参考文献

Diamond-Blackfan anemia (DBA) is a broad developmental disease characterized by anemia,bone marrow (BM) erythroblastopenia,and an increased incidence of malignancy. Mutations in ribosomal protein gene S19 (RPS19) are found in approximately 25% of DBA patients; however,the role of RPS19 in the pathogenesis of DBA remains unknown. Using global gene expression analysis,we compared highly purified multipotential,erythroid,and myeloid BM progenitors from RPS19 mutated and control individuals. We found several ribosomal protein genes downregulated in all DBA progenitors. Apoptosis genes,such as TNFRSF10B and FAS,transcriptional control genes,including the erythropoietic transcription factor MYB (encoding c-myb),and translational genes were greatly dysregulated,mostly in diseased erythroid cells. Cancer-related genes,including RAS family oncogenes and tumor suppressor genes,were significantly dysregulated in all diseased progenitors. In addition,our results provide evidence that RPS19 mutations lead to codownregulation of multiple ribosomal protein genes,as well as downregulation of genes involved in translation in DBA cells. In conclusion,the altered expression of cancer-related genes suggests a molecular basis for malignancy in DBA. Downregulation of c-myb expression,which causes complete failure of fetal liver erythropoiesis in knockout mice,suggests a link between RPS19 mutations and reduced erythropoiesis in DBA. View Publication

Chronic myeloid leukemia (CML) is caused by the constitutively activated tyrosine kinase breakpoint cluster (BCR)-ABL. Current frontline therapy for CML is imatinib,an inhibitor of BCR-ABL. Although imatinib has a high rate of clinical success in early phase CML,treatment resistance is problematic,particularly in later stages of the disease,and is frequently mediated by mutations in BCR-ABL. Dasatinib (BMS-354825) is a multitargeted tyrosine kinase inhibitor that targets oncogenic pathways and is a more potent inhibitor than imatinib against wild-type BCR-ABL. It has also shown preclinical activity against all but one of the imatinib-resistant BCR-ABL mutants tested to date. Analysis of the crystal structure of dasatinib-bound ABL kinase suggests that the increased binding affinity of dasatinib over imatinib is at least partially due to its ability to recognize multiple states of BCR-ABL. The structure also provides an explanation for the activity of dasatinib against imatinib-resistant BCR-ABL mutants. View Publication

B cell-activating factor of the tumor necrosis factor (TNF) family,or BAFF,is mainly produced in monocytes and dendritic cells,and indispensable for proliferation,differentiation and survival of B cells. BAFF is a type II membrane-bound protein and the extracellular C-terminal fragment is released from the cells as soluble BAFF (sBAFF),which binds to specific receptors on B cells. Accumulating evidence suggests that BAFF plays an important role in the pathogenesis of autoimmune diseases,such as systemic lupus erythematosus (SLE). In this study,we developed a sensitive sandwich ELISA system to quantify the amount of sBAFF using our own mAb. Treatment of peripheral T cells of SLE patients with an anti-CD3 antibody triggered robust expression of BAFF and subsequent release of sBAFF from the cells. On the other hand,the stimulus induced only marginal elevation of sBAFF from normal T cells. These data indicate that BAFF is expressed in T cells upon stimulation at least under pathological conditions. Expression of BAFF was also largely induced in a human T cell line,Loucy (American Type Tissue Collection CRL-2629),in response to several stimuli,while other T cell lines so far examined produced the cytokine almost constitutively. These data suggest that Loucy recapitulates some of the characteristics of SLE T cells. Investigation of molecular and cellular mechanisms of production of BAFF in Loucy demonstrated that expression of BAFF was regulated through a signal transduction pathway which involves c-jun NH2-terminal kinase and p38,and that shedding of BAFF was catalyzed by a membrane-bound protease,furin. View Publication

Stem cells hold a great potential for the regeneration of damaged tissues in cardiovascular or musculoskeletal diseases. Unfortunately,problems such as limited availability,control of cell fate,and allograft rejection need to be addressed before therapeutic applications may become feasible. Generation of multipotent progenitors from adult differentiated cells could be a very attractive alternative to the limited in vitro self-renewal of several types of stem cells. In this direction,a recently synthesized unnatural purine,named reversine,has been proposed to induce reversion of adult cells to a multipotent state,which could be then converted into other cell types under appropriate stimuli. Our study suggests that reversine treatment transforms primary murine and human dermal fibroblasts into myogenic-competent cells both in vitro and in vivo. Moreover,this is the first study to demonstrate that plasticity changes arise in primary mouse and human cells following reversine exposure. View Publication

The development of embryonic stem cell (ESC) therapies requires the establishment of efficient methods to differentiate ESCs into specific cell lineages. Here,we report the in vitro differentiation of common marmoset (CM) (Callithrix jacchus) ESCs into hematopoietic cells after exogenous gene transfer using vesicular stomatitis virus-glycoprotein-pseudotyped lentiviral vectors. We transduced hematopoietic genes,including tal1/scl,gata1,gata2,hoxB4,and lhx2,into CM ESCs. By immunochemical and morphological analyses,we demonstrated that overexpression of tal1/scl,but not the remaining genes,dramatically increased hematopoiesis of CM ESCs,resulting in multiple blood-cell lineages. Furthermore,flow cytometric analysis demonstrated that CD34,a hematopoietic stem/progenitor cell marker,was highly expressed in tal1/scl-overexpressing embryoid body cells. Similar results were obtained from three independent CM ESC lines. These results suggest that transduction of exogenous tal1/scl cDNA into ESCs is a promising method to induce the efficient differentiation of CM ESCs into hematopoietic stem/progenitor cells. View Publication

Supplementation of mesenchymal stem cells (MSCs) during hematopoietic stem cell (HSC) transplantation alleviates complications such as graft-versus-host disease,leading to a speedy recovery of hematopoiesis. To meet this clinical demand,a fast MSC expansion method is required. In the present study,we examined the feasibility of using a rotary bioreactor system to expand MSCs from isolated bone marrow mononuclear cells. The cells were cultured in a rotary bioreactor with Myelocult medium containing a combination of supplementary factors,including stem cell factor and interleukin-3 and -6. After 8 days of culture,total cell numbers,Stro-1(+)CD44(+)CD34(-) MSCs,and CD34(+)CD44(+)Stro-1(-) HSCs were increased 9-,29-,and 8-fold,respectively. Colony-forming efficiency-fibroblast per day of the bioreactor-treated cells was 1.44-fold higher than that of the cells without bioreactor treatment. The bioreactor-expanded MSCs showed expression of primitive MSC markers endoglin (SH2) and vimentin,whereas markers associated with lineage differentiation,including osteocalcin (osteogenesis),type II collagen (chondrogenesis),and C/EBP-alpha (CCAAT/enhancer-binding protein-alpha) (adipogenesis),were not detected. Upon induction,the bioreactor-expanded MSCs were able to differentiate into osteoblasts,chondrocytes,and adipocytes. We conclude that the rotary bioreactor with the modified Myelocult medium reported in this study may be used to rapidly expand MSCs. View Publication

Somatic activation of a conditional targeted Kras(G12D) allele induces a fatal myeloproliferative disease in mice that closely models juvenile and chronic myelomonocytic leukemia. These mice consistently develop severe and progressive anemia despite adequate numbers of clonogenic erythroid progenitors in the bone marrow and expanded splenic hematopoiesis. Ineffective erythropoiesis is characterized by impaired differentiation. These results demonstrate that endogenous levels of oncogenic Ras have cell lineage-specific effects and support efforts to modulate Ras signaling for therapy of anemia in patients with myelodysplastic syndromes and myeloproliferative disorders. View Publication

IL-7 plays a major role in T lymphocyte homeostasis and has been proposed as an immune adjuvant for lymphopenic patients. This prospect is based,at least in part,on the short-term expansion of peripheral T cells in rIL7-treated mice and primates. Nevertheless,in vivo,following initial increases in T cell proliferation and numbers,lymphocytes return to a quiescent state. As the bases for this cell cycle exit have not yet been elucidated,it is important to assess the long-term biological effects of IL-7 on quiescent human T lymphocyte subsets. In this study,we find that IL-7-stimulated CD4+ naive lymphocytes enter into cell cycle with significantly delayed kinetics as compared with the memory population. Importantly though,these lymphocytes exit from the cell cycle despite the continuous replenishment of rIL-7. This response is distinct in memory and naive CD4+ lymphocytes with memory cells starting to exit from cycle by day 10 vs day 18 for naive cells. Return to quiescence is associated with a cessation in IL-7R signaling as demonstrated by an abrogation of STAT-5 phosphorylation,despite an up-regulation of surface IL-7Ralpha. Indeed,an initial 10-fold decrease in IL-7Ralpha mRNA levels is followed by increased IL-7Ralpha expression in naive as well as memory T cells,with kinetics paralleling cell cycle exit. Altogether,our data demonstrate that IL-7 promotes the extended survival of both naive and memory CD4+ T cells,whereas cycling of these two subsets is distinct and transient. Thus,IL-7 therapy should be designed to allow optimal responsiveness of naive and memory T cell subsets. View Publication

The Wiskott-Aldrich syndrome protein (WASP) is a product of the gene defective in an Xid disorder,Wiskott-Aldrich syndrome. WASP expression is limited to hemopoietic cells,and WASP regulates the actin cytoskeleton. It has been reported that monocytes/macrophages from WASP-deficient Wiskott-Aldrich syndrome patients are severely defective in chemotaxis,resulting in recurrent infection. However,the molecular basis of such chemotactic defects is not understood. Recently,the WASP N-terminal region was found to bind to the three mammalian verprolin homologs: WASP interacting protein (WIP); WIP and CR16 homologous protein (WICH)/WIP-related protein (WIRE); and CR16. Verprolin was originally found to play an important role in the regulation of actin cytoskeleton in yeast. We have shown that WASP,WIP,and WICH/WIRE are expressed predominantly in the human monocyte cell line THP-1 and that WIP and WICH/WIRE are involved in monocyte chemotaxis. When WASP binding to verprolins was blocked,chemotactic migration of monocytes was impaired in both THP-1 cells and primary human monocytes. Increased expression of WASP and WIP enhanced monocyte chemotaxis. Blocking WASP binding to verprolins impaired cell polarization but not actin polymerization. These results indicate that a complex of WASP with mammalian verprolins plays an important role in chemotaxis of monocytes. Our results suggest that WASP and mammalian verprolins function as a unit in monocyte chemotaxis and that the activity of this unit is critical to establish cell polarization. In addition,our results also indicate that the WASP-verprolin complex is involved in other functions such as podosome formation and phagocytosis. View Publication

The translocation t(11;18)(q21;q21) that generates an API2-MALT1 fusion protein is the most common structural abnormality among the genetic defects reported in mucosa-associated lymphoid tissue (MALT)-type lymphomas,and its presence correlates with the apparent lack of further genetic instability or chromosomal imbalances. Hence,constitutive nuclear factor-kappaB (NF-kappaB) activation induced by the API2-MALT1 fusion protein is considered essential for B-cell transformation. To examine its role in B-cell development and lymphomagenesis,Emu-API2-MALT1 transgenic mice were produced. Our data show that expression of the API2-MALT1 fusion protein alone is not sufficient for the development of lymphoma masses within 50 weeks. Nevertheless,API2-MALT1 expression affected B-cell maturation in the bone marrow and triggered the specific expansion of splenic marginal zone B cells. Polyubiquitination of IkappaB kinase gamma (IKKgamma),indicative for enhanced NF-kappaB activation,was increased in splenic lymphocytes and promoted the survival of B cells ex vivo. In addition,we show that the API2-MALT1 fusion resided in the cholesterol- and sphingolipid-enriched membrane microdomains,termed lipid rafts. We provide evidence that association of the MALT1 COOH terminal with the lipid rafts,which is mediated by the API2 portion,is sufficient to trigger NF-kappaB activation via enhanced polyubiquitination of IKKgamma. Taken together,these data support the hypothesis that the API2-MALT1 fusion protein can contribute to MALT lymphoma formation via increased NF-kappaB activation. View Publication

Chronic treatment with antidepressants increases neurogenesis in the adult hippocampus. This increase in the production of new neurons may be required for the behavioral effects of antidepressants. However,it is not known which class of cells within the neuronal differentiation cascade is targeted by the drugs. We have generated a reporter mouse line,which allows identification and classification of early neuronal progenitors. It also allows accurate quantitation of changes induced by neurogenic agents in these distinct subclasses of neuronal precursors. We use this line to demonstrate that the selective serotonin reuptake inhibitor antidepressant fluoxetine does not affect division of stem-like cells in the dentate gyrus but increases symmetric divisions of an early progenitor cell class. We further demonstrate that these cells are the sole class of neuronal progenitors targeted by fluoxetine in the adult brain and suggest that the fluoxetine-induced increase in new neurons arises as a result of the expansion of this cell class. This finding defines a cellular target for antidepressant drug therapies. View Publication

To search for new indicators of self-renewing hematopoietic stem cells (HSCs),highly purified populations were isolated from adult mouse marrow,micromanipulated into a specially designed microscopic array,and cultured for 4 days in 300 ng/ml Steel factor,20 ng/ml IL-11,and 1 ng/ml flt3-ligand. During this period,each cell and its progeny were imaged at 3-min intervals by using digital time-lapse photography. Individual clones were then harvested and assayed for HSCs in mice by using a 4-month multilineage repopulation endpoint (textgreater1% contribution to lymphoid and myeloid lineages). In a first experiment,6 of 14 initial cells (43%) and 17 of 61 clones (28%) had HSC activity,demonstrating that HSC self-renewal divisions had occurred in vitro. Characteristics associated with HSC activity included longer cell-cycle times and the absence of uropodia on a majority of cells within the clone during the final 12 h of culture. Combining these criteria maximized the distinction of clones with HSC activity from those without and identified a subset of 27 of the 61 clones. These 27 clones included all 17 clones that had HSC activity; a detection efficiency of 63% (2.26 times more frequently than in the original group). The utility of these characteristics for discriminating HSC-containing clones was confirmed in two independent experiments where all HSC-containing clones were identified at a similar 2- to 3-fold-greater efficiency. These studies illustrate the potential of this monitoring system to detect new features of proliferating HSCs that are predictive of self-renewal divisions. View Publication