技术资料

The RSK (90 kDa ribosomal S6 kinase) family comprises a group of highly related serine/threonine kinases that regulate diverse cellular processes,including cell growth,proliferation,survival and motility. This family includes four vertebrate isoforms (RSK1,RSK2,RSK3 and RSK4),and single family member orthologues are also present in Drosophila and Caenorhabditis elegans. The RSK isoforms are downstream effectors of the Ras/ERK (extracellular-signal-regulated kinase) signalling pathway. Significant advances in the field of RSK signalling have occurred in the past few years,including several new functions ascribed to the RSK isoforms,the discovery of novel protein substrates and the implication of different RSK isoforms in cancer. Collectively,these new findings increase the diversity of biological functions regulated by RSK,and highlight potential new directions of research. In the present paper,we review the structure,expression and activation mechanisms of the RSK isoforms,and discuss their physiological roles on the basis of established substrates and recent discoveries. View Publication

Induced pluripotent stem (iPS) cells are being used increasingly to complement their embryonic counterparts to understand and develop the therapeutic potential of pluripotent cells. Our objectives were to identify an efficient cardiac differentiation protocol for human iPS cells as monolayers,and demonstrate that the resulting cardiac progenitors could provide a therapeutic benefit in a rodent model of myocardial infarction. Herein,we describe a 14-day protocol for efficient cardiac differentiation of human iPS cells as a monolayer,which routinely yielded a mixed population in which over 50% were cardiomyocytes,endothelium,or smooth muscle cells. When differentiating,cardiac progenitors from day 6 of this protocol were injected into the peri-infarct region of the rat heart; after coronary artery ligation and reperfusion,we were able to show that human iPS cell-derived cardiac progenitor cells engrafted,differentiated into cardiomyocytes and smooth muscle,and persisted for at least 10 weeks postinfarct. Hearts injected with iPS-derived cells showed a nonsignificant trend toward protection from decline in function after myocardial infarction,as assessed by magnetic resonance imaging at 10 weeks,such that the ejection fraction at 10 weeks in iPS treated hearts was 62%±4%,compared to that of control infarcted hearts at 45%±9% (Ptextless0.2). In conclusion,we demonstrated efficient cardiac differentiation of human iPS cells that gave rise to progenitors that were retained within the infarcted rat heart,and reduced remodeling of the heart after ischemic damage. View Publication

Signaling mediates cellular responses to extracellular stimuli. The c-Jun NH(2)-terminal kinase (JNK) pathway exemplifies one subgroup of the mitogen-activated protein (MAP) kinases,which,besides having established functions in stress response,also contribute to development by an unknown mechanism. We show by genome-wide location analysis that JNK binds to a large set of active promoters during the differentiation of stem cells into neurons. JNK-bound promoters are enriched with binding motifs for the transcription factor NF-Y but not for AP-1. NF-Y occupies these predicted sites,and overexpression of dominant-negative NF-YA reduces the JNK presence on chromatin. We find that histone H3 Ser10 (H3S10) is a substrate for JNK,and JNK-bound promoters are enriched for H3S10 phosphorylation. Inhibition of JNK signaling in post-mitotic neurons reduces phosphorylation at H3S10 and the expression of target genes. These results establish MAP kinase binding and function on chromatin at a novel class of target genes during stem cell differentiation. View Publication

Intercellular interactions in the cell microenvironment play a critical role in determining cell fate,but the effects of these interactions on pathways governing human embryonic stem cell (hESC) behavior have not been fully elucidated. We and others have previously reported that 3-D culture of hESCs affects cell fates,including self-renewal and differentiation to a variety of lineages. Here we have used a microwell culture system that produces 3-D colonies of uniform size and shape to provide insight into the effect of modulating cell-cell contact on canonical Wnt/??-catenin signaling in hESCs. Canonical Wnt signaling has been implicated in both self-renewal and differentiation of hESCs,and competition for ??-catenin between the Wnt pathway and cadherin-mediated cell-cell interactions impacts various developmental processes,including the epithelial-mesenchymal transition. Our results showed that hESCs cultured in 3-D microwells exhibited higher E-cadherin expression than cells on 2-D substrates. The increase in E-cadherin expression in microwells was accompanied by a downregulation of Wnt signaling,as evidenced by the lack of nuclear ??-catenin and downregulation of Wnt target genes. Despite this reduction in Wnt signaling in microwell cultures,embryoid bodies (EBs) formed from hESCs cultured in microwells exhibited higher levels of Wnt signaling than EBs from hESCs cultured on 2-D substrates. Furthermore,the Wnt-positive cells within EBs showed upregulation of genes associated with cardiogenesis. These results demonstrate that modulation of intercellular interactions impacts Wnt/??-catenin signaling in hESCs. ?? 2011 Elsevier Ltd. View Publication

BACKGROUND: Although both the alkylating agent temozolomide (TMZ) and oncolytic viruses hold promise for treating glioblastoma,which remains uniformly lethal,the effectiveness of combining the two treatments and the mechanism of their interaction on cancer stem cells are unknown. METHODS: We investigated the efficacy of combining TMZ and the oncolytic herpes simplex virus (oHSV) G47Δ in killing glioblastoma stem cells (GSCs),using Chou-Talalay combination index analysis,immunocytochemistry and fluorescence microscopy,and neutral comet assay. The role of treatment-induced DNA double-strand breaks,activation of DNA damage responses,and virus replication in the cytotoxic interaction between G47Δ and TMZ was examined with a panel of pharmacological inhibitors and short-hairpin RNA (shRNA)-mediated knockdown of DNA repair pathways. Comparisons of cell survival and virus replication were performed using a two-sided t test (unpaired). The survival of athymic mice (n = 6-8 mice per group) bearing GSC-derived glioblastoma tumors treated with the combination of G47Δ and TMZ was analyzed by the Kaplan-Meier method and evaluated with a two-sided log-rank test. RESULTS: The combination of G47Δ and TMZ acted synergistically in killing GSCs but not neurons,with associated robust induction of DNA damage. Pharmacological and shRNA-mediated knockdown studies suggested that activated ataxia telangiectasia mutated (ATM) is a crucial mediator of synergy. Activated ATM relocalized to HSV DNA replication compartments where it likely enhanced oHSV replication and could not participate in repairing TMZ-induced DNA damage. Sensitivity to TMZ and synergy with G47Δ decreased with O(6)-methylguanine-DNA-methyltransferase (MGMT) expression and MSH6 knockdown. Combined G47Δ and TMZ treatment extended survival of mice bearing GSC-derived intracranial tumors,achieving long-term remission in four of eight mice (median survival = 228 days; G47Δ alone vs G47Δ + TMZ,hazard ratio of survival = 7.1,95% confidence interval = 1.9 to 26.1,P = .003) at TMZ doses attainable in patients. CONCLUSIONS: The combination of G47Δ and TMZ acts synergistically in killing GSCs through oHSV-mediated manipulation of DNA damage responses. This strategy is highly efficacious in representative preclinical models and warrants clinical translation. View Publication

Induced pluripotent stem (iPS) cells are generated from somatic cells by the forced expression of a defined set of pluripotency-associated transcription factors. Human iPS cells can be propagated indefinitely,while maintaining the capacity to differentiate into all cell types in the body except for extra-embryonic tissues. This technology not only represents a new way to use individual-specific stem cells for regenerative medicine but also constitutes a novel method to obtain large amounts of disease-specific cells for biomedical research. Despite their great potential,the long reprogramming process (up to 1. month) remains one of the most significant challenges facing standard virus-mediated methodology. In this study,we report the accelerated generation of human iPS cells from adipose-derived stem (ADS) cells,using a new combination of chemical inhibitors under a setting of physiological hypoxia in conjunction with retroviral transduction of Oct4,Sox2,Klf4,and L-Myc. Under optimized conditions,we observed human embryonic stem (ES)-like cells as early as 6. days after the initial retroviral transduction. This was followed by the emergence of fully reprogrammed cells bearing Tra-1-81-positive and DsRed transgene-silencing properties on day 10. The resulting cell lines resembled human ES cells in many respects including proliferation rate,morphology,pluripotency-associated markers,global gene expression patterns,genome-wide DNA methylation states,and the ability to differentiate into all three of the germ layers,both in vitro and in vivo. Our method,when combined with chemical inhibitors under conditions of physiological hypoxia,offers a powerful tool for rapidly generating bona fide human iPS cells and facilitates the application of iPS cell technology to biomedical research. textcopyright 2011 Elsevier Inc. View Publication

Symptomatic dengue virus infection ranges in disease severity from an influenza-like illness to life-threatening shock. One model of the mechanism underlying severe disease proposes that weakly neutralizing,dengue serotype cross-reactive antibodies induced during a primary infection facilitate virus entry into Fc receptor-bearing cells during a subsequent secondary infection,increasing viral replication and the release of cytokines and vasoactive mediators,culminating in shock. This process has been termed antibody-dependent enhancement of infection and has significantly hindered vaccine development. Much of our understanding of this process has come from studies using mouse monoclonal antibodies (MAbs); however,antibody responses in mice typically exhibit less complexity than those in humans. A better understanding of the humoral immune response to natural dengue virus infection in humans is sorely needed. Using a high-efficiency human hybridoma technology,we isolated 37 hybridomas secreting human MAbs to dengue viruses from 12 subjects years or even decades following primary or secondary infection. The majority of the human antibodies recovered were broadly cross-reactive,directed against either envelope or premembrane proteins,and capable of enhancement of infection in vitro; few exhibited serotype-specific binding or potent neutralizing activity. Memory B cells encoding enhancing antibodies predominated in the circulation,even two or more decades following infection. Mapping the epitopes and activity of naturally occurring dengue antibodies should prove valuable in determining whether the enhancing and neutralizing activity of antibodies can be separated. Such principles could be used in the rational design of vaccines that enhance the induction of neutralizing antibodies,while lowering the risk of dengue shock syndrome. View Publication

Human pluripotent stem cells will likely be a significant part of the regenerative medicine-driven healthcare revolution. In order to realize this potential,culture processes must be standardized,scalable and able to produce clinically relevant cell numbers,whilst maintaining critical biological functionality. This review comprises a broad overview of important bioprocess considerations,referencing the development of biopharmaceutical processes in an effort to learn from current best practice in the field. Particular focus is given to the recent efforts to grow human pluripotent stem cells in microcarrier or aggregate suspension culture,which would allow geometric expansion of productive capacity were it to be fully realized. The potential of these approaches is compared with automation of traditional T-flask culture,which may provide a cost-effective platform for low-dose,low-incidence conditions or autologous therapies. This represents the first step in defining the full extent of the challenges facing bioprocess engineers in the exploitation of large-scale human pluripotent stem cell manufacture. View Publication

A method for the generation of human induced pluripotent stem (iPS) cells was established. This method employs adenovirus carrying the ecotropic retrovirus receptor mCAT1 and Moloney murine leukemia virus (MMLV)-based retroviral vectors carrying the four transcription factors POU5F1 (OCT3/4),KLF4,SOX2,and MYC (c-Myc) (Masaki H & Ishikawa T Stem Cell Res 1:105-15,2007). The differentiation of human iPS cells into hepatic cells was performed by a stepwise protocol (Song Z et al. Cell Res 19:1233-42,2009). These cells have potential as patient-specific in vitro models for studying disease etiology and could be used in drug discovery programs tailored to deal with genetic variations in drug efficacy and toxicity. View Publication

Human embryonic stem cells (hESC) have a unique capacity to self-renew and differentiate into all the cell types found in human body. Although the transcriptional regulators of pluripotency are well studied,the role of cytoplasmic regulators is still poorly characterized. Here,we report a new stem cell-specific RNA-binding protein L1TD1 (ECAT11,FLJ10884) required for hESC self-renewal and cancer cell proliferation. Depletion of L1TD1 results in immediate downregulation of OCT4 and NANOG. Furthermore,we demonstrate that OCT4,SOX2,and NANOG all bind to the promoter of L1TD1. Moreover,L1TD1 is highly expressed in seminomas,and depletion of L1TD1 in these cancer cells influences self-renewal and proliferation. We show that L1TD1 colocalizes and interacts with LIN28 via RNA and directly with RNA helicase A (RHA). LIN28 has been reported to regulate translation of OCT4 in complex with RHA. Thus,we hypothesize that L1TD1 is part of the L1TD1-RHA-LIN28 complex that could influence levels of OCT4. Our results strongly suggest that L1TD1 has an important role in the regulation of stemness. View Publication

Mutations in human induced pluripotent stem cells (iPSCs) pose a risk for their clinical use due to preferential reprogramming of mutated founder cell and selection of mutations during maintenance of iPSCs in cell culture. It is unknown,however,if mutations in iPSCs are due to stress associated with oncogene expression during reprogramming. We performed whole exome sequencing of human foreskin fibroblasts and their derived iPSCs at two different passages. We found that in vitro passaging contributed 7% to the iPSC coding point mutation load,and ultradeep amplicon sequencing revealed that 19% of the mutations preexist as rare mutations in the parental fibroblasts suggesting that the remaining 74% of the mutations were acquired during cellular reprogramming. Simulation suggests that the mutation intensity during reprogramming is ninefold higher than the background mutation rate in culture. Thus the factor induced reprogramming stress contributes to a significant proportion of the mutation load of iPSCs. View Publication

IL-27,which is produced by activated APCs,bridges innate and adaptive immunity by regulating the development of Th cells. Recent evidence supports a role for IL-27 in the activation of monocytic cells in terms of inflammatory responses. Indeed,proinflammatory and anti-inflammatory activities are attributed to IL-27,and IL-27 production itself is modulated by inflammatory agents such as LPS. IL-27 primes LPS responses in monocytes; however,the molecular mechanism behind this phenomenon is not understood. In this study,we demonstrate that IL-27 priming results in enhanced LPS-induced IL-6,TNF-α,MIP-1α,and MIP-1β expression in human primary monocytes. To elucidate the molecular mechanisms responsible for IL-27 priming,we measured levels of CD14 and TLR4 required for LPS binding. We determined that IL-27 upregulates TLR4 in a STAT3- and NF-κB-dependent manner. Immunofluorescence microscopy revealed enhanced membrane expression of TLR4 and more distinct colocalization of CD14 and TLR4 upon IL-27 priming. Furthermore,IL-27 priming enhanced LPS-induced activation of NF-κB family members. To our knowledge,this study is the first to show a role for IL-27 in regulating TLR4 expression and function. This work is significant as it reveals new mechanisms by which IL-27 can enhance proinflammatory responses that can occur during bacterial infections. View Publication