Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.148 (Thy1)
 1,210 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human hematopoietic stem cells are thought to express the CD34 stem cell antigen, low numbers of HLA-DR and Thy1 antigens, but no lineage commitment antigens, CD38, or CD45RA antigens. However, fluorescence-activated cell sorted CD34+ subpopulations contain not more than 1% to 5% primitive progenitors capable of initiating and sustaining growth in long-term bone marrow culture initiating cells (LTBMC-ICs). We have recently shown that culture of fresh human marrow CD34+/HLA-DR- cells separated from a stromal layer by a microporous membrane ("stroma-noncontact" culture) results in the maintenance of 40% of LTBMC-ICs. We hypothesized that reselection of CD34+ subpopulations still present after several weeks in stroma-noncontact cultures may result in the selection of cells more highly enriched for human LTBMC-ICs. Fresh marrow CD34+/HLA-DR- cells were cultured for 2 to 3 weeks in stroma-noncontact cultures. Cultured progeny was then sorted on the basis of CD34, HLA-DR, or CD33 antigen expression, and sorted cells evaluated for the presence of LTBMC-ICs by limiting dilution analysis. We show that (1) LTBMC-ICs are four times more frequent in cultured CD34+/HLA-DR- cells (4.6% +/- 1.7%) than in cultured CD34+/HLA-DR- cells (1.3% +/- 0.4%). This suggests that HLA-DR antigen expression may depend on the activation status of primitive cells rather than their lineage commitment. We then sorted cultured cells on the basis of the myeloid commitment antigen, CD33. (2) These studies show that cultured CD34+/CD33- cells contain 4% to 8% LTBMC-ICs, whereas cultured CD34+/CD33+bright cells contain only 0.1% +/- 0.03% LTBMC-ICs. Because LTBMC-ICs are maintained significantly better in stroma-noncontact cultures supplemented with macrophage inflammatory protein 1 alpha (MIP-1 alpha) and interleukin-3 (IL-3) (Verfaillie et al, J Exp Med 179:643, 1994), we evaluated the frequency of LTBMC-ICs in CD34+/CD33- cells present in such cultures. (3) CD34+/CD33- cells present in MIP-1 alpha + IL-3-supplemented cultures contain up to 30% LTBMC-ICs. The increased frequency of LTBMC-ICs in cultured CD34+ subpopulations may be the result of terminal differentiation of less primitive progenitors, loss of cells that fail to respond to the culture conditions or recruitment of quiescent LTBMC-ICs. The capability to select progenitor populations containing up to 30% LTBMC-ICs should prove useful in studies examining the growth requirements, self-renewal, and multilineage differentiation capacity of human hematopoietic stem cells at the single-cell level.
 ...
PMID:CD34+/CD33- cells reselected from macrophage inflammatory protein 1 alpha+interleukin-3--supplemented "stroma-noncontact" cultures are highly enriched for long-term bone marrow culture initiating cells. 752 Jul 71

This phenotype study of uncommitted hematopoietic cells (UHC) and early T cell precursors (ETCP) in the thymus provides an understanding of the commitment process from UHC to ETCP. The study of genes that are involved in this process depends on the proper identification of these early cells. Nonetheless, most current phenotype studies of these cells are based on the observations from the late stages of fetal or adult thymocytes. Though conclusions drawn from these studies are insightful, cell maturation occurs so fast during thymus development that some important phenotypic nuances go unnoticed if one only looks at late-stage cells. Furthermore, even though early-stage thymocytes are phenotypically similar to those of late stage, they may have different properties. In order to study those thymus populations at the very beginning of their differentiation and commitment, 11-day mouse fetal thymuses were tested. This shows, using day-12 CFU-S as a measure, that at this stage of development there are UHC present. Thymocytes at this very initial stage of development are isolated for the first time, and their phenotypes as well as their differentiation potentials are analyzed. The result shows that UHC are detected only in the Mac-1- C-kit+ subset, which comprises 2% of the total thymus population. Surprisingly, 93% of the C-kit+ population is Mac-1+, which generates T cells with a frequency of 1/72. This indicates that the Mac-1 molecule is a differentiation marker rather than a lineage-specific marker. In addition, C-kit+ thymocytes at this stage do not express any T cell markers, such as Thy1.2, IL-2R alpha, CD2 and Mel-14. These thymocytes are very akin to UHC, since they express Sca-1, Wga, and CD34, and are likewise similar to ETCP, as they express Pgphigh, Mhc-Ihigh, Hsalow, and FcRlow. Moreover, they express a high level of adhesion molecules such as Lfa-1, Icam-1 and Lpam-1. As expected, these C-kit+ all contain the hematopoietic cell marker CD45. Low expression of CD4 (the typical marker associated to the earliest T cell precursor in adult thymuses) is also found in 10% of the C-kit+ population. While the C-kit+ population at this stage is more homogeneous than at any other stage of fetal thymus development, there are still markers (B220, CD5, Tsa, Mac-1, CD4, and Sca-1) that can split this population into other subsets. However, the majority of these markers are present in the Mac-1+ C-kit+ population, indicating that the C-kit+ population is essentially made of two populations (Mac-1+ and Mac-1- subsets). Interestingly, two major single-positive populations appear to emerge from this C-kit+ population one day later, namely Thy1.2+ IL-2R alpha-and Thy1.2- IL-2R alpha +. These two major single-positive populations seem to be derived directly from the Mac-1+ rather than from the Mac-1- subset of the C-kit+ population. Thus, these data suggest that important phenotypes are present during the early differentiation process. These phenotypes have never been shown before. Hopefully, this study will open up a new avenue for the study of very early stage T cell sublineages and their relationship to uncommitted thymic hematopoietic cells.
 ...
PMID:Day 11 mouse fetal thymus: phenotype and search for the point of commitment. 892 85

The subset of blood cells that expresses both CD34 and Thy1 (CD90) cell surface molecules is enriched in hematopoietic stem cell activity and can be obtained from the peripheral blood of cancer patients after mobilization by chemotherapy and granulocyte colony-stimulating factor (G-CSF). Because transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of hematopoietic progenitor proliferation and differentiation, in this study we analyzed the impact of neutralizing TGF-beta1 activity during culture and retroviral transduction of CD34+Thy1+ cells. When purified CD34+Thy1+ cells were cultured in the presence of a neutralizing antibody against TGF-beta1, the percentage of cycling cells, proliferation, and absolute number of clonogenic progenitors were increased in comparison to the cultures performed without the addition of antibody. Antibody-mediated neutralization of TGF-beta1 during retroviral transduction performed by coculture of CD34+Thy1+ cells with a MFG-S-nlsLacZ retroviral vector-producing cell line did not affect the percentage of transduced progenitors as assessed by direct X-Gal staining of colonies in clonogenic assays. However, due to the better expansion of CD34+Thy1+ cells in the presence of anti-TGF-beta1, the absolute number of transduced progenitors recovered at the end of the culture was increased.
 ...
PMID:A neutralizing anti-TGF-beta1 antibody promotes proliferation of CD34+Thy-1+ peripheral blood progenitors and increases the number of transduced progenitors. 959 Jun 53

Efficient gene transfer into hematopoietic stem cells offers a number of potential therapeutic applications. However, the relatively low titer of retroviral supernatants and the requirement for cell division to ensure integration have meant that transduction efficiency has been low. We have modified a flowthrough approach to cell transduction and have been able consistently to increase gene transfer efficiency into human hematopoietic progenitor cells. We transduced CD34 cells with retroviral vectors encoding a truncated nerve growth factor receptor (NGFR) or neo. Retroviral supernatant was pulled through 0.2-micron polycarbonated membranes, followed by placement of cells on the filter. In the absence of cytokines, the transduction efficiency of CD34 cells with a NGFR vector was increased 3-11-fold over that obtained at an identical MOI in liquid culture to produce 11%-44% transduction. Furthermore, both Thy1+ and Thy1- subsets in a total CD34 population were transduced with similar efficiency, and transduction with a neo vector, as measured by G418 resistance in clonogenic assays, increased 1.5-5-fold. The mechanism by which gene transfer is improved may reflect colocalization of cells and retrovirus. Costaining of cells transduced on the filter with an NGFR retrovirus with both an NGFR antibody and a gp70 antibody that recognizes viral coat protein revealed high-level coexpression. The levels of in vitro gene transfer we obtain are equivalent to those observed when CD34 cells are cocultured in liquid culture with cytokines. However, culture with cytokines may commit CD34 cells to differentiation and has produced disappointingly low levels of subsequent in vivo gene transfer. Gene marking studies using distinguishable retroviral vectors will provide a means of learning whether the effects of flowthrough transduction genuinely enhance the efficiency of gene transfer to human marrow-repopulating cells.
 ...
PMID:Increased transduction efficiency of primary hematopoietic cells by physical colocalization of retrovirus and target cells. 962 Dec 55

Myelodysplastic syndrome (MDS) is believed to be a stem-cell disorder involving cytopenia and dysplastic changes in three hematopoietic lineages. However, the involvement of pluripotent stem cells and progenitor cells has not been clarified conclusively. To address this issue, we used fluorescence in situ hybridization (FISH) of blood and bone marrow (BM) smears for mature cells and FISH of cells sorted by fluorescence-activated cell sorting for progenitor cells. Seven patients with MDS associated with trisomy 8 were studied. FISH showed +8 in granulocytes, monocytes, and erythroblasts, but not in lymphocytes. Sorted cells of T (CD3(+)), B (CD19(+)), and NK cells (CD3(-)CD56(+)) from peripheral blood did not contain +8, nor did CD34(+) subpopulations from BM including B (CD34(+)CD19(+)), T/NK (CD34(+)CD7(+)) progenitors, and pluripotent stem cells (CD34(+)Thy1(+)). The +8 chromosome abnormality was identified in stem cells only at the level of colony-forming unit of granulocyte-erythrocyte-macrophage-megakaryocyte (CFU-GEMM; CD34(+)CD33(+)). It may thus be concluded that cells affected by trisomy 8 in the context of MDS are at the CFU-GEMM level and that cells of lymphoid lineage are not involved. These results provide new insights into the biology of MDS and suggest that intensive chemotherapy and autologous BM transplantation may become important therapeutic strategies.
 ...
PMID:Fluorescence in situ hybridization of progenitor cells obtained by fluorescence-activated cell sorting for the detection of cells affected by chromosome abnormality trisomy 8 in patients with myelodysplastic syndromes. 976 74

Transplantation of genetically marked donor cells in mice have unambiguously identified individual clones with full differentiative potential in all lymphoid and myeloid pathways. Such evidence has been lacking in humans because of limitations inherent to clonal stem cell assays. In this work, we used single cell cultures to show that human cord blood (CB) contains totipotent CD34(+) cells capable of T, B, natural killer, and granulocytic cell differentiation. Single CD34(+) CD19(-)Thy1(+) (or CD38(-)) cells from fresh CB were first induced to proliferate and their progeny separately studied in mouse fetal thymic organotypic cultures (FTOCs) and cocultures on murine stromal feeder layers. 10% of the clones individually analyzed produced CD19(+), CD56(+), and CD15(+) cells in stromal cocultures and CD4(+)CD8(+) T cells in FTOCs, identifying totipotent progenitor cells. Furthermore, we showed that totipotent clones with similar lymphomyeloid potential are detected in the bone marrow of nonobese diabetic severe combined immunodeficient (NOD-SCID) mice transplanted 4 mo earlier with human CB CD34(+) cells. These results provide the first direct demonstration that human CB contains totipotent lymphomyeloid progenitors and transplantable CD34(+) cells with the ability to reconstitute, in the marrow of recipient mice, the hierarchy of hematopoietic compartments, including a compartment of functional totipotent cells. These experimental approaches can now be exploited to analyze mechanisms controlling the decisions of such primitive human progenitors and to design conditions for their ampification that can be helpful for therapeutic purposes.
 ...
PMID:Identification of lymphomyeloid primitive progenitor cells in fresh human cord blood and in the marrow of nonobese diabetic-severe combined immunodeficient (NOD-SCID) mice transplanted with human CD34(+) cord blood cells. 1033 Apr 39

Fanconi anemia (FA) is a complex recessive genetic disease that causes bone marrow failure in children. The mechanism by which the gene for FA group C (Fancc) impinges on the normal hematopoietic program is unknown. Here we demonstrate that the bone marrow from Fancc-/- mice have reduced ability for primary and secondary long-term reconstitution of myeloablated recipients compared to wild-type or heterozygous mice, indicating that the Fancc gene product is required for the maintenance of normal numbers of hematopoietic stem cells. Long-term and secondary transplant studies suggested that there also were qualitative changes in their developmental potential. Consistent with the reduction in reconstitution, flow cytometric analysis of the primitive subfractions of hematopoietic cells obtained from the bone marrow of Fancc -/- mice demonstrated that they contained 40 to 70% fewer lineage-negative (Lin-)Thy1.2-/lowScal(+) c-Kit(+)CD34+ cells compared to controls. In contrast, the number of Lin Thy1.2-/ lowScal(+)c-Kit CD34(-)cells was comparable to that of wild-type mice. The differential behavior of Lin(-)Thy1.2-/lowScal+c-Kit+CD34+ and Lin(-)Thy1.2-/lowScal(+)c-Kit CD34 subfractions also was observed in mice treated with the DNA cross-linking agent mitomycin C(MMC). Fancc-/- mice treated with MMC had an 92% reduction of CD34 cells as compared to Fancc+/+ mice. The number of CD34 cells only was reduced about 20%. These results suggest that the Fancc gene may act at a stage of primitive hematopoietic cell development identified by CD34 expression.
 ...
PMID:Hematopoietic compartment of Fanconi anemia group C null mice contains fewer lineage-negative CD34+ primitive hematopoietic cells and shows reduced reconstruction ability. 1056 Sep 14

Adhesion molecules on CD34(+) cells were implicated in the process of peripheral blood stem cell (PBSC) mobilization and homing. We studied the mobilization of CD34(+)Thy1(+) cells, CD34(+) very late-acting antigen (VLA)4(+) cells, and CD34(+)L-selectin(+) cells in non-Hodgkin's lymphoma patients mobilized with cyclophosphamide plus G-CSF, GM-CSF, or GM-CSF followed by G-CSF. The mean percentage of CD34(+) cells in the bone marrow (BM) expressing Thy1 was 23.6% +/- 11% and 17.8% +/- 8% in the PB before mobilization, and was markedly decreased to 4.5% +/- 3.3% in the apheresis collections. Similarly, the mean percentage of CD34(+) cells expressing L-selectin was 35.8% +/- 4.3% in the BM, 21.6% +/- 4.1% in the PB before mobilization and was markedly decreased to 9.1% +/- 2.5% in the apheresis collections. Patients in the three arms of the study had a similar pattern of CD34(+)Thy1(+) and CD34(+)L-selectin(+) cell mobilization. Also, a similar pattern of coexpression of CD34(+)Thy1(+) and CD34(+)L-selectin(+) cells was observed when the patients were regrouped as "good mobilizers" (> or =2 x 10(6) CD34(+)CD45(dim) cells/kg, in four collections) and "poor mobilizers" (<0.4 x 10(6) CD34(+)CD45(dim) cells/kg, in two collections). The mean percentage of CD34(+) cells expressing VLA-4 in the BM and PB was relatively high (73.4% +/- 12% and 65.4% +/- 6.6%, respectively) and dropped considerably in the PBSC collections to 43.5% +/- 7.1% with a similar pattern observed for patients in arms A, B, and C. However, when the patients were regrouped as "good mobilizers" and "poor mobilizers," a higher percentage of CD34(+) cells expressing VLA-4 was observed in the PBSC of the pooled "good mobilizers" (50.5% +/- 9% versus 36.3% +/- 6.4%; p = 0.01). We conclude that release of CD34(+) cells to the PB involves a general downregulation of Thy1, L-selectin and VLA-4 on CD34(+) cells, irrespective of the growth factor used for mobilization. However, good mobilizers had a relatively higher percentage of CD34(+) cells expressing the VLA-4 antigen.
 ...
PMID:Expression of adhesion molecules on CD34(+) cells in peripheral blood of non-hodgkin's lymphoma patients mobilized with different growth factors. 1123 68

It is shown that the tetraspanin CD9 has a complex pattern of distribution in hematopoietic cells and is heterogeneously expressed on human bone marrow CD34(+) cells. CD34(high)CD38(low)Thy1(+) primitive progenitors are contained in the population with intermediate CD9 expression, thus suggesting that CD9 expression may precede CD38 appearance. Cell sorting shows that colony-forming unit (CFU)-GEMM and CFU-GM are present in high proportions in this fraction and in the fraction with the lowest CD9 expression. Cells with the highest level of CD9 are committed to the B-lymphoid or megakaryocytic (MK) lineages, as shown by the co-expression of either CD19 or CD41/GPIIb and by their strong potential to give rise to CFU-MK. In liquid cultures, CD9(high)CD41(neg) cells give rise to cells with high CD41 expression as early as 2 days, and this was delayed by at least 3 to 4 days for the CD9(mid) cells; few CD41(high) cells could be detected in the CD9(low) cell culture, even after 6 days. Antibody ligation of cell surface CD9 increased the number of human CFU-MK progenitors and reduced the production of CD41(+) megakaryocytic cells in liquid culture. This was associated with a decreased expression of MK differentiation antigens and with an alteration of the membrane structure of MK cells. Altogether these data show a precise regulation of CD9 during hematopoiesis and suggest a role for this molecule in megakaryocytic differentiation, possibly by participation in membrane remodeling. (Blood. 2001;97:1982-1989)
 ...
PMID:CD9 and megakaryocyte differentiation. 1126 62

Introduction of foreign genes into human CD34(+) hematopoietic precursor cells offers a means to correct inborn errors or to protect human stem cells from chemotherapeutic damage. Electroporation is a non-chemical, nonviral, highly reproducible means to introduce foreign genes into mammalian cells that has been used primarily for rapidly dividing cells. CD34(+) cells isolated from mobilized peripheral blood of patients were cultured for 48 h in serum-free culture medium supplemented with Flt-3 ligand, stem cell factor and thrombopoietin. Cell cycle analysis showed an increase in % S-phase from 2% on day 0 to 28% on day 2 without significant loss of mean fluorescence intensity (MFI). Optimal electroporation conditions for CD34(+) cells were 550 V/cm, 38 ms, 30 microg DNA/500 microl at cell densities between 0.2 x 10(6) and 10 x 10(6) cells/ml resulting in transient EGFP gene expression in 21% (+/- 1%) of CD34(+) precursor cells, as determined by flow cytometry 48 h after electroporation. The more primitive cells were also found to be EGFP(+) as determined by subset analysis using Thy1, CD38, AC133 and c-kit conjugated monoclonal antibodies. Methylcellulose assays on electroporated CD34(+) cells yielded 20% (+/- 7%) EGFP(+) colonies (CFU-GM, BFU-E and CFU-mix) and 22% (+/- 5%) EGFP(+) long-term colony-initiating cells (LTC-IC). The reporter gene was found to be integrated into the LTC-IC genomic DNA as determined by inverse PCR and DNA sequencing. These results suggest that electroporation has the potential to effectively and stably deliver exogenous genes into human hematopoietic precursor cells.
 ...
PMID:Efficient expression of foreign genes in human CD34(+) hematopoietic precursor cells using electroporation. 1131 15


1 2 3 Next >>