid cells, c-Kit appears to provide the primary route to MAPK activation. Thus, integration circuits exist in only select downstream pathways within Epo and stem call factor receptor signaling.
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PMID:Integrative signaling by minimal erythropoietin receptor forms and c-Kit. 1112 55

T cells develop through distinct stages directed by a series of signals. We explored the roles of SWI/SNF-like BAF chromatin remodeling complexes in this process by progressive deletion of the ATPase subunit, Brg, through successive stages of early T cell development. Brg-deficient cells were blocked at each of the developmental transitions examined. Bcl-xL overexpression suppressed cell death without relieving the developmental blockades, leading to the accumulation of Brg-deleted cells that were unexpectedly cell cycle arrested. These defects resulted partly from the disruptions of pre-TCR and potentially Wnt signaling pathways controlling the expression of genes such as c-Kit and c-Myc critical for continued development. Our studies indicate that BAF complexes dynamically remodel chromatin to propel sequential developmental transitions in response to external signals.
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PMID:Sequential roles of Brg, the ATPase subunit of BAF chromatin remodeling complexes, in thymocyte development. 1293 48

Congenital melanocytic nevi (CMN) occur in 1% to 2% of newborns, and the risk of malignant melanoma is increased in patients with large CMN. Appearance at birth or later of a nodular or hyperpigmented area within a CMN simulates malignant melanoma and prompts biopsy. Although their clinical and pathologic features seem ominous, proliferative nodules (PNs) typically are benign and may regress, although atypical features cause greater concern. Here we report clinical and pathologic findings with outcome in 10 children who had multiple biopsies of large CMN with PNs. We reviewed 78 separate samples from the 10 patients and classified the 60 PNs according to published criteria. A subset of 30 samples containing both the CMN and a PNs was analyzed for immunohistochemical reactivity for melanocytic (S-100 protein, HMB45, melan-A), lymphocytic (CD45), cell-cycle/proliferative (Mib-1, p16, p21, p27, c-Myc), apoptotic (p53, Bax, c-kit, CD95), and anti-apoptotic (bcl-2) markers. Both CMN and PNs had similar expression of melanocytic, lymphocytic, and most cell-cycle/proliferative and apoptotic markers, including Mib-1, p16, p21, p27, c-Myc, Bax, CD95, and bcl-2. A greater proportion of PNs than CMN were reactive for p53 (67% vs. 30%, P < 0.0098) and c-kit (97% vs. 3%, P < 0.0001). p53 and p21 expression in CMN and all types of PNs were inversely correlated. When ordinary and atypical PNs were compared, the atypical PNs more frequently expressed p53, Mib-1, Bax, and bcl-2, but less frequently expressed p21. The c-kit expression in nearly all PNs and its absence in nearly all CMN is potentially useful for recognition of PN, suggests a delayed melanocytic maturation process in proliferative nodules, and may be likely indicative of their benign nature. p53 reactivity in concert with a lack of p21 up-regulation by immunohistochemistry suggests that a p53 mutation may be present in PN, although the immunohistochemical findings alone cannot exclude possible overexpression of wild-type p53. Regressive, involutional, or maturational changes were observed in sequential samples from 4 patients. No patient developed malignant melanoma or another melanocytic nevus-associated malignancy during the follow-up period. These findings underscore the similarities between PNs and the underlying CMN and suggest that maturational, proliferative, and apoptotic processes are involved in their clinical evolution.
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PMID:Proliferative nodules in congenital melanocytic nevi: a clinicopathologic and immunohistochemical analysis. 1525 7

Stem cell factor (SCF), erythropoietin (Epo), and GATA-1 play an essential role(s) in erythroid development. We examined how these proteins interact functionally in G1E cells, a GATA-1(-) erythroblast line that proliferates in an SCF-dependent fashion and, upon restoration of GATA-1 function, undergoes GATA-1 proliferation arrest and Epo-dependent terminal maturation. We show that SCF-induced cell cycle progression is mediated via activation of the Src kinase/c-Myc pathway. Restoration of GATA-1 activity induced G1 cell cycle arrest coincident with repression of c-Kit and its downstream effectors Vav1, Rac1, and Akt. Sustained expression of each of these individual signaling components inhibited GATA-1-induced cell cycle arrest to various degrees but had no effects on the expression of GATA-1-regulated erythroid maturation markers. Chromatin immunoprecipitation analysis revealed that GATA-1 occupies a defined Kit gene regulatory element in vivo, suggesting a direct mechanism for gene repression. Hence, in addition to its well-established function as an activator of erythroid genes, GATA-1 also participates in a distinct genetic program that inhibits cell proliferation by repressing the expression of multiple components of the c-Kit signaling axis. Our findings reveal a novel aspect of molecular cross talk between essential transcriptional and cytokine signaling components of hematopoietic development.
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PMID:Repression of c-kit and its downstream substrates by GATA-1 inhibits cell proliferation during erythroid maturation. 1602 8

Heparanase is involved in tumor growth and metastasis. Because of its unique cleavage of heparan sulfate, which binds cytokines, chemokines and proteases, we hypothesized that heparanase is also involved in regulation of early stages of hematopoiesis. We report reduced numbers of maturing leukocytes but elevated levels of undifferentiated Sca-1(+)/c-Kit(+)/Lin(-) cells in the bone marrow (BM) of mice overexpressing heparanase (hpa-Tg). This resulted from increased proliferation and retention of the primitive cells in the BM microenvironment, manifested in increased SDF-1 turnover. Furthermore, heparanase overexpression in mice was accompanied by reduced protease activity of MMP-9, elastase, and cathepsin K, which regulate stem and progenitor cell mobilization. Moreover, increased retention of the progenitor cells also resulted from up-regulated levels of stem cell factor (SCF) in the BM, in particular in the stem cell-rich endosteum and endothelial regions. Increased SCF-induced adhesion of primitive Sca-1(+)/c-Kit(+)/Lin(-) cells to osteoblasts was also the result of elevation of the receptor c-Kit. Regulation of these phenomena is mediated by hyperphosphorylation of c-Myc in hematopoietic progenitors of hpa-Tg mice or after exogenous heparanase addition to wildtype BM cells in vitro. Altogether, our data suggest that heparanase modification of the BM microenvironment regulates the retention and proliferation of hematopoietic progenitor cells.
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PMID:Heparanase regulates retention and proliferation of primitive Sca-1+/c-Kit+/Lin- cells via modulation of the bone marrow microenvironment. 1833 74

Our previous studies showed that EDRF1 influenced expression of alpha-globin mRNA and synthesis of hemoglobin in K562 cells and modulated self-renewal of K562 cells. To illuminate the function of EDRF1 in K562 cells, sense and antisense EDRF1 constructs were prepared and transfected into K562 cells. By using microarray and dot blot assay, 60 cytokine receptors and some oncogenes sharing important functions in cell proliferation and differentiation were investigated. The results of this study demonstrated that IL-6 receptor, GM-CSF receptor, c-Jun/c-Fos, c-Myc and c-kit genes were regulated by antisense EDRF1 expression. The regulation was confirmed by RNA blot assay. GATA-1 mRNA expression was modulated by EDRF1 gene transfection. Electrophoretic mobility shift assay suggested that the DNA-binding activity of GATA-1 was remarkably inhibited in K562 cells expressing EDRF1 antisense gene. DNA binding activity of NF-E2 was at the same level as control experiment. Therefore EDRF1 may play a role in erythroid proliferation and differentiation by affecting the interaction between GATA-1 and its cis-elements.
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PMID:Antisense EDRF1 gene inhibited GATA-1 transcription factor DNA-binding activity in K562 cells. 1875 52

The presence and biological importance of DNA secondary structures in eukaryotic promoters are becoming increasingly recognized among chemists and biologists as bioinformatics in vitro and in vivo evidence for these structures in the c-Myc, c-Kit, KRAS, PDGF-A, hTERT, Rb, RET and Hif-1alpha promoters accumulates. Nevertheless, the evidence remains largely circumstantial. This minireview differs from previous ones in that here we examine the diversity of G-quadruplex and i-motif structures in promoter elements and attempt to categorize the different types of arrangements in which they are found. For the c-Myc G-quadruplex and Bcl-2 i-motif, we summarize recent biological and structural studies.
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PMID:Making sense of G-quadruplex and i-motif functions in oncogene promoters. 2067 Feb 78


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