Showing papers on "Cellular differentiation published in 1992"
TL;DR: The introduction of a mutation in RAG-1 into the germline of mice via gene targeting in embryonic stem cells is described and it is shown that this mutation either activates or catalyzes the V(D)J recombination reaction of immunoglobulin and T cell receptor genes.
2,821 citations
TL;DR: For some mammalian cells, programmed death seems to occur by default unless suppressed by signals from other cells, so dependence on specific survival signals provides a simple way to eliminate misplaced cells, for regulating cell numbers and, perhaps, for selecting the fittest cells.
Abstract: Programmed cell death occurs in most animal tissues at some stage of their development, but the molecular mechanism by which it is executed is unknown. For some mammalian cells, programmed death seems to occur by default unless suppressed by signals from other cells. Such dependence on specific survival signals provides a simple way to eliminate misplaced cells, for regulating cell numbers and, perhaps, for selecting the fittest cells. But how general is this dependence on survival signals?
2,667 citations
TL;DR: It is shown that addition of bFGF to cultures in the presence of membrane-associated SF and LIF enhances the growth of PGCs and allows their continued proliferation beyond the time when they normally stop dividing in vivo.
1,299 citations
TL;DR: It is shown that human and viral IL-10 stimulate DNA replication of B lymphocytes activated either via their antigen receptor or via their CD40 antigen, and the combination ofIL-10 and IL-4 results in the secretion of the four immunoglobulin isotypes.
Abstract: Interleukin 10 (IL-10), originally identified as a TH2 helper T-cell product able to inhibit cytokine production by TH1 cells, is highly homologous to BCRF1 (viral IL-10), an open reading frame in the Epstein-Barr virus genome. Here, we show that human and viral IL-10 stimulate DNA replication of B lymphocytes activated either via their antigen receptor or via their CD40 antigen. IL-4 and IL-10 display additive effects and induce a strong increase in the number of viable cells. Moreover, IL-10 induces activated B cells to secrete large amounts of IgG, IgA, and IgM, and the combination of IL-10 and IL-4 results in the secretion of the four immunoglobulin isotypes. Thus, IL-10 may play an important role in the amplification of humoral responses.
1,253 citations
TL;DR: New insulin-secreting cell lines established from cells isolated from an x-ray-induced rat transplantable insulinoma indicate that INS-1 cells have remained stable and retain a high degree of differentiation which should make them a suitable model for studying various aspects of beta-cell function.
Abstract: New insulin-secreting cell lines (INS-1 and INS-2) were established from cells isolated from an x-ray-induced rat transplantable insulinoma. The continuous growth of these cells was found to be dependent on the reducing agent 2-mercaptoethanol. Removal of this thiol compound caused a 15-fold drop in total cellular glutathione levels. These cells proliferated slowly (population doubling time about 100 h) and, in general, showed morphological characteristics typical of native beta-cells. Most cells stained positive for insulin and did not react with antibodies against the other islet hormones. The content of immunoreactive insulin was about 8 micrograms/10(6) cells, corresponding to 20% of the native beta-cell content. These cells synthesized both proinsulin I and II and displayed conversion rates of the two precursor hormones similar to those observed in rat islets. However, glucose failed to stimulate the rate of proinsulin biosynthesis. In static incubations, glucose stimulated insulin secretion from floating cell clusters or from attached cells. Under perifusion conditions, 10 mM but not 1 mM glucose enhanced secretion 2.2-fold. In the presence of forskolin and 3-isobutyl-1-methylxanthine, increase of glucose concentration from 2.8-20 mM caused a 4-fold enhancement of the rate of secretion. Glucose also depolarized INS-1 cells and raised the concentration of cytosolic Ca2+. This suggests that glucose is still capable of eliciting part of the ionic events at the plasma membrane, which leads to insulin secretion. The structural and functional characteristics of INS-1 cells remained unchanged over a period of 2 yr (about 80 passages). Although INS-2 cells have not been fully characterized, their insulin content was similar to that of INS-1 cells and they also remain partially sensitive to glucose as a secretagogue. INS-1 cells retain beta-cell surface antigens, as revealed by reactivity with the antigangloside monoclonal antibodies R2D6 and A2B5. These findings indicate that INS-1 cells have remained stable and retain a high degree of differentiation which should make them a suitable model for studying various aspects of beta-cell function.
1,169 citations
TL;DR: It is shown that a reconstituted basement membrane (BM) can be used to culture all normal human breast epithelial cells and a subset of human breast carcinoma cells and it is proposed that the ability to sense BM appropriately and to form three-dimensional organotypic structures may be the function of a class of "suppressor" genes that are lost as cells become malignant.
Abstract: Normal human breast epithelial cells show a high degree of phenotypic plasticity in monolayer culture and express many traits that otherwise characterize tumor cells in vivo. Paradoxically, primary human breast carcinoma cells are difficult to establish in culture: most outgrowths arise from the normal tissue surrounding the tumor. These characteristics have posed major obstacles to the establishment of simple reliable criteria for mammary epithelial transformation in culture. In the present study, we show that a reconstituted basement membrane (BM) can be used to culture all normal human breast epithelial cells and a subset of human breast carcinoma cells. The two cell types can be readily distinguished by virtue of the ability of normal cells to reexpress a structurally and functionally differentiated phenotype within BM. Twelve specimens of normal breast tissue and 2 normal breast epithelial cell lines (total 14 samples) embedded in BM as single cells were able to form multicellular spherical colonies with a final size close to that of true acini in situ. Sections of mature spheres revealed a central lumen surrounded by polarized luminal epithelial cells expressing keratins 18 and 19 and sialomucin at the apical membrane. Significantly, two-thirds of normal spheres deposited a visible endogenous type IV collagen-containing BM even though they were in contact with exogenously provided BM. Growth was arrested completely within the same time period. In contrast, none of 6 carcinoma cell lines or 2 cultures of carcinoma from fresh samples (total 8 samples) responded to BM by growth regulation, lumen formation, correct polarity, or deposition of endogenous BM. These findings may provide the basis of a rapid assay for discriminating normal human breast epithelial cells from their malignant counterparts. Furthermore, we propose that the ability to sense BM appropriately and to form three-dimensional organotypic structures may be the function of a class of "suppressor" genes that are lost as cells become malignant.
1,092 citations
TL;DR: Analysis of mice carrying mutant T-cell antigen receptor (TCP) genes indicates that TCP-β gene rearrangement or expression is critical for the differentiation of CD4− CD8− thymocyte to CD4+CD8+ thymocytes, as well as for the expansion of the pool ofCD4+ CD8+ cells.
Abstract: Analysis of mice carrying mutant T-cell antigen receptor (TCP) genes indicates that TCP-β gene rearrangement or expression is critical for the differentiation of CD4− CD8− thymocytes to CD4+CD8+ thymocytes, as well as for the expansion of the pool of CD4+CD8+ cells. TCR-α is irrelevant in these developmental processes. The development of γδ T cells does not depend on either TCR-α or TCP-β.
1,059 citations
TL;DR: Data indicate that generating immortalized cell lines for repair of, or transport of genes into, the CNS may be feasible and may also provide a model for commitment and differentiation of cerebellar progenitor cells.
922 citations
TL;DR: This analysis indicates that single mammalian neural crest cells are multipotent, able to generate at least neurons and Schwann cells like their avian counterparts, and generate multipotent progeny, indicating that they are capable of self-renewal and therefore are stem cells.
897 citations
TL;DR: Data indicate that the 39-kDa membrane protein expressed on activated Th is a binding protein for CD40 and functions to transduce the signal for Th-dependent B-cell activation.
Abstract: CD40 is a B-cell surface molecule that has been shown to induce B-cell growth upon ligation with monoclonal antibodies. This report shows that triggering via CD40 is essential for the activation of resting B cells by helper T cells (Th). A soluble fusion protein of CD40 and human immunoglobulin, CD40-Ig, inhibited the induction of B-cell cycle entry, proliferation, and differentiation by activated Th1 and Th2. The ligand for CD40 was identified as a 39-kDa membrane protein that was selectively expressed on activated Th. A monoclonal antibody specific for the 39-kDa protein inhibited CD40-Ig binding and also inhibited the activation of B cells by Th. These data indicate that the 39-kDa membrane protein expressed on activated Th is a binding protein for CD40 and functions to transduce the signal for Th-dependent B-cell activation.
853 citations
TL;DR: In this paper, the differentiation of adipocytic and osteogenic cells was investigated in cultures of adult rat marrow stromal cells using morphological criteria, changes in expression of procollagen mRNAs, consistent with a switch from the synthesis of predominantly fibrillar (types I and III) to basement membrane (type IV) collagen, and the induction of expression of aP2, a specific marker for differentiation.
Abstract: The differentiation of adipocytic and osteogenic cells has been investigated in cultures of adult rat marrow stromal cells. Adipocytic differentiation was assessed using morphological criteria, changes in expression of procollagen mRNAs, consistent with a switch from the synthesis of predominantly fibrillar (types I and III) to basement membrane (type IV) collagen, and the induction of expression of aP2, a specific marker for differentiation of adipocytes. Osteogenic differentiation was assessed on the basis of changes in the abundance of the mRNAs for the bone/liver/kidney isozyme of alkaline phosphatase and the induction of mRNAs for bone sialoprotein and osteocalcin. In the presence of foetal calf serum and dexamethasone (10(-8) M) there was always differentiation of both adipocytic and osteogenic cells. When the steroid was present throughout primary and secondary culture the differentiation of osteogenic cells predominated. Conversely, when dexamethasone was present in secondary culture only, the differentiation of adipocytes predominated. When marrow stromal cells were cultured in the presence of dexamethasone in primary culture and dexamethasone and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3; 10(-8) M) in secondary culture, the differentiation of adipocytes was inhibited whereas the differentiation of osteogenic cells was enhanced, as assessed by an increase in expression of osteocalcin mRNA. The results, therefore, demonstrate an inverse relationship between the differentiation of adipocytic and osteogenic cells in this culture system and are consistent with the possibility that the regulation of adipogenesis and osteogenesis can occur at the level of a common precursor in vivo.
TL;DR: The receptor system for CNTF is surprisingly unlike those used by the nerve growth factor family of neurotrophic factors, but is instead related to those usedBy a subclass of hematopoietic cytokines.
TL;DR: Evaluation of hOP-1 effects on cell growth and collagen synthesis in rat osteoblast-enriched bone cell cultures showed that both cell proliferation andcollagen synthesis were stimulated in a dose-dependent manner and increased 3-fold in response to 40 ng of hop-1/ml.
TL;DR: Considerable evidence now supports the view that BAT and WAT are distinct organs; in addition, the existence of distinct BAT precursor cells is demonstrated by their unique ability to express the UCP gene.
Abstract: Both in animals and humans, before or after birth, angiogenesis appears to be closely coordinated in time and space with the formation of fat cell clusters. Monobutyrin, a novel fat-specific angiogenesis factor, may play a role in this process. The potential to acquire new fat cells appears to be permanent throughout life in both animals and humans, as revealed by in vitro experiments. Considerable evidence now supports the view that BAT and WAT are distinct organs; in addition, the existence of distinct BAT precursor cells is demonstrated by their unique ability to express the UCP gene. In bovine and ovine, the transformation of BAT into WAT is strongly suggested by the rapid disappearance after birth of UCP from the various BAT depots. Despite the initial cell heterogeneity of the stromal-vascular fraction, cultured stromal-vascular cells of adipose tissue are adipose precursor cells that show varying capacities for replication and differentiation, according to age and fat depot. Studies of adipose cell differentiation in vitro correspond to the sequence: adipoblast (unipotential cells)----commitment preadipose cell (preadipocyte)----terminal differentiation immature adipose cell----terminal differentiation mature adipose cell (adipocyte). Cell commitment is triggered by growth arrest and characterized by the expression of early markers (A2COL6/pOb24; clone 5; LPL), whereas only terminal differentiation of preadipocytes requires the presence of various hormones. Multiple signaling pathways have been characterized and shown to cooperate in the process of terminal differentiation. The concept that adipose cells behave as secretory cells is now emerging from in vitro data, since secretion of various proteins (LPL, adipsin, CETP) and important metabolites (fatty acids, monobutyrin, androgens, estrogens, prostaglandins) takes place both constitutively and upon hormonal stimulation. This suggests that adipose tissue participates more directly than previously thought in metabolic activities and energy balance.
Journal Article•
TL;DR: The TGF-beta s are of great interest as growth inhibitors, regulators of cell phenotype and regulators ofcell adhesion, which strongly influence the growth and phenotype of an array of cell types.
Abstract: This chapter has described some of the most salient features of the biology of the TGF-beta s. The TGF-beta s are of great interest as growth inhibitors, regulators of cell phenotype and regulators of cell adhesion. The various TGF-beta isoforms are highly conserved and display a complex pattern of interactions with multiple membrane receptor components. Activation of these receptors leads to inhibition of epithelial cell proliferation by a mechanism that may involve proteins related to the growth suppressor, RB. TGF-beta receptors are also coupled to mechanisms that control expression of differentiation commitment genes and differentiated cell functions. TGF-beta can affect cell proliferation and differentiation through indirect mechanisms involving regulation of expression of cytokines, extracellular matrix molecules and their respective receptors. These responses strongly influence the growth and phenotype of an array of cell types. Excess or reduced TGF-beta activity may contribute to the pathogenesis of certain fibrotic disorders and certain hyperproliferative disorders including cancer, respectively.
TL;DR: The results establish Islet-1 as the earliest marker of developing motor neurons, and suggest that it may be involved in the establishment of motor neuron fate.
Abstract: Motor neurons in the embryonic chick spinal cord express a homeobox gene, Islet-1, soon after their final mitotic division and before the appearance of other differentiated motor neuron properties. The expression of Islet-1 by neural cells is regulated by inductive signals from the floor plate and notochord. These results establish Islet-1 as the earliest marker of developing motor neurons. The molecular nature of the Islet-1 protein suggests that it may be involved in the establishment of motor neuron fate.
TL;DR: It is concluded that NT2 cells and NT2-N cells represent a unique model system for studies of human neurons, and a novel vehicle for the expression of diverse gene products in terminally differentiated polarized neurons.
Abstract: NTera 2/cl.D1 (NT2) cells, a human teratocarcinoma cell line, were manipulated following retinoic acid treatment to yield greater than 95% pure cultures of neuronal cells (NT2-N cells). The commitment of NT2-N cells to a stable neuronal phenotype is irreversible as judged by the lack of mitotic activity or phenotypic reversion over a period of 2 months in culture. Furthermore, NT2-N cells express a variety of neuronal markers including many neuronal cytoskeletal proteins, secretory markers, and surface markers. NT2-N cells resemble primary neuronal cultures from rodents morphologically and in density of process outgrowth and, like primary neurons, go on to elaborate processes that differentiate into axons and dendrites. This culture method yields sufficient highly differentiated postmitotic NT2-N cells for both biochemical and molecular biological studies. Indeed, when undifferentiated NT2 cells were stably transfected with a beta-galactosidase (beta-gal) expression plasmid, beta-gal expression was shown to be present in both undifferentiated NT2 and postmitotic NT2-N cells. Thus, the ability to transfect expression plasmids into undifferentiated NT2 cells will allow the introduction of normal and mutant gene products into cells that can then be induced to become stable, postmitotic human neurons. We conclude that NT2 cells and NT2-N cells represent a unique model system for studies of human neurons, and a novel vehicle for the expression of diverse gene products in terminally differentiated polarized neurons.
TL;DR: The deduced structure of the precursor of NDF indicated that it is a transmembrane protein whose extracellular portion contains an EGF-like domain that probably functions as a receptor recognition site and is released into the medium of transfected COS-7 cells in a biologically active form.
TL;DR: It is found that oncogene expression in proliferating osteoblasts contributes to the suppression of genes expressed postproliferatively, and that chromatin structure and the presence of nucleosomes contribute to three-dimensional organization of gene promoters that support synergistic and/or antagonistic activities of physiologic mediators of bone cell growth and differentiation.
Abstract: The combined application of molecular, biochemical, histochemical, and ultrastructural approaches has defined a temporal sequence of gene expression associated with development of the bone cell phenotype in primary osteoblast cultures. The peak levels of expressed genes reflect a developmental sequence of bone cell differentiation characterized by three principal periods: proliferation, extracellular matrix maturation and mineralization, and two restriction points to which the cells can progress but cannot pass without further signals. The regulation of cell growth and bone-specific gene expression has been examined during this developmental sequence and is discussed within the context of several unique concepts. These are (1) that oncogene expression in proliferating osteoblasts contributes to the suppression of genes expressed postproliferatively, (2) that hormone modulation of a gene is dependent upon the maturational state of the osteoblast, and (3) that chromatin structure and the presence of nucleosomes contribute to three-dimensional organization of gene promoters that support synergistic and/or antagonistic activities of physiologic mediators of bone cell growth and differentiation.
TL;DR: The purified protein induces phenotypic differentiation of cultured human breast cancer cells, including altered morphology and synthesis of milk components, and is proposed the name Neu differentiation factor (NDF) for p44.
TL;DR: The results suggest that neuronal precursors exist in the adult mammalian brain, but they require discrete epigenetic signals for their proliferation and differentiation.
Abstract: Cells of neuronal morphology, expressing the 150- and 200-kDa neurofilament proteins, were generated in vitro from populations of neural cells dissociated from adult (greater than 60-day-old) mouse brain. Most of these neurons arose from dividing precursors, as demonstrated by the incorporation of [3H]thymidine during the culture period and autoradiography. Neuronal production was optimal under the conditions in which precursors were initially stimulated with basic fibroblast growth factor and then exposed to medium conditioned by an astrocytic cell line, Ast-1, in serum-free medium. Few, if any, neurons arose in control cultures or in cultures kept in serum and fibroblast growth factor. These results suggest that neuronal precursors exist in the adult mammalian brain, but they require discrete epigenetic signals for their proliferation and differentiation.
TL;DR: Fyn- thymocytes were impaired at a late stage of maturation and showed limited clonal deletion to the Mls-1a self-super-antigen but not to staphylococcal enterotoxin A, implicate fyn as a critical component in TCR signaling in thymocyte and, potentially, in the process that determines T cell repertoire in the adult mouse.
TL;DR: Using a subtraction cloning approach, a set of cDNA clones from mouse neural precursor cells whose respective mRNA levels are down-regulated during the development of mouse brain are isolated and indicate that these genes may play important roles during the embryonic development and differentiation of central nervous system.
TL;DR: The lambda 5 gene is a homolog of immunoglobulin J lambda-C lambda genes, expressed specifically in immature B-lineage cells as discussed by the authors, and it is inactivated by targeted gene disruption in embryonic stem cells.
TL;DR: Although c-kit is found both on the primitive hematopoietic stem cells and progenitors, Sca-1+ cells are more primitive and respond better than ScA-1- cells to a combination of hematopolietic factors, including SCF and stromal cells.
TL;DR: An asymmetric cell division need not produce sister cells of different sizes and can produce initially identical cells with fates that differ as a consequence of subsequent cell interactions, as well as any cell division in which sister cells have different fates.
TL;DR: Biochemical purification and cDNA cloning has revealed that BSAP belongs to the family of paired domain proteins and indicates that the transcription factor BSAP may not only play an important role in B-cell differentiation but also in neural development and spermatogenesis.
Abstract: BSAP has been identified previously as a transcription factor that is expressed at early, but not late, stages of B-cell differentiation. Biochemical purification and cDNA cloning has now revealed that BSAP belongs to the family of paired domain proteins. BSAP is encoded by the Pax-5 gene and has been highly conserved between human and mouse. An intact paired domain was shown to be both necessary and sufficient for DNA binding of BSAP. Binding studies with several BSAP recognition sequences demonstrated that the sequence specificity of BSAP differs from that of the distantly related paired domain protein Pax-1. During embryogenesis, the BSAP gene is transiently expressed in the mesencephalon and spinal cord with a spatial and temporal expression pattern that is distinct from that of other Pax genes in the developing central nervous system (CNS). Later, the expression of the BSAP gene shifts to the fetal liver where it correlates with the onset of B lymphopoiesis. BSAP expression persists in B lymphocytes and is also seen in the testis of the adult mouse. All of this evidence indicates that the transcription factor BSAP may not only play an important role in B-cell differentiation but also in neural development and spermatogenesis.
TL;DR: The final part of the review on regulation of steroidogenesis includes a description of the normal physiological fluctuations in the steroid output of adrenal cortex and gonads, and provides an analysis of the relative role of enzyme levels in the determination of these fluctuations.
TL;DR: This review will discuss some of the more recent findings relevant to antioxidant enzyme regulation in bacteria and higher organisms and the full details of that regulation arc slowly coming to light.
Abstract: Free radicals generated by a partial reduction of O2 pose a serious hazard to tissues and vital organs, especially membrane lipids, connective tissues, and the nucleic acids of cells. For protection, enzymes have evolved that specifically attack O2-, hydrogen, and organic peroxides, and repair any damage incurred to DNA. With few exceptions, antioxidant enzymes are found in all aerobic and aerotolerant anaerobic organisms. Logic assumes that a basal level of antioxidant enzyme activity is maintained at all times. This may be true. Yet cells must have ways to amplify antioxidant enzyme activity to counter sudden increases in oxygen metabolites. The full details of that regulation are slowly coming to light. Bacteria possess a series of elaborate and interacting genes that can sense specific increases in intracellular H2O2 and O2-. In higher organisms, hormones and metal ion cofactors impose pre- and posttranslational control over the genetic expression of antioxidant enzymes. Furthermore, aging, cellular differentiation, and organ specificity must also be factored into the final equation in higher organisms. This review will discuss some of the more recent findings relevant to antioxidant enzyme regulation in bacteria and higher organisms.