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Optimization of pluripotent stem cell expansion and differentiation is facilitated by biological tools that permit non-invasive and dynamic monitoring of pluripotency,and the ability to select for an undifferentiated input cell population. Here we report on the generation and characterisation of clonal human embryonic stem (HES3,H9) and human induced pluripotent stem cell lines (UQEW01i-epifibC11) that have been stably modified with an artificial EOS(C3+) promoter driving expression of EGFP and puromycin resistance-conferring proteins. We show that EGFP expression faithfully reports on the pluripotency status of the cells in these lines and that antibiotic selection allows for an efficient elimination of differentiated cells from the cultures. We demonstrate that the extinction of the expression of the pluripotency reporter during differentiation closely correlates with the decrease in expression of conventional pluripotency markers,such as OCT4 (POU5F1),TRA-1-60 and SSEA4 when screening across conditions with various levels of pluripotency-maintaining or differentiation-inducing signals. We further illustrate the utility of these lines for real-time monitoring of pluripotency in embryoid bodies and microfluidic bioreactors. View Publication

Fanconi anemia (FA) is an autosomal recessive disorder characterized by progressive bone marrow failure (BMF) during childhood,aside from numerous congenital abnormalities. FA mouse models have been generated; however,they do not fully mimic the hematopoietic phenotype. As there is mounting evidence that the hematopoietic impairment starts already in utero,a human pluripotent stem cell model would constitute a more appropriate system to investigate the mechanisms underlying BMF in FA and its developmental basis. Using zinc finger nuclease (ZFN) technology,we have created a knockout of FANCA in human embryonic stem cells (hESC). We introduced a selection cassette into exon 2 thereby disrupting the FANCA coding sequence and found that whereas mono-allelically targeted cells retain an unaltered proliferation potential,disruption of the second allele causes a severe growth disadvantage. As a result,heterogeneous cultures arise due to the presence of cells still carrying an unaffected FANCA allele,quickly outgrowing the knockout cells. When pure cultures of FANCA knockout hESC are pursued either through selection or single cell cloning,this rapidly results in growth arrest and such cultures cannot be maintained. These data highlight the importance of a functional FA pathway at the pluripotent stem cell stage. ?? 2014. View Publication

The repurposed CRISPR-Cas9 system has recently emerged as a revolutionary genome-editing tool. Here we report a modification in the expression of the guide RNA (gRNA) required for targeting that greatly expands the targetable genome. gRNA expression through the commonly used U6 promoter requires a guanosine nucleotide to initiate transcription,thus constraining genomic-targeting sites to GN19NGG. We demonstrate the ability to modify endogenous genes using H1 promoter-expressed gRNAs,which can be used to target both AN19NGG and GN19NGG genomic sites. AN19NGG sites occur ˜15% more frequently than GN19NGG sites in the human genome and the increase in targeting space is also enriched at human genes and disease loci. Together,our results enhance the versatility of the CRISPR technology by more than doubling the number of targetable sites within the human genome and other eukaryotic species. View Publication

Mesenchymal stem cells (MSCs) may be used as powerful tools for the repair and regeneration of damaged tissues. However,isolating tissue specific-derived MSCs may cause pain and increased infection rates in patients,and repetitive isolations may be required. To overcome these difficulties,we have examined alternative methods for MSC production. Here,we show that induced pluripotent stem cells (iPSCs) may be differentiated into mesenchymal stem cells (iMSCs) following exposure to SB431542. Purified iMSCs were administered to mdx mice to study skeletal muscle regeneration in a murine model of muscular dystrophy. Purified iMSCs displayed fibroblast-like morphology,formed three-dimensional spheroid structures,and expressed characteristic mesenchymal stem cell surface markers such as CD29,CD33,CD73,CD90,and CD105. Moreover,iMSCs were capable of differentiating into adipogenic,osteogenic,and chondrogenic lineages. Transplanting iMSC cells to tibialis anterior skeletal muscle tissue in mdx mice lowered oxidative damage as evidenced by a reduction in nitrotyrosine levels,and normal dystrophin expression levels were restored. This study demonstrates the therapeutic potential of purified iMSCs in skeletal muscle regeneration in mdx mice,and suggests that iPSCs are a viable alternate source for deriving MSCs as needed. textcopyright 2014 Elsevier Inc. View Publication

AbstractBack to TopbackslashnNeurons produced from stem cells have emerged as a tool to identify new therapeutic targets for neurological diseases such as amyotrophic lateral sclerosis (ALS). However,it remains unclear to what extent these new mechanistic insights will translate to animal models,an important step in the validation of new targets. Previously,we found that glia from mice carrying the SOD1G93A mutation,a model of ALS,were toxic to stem cell–derived human motor neurons. We use pharmacological and genetic approaches to demonstrate that the prostanoid receptor DP1 mediates this glial toxicity. Furthermore,we validate the importance of this mechanism for neural degeneration in vivo. Genetic ablation of DP1 in SOD1G93A mice extended life span,decreased microglial activation,and reduced motor neuron loss. Our findings suggest that blocking DP1 may be a therapeutic strategy in ALS and demonstrate that discoveries from stem cell models of disease can be corroborated in vivo. View Publication

Ligation of erythropoietin (EPO) receptor (EPOR) JAK2 kinase complexes propagates signals within erythroid progenitor cells (EPCs) that are essential for red blood cell production. To reveal hypothesized novel EPOR/JAK2 targets,a phosphotyrosine (PY) phosphoproteomics approach was applied. Beyond known signal transduction factors,32 new targets of EPO-modulated tyrosine phosphorylation were defined. Molecular adaptors comprised one major set including growth factor receptor-bound protein 2 (GRB2)-associated binding proteins 1-3 (GAB1-3),insulin receptor substrate 2 (IRS2),docking protein 1 (DOK1),Src homology 2 domain containing transforming protein 1 (SHC1),and sprouty homologue 1 (SPRY1) as validating targets,and SPRY2,SH2 domain containing 2A (SH2D2A),and signal transducing adaptor molecule 2 (STAM2) as novel candidate adaptors together with an ORF factor designated as regulator of human erythroid cell expansion (RHEX). RHEX is well conserved in Homo sapiens and primates but absent from mouse,rat,and lower vertebrate genomes. Among tissues and lineages,RHEX was elevated in EPCs,occurred as a plasma membrane protein,was rapidly PY-phosphorylated textgreater20-fold upon EPO exposure,and coimmunoprecipitated with the EPOR. In UT7epo cells,knockdown of RHEX inhibited EPO-dependent growth. This was associated with extracellular signal-regulated kinase 1,2 (ERK1,2) modulation,and RHEX coupling to GRB2. In primary human EPCs,shRNA knockdown studies confirmed RHEX regulation of erythroid progenitor expansion and further revealed roles in promoting the formation of hemoglobinizing erythroblasts. RHEX therefore comprises a new EPO/EPOR target and regulator of human erythroid cell expansion that additionally acts to support late-stage erythroblast development. View Publication

Potential teratogenic effects of alcohol on fetal development have been documented. Especially studies have demonstrated deleterious effect of ethanol exposure on neuronal development in animal models and on the maintenance and differentiation of neuronal precursor cells derived from stem cells. To better understand the molecular effect of alcohol on the process of neural differentiation,we have performed gene expression microarray analysis on human embryonic stem cells being directed to neural rosettes and neural precursor cells in the presence of ethanol treatment. Here we provide detailed experimental methods,analysis and information associated with our data deposited into Gene Expression Omnibus (GEO) under GSE56906. Our data provide scientific insight on potential molecular effects of fetal alcohol exposure on neural differentiation of early embryo development. View Publication

THAP1 encodes a transcription factor but its regulation is largely elusive. TOR1A was shown to be repressed by THAP1 in vitro. Notably,mutations in both of these genes lead to dystonia (DYT6 or DYT1). Surprisingly,expressional changes of TOR1A in THAP1 mutation carriers have not been detected indicating additional levels of regulation. Here,we investigated whether THAP1 is able to autoregulate its own expression. Using in-silico prediction,luciferase reporter gene assays,and (quantitative) chromatin immunoprecipitation (ChIP),we defined the THAP1 minimal promoter to a 480. bp-fragment and demonstrated specific binding of THAP1 to this region which resulted in repression of the THAP1 promoter. This autoregulation was disturbed by different DYT6-causing mutations. Two mutants (Ser6Phe,Arg13His) were shown to be less stable than wildtype THAP1 adding to the effect of reduced binding to the THAP1 promoter. Overexpressed THAP1 is preferably degraded through the proteasome. Notably,endogenous THAP1 expression was significantly reduced in cells overexpressing wildtype THAP1 as demonstrated by quantitative PCR. In contrast,higher THAP1 levels were detected in induced pluripotent stem cell (iPS)-derived neurons from THAP1 mutation carriers. Thus,we identified a feedback-loop in the regulation of THAP1 expression and demonstrated that mutant THAP1 leads to higher THAP1 expression levels. This compensatory autoregulation may contribute to the mean age at onset in the late teen years or even reduced penetrance in some THAP1 mutation carriers. View Publication

Despite major progress in the management of human liver disease,the only cure for a critically failing organ is liver transplantation. While a highly successful approach,the use of cadaveric organs as a routine treatment option is severely limited by organ availability. Therefore,the use of cell-based therapies has been explored to provide support for the failing liver. In addition to developing new treatments,there is also an imperative to develop better human models 'in a dish'. Such approaches will undoubtedly lead to a better understanding of the disease process,offering new treatment or preventative strategies. With both approaches in mind,we have developed robust hepatocyte differentiation methodologies for use with pluripotent stem cells. Importantly,our procedure is highly efficient (∼ 90%) and delivers active,drug-inducible,and predictive human hepatocyte populations. View Publication

Human pluripotent stem cells (hPSCs) hold great promise for regenerative medicine and biopharmaceutical applications. Currently,optimal culture and efficient expansion of large amounts of clinical-grade hPSCs are critical issues in hPSC-based therapies. Conventionally,hPSCs are propagated as colonies on both feeder and feeder-free culture systems. However,these methods have several major limitations,including low cell yields and generation of heterogeneously differentiated cells. To improve current hPSC culture methods,we have recently developed a new method,which is based on non-colony type monolayer (NCM) culture of dissociated single cells. Here,we present detailed NCM protocols based on the Rho-associated kinase (ROCK) inhibitor Y-27632. We also provide new information regarding NCM culture with different small molecules such as Y-39983 (ROCK I inhibitor),phenylbenzodioxane (ROCK II inhibitor),and thiazovivin (a novel ROCK inhibitor). We further extend our basic protocol to cultivate hPSCs on defined extracellular proteins such as the laminin isoform 521 (LN-521) without the use of ROCK inhibitors. Moreover,based on NCM,we have demonstrated efficient transfection or transduction of plasmid DNAs,lentiviral particles,and oligonucleotide-based microRNAs into hPSCs in order to genetically modify these cells for molecular analyses and drug discovery. The NCM-based methods overcome the major shortcomings of colony-type culture,and thus may be suitable for producing large amounts of homogeneous hPSCs for future clinical therapies,stem cell research,and drug discovery. View Publication

Adaptive immunity to self-antigens causes autoimmune disorders,such as multiple sclerosis,psoriasis and type 1 diabetes; paradoxically,T- and B-cell responses to amyloid-$\$(A$\$) reduce Alzheimer's disease (AD)-associated pathology and cognitive impairment in mouse models of the disease. The manipulation of adaptive immunity has been a promising therapeutic approach for the treatment of AD,although vaccine and anti-A$\$ approaches have proven difficult in patients,thus far. CD4(+) T cells have a central role in regulating adaptive immune responses to antigens,and A$\$-specific CD4(+) T cells have been shown to reduce AD pathology in mouse models. As these cells may facilitate endogenous mechanisms that counter AD,an evaluation of their abundance before and during AD could provide important insights. A$\$-CD4see is a new assay developed to quantify A$\$-specific CD4(+) T cells in human blood,using dendritic cells derived from human pluripotent stem cells. In tests of textgreater50 human subjects A$\$-CD4see showed an age-dependent decline of A$\$-specific CD4(+) T cells,which occurs earlier in women than men. In aggregate,men showed a 50% decline in these cells by the age of 70 years,but women reached the same level before the age of 60 years. Notably,women who carried the AD risk marker apolipoproteinE-ɛ4 (ApoE4) showed the earliest decline,with a precipitous drop between 45 and 52 years,when menopause typically begins. A$\$-CD4see requires a standard blood draw and provides a minimally invasive approach for assessing changes in A$\$ that may reveal AD-related changes in physiology by a decade. Furthermore,CD4see probes can be modified to target any peptide,providing a powerful new tool to isolate antigen-specific CD4(+) T cells from human subjects. View Publication

Many protocols have been designed to differentiate human embryonic stem cells (ESCs) and human induced pluripotent stem cells (iPSCs) into neurons. Despite the relevance of electrophysiological properties for proper neuronal function,little is known about the evolution over time of important neuronal electrophysiological parameters in iPSC-derived neurons. Yet,understanding the development of basic electrophysiological characteristics of iPSC-derived neurons is critical for evaluating their usefulness in basic and translational research. Therefore,we analyzed the basic electrophysiological parameters of forebrain neurons differentiated from human iPSCs,from day 31 to day 55 after the initiation of neuronal differentiation. We assayed the developmental progression of various properties,including resting membrane potential,action potential,sodium and potassium channel currents,somatic calcium transients and synaptic activity. During the maturation of iPSC-derived neurons,the resting membrane potential became more negative,the expression of voltage-gated sodium channels increased,the membrane became capable of generating action potentials following adequate depolarization and,at day 48-55,50% of the cells were capable of firing action potentials in response to a prolonged depolarizing current step,of which 30% produced multiple action potentials. The percentage of cells exhibiting miniature excitatory post-synaptic currents increased over time with a significant increase in their frequency and amplitude. These changes were associated with an increase of Ca2+ transient frequency. Co-culturing iPSC-derived neurons with mouse glial cells enhanced the development of electrophysiological parameters as compared to pure iPSC-derived neuronal cultures. This study demonstrates the importance of properly evaluating the electrophysiological status of the newly generated neurons when using stem cell technology,as electrophysiological properties of iPSC-derived neurons mature over time. View Publication