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Biomedical subjects

M F Greaves

Publications and source records attributed to M F Greaves.

At least 73 records · Page 4Linked to original sources
PubMed1992

Clonal characteristics of acute lymphoblastic cells derived from BCR/ABL p190 transgenic mice.

The clonal and immunophenotypic characteristics of blood leukemic cells from BCR/ABL p190 transgenic mice were investigated. All cell populations evaluated in vivo and in vitro had B-lymphocyte progenitor immunophenotypes. Immunoglobulin (JH) rearrangement patterns provided evidence for clonal diversification at different sites in vivo. Multiple clones were established in vitro from two of these mice (nos. 730 and 753). These cells expressed BCR/ABL p190 protein tyrosine kinase (PTK) and were highly malignant on transfer to secondary recipients. Cells independently cloned in vitro shared identical immunophenotypes and clonal IgH rearrangements, but these were distinct from those of the dominant clones in the mouse from which they were derived. Nevertheless, in vitro clones from mouse no. 753 had an abnormal karyotype (chromosome 14 trisomy) in common with the dominant clone in blood, providing evidence for a hierarchy or clonal selection in vivo and in vitro. Two sets of in vitro clones proliferated independently of exogenous growth factors and stroma and released autocrine interleukin 7 growth factor activity. These data provide evidence for rapid divergent clonal evolution and selection of B-cell progenitors initiated by BCR/ABL p190, followed by other, secondary genetic events mirroring similar changes in the equivalent, highly malignant human leukemia Philadelphia (Ph)-positive/B-precursor acute lymphoblastic leukemia (ALL).

Animals↗
PubMed1991

The gene encoding the stem cell antigen, CD34, is conserved in mouse and expressed in haemopoietic progenitor cell lines, brain, and embryonic fibroblasts.

The human haemopoietic cell surface antigen, CD34, is a 105 - 120 kd cell surface glycoprotein whose stage-specific expression by stem cells and lineage-specific progenitor cells suggests a role in regulating early events in blood cell differentiation. A murine gene and cDNA encoding a closely homologous protein have been isolated. The gene is organized in eight exons in 22 kb of DNA. The first exon lies in a GC- and CpG-rich island. The sequence of the gene and the cDNA predict a 382 amino acid-long protein containing an N-terminal signal peptide and one transmembrane region 73 amino acids from the C-terminus. The extracellular part of the protein contains: a 140 amino acid-long-N-terminal region, 40% of whose residues are serine or threonine potential attachment sites for O-linked carbohydrate, as well as five potential attachment sites for N-linked carbohydrate. Proximal to the extracellular membrane there is a 79 amino acid-long cysteine-rich region. The homology with the human sequence is highest in the intracellular domain (90% amino acid identity) and lowest in the N-terminal region (43% amino acid identity). The protein is not homologous with any other proteins currently in the databases. The expression of the murine gene by a number of haemopoietic progenitor cell lines suggests that the CD34 function in haemopoiesis may be conserved between man and mouse. The high level of expression in a number of embryonic fibroblast cell lines and in brain imply a function outside of haemopoiesis.

Amino Acid Sequence↗
PubMed1991

Deficiency of a phosphatidylinositol-anchored cell adhesion molecule influences haemopoietic progenitor binding to marrow stroma in chronic myeloid leukaemia.

The interactions between haemopoietic progenitor cells and marrow stromal cells that are essential for the regulation of normal haemopoiesis are defective in chronic phase chronic myeloid leukaemia (CML). The presence of primitive progenitor cells (blast colony-forming cells, Bl-CFC) in the blood of patients with CML is reflected by their reduced capacity to bind to marrow derived stromal layers in vitro. Whereas normal bone marrow Bl-CFC bind irreversibly to cultured stromal layers (and none are found in normal blood), the Bl-CFC in CML bind transiently and then detach. The normal cell adhesion mechanism is partially sensitive to treatment with phosphatidylinositol-specific phospholipase C (Pl-PLC), indicating the participation of a phosphatidylinositol (Pl)-linked structure; however, when CML cells were treated with Pl-PLC it had no effect on progenitor binding. Two other Pl-linked structures, decay-accelerating factor (DAF) and lymphocyte function associated antigen-3 (LFA-3) were normally expressed on CD34 positive CML cells and normally susceptible to Pl-PLC treatment. The treatment of normal cells with Pl-PLC, to mimic the situation in CML, resulted in the indiscriminate and inefficient binding of Bl-CFC to stroma. Moreover, treatment of the normal cells with 5637 conditioned medium (CM), which contains haemopoietic growth factors, also reduced the binding capacity of normal Bl-CFC; 5637CM treatment did not alter the expression of DAF. It is proposed that a Pl-linked cell adhesion molecule (CAM) is deficient in CML as a consequence of the constitutive activation of ABL kinase whilst, in normal cells, CAMs attached in this manner are responsible for efficient adhesion to stroma and are regulated by growth factors.

Antigens, CD↗
PubMed1991

Simultaneous adult T-cell leukemia/lymphoma and sub-acute polyneuropathy in a patient from Chile.

This paper reports a case of adult T-cell leukemia/lymphoma associated with human T-cell lymphotropic virus type I (HTLV-I) diagnosed in a Chilean patient who developed after 1 1/2 years a crisis with a progressive sensorimotor polyneuropathy. Serum and cerebrospinal fluid HTLV-I antibody tests were positive and HTLV-I DNA was clonally integrated in peripheral lymphocytes. This case is unusual in having simultaneous neurological disease. Along with other recent data from South America, this suggests that the endemic area of HTLV-I may spread far beyond the Caribbean area.

Adult↗
PubMed1990

Expression of the CD34 gene in vascular endothelial cells.

All seven of a set of CD34 monoclonal antibodies that recognize epitopes on an approximately 110 Kd glycoprotein on human hemopoietic progenitor cells also bind to vascular endothelium. Capillaries of most tissues are CD34 positive, as are umbilical artery and, to a lesser extent, vein, but the endothelium of most large vessels and the endothelium of placental sinuses are not. Angioblastoma cells and parafollicular mesenchymal cells in fetal skin are also CD34 positive, as are some stromal elements. An approximately 110 Kd protein can be identified by Western blot analysis with CD34 antibodies in detergent extracts of freshly isolated umbilical vessel endothelial cells, and CD34 mRNA is present in cultured umbilical vein cells as well as other tissues rich in vascular endothelium (breast, placenta). These data indicate that the binding of CD34 antibodies to vascular endothelium is to the CD34 gene product, and not to crossreactive epitopes. Despite the presence of CD34 mRNA in cultured, proliferating endothelial cells, the latter do not bind CD34 antibodies. In addition, CD34 antigen cannot be upregulated by growth factors. We conclude that under these conditions, CD34 protein is downregulated or processed into another form that is unreactive with CD34 antibodies. Electron microscopy of umbilical artery, breast, and kidney capillary vessels reveals that in all three sites, CD34 molecules are concentrated on membrane processes, many of which interdigitate between adjacent endothelial cells. However, well-established endothelial cell contacts with tight junctions are CD34 negative. CD34 may function as an adhesion molecule on both endothelial cells and hematopoietic progenitors.

Antibodies, Monoclonal↗
PubMed1990

Cell interactions and gene expression in early hematopoiesis.

As part of an investigation of the mechanisms controlling gene expression during lineage commitment, we have investigated the transcriptional status of hematopoietic lineage-specific genes and the interactions of early hematopoietic progenitor cells with stromal cells of the marrow microenvironment. The results indicate that a subset of otherwise lineage-restricted genes are transcriptionally active and/or DNAse I hypersensitive (i.e., "primed" for transcription) in multipotent, interleukin 3-dependent hematopoietic cells, and that they may become inaccessible and transcriptionally silent when cells are induced to adopt a single lineage during commitment. The external influences regulating gene expression in hematopoietic cells include binding interactions with stromal cells and exposure to locally presented growth factors. These interactions are thought to be essential for hematopoietic cell development and may be dysregulated in chronic myeloid leukemia.

Animals↗
PubMed1990

Leukocyte antigen CD34 is expressed by a subset of cultured endothelial cells and on endothelial abluminal microprocesses in the tumor stroma.

It has been reported that the human haemopoietic progenitor cell antigen CD34 is also expressed by vascular structures. To investigate its precise vascular localization, we have studied the cellular and subcellular distribution of CD34 in normal tissues and pathologic tissues with neovascularization. In normal resting tissues, anti-CD34 antibodies, ICH3 and QBEND-10 predominantly stain the luminal endothelial membrane, whereas the abluminal membrane is negative or weakly positive. In contrast, a striking staining of endothelial abluminal microprocesses (EAM) was found in the tumor stroma. These structures, measuring up to 20 microns in length, could be observed in thick vibratome sections both at the tips of vascular sprouts and, also frequently, on fully formed microvessels. The number of vascular sprouts and EAM varied widely between different tumors. CD34-stained EAM were sparsely present in fetal tissue of 10 weeks gestation, but they could not be demonstrated in granulation tissue of wound healing. By immunoelectron microscopy, the EAM were continuous with the cytoplasm of endothelial cells showing an immature phenotype as seen in regeneration. In cultured human umbilical vein endothelium, CD34 was preferentially found on a small subset of cells with the morphologic appearance of migrating cells. These findings suggest that CD34 is an endothelial marker for EAM present during angiogenesis.

Antibodies, Monoclonal↗
PubMed1990

Hemopoietic progenitor cell binding to the stromal microenvironment in vitro.

Primitive clonogenic progenitor cells in human bone marrow bind to preformed marrow-derived stromal layers in vitro and generate colonies of blast cells. The binding interaction does not require calcium or magnesium ions and occurs equally well in serum-free and serum-supplemented culture medium. It does not appear to involve known cell adhesion molecules (CAMs) for which monoclonal antibodies are available (integrins, N-CAM, LFA-1, and ICAM-1), and we were unable to demonstrate a role for the progenitor cell antigen CD34 in progenitor cell adhesion to cultured stroma. The CAM expressed by the blast colony-forming cells may exist in transmembrane or phosphatidylinositol (PI)-linked forms because it is only partially degraded by exposure to trypsin or to PI-specific phospholipase C. However, binding of these cells to stroma is not prevented in the presence of monoclonal antibodies reacting with known PI-linked structures (Thy-1, CD14, and CD16). It is either masked by neuraminidase-sensitive residues or is no longer expressed as cells mature, respectively, along the granulocytic or erythroid lineages. The properties of the hemopoietic progenitor CAM are discussed with reference to the properties of other CAMs and of hemopoietic progenitor cell markers.

Antibodies, Monoclonal↗
PubMed1988

Cell lineage specificity of chromatin configuration around the immunoglobulin heavy chain enhancer.

As tested by DNase I hypersensitivity, the chromatin structure of the IgH enhancer region in human B cell precursor cell lines is in an open or accessible conformation. All T cell lines, with either germline or rearranged IgH genes, were also hypersensitive to DNase I but in contrast to B cell precursors showed no detectable Cmu expression. Normal thymocytes similarly had a hypersensitive IgH enhancer site. In contrast to lymphoid cells, all myeloid cell lines tested, as well as normal granulocytes, were not DNase I hypersensitive and did not express Cmu. A putative lymphomyeloid progenitor cell line KG1, although having a germline configuration of Ig genes, produced Cmu transcripts and was hypersensitive to DNase I in the IgH enhancer region. After induction of myeloid differentiation the Ig enhancer region of KG1 cells is no longer hypersensitive or transcriptionally active. Two HhaI restriction sites on either side of the IgH enhancer were not methylated in all Cmu-expressing lines but methylated in non-expressing cell lines. These results show that an open chromatin structure around the heavy chain enhancer is necessary but insufficient for initiating transcription from unrearranged IgH genes and further suggests this region may be in an open or accessible configuration prior to lineage commitment and closed following adoption of the myeloid lineage.

Blotting, Northern↗