参考文献

The human naive pluripotent stem cell (PSC) state,corresponding to a pre-implantation stage of development,has been difficult to capture and sustain in vitro. We report that the Hippo pathway effector YAP is nuclearly localized in the inner cell mass of human blastocysts. Overexpression of YAP in human embryonic stem cells (ESCs) and induced PSCs (iPSCs) promotes the generation of naive PSCs. Lysophosphatidic acid (LPA) can partially substitute for YAP to generate transgene-free human naive PSCs. YAP- or LPA-induced naive PSCs have a rapid clonal growth rate,a normal karyotype,the ability to form teratomas,transcriptional similarities to human pre-implantation embryos,reduced heterochromatin levels,and other hallmarks of the naive state. YAP/LPA act in part by suppressing differentiation-inducing effects of GSK3 inhibition. CRISPR/Cas9-generated YAP-/- cells have an impaired ability to form colonies in naive but not primed conditions. These results uncover an unexpected role for YAP in the human naive state,with implications for early human embryology. View Publication

Human embryonic stem cells (hESCs) have an abbreviated G1 phase of the cell cycle that allows rapid proliferation and maintenance of pluripotency. Lengthening of G1 corresponds to loss of pluripotency during differentiation. However,precise mechanisms that link alterations in the cell cycle and early differentiation remain to be defined. We investigated initial stages of mesendodermal lineage commitment in hESCs,and observed a cell cycle pause. Transcriptome profiling identified several genes with known roles in regulation of the G2/M transition that were differentially expressed early during lineage commitment. WEE1 kinase,which blocks entry into mitosis by phosphorylating CDK1 at Y15,was the most highly expressed of these genes. Inhibition of CDK1 phosphorylation by a specific inhibitor of WEE1 restored cell cycle progression by preventing the G2 pause. Directed differentiation of hESCs revealed that cells paused during commitment to the endo- and mesodermal,but not ectodermal,lineages. Functionally,WEE1 inhibition during meso- and endodermal differentiation selectively decreased expression of definitive endodermal markers SOX17 and FOXA2. Our findings identify a novel G2 cell cycle pause that is required for endodermal differentiation and provide important new mechanistic insights into early events of lineage commitment. Stem Cells 2016;34:1765-1775. View Publication

Probing a wide range of cellular phenotypes in neurodevelopmental disorders using patient-derived neural progenitor cells (NPCs) can be facilitated by 3D assays,as 2D systems cannot entirely recapitulate the arrangement of cells in the brain. Here,we developed a previously unidentified 3D migration and differentiation assay in layered hydrogels to examine how these processes are affected in neurodevelopmental disorders,such as Rett syndrome. Our soft 3D system mimics the brain environment and accelerates maturation of neurons from human induced pluripotent stem cell (iPSC)-derived NPCs,yielding electrophysiologically active neurons within just 3 wk. Using this platform,we revealed a genotype-specific effect of methyl-CpG-binding protein-2 (MeCP2) dysfunction on iPSC-derived neuronal migration and maturation (reduced neurite outgrowth and fewer synapses) in 3D layered hydrogels. Thus,this 3D system expands the range of neural phenotypes that can be studied in vitro to include those influenced by physical and mechanical stimuli or requiring specific arrangements of multiple cell types. View Publication

BACKGROUND: Dystrophin-deficient cardiomyopathy is a growing clinical problem without targeted treatments. We investigated whether nicorandil promotes cardioprotection in human dystrophin-deficient induced pluripotent stem cell (iPSC)-derived cardiomyocytes and the muscular dystrophy mdx mouse heart. METHODS AND RESULTS: Dystrophin-deficient iPSC-derived cardiomyocytes had decreased levels of endothelial nitric oxide synthase and neuronal nitric oxide synthase. The dystrophin-deficient cardiomyocytes had increased cell injury and death after 2 hours of stress and recovery. This was associated with increased levels of reactive oxygen species and dissipation of the mitochondrial membrane potential. Nicorandil pretreatment was able to abolish these stress-induced changes through a mechanism that involved the nitric oxide-cyclic guanosine monophosphate pathway and mitochondrial adenosine triphosphate-sensitive potassium channels. The increased reactive oxygen species levels in the dystrophin-deficient cardiomyocytes were associated with diminished expression of select antioxidant genes and increased activity of xanthine oxidase. Furthermore,nicorandil was found to improve the restoration of cardiac function after ischemia and reperfusion in the isolated mdx mouse heart. CONCLUSION: Nicorandil protects against stress-induced cell death in dystrophin-deficient cardiomyocytes and preserves cardiac function in the mdx mouse heart subjected to ischemia and reperfusion injury. This suggests a potential therapeutic role for nicorandil in dystrophin-deficient cardiomyopathy. View Publication

Human melanoma cells express various tumour antigens that are recognized by CD8(+) cytotoxic T lymphocytes (CTLs) and elicit tumour-specific responses in vivo. However,natural and therapeutically enhanced CTL responses in melanoma patients are of limited efficacy. The mechanisms underlying CTL effector phase failure when facing melanomas are still largely elusive. Here we show that,on conjugation with CTL,human melanoma cells undergo an active late endosome/lysosome trafficking,which is intensified at the lytic synapse and is paralleled by cathepsin-mediated perforin degradation and deficient granzyme B penetration. Abortion of SNAP-23-dependent lysosomal trafficking,pH perturbation or impairment of lysosomal proteolytic activity restores susceptibility to CTL attack. Inside the arsenal of melanoma cell strategies to escape immune surveillance,we identify a self-defence mechanism based on exacerbated lysosome secretion and perforin degradation at the lytic synapse. Interfering with this synaptic self-defence mechanism might be useful in potentiating CTL-mediated therapies in melanoma patients. View Publication

Genome instability is a potential limitation to the research and therapeutic application of induced pluripotent stem cells (iPSCs). Observed genomic variations reflect the combined activities of DNA damage,cellular DNA damage response (DDR),and selection pressure in culture. To understand the contribution of DDR on the distribution of copy number variations (CNVs) in iPSCs,we mapped CNVs of iPSCs with mutations in the central DDR gene ATM onto genome organization landscapes defined by genome-wide replication timing profiles. We show that following reprogramming the early and late replicating genome is differentially affected by CNVs in ATM deficient iPSCs relative to wild type iPSCs. Specifically,the early replicating regions had increased CNV losses during retroviral reprogramming. This differential CNV distribution was not present after later passage or after episomal reprogramming. Comparison of different reprogramming methods in the setting of defective DNA damage response reveals unique vulnerability of early replicating open chromatin to retroviral vectors. View Publication

Human urine cells (HUCs) can be reprogrammed into neural progenitor cells (NPCs) or induced pluripotent stem cells (iPSCs) with defined factors and a small molecule cocktail,but the underlying fate choice remains unresolved. Here,through sequential removal of individual compound from small molecule cocktail,we showed that A8301,a TGF$$ signaling inhibitor,is sufficient to switch the cell fate from iPSCs into NPCs in OSKM-mediated HUCs reprogramming. However,TGF$$ exposure at early stage inhibits HUCs reprogramming by promoting EMT. Base on these data,we developed an optimized approach for generation of NPCs or iPSCs from HUCs with significantly improved efficiency by regulating TGF$$ activity at different reprogramming stages. This approach provides a simplified and improved way for HUCs reprogramming,thus would be valuable for banking human iPSCs or NPCs from people with different genetic background. View Publication

Cancer stem cells (CSCs) have been associated with metastasis and therapeutic resistance and can be generated via epithelial mesenchymal transition (EMT). Some studies suggest that the hormone melatonin acts in CSCs and may participate in the inhibition of the EMT. The objectives of this study were to evaluate the formation of mammospheres from the canine and human breast cancer cell lines,CMT-U229 and MCF-7,and the effects of melatonin treatment on the modulation of stem cell and EMT molecular markers: OCT4,E-cadherin,N-cadherin and vimentin,as well as on cell viability and invasiveness of the cells from mammospheres. The CMT-U229 and MCF-7 cell lines were subjected to three-dimensional culture in special medium for stem cells. The phenotype of mammospheres was first evaluated by flow cytometry (CD44+/CD24low/- marking). Cell viability was measured by MTT colorimetric assay and the expression of the proteins OCT4,E-cadherin,N-cadherin and vimentin was evaluated by immunofluorescence and quantified by optical densitometry. The analysis of cell migration and invasion was performed in Boyden Chamber. Flow cytometry proved the stem cell phenotype with CD44+/CD24low/- positive marking for both cell lines. Cell viability of CMT-U229 and MCF-7 cells was reduced after treatment with 1mM melatonin for 24 h (Ptextless0.05). Immunofluorescence staining showed increased E-cadherin expression (Ptextless0.05) and decreased expression of OCT4,N-cadherin and vimentin (Ptextless0.05) in both cell lines after treatment with 1 mM melatonin for 24 hours. Moreover,treatment with melatonin was able to reduce cell migration and invasion in both cell lines when compared to control group (Ptextless0.05). Our results demonstrate that melatonin shows an inhibitory role in the viability and invasiveness of breast cancer mammospheres as well as in modulating the expression of proteins related to EMT in breast CSCs,suggesting its potential anti-metastatic role in canine and human breast cancer cell lines. View Publication

Although clonal studies of lineage potential have been extensively applied to organ specific stem and progenitor cells,much less is known about the clonal origins of lineages formed from the germ layers in early embryogenesis. We applied lentiviral tagging followed by vector integration site analysis (VISA) with high-throughput sequencing to investigate the ontogeny of the hematopoietic,endothelial and mesenchymal lineages as they emerge from human embryonic mesoderm. In contrast to studies that have used VISA to track differentiation of self-renewing stem cell clones that amplify significantly over time,we focused on a population of progenitor clones with limited self-renewal capability. Our analyses uncovered the critical influence of sampling on the interpretation of lentiviral tag sharing,particularly among complex populations with minimal clonal duplication. By applying a quantitative framework to estimate the degree of undersampling we revealed the existence of tripotent mesodermal progenitors derived from pluripotent stem cells,and the subsequent bifurcation of their differentiation into bipotent endothelial/hematopoietic or endothelial/mesenchymal progenitors. This article is protected by copyright. All rights reserved. View Publication

Abnormal glucose metabolism and enhanced oxidative stress accelerate cardiovascular disease,a chronic inflammatory condition causing high morbidity and mortality. Here,we report that in monocytes and macrophages of patients with atherosclerotic coronary artery disease (CAD),overutilization of glucose promotes excessive and prolonged production of the cytokines IL-6 and IL-1β,driving systemic and tissue inflammation. In patient-derived monocytes and macrophages,increased glucose uptake and glycolytic flux fuel the generation of mitochondrial reactive oxygen species,which in turn promote dimerization of the glycolytic enzyme pyruvate kinase M2 (PKM2) and enable its nuclear translocation. Nuclear PKM2 functions as a protein kinase that phosphorylates the transcription factor STAT3,thus boosting IL-6 and IL-1β production. Reducing glycolysis,scavenging superoxide and enforcing PKM2 tetramerization correct the proinflammatory phenotype of CAD macrophages. In essence,PKM2 serves a previously unidentified role as a molecular integrator of metabolic dysfunction,oxidative stress and tissue inflammation and represents a novel therapeutic target in cardiovascular disease. View Publication