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Macrophages and stromal cells phagocytose apoptotic bone marrow-derived B lineage cells.

It has been hypothesized that B cell precursors that undergo programmed cell death due to nonproductive Ig gene rearrangements are cleared from the bone marrow by macrophages. However, a role for macrophages in this process is supported only by micrographs showing their association with apoptotic-appearing, B lineage cells. Functional data demonstrating phagocytosis of apoptotic, bone marrow lymphocytes by macrophages have not been presented, nor have receptors potentially involved in that process been identified. The data in this report demonstrate that macrophages isolated from murine bone marrow efficiently phagocytose apoptotic murine B lineage cells using multiple receptors that include CD14, integrins, class A scavenger receptor, and CD31 (PECAM-1). In addition, the results further reveal a new role for the hemopoietic microenvironment in B cell development in view of data demonstrating that murine bone marrow stromal cells are also capable of clearing apoptotic cells via an integrin-dependent mechanism.

Animals↗

A novel cell surface molecule on early B-lineage cells.

B cells and their antibody-secreting progeny represent one of several differentiation pathways that haematopoietic stem cells (HSC) may enter. Cells representing intermediate stages between HSC and B cells have been identified in mammalian haematopoietic tissues and studied intensively over the past decade. This population of early B-lineage cells, termed pre-B, is characterized by cellular proliferation and an orderly cascade of immunoglobulin gene rearrangements, a combination of events leading to the generation of clonally diverse B cells which then migrate to peripheral lymphoid tissues. It remains to be determined what elements determine the polyclonal growth of pre-B cells, how immunoglobulin gene rearrangements are regulated, and what happens to pre-B cells undergoing 'non-productive' immunoglobulin gene rearrangements. These issues could be resolved more easily if early B-lineage cells could be identified precisely and isolated. Here, we describe a cell surface glycoprotein that is selectively expressed by pre-B and newly formed B cells in murine haematopoietic tissues. The molecule, a homodimer formed by disulphide-linked chains of relative molecular mass (Mr) 140,000, is identified by a mouse monoclonal alloantibody called BP-1.

Animals↗

Cell lineage ablation in transgenic mice by cell-specific expression of a toxin gene.

A method of deleting specific cell lineages has been developed that entails microinjection into fertilized eggs of a chimeric gene in which a cell-specific enhancer/promoter is used to drive the expression of a toxic gene product. We show that microinjection of a construct in which the elastase I promoter/enhancer is fused to a gene for diphtheria toxin A polypeptide results in birth of mice lacking a normal pancreas because of expression of the toxin in pancreatic acinar cells. A small pancreatic rudiment, containing islet and duct-like cells, was observed in some of the transgenic mice. This method provides a new approach for studying cell-lineage relationships and for analyzing cellular interactions during development.

Animals↗

Step-wise divergence of primitive and definitive haematopoietic and endothelial cell lineages during embryonic stem cell differentiation.

BACKGROUND: The developmental processes leading from the mesoderm to primitive and definitive haematopoietic and endothelial lineages, although of great importance, are still poorly defined. Recent studies have suggested a model in which common precursors give rise to endothelial progenitors and haematopoietic progenitors, the latter subsequently generating both primitive and definitive haematopoietic lineages. However, this model is contradicted by findings that suggest the emergence of haematopoietic cells from the endothelial lineage. RESULTS: We found sequential steps in the differentiation of FLK1+ mesoderm into haematopoietic and endothelial lineages in an in vitro differentiation system of embryonic stem (ES) cells: (i) the GATA-1+ subset of FLK1+ mesodermal cells loses the capacity to give rise to endothelial cells and is restricted to primitive erythroid, macrophage and definitive erythroid progenitors; (ii) the remaining GATA-1- cells give rise to VE-cadherin+ endothelial cells; and subsequently (iii) multiple definitive haematopoietic progenitors and endothelial cells branch off from a subset of VE-cadherin+ cells. CONCLUSIONS: These observations strongly suggest that the divergence of primitive and multilineage definitive haematopoietic/endothelial lineages occurs first, and then multilineage definitive haematopoietic progenitors arise from VE-cadherin+ endothelial cells in the development of haematopoietic and endothelial cells.

Animals↗

Immortalization of equine trophoblast cell lines of chorionic girdle cell lineage by simian virus-40 large T antigen.

Immortalized cell lines have many potential experimental applications including the analysis of molecular mechanisms underlying cell-specific gene expression. We have utilized a recombinant retrovirus encoding the simian virus-40 (SV-40) large T antigen to construct several immortalized cell lines of equine chorionic girdle cell lineage - the progenitor cells that differentiate into the equine chorionic gonadotropin (eCG) producing endometrial cups. Morphologically, the immortalized cell lines appear similar to normal chorionic girdle cells. Derivation of the immortalized cell lines from a chorionic girdle cell lineage was verified by immunological detection of cell-surface antigens specific to equine invasive trophoblasts. The cell lines differed, however, from mature chorionic girdle cells or endometrial cup cells in that they did not produce eCG and did express MHC class I molecules. Thus, these cell lines appear to have been arrested at a stage of development prior to final differentiation into endometrial cup cells. It was also determined that some of these cell lines as well as endometrial cups express the estrogen receptor-related receptor beta gene, but not the glial cell missing gene (GCMa) both of which are expressed in the murine and human placenta. Among these cell lines, three (eCG 50.5, 100.6 and 500.1) express eCG alpha mRNA. Since regulation of eCG alpha subunit gene is largely unknown, we investigated the signal transduction pathways regulating the eCG alpha subunit gene. Both activators of protein kinase A (PKA) and protein kinase C (PKC) induced the expression of eCG alpha subunit expression 3.2 (P<0.05)- and 1.9 (P<0.05)-fold respectively, in the eCG 500.1 cell line. However, activation of these pathways failed to induce eCG beta subunit expression. In conclusion, lines of equine trophoblast cells have been immortalized that display markers characteristic of those with the equine chorionic girdle and endometrial cup cell lineage. A subset of these cells expresses the eCG alpha subunit gene which is responsive to activators of the PKA and PKC signal transduction pathways.

Analysis of Variance↗

Differentiation of rat bone marrow cells cultured on artificial basement membrane containing extracellular matrix into a liver cell lineage.

BACKGROUND/AIMS: Bone marrow (BM) cells have been shown to be capable of differentiating into a liver cell lineage in vitro. However, their differentiation and proliferation is poor, and the cell characteristics are poorly understood. METHODS: We cultured rat BM cells on an artificial basement membrane containing extracellular matrix (ECM) with hepatocyte growth factor (HGF). The expression of mRNA for liver-specific genes was analyzed by reverse transcription PCR. The expression of albumin and Musashi-1 by cultured cells was analyzed using a fluorescence-activated cell sorter (FACS). The proportions of albumin-positive cells when culture was performed with different concentrations of HGF were analyzed by FACS. RESULTS: On culture day 21, polygonal cells proliferated and formed cell colonies. These cells expressed mRNA for all the liver-specific genes analyzed, and showed heterogeneous differentiation, some cells expressing albumin, others expressing Musashi-1. Albumin-positive differentiated cells were large and rich in intracellular structures, while Musashi-1-positive undifferentiated cells had the opposite characteristics. Culturing cells with higher concentrations of HGF induced an increased proportion of albumin-positive cells. CONCLUSIONS: The results suggest that cell culture on an ECM with a high concentration of HGF increases the extent to which BM cells differentiate into a liver cell lineage and proliferate in vitro.

Albumins↗

Developmental cell lineage.

Studies of the role of cell lineage in development began in the 1870s, fell into decline in the first half of the 20th century, and were revived in the 1960s. This revival was attended by the introduction of new and powerful analytical techniques. Cell lineage can be inferred to have a causative role in developmental cell fate in embryos in which induced changes in cell division pattern lead to changes in cell fate. Such a causative role of cell lineage is suggested also by cases where homologous cell types characteristic of symmetrical and longitudinally metameric body plan arise via homologous cell lineages. The developmental pathways of commitment to particular cell fates proceed according to a mixed typologic and topographic hierarchy, which appears to reflect an evolutionary compromise between maximizing the ease of ordering the spatial distribution of determinants of commitment and minimizing the need for migration of differentially committed embryonic cells.

Animals↗

Propagation of human parvovirus B19 in primary culture of erythroid lineage cells derived from fetal liver.

Erythroid lineage cells derived from fetal liver were demonstrated to be target cells for human parvovirus B19 infection. B19 virus antigen-positive serum was inoculated into primary cultures containing erythroid lineage cells enriched from fetal liver. The B19 virus antigen was detected on about 5% of cells in the culture by immunofluorescence staining, and the stained cells were identified as erythroid lineage cells by double staining with anti-B19 virus-positive serum and anti-erythroid lineage monoclonal antibody. The immunofluorescence staining study also revealed that the B19 virus antigen localized in the nucleus and the periphery of cytoplasm. We also detected B19 virus DNA, which was generated by replication in the infected cells, not only in the cells but also in the culture supernatants, in which the amount of B19 DNA increased depending on the period of culture, indicating that the cells infected with B19 virus produced B19 virus and released it into the medium. The ability of B19 virus released into the medium to infect fetal erythroid lineage cells was demonstrated quantitatively. Because of the absence of any cytopathic effect of B19 virus during culture periods of at least 15 days, this culture system should be useful in the study of B19 virus replication and in vitro generation of B19 virus. In addition, the present study may contribute to a better understanding of the pathogenesis of hydrops fetalis, which is probably associated with B19 virus infection during pregnancy.

Cell Separation↗

Reed-Sternberg-like cells in low-grade lymphomas are transformed neoplastic cells of B-cell lineage.

Multinucleated giant cells resembling Reed-Sternberg (RS) cells are occasionally observed in high-grade lymphomas of the large-cell or immunoblastic type, but much less commonly in low-grade lymphomas. This study was conducted to determine whether RS-like cells found in seven B-cell low-grade lymphomas were immunologically similar to the neoplastic cells in the lymphoma or to the true RS cells seen in Hodgkin's disease, and whether they were therefore indicative of a composite lymphoma. Immunohistochemical studies were performed on paraffin sections of the seven low-grade (one small lymphocytic, one mantle zone, and five follicular) lymphomas with a panel of antibodies reactive with leukocyte common antigen (LCA), B-cell, T-cell, and Hodgkin's disease associated antigens. The RS-like cells were reactive with LCA (four of six), L26 (seven of seven), LN1 (five of six), LN2 (two of six), and MB2 (three of six). No positive staining was seen with either Leu-M1 or Ber-H2. The RS-like cells in the mantle zone lymphoma expressed L26, Leu-22, and kappa cytoplasmic light chains. This immunophenotype is similar to that of the neoplastic small lymphocytic cells. One of the low-grade follicular lymphomas progressed to an immunoblastic lymphoma with many RS-like cells. Paraffin immunohistochemistry on both lesions revealed a similar B-cell phenotype for the RS-like cells. Immunogenetic studies revealed B-cell and bcl-2 gene rearrangements in the immunoblastic lymphoma. These results indicate that RS-like cells in low-grade lymphomas are transformed neoplastic cells of B-cell lineage. With careful morphologic examination augmented by immunohistochemical studies, these lesions can be differentiated from Hodgkin's disease and from composite lymphomas of the combined Hodgkin's and non-Hodgkin's type.

Adult↗

Automated cell lineage tracing in Caenorhabditis elegans.

The invariant cell lineage and cell fate of Caenorhabditis elegans provide a unique opportunity to decode the molecular mechanisms of animal development. To exploit this opportunity, we have developed a system for automated cell lineage tracing during C. elegans embryogenesis, based on 3D, time-lapse imaging and automated image analysis. Using ubiquitously expressed histone-GFP fusion protein to label cells/nuclei and a confocal microscope, the imaging protocol captures embryogenesis at high spatial (31 planes at 1 microm apart) and temporal (every minute) resolution without apparent effects on development. A set of image analysis algorithms then automatically recognizes cells at each time point, tracks cell movements, divisions and deaths over time and assigns cell identities based on the canonical naming scheme. Starting from the four-cell stage (or earlier), our software, named starrynite, can trace the lineage up to the 350-cell stage in 25 min on a desktop computer. The few errors of automated lineaging can then be corrected in a few hours with a graphic interface that allows easy navigation of the images and the reported lineage tree. The system can be used to characterize lineage phenotypes of genes and/or extended to determine gene expression patterns in a living embryo at the single-cell level. We envision that this automation will make it practical to systematically decipher the developmental genes and pathways encoded in the genome of C. elegans.

Animals↗

A delta T-cell receptor deleting element transgenic reporter construct is rearranged in alpha beta but not gamma delta T-cell lineages.

T cells can be divided into two groups on the basis of the expression of either alpha beta or gamma delta T-cell receptors (TCRs). Because the TCR delta chain locus lies within the larger TCR alpha chain locus, control of the utilization of these two receptors is important in T-cell development, specifically for determination of T-cell type: rearrangement of the alpha locus results in deletion of the delta coding segments and commitment to the alpha beta lineage. In the developing thymus, a relative site-specific recombination occurs by which the TCR delta chain gene segments are deleted. This deletion removes all D delta, J delta, and C delta genes and occurs on both alleles. This delta deletional mechanism is evolutionarily conserved between mice and humans. Transgenic mice which contain the human delta deleting elements and as much internal TCR delta chain coding sequence as possible without allowing the formation of a complete delta chain gene were developed. Several transgenic lines showing recombinations between deleting elements within the transgene were developed. These lines demonstrate that utilization of the delta deleting elements occurs in alpha beta T cells of the spleen and thymus. These recombinations are rare in the gamma delta population, indicating that the machinery for utilization of delta deleting elements is functional in alpha beta T cells but absent in gamma delta T cells. Furthermore, a discrete population of early thymocytes containing delta deleting element recombinations but not V alpha-to-J alpha rearrangements has been identified. These data are consistent with a model in which delta deletion contributes to the implementation of a signal by which the TCR alpha chain locus is rearranged and expressed and thus becomes an alpha beta T cell.

Animals↗

Blimp1 is a critical determinant of the germ cell lineage in mice.

Germ cell fate in mice is induced in pluripotent epiblast cells in response to signals from extraembryonic tissues. The specification of approximately 40 founder primordial germ cells and their segregation from somatic neighbours are important events in early development. We have proposed that a critical event during this specification includes repression of a somatic programme that is adopted by neighbouring cells. Here we show that Blimp1 (also known as Prdm1), a known transcriptional repressor, has a critical role in the foundation of the mouse germ cell lineage, as its disruption causes a block early in the process of primordial germ cell formation. Blimp1-deficient mutant embryos form a tight cluster of about 20 primordial germ cell-like cells, which fail to show the characteristic migration, proliferation and consistent repression of homeobox genes that normally accompany specification of primordial germ cells. Furthermore, our genetic lineage-tracing experiments indicate that the Blimp1-positive cells originating from the proximal posterior epiblast cells are indeed the lineage-restricted primordial germ cell precursors.

Animals↗

Determination and regulation in the pigment cell lineage of the ascidian embryo.

The brain of the ascidian larva comprises two pigment cells, termed the ocellus melanocyte and the otolith melanocyte. Cell lineage analysis has shown that the two bilateral pigment lineage cells (a-line blastomeres) in the animal hemisphere give rise to these melanocytes in a complementary manner. The results of the present investigation suggest that the specification of the fate of pigment cells proceeds in two distinct steps. First, the determination of pigment lineage cells requires an inductive interaction from the vegetal blastomeres of the A-line. Cell dissociation experiments demonstrated that the inductive interaction is completed by the midgastrula stage. However, the two bilaterally positioned cells destined to become the pigment cells in the first step are still equipotent at this stage in that they can give rise to either the ocellus or otolith. Thus, they constitute what is termed an "equivalence group." In the second step, the individual fates of the two cells that compose the equivalence group are determined. Namely, one cell develops into an ocellus and the other cell develops into an otolith. Photoablation of one of the pigment precursor cells at various stages indicated that the second step of determination occurs at the midtailbud stage. It is suggested that the cue to choose one of the alternative developmental pathways may be positional information that exists along the anteroposterior axis. The second step of determination is thought to be mediated by a hierarchical interaction. In the absence of this interaction, melanocyte specification proceeds along the dominant pathway that results in the differentiation of an ocellus.

Animals↗

Transplanted hematopoietic stem cells from bone marrow differentiate into neural lineage cells and promote functional recovery after spinal cord injury in mice.

Recovery in central nervous system disorders is hindered by the limited ability of the vertebrate central nervous system to regenerate lost cells, replace damaged myelin, and re-establish functional neural connections. Cell transplantation to repair central nervous system disorders is an active area of research, with the goal of reducing functional deficits. Recent animal studies showed that cells of the hematopoietic stem cell (HSC) fraction of bone marrow transdifferentiated into various nonhematopoietic cell lineages. We employed a mouse model of spinal cord injury and directly transplanted HSCs into the spinal cord 1 week after injury. We evaluated functional recovery using the hindlimb motor function score weekly for 5 weeks after transplantation. The data demonstrated a significant improvement in the functional outcome of mice transplanted with hematopoietic stem cells compared with control mice in which only medium was injected. Fluorescent in situ hybridization for the Y chromosome and double immunohistochemistry showed that transplanted cells survived 5 weeks after transplantation and expressed specific markers for astrocytes, oligodendrocytes, and neural precursors, but not for neurons. These results suggest that transplantation of HSCs from bone marrow is an effective strategy for the treatment of spinal cord injury.

Animals↗

Cytokine-regulated expression of activated leukocyte cell adhesion molecule (CD166) on monocyte-lineage cells and in rheumatoid arthritis synovium.

OBJECTIVE: To determine whether monocyte/macrophage expression of the CD6 ligand, activated leukocyte cell adhesion molecule (ALCAM) (CD166), is regulated by cytokines during inflammation in rheumatoid arthritis (RA). METHODS: We used flow cytometry to test whether cytokines present in rheumatoid synovium could regulate ALCAM cell surface expression on peripheral blood (PB) monocytes and RA synovial fluid (SF) macrophages, and we examined ALCAM expression in situ in RA synovium by immunofluorescence. RESULTS: The monocyte differentiation factors interleukin-3, macrophage colony-stimulating factor (M-CSF), and granulocyte-macrophage colony-stimulating factor augmented ALCAM expression on PB monocytes. ALCAM was expressed on monocyte-lineage cells in situ in inflamed synovium from patients with RA (9 of 9), but not in uninflamed synovium from patients with joint trauma (0 of 3). Furthermore, in vitro culture-induced ALCAM expression on PB monocytes and CD14+ RA SF cells was inhibited by an M-CSF neutralizing antibody. CONCLUSION: ALCAM expression on PB and SF monocytes/macrophages is enhanced by M-CSF.

Adult↗

The role of cell lineage in development.

Studies of the role of cell lineage in development began in the latter part of the 19th century, fell into decline in the early part of the 20th, and were revived about 20 years ago. This recent revival was accompanied by the introduction of new and powerful analytical techniques. Concepts of importance for cell lineage studies include the principal division modes by which a cell may give rise to its descendant clone (proliferative, stem cell and diversifying); developmental determinacy, or indeterminacy, which refer to the degree to which the normal cleavage pattern of the early embryo and the developmental fate of its individual cells is, or is not, the same in specimen after specimen; commitment, which refers to the restriction of the developmental potential of a pluripotent embryonic cell; and equivalence group, which refers to two or more equivalently pluripotent cell clones that normally take on different fates but of which under abnormal conditions one clone can take on the fate of another. Cell lineage can be inferred to have a causative role in developmental cell fate in embryos in which induced changes in cell division patterns lead to changes in cell fate. Moreover, such a causative role of cell lineage is suggested by cases where homologous cell types characteristic of a symmetrical and longitudinally metameric body plan arise via homologous cell lineages. The developmental pathways of commitment to particular cell fates proceed according to a mixed typologic and topographic hierarchy, which appears to reflect an evolutionary compromise between maximizing the ease of ordering the spatial distribution of the determinants of commitment and minimizing the need for migration of differentially committed embryonic cells. Comparison of the developmental cell lineages in leeches and insects indicates that the early course of embryogenesis is radically different in these phyletically related taxa. This evolutionary divergence of the course of early embryogenesis appears to be attributable to an increasing prevalence of polyclonal rather than monoclonal commitment in the phylogenetic line leading from an annelid-like ancestor to insects.

Animals↗

The AN2 protein is a novel marker for the Schwann cell lineage expressed by immature and nonmyelinating Schwann cells.

The expression of the 330 kDa AN2 glycoprotein was studied in the rodent peripheral nervous system. AN2 is expressed by immature Schwann cells in vitro and in vivo and downregulated as the cells upregulate myelin genes. A subpopulation of nonmyelinating Schwann cells in the adult sciatic nerve retains expression of AN2. In rat sciatic nerve crushes, where Schwann cell numbers increase after initial axonal loss and markers of immature Schwann cells show an upregulation, no increased expression of AN2 was observed. In contrast, AN2 expression was upregulated in nerves from peripheral myelin protein-22-transgenic rats, where immature Schwann cells expand without axonal loss. Furthermore, coculture with neurons upregulated AN2 expression on Schwann cells in vitro. Polyclonal antibodies against AN2 inhibited the migration of an immortalized Schwann cell clone in an in vitro migration assay, and the purified AN2 protein was shown to be neither inhibitory nor permissive for outgrowing dorsal root ganglion neurites. AN2 is thus a novel marker for the Schwann cell lineage. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of purified AN2 from early postnatal mouse brain demonstrated that AN2 is the murine homolog of the rat NG2 proteoglycan.

Animals↗

Apoptosis-mediated cell death within the ovarian polar cell lineage of Drosophila melanogaster.

Polar cells have been described as pairs of specific follicular cells present at each pole of Drosophila egg chambers. They are required at different stages of oogenesis for egg chamber formation and establishment of both the anteroposterior and planar polarities of the follicular epithelium. We show that definition of polar cell pairs is a progressive process since early stage egg chambers contain a cluster of several polar cell marker-expressing cells at each pole, while as of stage 5, they contain invariantly two pairs of such cells. Using cell lineage analysis, we demonstrate that these pre-polar cell clusters have a polyclonal origin and derive specifically from the polar cell lineage, rather than from that giving rise to follicular cells. In addition, selection of two polar cells from groups of pre-polar cells occurs via an apoptosis-dependent mechanism and is required for correct patterning of the anterior follicular epithelium of vitellogenic egg chambers.

Animals↗