Adult hematopoietic progenitors are multipotent in chimeric mice

Embryonic stem cells (ESCs) and adult somatic cells, induced to pluripotency (iPSCs), can differentiate into multiple cell lineages. We previously reported that adult mammalian bone marrow contains a sub-population of CD34+ cells that express genes of ESCs and genes required to generate iPSCs. They also express lineage genes of the three embryonic germ layers. Are these CD34+ cells multipotent? Here, CD34+ bone marrow stem cells from adult male ROSA mice, which carry two markers: the β-galactosidase gene and the male Y chromosome, were transplanted into blastocysts of wildtype mice. Each female ROSA chimera generated had a distinct pattern of male-derived organs expressing β-galactosidase; e.g., ectodermal brain, dorsal root ganglia and skin; mesodermal heart, bone and bone marrow; and endodermal pancreas, intestine, and liver. Thus, adult mammals carry cells that appear to exhibit a developmental potential reminiscent of ESCs and iPSCs suggesting they could be used for cell replacement therapy.     

Axial progenitors with extensive potency are localised to the mouse chordoneural hinge

Elongation of the mouse anteroposterior axis depends on a small population of progenitors initially located in the primitive streak and later in the tail bud. Gene expression and lineage tracing have shown that there are many features common to these progenitor tissues throughout axial elongation. However, the identity and location of the progenitors is unclear. We show by lineage tracing that the descendants of 8.5 d.p.c. node and anterior primitive streak which remain in the tail bud are located in distinct territories: (1) ventral node descendants are located in the widened posterior end of the notochord; and (2) descendants of anterior streak are located in both the tail bud mesoderm, and in the posterior end of the neurectoderm. We show that cells from the posterior neurectoderm are fated to give rise to mesoderm even after posterior neuropore closure. The posterior end of the notochord, together with the ventral neurectoderm above it, is thus topologically equivalent to the chordoneural hinge region defined in Xenopus and chick. A stem cell model has been proposed for progenitors of two of the axial tissues, the myotome and spinal cord. Because it was possible that labelled cells in the tail bud represented stem cells, tail bud mesoderm and chordoneural hinge were grafted to 8.5 d.p.c. primitive streak to compare their developmental potency. This revealed that cells from the bulk of the tail bud mesoderm are disadvantaged in such heterochronic grafts from incorporating into the axis and even when they do so, they tend to contribute to short stretches of somites suggesting that tail bud mesoderm is restricted in potency. By contrast, cells from the chordoneural hinge of up to 12.5 d.p.c. embryos contribute efficiently to regions of the axis formed after grafting to 8.5 d.p.c. embryos, and also repopulate the tail bud. These cells were additionally capable of serial passage through three successive generations of embryos in culture without apparent loss of potency. This potential for self-renewal in chordoneural hinge cells strongly suggests that stem cells are located in this region.     

Greater epithelial ridge cells are the principal organoid-forming progenitors of the mouse cochlea

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Expression profiles of mouse dendritic cell sarcoma are similar to those of hematopoietic stem cells or progenitors by clustering and principal component analyses

We isolated and screened two tumor cell clones DD1 and DG6 with different capacity of metastasis from the same parent cell line, a mouse dendritic cell (DC) sarcoma, using limited dilution method. The genome-wide expressions of DD1 and DG6 cells were detected by Affymetrix's MOE-430A microarray. The expression profiles related with mouse DC development were downloaded from GEO at NCBI and ArrayExpress at EBI database. In order to compare the expression of DC sarcoma and DC developmental arrays which was performed by MG-U74av2, we had screened the best matched probesets between MOE-430A and MG-U74av2 according to the probe identities from Affymetrix technical annotation. After the normalization of 11 housekeeping genes across the 34 arrays (2 DC sarcoma and 32 DC developmental arrays), all these expression profiles were analyzed by the methods of hierarchical clustering, principal component analysis, nearest-neighborhood, and self-organizing maps. The results indicate that expression profiles of DC sarcoma are closer to those of the DC progenitors and hematopoietic stem cells from bone marrow compared with the sorted DCs from spleen. The results support the hypothesis that cancers (tumors or sarcomas) arise from stem cells. It is suggested that the DC sarcomas are more similar to the DC progenitors and hematopoietic stem cells than the relative mature DCs in gene expressions on the large-scale.     

Regulation of cellular respiration in myoglobin-deficient mouse heart

The regulation of cardiac O2 consumption according to energy demand is best studied in the intact organ by non-destructive methods, using probes detectable by their fluorescence or light absorption. However, myoglobin is normally present in high concentrations and swamps the cytochrome spectra, thereby bringing about an oxygen-dependent internal filter effect which quenches the fluorescence of probes. A viable myoglobin-deficient mouse strain (Myo(-/-)) has been generated previously and isolated perfused Myo(-/-) hearts are used here as an ideal model for studying mitochondrial metabolism by non-destructive optical methods. In this model we monitored the redox state of cytochrome aa3 and flavoprotein (Fp) during perturbations of myocardial work output upon changes in extracellular [Ca2+], KCl-induced arrest and pacing. Increased consumption of energy and O2 led to a concomitant reduction of cytochrome aa3 and oxidation of Fp. Administration of a medium chain-length fatty acid caused a marked reduction of Fp, but even then an increase in energy consumption caused Fp oxidation. The results show that cell respiration in the intact myocardium is regulated at the site of the respiratory chain. Our findings do not support the NMR-based hypothesis that O2 consumption is mainly regulated at the level of intermediary metabolism and by the pressure of reducing equivalents to the mitochondrial respiratory chain.     

Supramaximal exercise mobilizes hematopoietic progenitors and reticulocytes in athletes

Marathon runners show increased circulating CD34+ cell counts and postexercise release of interleukin-6 (IL-6), granulocyte-colony stimulating factor (G-CSF) and flt3-ligand (Bonsignore MR, Morici G, Santoro A, Pegano M, Cascio L, Bonnano A, Abate P, Mirabella F, Profita M, Insalaco G, Gioia M, Vignola AM, Majolino I, Testa U, and Hogg JC. J Appl Physiol 93: 1691-1697, 2002). In the present study we hypothesized that supramaximal ("all-out") exercise may acutely affect circulating progenitors and reticulocytes and investigated possible mechanisms involved. Progenitor release was measured by flow cytometry (n = 20) and clonogenic assays (n = 6) in 20 young competitive rowers (13 M, 7 F, age +/- SD: 17.1 +/- 2.1 yr, peak O2 consumption: 56.5 +/- 11.4 ml.min(-1).kg(-1)) at rest and shortly after 1,000 m "all-out." Release of reticulocytes, cortisol, muscle enzymes, neutrophil elastase, and several cytokines/growth factors was measured. Supramaximal exercise doubled circulating CD34+ cells (rest: 7.6 +/- 3.0, all-out: 16.3 +/- 9.1 cells/mul, P < 0.001), and increased immature reticulocyte fractions; AC133+ cells doubled, suggesting release of angiogenetic precursors. Erythrocyte burst forming units and colony forming units for granulocytes-monocytes and all blood series increased postexercise by 3.4-, 5.5-, and 4.8-fold, respectively (P < 0.01 for all). All-out rowing acutely increased plasma cortisol, neutrophil elastase, flt3-ligand, hepatocyte growth factor, VEGF, and transforming growth factor-beta1, and decreased erythropoietin; K-ligand, stromal-derived factor-1, IL-6, and G-CSF were unchanged. Therefore, all-out exercise is a physiological stimulus for progenitor release in athletes. Release of reticulocytes and proangiogenetic cells and mediators suggests tissue hypoxia as possibly involved in progenitor mobilization.     

Three paternally imprinted regions are sequentially required in prenatal and postnatal mouse development

正Reproduction in mammals is primarily through fertilization of the oocytes and sperms generated by the females and males, respectively. Fusion of two haploid genomes leads to formation of the diploid zygotes, which sequentially gives rise to the pre-implantation and post-implantation embryos     

Definitive hematopoietic stem cells first develop within the major arterial regions of the mouse embryo

The aorta-gonad-mesonephros (AGM) region is a potent hematopoietic site within the mammalian embryo body, and the first place from which hematopoietic stem cells (HSCs) emerge. Within the complex embryonic vascular, excretory and reproductive tissues of the AGM region, the precise location of HSC development is unknown. To determine where HSCs develop, we subdissected the AGM into aorta and urogenital ridge segments and transplanted the cells into irradiated adult recipients. We demonstrate that HSCs first appear in the dorsal aorta area. Furthermore, we show that vitelline and umbilical arteries contain high frequencies of HSCs coincident with HSC appearance in the AGM. While later in development and after organ explant culture we find HSCs in the urogenital ridges, our results strongly suggest that the major arteries of the embryo are the most important sites from which definitive HSCs first emerge.     

Isolation of adult mouse myogenic progenitors: functional heterogeneity of cells within and engrafting skeletal muscle

Skeletal muscle regeneration in adults is thought to occur through the action of myogenic satellite cells located in close association with mature muscle fibers; however, these precursor cells have not been prospectively isolated, and recent studies have suggested that additional muscle progenitors, including cells of bone marrow or hematopoietic origin, may exist. To clarify the origin(s) of adult myogenic cells, we used phenotypic, morphological, and functional criteria to identify and prospectively isolate a subset of myofiber-associated cells capable at the single cell level of generating myogenic colonies at high frequency. Importantly, although muscle-engrafted cells from marrow and/or circulation localized to the same anatomic compartment as myogenic satellite cells and expressed some though not all satellite cell markers, they displayed no intrinsic myogenicity. Together, these studies describe the clonal isolation of functional adult myogenic progenitors and demonstrate that these cells do not arise from hematopoietic or other bone marrow or circulating precursors.     

Direct evidence for the pancreatic lineage: NGN3+ cells are islet progenitors and are distinct from duct progenitors

The location and lineage of cells that give rise to endocrine islets during embryogenesis has not been established nor has the origin or identity of adult islet stem cells. We have employed an inducible Cre-ER(TM)-LoxP system to indelibly mark the progeny of cells expressing either Ngn3 or Pdx1 at different stages of development. The results provide direct evidence that NGN3+ cells are islet progenitors during embryogenesis and in adult mice. In addition, we find that cells expressing Pdx1 give rise to all three types of pancreatic tissue: exocrine, endocrine and duct. Furthermore, exocrine and endocrine cells are derived from Pdx1-expressing progenitors throughout embryogenesis. By contrast, the pancreatic duct arises from PDX1+ progenitors that are set aside around embryonic day 10.5 (E9.5-E11.5). These findings suggest that lineages for exocrine, endocrine islet and duct progenitors are committed at mid-gestation.     

Roles of Bim in apoptosis of normal and Bcr-Abl-expressing hematopoietic progenitors

Bcr-Abl kinase is known to reverse apoptosis of cytokine-dependent cells due to cytokine deprivation, although it has been controversial whether chronic myeloid leukemia (CML) progenitors have the potential to survive under conditions in which there are limited amounts of cytokines. Here we demonstrate that early hematopoietic progenitors (Sca-1(+) c-Kit(+) Lin(-)) isolated from normal mice rapidly undergo apoptosis in the absence of cytokines. In these cells, the expression of Bim, a proapoptotic relative of Bcl-2 which plays a key role in the cytokine-mediated survival system, is induced. In contrast, those cells isolated from our previously established CML model mice resist apoptosis in cytokine-free medium without the induction of Bim expression, and these effects are reversed by the Abl-specific kinase inhibitor imatinib mesylate. In addition, the expression levels of Bim are uniformly low in cell lines established from patients in the blast crisis phase of CML, and imatinib induced Bim in these cells. Moreover, small interfering RNA that reduces the expression level of Bim effectively rescues CML cells from apoptosis caused by imatinib. These findings suggest that Bim plays an important role in the apoptosis of early hematopoietic progenitors and that Bcr-Abl supports cell survival in part through downregulation of this cell death activator.     

Ontogeny of the mouse hematopoietic system

In vertebrates the extraembryonic mesoderm of the yolk sac (YS) is the first site during embryogenesis where morphologically discernible hematopoiesis may be found. Later hematopoiesis shifts into the embryo proper, first to the liver, the major fetal hematopoietic site, then to definitive hematopoietic territories, the spleen and bone marrow. It is widely accepted that in the mouse this picture reflects the migration of pluripotent hematopoietic stem cells (HSC) from the YS accompanied by subsequent colonization of the hematopoietic tissues during embryogenesis. However, there is no conclusive evidence showing unequivocally the initiating role of the YS in murine adult hematopoiesis. Recently, we have demonstrated the important role of embryo body tissues in the development of CFU-S before the establishment of definitive hematopoiesis in the fetal liver. This finding suggests that the early development of the hematopoietic system in the mouse is more complex than has been previously proposed and we consider here the early hematopoietic events in the developing mouse embryo.     

Extracellular complexes of the hematopoietic human and mouse CSF-1 receptor are driven by common assembly principles

The hematopoietic colony stimulating factor-1 receptor (CSF-1R or FMS) is essential for the cellular repertoire of the mammalian immune system. Here, we report a structural and mechanistic consensus for the assembly of human and mouse CSF-1:CSF-1R complexes. The EM structure of the complete extracellular assembly of the human CSF-1:CSF-1R complex reveals how receptor dimerization by CSF-1 invokes a ternary complex featuring extensive homotypic receptor contacts and striking structural plasticity at the extremities of the complex. Studies by small-angle X-ray scattering of unliganded hCSF-1R point to large domain rearrangements upon CSF-1 binding, and provide structural evidence for the relevance of receptor predimerization at the cell surface. Comparative structural and binding studies aiming to dissect the assembly principles of human and mouse CSF-1R complexes, including a quantification of the CSF-1/CSF-1R species cross-reactivity, show that bivalent cytokine binding to receptor coupled to ensuing receptor-receptor interactions are common denominators in extracellular complex formation.     

Ontogenic shifts in cellular fate are linked to proteotype changes in lineage-biased hematopoietic progenitor cells

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The cellular oncogenes c-myc, c-myb and c-erb are transcribed in defined types of avian hematopoietic cells

The possible role of normal chicken cellular sequences c-erb, c-myb and c-myc, together referred to as c-onc genes and related to the oncogenes of defective avian acute leukemia retroviruses (DLVs), was investigated by determining the accumulation of c-onc RNA in different avian cells an cell lines. Levels of c-myc and in some instances c-myb RNA are elevated in immature hematopoietic cells or cell lines from various lineages but more mature hematopoietic cells, as well as non-hematopoietic cells, contain only low levels. In contrast, the level of c-erb RNA is generally low, but high in a small number of normal bone marrow cells. The results indicate that the cellular homologues of the viral oncogenes are differentially expressed during hematopoiesis. They also indicate that the hypothesis that DLV target cells express their homologous c-onc genes might hold for c-erb, but is not valid in its simple form for c-myc and c-myb.