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Macrophage lineage switching of murine early pre-B lymphoid cells expressing transduced fms genes.

fms genes encoding either wild-type or constitutively activated colony-stimulating factor 1 receptors (CSF-1R) were introduced by retroviral infection into long-term mouse lymphoid cultures. Four early pre-B-cell lines transformed by the feline v-fms oncogene underwent spontaneous and irreversible differentiation to macrophages when transferred from RPMI 1640 to Iscove modified Dulbecco medium. Expression of wild-type human CSF-1R in early pre-B cells conferred no proliferative advantage unless human CSF-1 was added to the culture medium. A clonal, factor-dependent early pre-B-cell line (D1F9), selected for continuous growth on NIH 3T3 cell feeder layers producing human CSF-1, could be maintained in RPMI 1640 medium containing interleukin-7 (IL-7) but also differentiated to macrophages when grown in Iscove modified Dulbecco medium containing human CSF-1. The macrophages retained parental immunoglobulin gene rearrangements and proviral insertions, lost B-cell antigens, expressed butyrate esterase and MAC-1, were actively phagocytic, and no longer survived in IL-7. Unlike factor-independent v-fms transformants, the irreversible commitment of D1F9 cells to differentiate in the macrophage lineage could be suppressed by IL-7, depended on human (but not mouse) CSF-1, and was inhibited by an antibody to human CSF-1R. Signals mediated by transduced CSF-1R can therefore play a deterministic role in cell differentiation.

Animals↗

Biological consequences of a point mutation at codon 969 of the FMS gene.

The FMS proto-oncogene encodes the cell surface receptor for colony stimulating factor-1 (CSF-1). Mutations of the FMS gene at codon 969, in the C-terminal region of the gene, have been detected in haematological malignancies. To ascertain the biological significance of a mutation at this codon, we have used a murine haematopoietic cell line, FDC-P1, containing a mutation at codon 969 that results in a phenylalanine replacing a tyrosine. FMS 969 mutant cells and v-fms transfected cells conferred interleukin 3 (IL-3) independent stimulation of FDC-P1 cells, whereas cells transfected with a wild-type FMS construct required exogenous IL-3 for growth. FDC-P1 cells containing a FMS 969 mutation and v-fms transfected cells were tumorigenic in nude mice. Binding studies with radioidonated CSF-1 revealed saturable specific binding in FMS wild-type cells with a Km of 0.9 mM; however, mutant FMS-containing cells did not display saturation kinetics, but instead exhibited a linear relationship between ligand concentration and amount bound. Constitutive expression of FOS was detected in 969 mutant cells in the absence of exogenous CSF-1, a phenotype that was only inducible in wild-type cells in response to CSF-1. FOS and JUNB expression by v-FMS transfected cells showed a similar pattern to FMS wild-type cells. This mutation has been detected in patients with haematological malignancies, and illustrates that the pathway of FMS 969 phenylalanine mutations and v-fms induced pathogenesis can be distinguished. These data indicate that there is a biological role for FMS codon 969 phenylalanine mutation which results in transformation of FDC-P1 cells.

Animals↗

[Mapping of cloned fragments of the macrophage-stimulating factor receptor gene (FMS) from a non-amplified library of human leukocyte genes].

For investigation of FMS gene polymorphism and mutations that reveal functionally meaning in leukemia and myelodysplastic disorders the overlapping recombinants lambda-clones inserted by FMS gene fragments have been obtained from human leukocyte genomic library in the EMBL 3A phage by using oligonucleotide prode (27 nucleotides) based on 12 exon of the FMS gene. 15 DNA probes were prepared by subcloning the lambda-clones obtained in the pBSKS+ plasmid. The probes obtained allow to analyse extracellular, transmembrane and tyrosine kinase regions of the FMS gene independently.

Cloning, Molecular↗

Isolation of new oncogenic forms of the murine c-fms gene.

The c-fms gene encodes the receptor for the macrophage colony-stimulating factor, which plays a key role in the proliferation and differentiation of cells of the myelomonocytic lineage. In order to study the effects of overexpression of the macrophage colony-stimulating factor receptor in hematopoietic cells, a Harvey sarcoma virus-derived retroviral vector containing the murine c-fms cDNA was pseudotyped with Friend murine leukemia virus and inoculated into newborn DBA/2 mice. This viral complex induced monoclonal or oligoclonal leukemias with a shorter latency than that for Friend murine leukemia virus alone. Unexpectedly, 60% of the integrated fms proviruses had deletions at the 5' end of the c-fms gene. Sequence analysis of seven mutant proviruses indicated that the deletions always included the c-fms ligand binding domain and either occurred within the c-fms sequences, leaving the fms open reading frame unchanged, or joined VL30 sequences located at the 5' end of the parental retroviral vector to internal c-fms sequences, resulting in truncated fms proteins devoid of the canonical signal peptide. In contrast to all tyrosine kinase receptors transduced in retroviruses, no helper gag- or env-derived sequences were fused to the rearranged fms sequences. Viral supernatants isolated from hematopoietic tumors with viruses with deletions were able to transform NIH 3T3 cells as efficiently as parental fms virus, indicating that deletions resulted in constitutive activation of the c-fms gene. These oncogenic variants differ from those transduced in the Suzan McDonough strain of feline sarcoma viruses (L. Donner, L. A. Fedele, C. F. Garon, S. J. Anderson, and C. J. Sherr, J. Virol. 41:489-500, 1982). The high rate of c-fms rearrangement and its relevance in the occurrence of hematopoietic tumors are discussed.

3T3 Cells↗

Allelic loss of the FMS gene in acute myeloid leukaemia.

The FMS proto-oncogene encodes for the colony stimulating factor-1 receptor expressed on monocytes and B lymphocytes within the peripheral blood system. Allelic loss of the FMS gene occurs in patients with refractory anaemia and the 5q- syndrome associated with the myelodysplastic syndromes. To determine the frequency of FMS gene loss in patients with myeloid malignancy, 50 DNA samples from patients with acute myeloid leukaemia (AML) and 30 samples from haematologically normal samples were analysed using a quantitative Southern blotting technique. Allelic loss of one allele (hemizygous) was detected in five of 18 samples of AM-M4 and eight of 27 samples of AML M1, M2 and M3. In addition, loss of both FMS alleles (homozygous) was demonstrated in three of 18 samples of AML M4 and 0127 samples of AML M1, M2 and M3. One patient with AML M5 and one with AML M6 were assessed although no allelic loss of FMS was detected. Three samples from patients with secondary AML were also analysed and hemizygous loss was detected in one case. Homozygous or hemizygous loss of FMS was not detected in any of 30 DNA samples isolated from haematologically normal individuals. These data indicate that loss of the FMS gene is common in AML, with an increased frequency in those patients with AML subtype M4.

Aged↗

The fms gene and the CSF-1 receptor.

The c-fms proto-oncogene encodes an integral transmembrane glycoprotein with tyrosine specific protein kinase activity whose properties resemble those of receptors for polypeptide growth factors. The relatively restricted expression of the feline c-fms gene in mononuclear phagocytes (peripheral blood monocytes and tissue macrophages) and their committed bone marrow progenitors suggested that c-fms encoded a receptor for a macrophage specific growth factor. We found that the receptor for the mononuclear phagocyte colony stimulating factor, CSF-1 (M-CSF), is biochemically and immunologically related to the c-fms gene product, consistent with the hypothesis that c-fms is identical to the CSF-1 receptor gene (Sherr et al, 1985). Although the activity of CSF-1 has been defined through its action on haemopoietic cells, the c-fms gene is expressed in human placenta (Müller et al, 1983a) and in human choriocarcinoma cell lines derived from placental trophoblasts (Müller et al, 1983b). The latter cell lines exhibit binding sites for CSF-1, suggesting that this colony stimulating factor might also have an embryological role in placental development. The retroviral oncogene v-fms is a potent fibroblast transforming gene, whereas c-fms can be expressed at relatively high levels in certain normal tissues without causing neoplastic transformation. The glycoprotein encoded by v-fms is closely related to the c-fms gene product but differs at its extreme carboxy terminal end. Because v-fms, like c-fms, encodes a competent ligand binding domain, cells producing the v-fms gene product acquire the ability to bind CSF-1. Moreover, many fibroblast cell lines susceptible to transformation by v-fms produce the growth factor. Although this raises the possibility that v-fms transforms cells by an autocrine mechanism, antibodies to epitopes in the v-fms-coded ligand binding domain that interfere with CSF-1 binding, or antibodies to CSF-1 itself, do not affect the transformed phenotype. In membrane preparations, tyrosine-specific phosphorylation of the v-fms product appears to be constitutive, whereas in vitro phosphorylation of the c-fms-coded glycoprotein on tyrosine is enhanced in the presence of CSF-1. These results are most compatible with the possibility that critical alterations in the 3' coding region of the c-fms gene activate its kinase activity and unmask its latent transforming potential. An implication of these findings is that chromosomal rearrangements affecting c-fms could contribute to myeloid leukaemogenesis.

Animals↗

A two-step, PU.1-dependent mechanism for developmentally regulated chromatin remodeling and transcription of the c-fms gene.

Hematopoietic stem cells and multipotent progenitors exhibit low-level transcription and partial chromatin reorganization of myeloid cell-specific genes including the c-fms (csf1R) locus. Expression of the c-fms gene is dependent on the Ets family transcription factor PU.1 and is upregulated during myeloid differentiation, enabling committed macrophage precursors to respond to colony-stimulating factor 1. To analyze molecular mechanisms underlying the transcriptional priming and developmental upregulation of the c-fms gene, we have utilized myeloid progenitors lacking the transcription factor PU.1. PU.1 can bind to sites in both the c-fms promoter and the c-fms intronic regulatory element (FIRE enhancer). Unlike wild-type progenitors, the PU.1(-/-) cells are unable to express c-fms or initiate macrophage differentiation. When PU.1 was reexpressed in mutant progenitors, the chromatin structure of the c-fms promoter was rapidly reorganized. In contrast, assembly of transcription factors at FIRE, acquisition of active histone marks, and high levels of c-fms transcription occurred with significantly slower kinetics. We demonstrate that the reason for this differential activation was that PU.1 was required to promote induction and binding of a secondary transcription factor, Egr-2, which is important for FIRE enhancer activity. These data suggest that the c-fms promoter is maintained in a primed state by PU.1 in progenitor cells and that at FIRE PU.1 functions with another transcription factor to direct full activation of the c-fms locus in differentiated myeloid cells. The two-step mechanism of developmental gene activation that we describe here may be utilized to regulate gene activity in a variety of developmental pathways.

Animals↗

Frequent rearrangements of retinoic acid receptor alpha gene and myl gene, and rare mutations of RAS and FMS genes in acute promyelocytic leukemia.

To investigate leukemogenesis of acute promyelocytic leukemia (APL), we studied the involvements of retinoic acid receptor alpha (RAR alpha) and myl genes, and also the frequency of N-RAS, K-RAS, H-RAS, and FMS point mutations in sixteen patients with APL. By Southern blot analysis, the rearrangements of RAR alpha gene were detected in 13 patients (81.2%), and myl gene in 14 (87.5%). Either RAR alpha or myl gene rearrangements were found in all patients including one with normal karyotype. Breakpoints of both genes were clustered. By direct sequencing, no point mutations were found at codons 12, 13, and 61 of N-, K-, and H-RAS genes, and at codons 301 and 969 of FMS gene. These data indicate that myl-RAR alpha translocation occurs frequently in APL, whereas RAS and FMS mutations are rare in APL. It may be suggested that leukemogenesis of APL is different from other subtypes of acute myelogenous leukemia, and multistep leukemogenesis may not be a prevalent feature in APL.

Adolescent↗

Antibodies to distal carboxyl terminal epitopes in the v-fms-coded glycoprotein do not cross-react with the c-fms gene product.

The product of the v-fms oncogene is an integral transmembrane glycoprotein that is closely related to the cell surface receptor for the macrophage colony stimulating factor, CSF-1. A fragment of the v-fms gene encoding a major portion of the extracellular amino terminal domain, the membrane-spanning segment, and the entire carboxyl terminal tyrosine kinase domain of the glycoprotein was molecularly cloned into an inducible prokaryotic expression plasmid. Polypeptide products consisting only of v-fms-coded amino acids were produced in bacteria and were used to prepare immune reagents that precipitated the v-fms-coded glycoproteins expressed in transformed cells. Whereas rabbit antisera to recombinant polypeptides detected antigenic determinants of the c-fms proto-oncogene product, seven mouse monoclonal antibodies to these same antigens reacted only with v-fms-specific epitopes. Proteolytic mapping experiments and studies with a mutant v-fms-coded glycoprotein lacking the 37 carboxyl terminal amino acids of the wild-type product showed that the monoclonal antibodies were restricted in their reactivity to epitopes at the extreme carboxyl terminus of the glycoprotein. The v-fms and c-fms gene products must differ significantly in this region.

Amino Acid Sequence↗

Alteration of the c-fms gene in a blood sample from a Thorotrast individual.

We analyzed six different tissue DNA samples from a leukemic individual who received an injection of Thorotrast for alterations in proto-oncogene or tumor-suppressor gene structure. Our examination of the DNA indicated an alteration of the c-fms gene in the blood sample from this individual. This locus showed a deletion in which the 3' end of the deleted region maps between exons 11 and 12. In this particular case, the type of leukemia is unknown but myeloid leukemia is a neoplasm associated with individuals injected with Thorotrast. It is possible that the alteration in the c-fms gene of this individual is a consequence of the radiation exposure. No apparent alterations in the c-mos gene were observed in any of the tissues from the individual. This is in contrast to previous studies that described alterations in methylation patterns associated with the c-mos locus in radium-exposed individuals. A number of the individuals exposed to radium also had alterations of the retinoblastoma gene while no such alterations were observed in any tissue DNA samples from this Thorotrast case. It is possible that our inability to detect alterations of the c-mos and retinoblastoma gene may be attributable to the nature of alpha-emitting radionuclides or their distribution, or to the limited set of tissues available for analysis.

Aged↗

Human-fms gene is retained in acute lymphoblastic leukemia cells with del(5)(q32).

Cytogenetic and molecular investigations of NALM 6 cells (a pre-B-lymphoblastic acute leukemia cell line) revealed them to contain both alleles of the c-fms gene, though the cells had chromosomal changes of 5q- and 12p+. The amount of DNA fragments hybridized to the 1.4 kb PstI/PstI v-fms probe in the NALM 6 cells was approximately the same, when compared with cells of an Epstein-Barr virus-transformed lymphoblastoid cell line with a normal karyotype. Chromosome banding analysis revealed that the breakpoint of the 5q- in the NALM 6 cells was at the proximal portion of the 5q32 band. Chromosomal in situ hybridization of NALM 6 cells showed a significant accumulation of grains on the terminal portions of the abnormal 5q- chromosomes (5q32), as well as on the normal chromosomes #5 with a peak at 5q32-q33. These findings indicate that the human c-fms gene is not deleted in the lymphoblastic leukemia cells with a 5q- studied by us and that it does not show rearrangement or amplification. Thus, the results indicate that a difference in the dosage of the c-fms gene in acute lymphoblastic leukemia cells with the 5q- versus that in cells with the 5q- change in nonlymphocytic neoplasia; in the latter a hemizgosity of the c-fms gene has been suggested.

Cell Line↗

[Detection of two polymorphic sites in the human c-fms gene: allele frequency and genotype in some populations of Russia].

Two polymorphic sites were found in the human c-fms gene: one (G-->A) was in position 34,047 in the last intron, and the other (dinucleotide TC-->CA) was in positions 34,293 and 34,294 in the 3'-untranslated gene region, 34 bp downstream of the translation stop codon. The polymorphic dinucleotide appeared to be immediately upstream of an octamer showing 100% homology to cis element -CAAACTTC-, which is responsible for controlled instability of mRNAs of several genes. Based on these data, functional significance was assumed for this polymorphism of the c-fms gene. Allele frequencies were established for several populations. The mutant allele of the polymorphism located in the intron were detected only in one family of ethnic Germans from the Altaiskii krai. Polymorphism of the second site, which is in the 3'-untranslated region of the c-fms gene, was observed in all Caucasoid and Mongoloid populations examined. Frequency of the rare allele varied from 19.7-25% in Arctic Mongoloids to 31-42.6% in Central Asian Mongoloids and was similar in two Caucasoid populations (22.6% in ethnic Russians and 26.5% in ethnic Germans). The wide distribution of the mutant allele in human populations of the two races was considered indicative of an adaptive role of the polymorphism in providing a certain level of the gene product, a receptor, in certain cell processes.

Alleles↗

Inhibition of phorbol ester-induced monocytic differentiation and c-fms gene expression by dexamethasone: potential involvement of arachidonic acid metabolites.

The treatment of human U-937 leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with induction of monocytic differentiation. However, the signaling pathways responsible for induction of the differentiated monocytic phenotype remain unclear. The present studies demonstrate that dexamethasone blocks TPA-induced U-937 cell growth inhibition, adherence, and alpha-naphthyl acetate esterase staining. The results also demonstrate that dexamethasone inhibits the appearance of c-fms transcripts associated with TPA treatment. Run-on transcription assays demonstrated that the c-fms gene is transcriptionally active in uninduced U-937 cells and that the rate of transcription is unchanged after dexamethasone and/or TPA treatment. These findings indicated that TPA increases c-fms expression by a dexamethasone-sensitive posttranscriptional mechanism. Treatment of U-937 cells with TPA was also associated with stimulation of arachidonic acid metabolism. Furthermore, dexamethasone, an inhibitor of phospholipase A2 activity, blocked TPA-induced increases in arachidonic acid release. These findings suggested that TPA may regulate certain features of monocytic differentiation, such as c-fms gene expression, through the formation of arachidonic acid metabolites. Indomethacin, an inhibitor of cyclooxygenase, had no detectable effect on c-fms gene expression. However, the cyclooxygenase metabolite, prostaglandin E2, inhibited the TPA-induced increases in c-fms mRNA levels. Taken together, the results indicate that TPA regulates c-fms gene expression by a dexamethasone-sensitive mechanism and that c-fms mRNA levels are controlled by metabolites of the arachidonic acid pathway.

Arachidonic Acids↗

Self cloning in Micromonospora olivasterospora of fms genes for fortimicin A (astromicin) biosynthesis.

We have cloned the seven genes that are responsible for biosynthesis of the antibiotic fortimicin A (FTM A) using a recently developed self-cloning system that employes the plasmid vector pMO116 for Micromonospora olivasterospora. Five chimeric plasmids that restored FTM A production in M. olivasterospora mutants blocked at different biosynthetic steps were isolated by shotgun cloning. Secondary transformation using other non-producing mutants showed that two additional FTM A biosynthetic genes were included on these plasmids, and that at least four of the genes were clustered. Interestingly AN38-1, a non-producing mutant that had a defect in dehydroxylation of a precursor of FTM A, was complemented by the DNA fragment containing a neomycin resistance gene that had been cloned from a neomycin-producing strain (Micromonospora sp. FTM A non-producing strain) in the course of constructing the plasmid vector pMO116. These results clearly show that this novel gene cloning system in Micromonospora is of practical use.

Aminoglycosides↗

Regulation of low density lipoprotein receptor activity in Chinese hamster ovary cells transfected with the c-fms gene.

Chinese hamster ovary (CHO) cells were transfected with the human c-fms gene, which encodes the receptor for macrophage colony-stimulating factor, to examine the effects on the low density lipoprotein (LDL) receptor activity. Degradation of [125I]LDL was significantly reduced in the transfected CHO cells as compared to non-transfected cells when incubated in lipoprotein-deficient serum. Quantitative analysis of LDL receptor mRNA using a competitive PCR method demonstrated that LDL receptor suppression occurred at transcription. These findings suggest that expression of the c-fms gene is involved in the regulation of LDL receptors on macrophages.

Animals↗

Restriction fragment length polymorphism of the c-fms gene in the human oral squamous cell carcinomas.

A restriction fragment length polymorphism (RFLP) for the c-fms gene was identified in the human oral squamous cell carcinoma cell lines, Ca9-22, HSC-2 and -3. The RFLP was detected after EcoR I, BamH I and Hind III endonuclease digestion, indicating the presence of two alleles, a and b. The allele a deleted 426bp length of allele b. We determined the sequence of this deletion, that localized in intron 11 with an EcoR I site. The phenotype of Ca9-22 was aa, and the others were bb. Both phenotypes were equally expressed and the transcripts were phosphorylated in these cell lines. The distribution in the analyzed population (66 patients and normal individuals) was 3.1% homozygotic aa, 13.5% heterozygotic ab and 83.4% homozygotic bb.

Base Sequence↗