技术资料

One of the differences between murine and human embryonic stem cells (ESCs) is the epigenetic state of the X chromosomes in female lines. Murine ESCs (mESCs) present two transcriptionally active Xs that will undergo the dosage compensation process of XCI upon differentiation,whereas most human ESCs (hESCs) spontaneously inactivate one X while keeping their pluripotency. Whether this reflects differences in embryonic development of mice and humans,or distinct culture requirements for the two kinds of pluripotent cells is not known. Recently it has been shown that hESCs established in physiological oxygen levels are in a stable pre-XCI state equivalent to that of mESCs,suggesting that culture in low oxygen concentration is enough to preserve that epigenetic state of the X chromosomes. Here we describe the establishment of two new lines of hESCs under physiological oxygen level and the characterization of the XCI state in the 46,XX line BR-5. We show that a fraction of undifferentiated cells present XIST RNA accumulation and single H3K27me foci,characteristic of the inactive X. Moreover,analysis of allele specific gene expression suggests that pluripotent BR-5 cells present completely skewed XCI. Our data indicate that physiological levels of oxygen are not sufficient for the stabilization of the pre-XCI state in hESCs. View Publication

Mesenchymal stem cells (MSCs) have a high potential for therapeutic efficacy in treating diverse musculoskeletal injuries and cardiovascular diseases,and for ameliorating the severity of graft-versus-host and autoimmune diseases. While most of these clinical applications require substantial cell quantities,the number of MSCs that can be obtained initially from a single donor is limited. Reports on the derivation of MSC-like cells from pluripotent stem cells (PSCs) are,thus,of interest,as the infinite proliferative capacity of PSCs opens the possibility to generate large amounts of uniform batches of MSCs. However,characterization of such MSC-like cells is currently inadequate,especially with regard to the question of whether these cells are equivalent or identical to MSCs. In this study,we have derived MSC-like cells [induced PSC-derived MSC-like progenitor cells (iMPCs)] using four different methodologies from a newly established induced PSC line reprogrammed from human bone marrow stromal cells (BMSCs),and compared the iMPCs directly with the originating parental BMSCs. The iMPCs exhibited typical MSC/fibroblastic morphology and MSC-typical surface marker profile,and they were capable of differentiation in vitro along the osteogenic,chondrogenic,and adipogenic lineages. However,compared with the parental BMSCs,iMPCs displayed a unique expression pattern of mesenchymal and pluripotency genes and were less responsive to traditional BMSC differentiation protocols. We,therefore,conclude that iMPCs generated from PSCs via spontaneous differentiation represent a distinct population of cells which exhibit MSC-like characteristics. View Publication

Approximately 70% of KRAS-positive colorectal cancers (CRCs) have a CpG island methylator phenotype (CIMP) characterized by aberrant DNA hypermethylation and transcriptional silencing of many genes. The factors involved in,and the mechanistic basis of,CIMP is not understood. Among the CIMP genes are the tumor suppressors p14(ARF),p15(INK4B),and p16(INK4A),encoded by the INK4-ARF locus. In this study,we perform an RNA interference screen and identify ZNF304,a zinc-finger DNA-binding protein,as the pivotal factor required for INK4-ARF silencing and CIMP in CRCs containing activated KRAS. In KRAS-positive human CRC cell lines and tumors,ZNF304 is bound at the promoters of INK4-ARF and other CIMP genes. Promoter-bound ZNF304 recruits a corepressor complex that includes the DNA methyltransferase DNMT1,resulting in DNA hypermethylation and transcriptional silencing. KRAS promotes silencing through upregulation of ZNF304,which drives DNA binding. Finally,we show that ZNF304 also directs transcriptional silencing of INK4-ARF in human embryonic stem cells. DOI: http://dx.doi.org/10.7554/eLife.02313.001. View Publication

Efficient derivation of large-scale motor neurons (MNs) from human pluripotent stem cells is central to the understanding of MN development,modelling of MN disorders in vitro and development of cell-replacement therapies. Here we develop a method for rapid (20 days) and highly efficient (˜70%) differentiation of mature and functional MNs from human pluripotent stem cells by tightly modulating neural patterning temporally at a previously undefined primitive neural progenitor stage. This method also allows high-yield (textgreater250%) MN production in chemically defined adherent cultures. Furthermore,we show that Islet-1 is essential for formation of mature and functional human MNs,but,unlike its mouse counterpart,does not regulate cell survival or suppress the V2a interneuron fate. Together,our discoveries improve the strategy for MN derivation,advance our understanding of human neural specification and MN development,and provide invaluable tools for human developmental studies,drug discovery and regenerative medicine. View Publication

Cardiomyocytes (CM) derived from human embryonic stem cells (hESC) are used for cardio-toxicity evaluation and tested in many preclinical trials for their potential use in regenerative therapeutics. As more efficient CM differentiation protocols are developed,reliable automated platforms for characterization and detection are needed. An automated time-resolved video analysis and management system (TVAMS) has been developed for the evaluation of hESC differentiation to CM. The system was used for monitoring the kinetics of embryoid bodies (EB) generation (numbers and size) and differentiation into beating EBs (percentage beating area and beating EB count) in two differentiation protocols. We show that the percentage beating areas of EBs (from total area of the EBs) is a more sensitive and better predictor of CM differentiation efficiency than percentage of beating EBs (from total EBs) as the percentage beating areas of EBs correlates with cardiac troponin-T and myosin heavy chain expression levels. TVAMS can also be used to evaluate the effect of drugs and inhibitors (e.g. isoproterenol and ZD7288) on CM beating frequency. TVAMS can reliably replace the commonly practiced,time consuming,manual counting of total and beating EBs during CM differentiation. TVAMS is a high-throughput non-invasive video imaging platform that can be applied for the development of new CM differentiation protocols,as well as a tool to conduct CM toxicology assays. View Publication

Transplantation of human neural progenitor cells (NPCs) into the brain or spinal cord to replace lost cells,modulate the injury environment,or create a permissive milieu to protect and regenerate host neurons is a promising therapeutic strategy for neurological diseases. Deriving NPCs from human fetal tissue is feasible,although problematic issues include limited sources and ethical concerns. Here we describe a new and abundant source of NPCs derived from human induced pluripotent stem cells (iPSCs). A novel chopping technique was used to transform adherent iPSCs into free-floating spheres that were easy to maintain and were expandable (EZ spheres) (Ebert et al. [2013] Stem Cell Res 10:417–427). These EZ spheres could be differentiated towards NPC spheres with a spinal cord phenotype using a combination of all-trans retinoic acid (RA) and epidermal growth factor (EGF) and fibroblast growth factor-2 (FGF-2) mitogens. Suspension cultures of NPCs derived from human iPSCs or fetal tissue have similar characteristics,although they were not similar when grown as adherent cells. In addition,iPSC-derived NPCs (iNPCs) survived grafting into the spinal cord of athymic nude rats with no signs of overgrowth and with a very similar profile to human fetal-derived NPCs (fNPCs). These results suggest that human iNPCs behave like fNPCs and could thus be a valuable alternative for cellular regenerative therapies of neurological diseases. J. Comp. Neurol. 522:2707–2728,2014. textcopyright 2014 Wiley Periodicals,Inc. View Publication

Human Nanog1 is a 305-amino acid (aa) homeodomain-containing transcription factor critical for the pluripotency of embryonic stem (ES) and embryonal carcinoma (EC) cells. Somatic cancer cells predominantly express a retrogene homolog of Nanog1 called NanogP8,which is ˜99% similar to Nanog at the aa level. Although the predicted M.W of Nanog1/NanogP8 is ∼35 kD,both have been reported to migrate,on Western blotting (WB),at apparent molecular masses of 29-80 kD. Whether all these reported protein bands represent authentic Nanog proteins is unclear. Furthermore,detailed biochemical studies on Nanog1/NanogpP8 have been lacking. By combining WB using 8 anti-Nanog1 antibodies,immunoprecipitation,mass spectrometry,and studies using recombinant proteins,here we provide direct evidence that the Nanog1 protein in NTERA-2 EC cells exists as multiple M.W species from ˜22 kD to 100 kD with a major 42 kD band detectable on WB. We then demonstrate that recombinant NanogP8 (rNanogP8) proteins made in bacteria using cDNAs from multiple cancer cells also migrate,on denaturing SDS-PAGE,at ˜28 kD to 180 kD. Interestingly,different anti-Nanog1 antibodies exhibit differential reactivity towards rNanogP8 proteins,which can spontaneously form high M.W protein species. Finally,we show that most long-term cultured cancer cell lines seem to express very low levels of or different endogenous NanogP8 protein that cannot be readily detected by immunoprecipitation. Altogether,the current study reveals unique biochemical properties of Nanog1 in EC cells and NanogP8 in somatic cancer cells. View Publication

Schizophrenia has been considered a devastating clinical syndrome rather than a single disease. Nevertheless,the mechanisms behind the onset of schizophrenia have been only partially elucidated. Several studies propose that levels of trace elements are abnormal in schizophrenia; however,conflicting data generated from different biological sources prevent conclusions being drawn. In this work,we used synchrotron radiation X-ray microfluorescence spectroscopy to compare trace element levels in neural progenitor cells (NPCs) derived from two clones of induced pluripotent stem cell lines of a clozapine-resistant schizophrenic patient and two controls. Our data reveal the presence of elevated levels of potassium and zinc in schizophrenic NPCs. Neural cells treated with valproate,an adjunctive medication for schizophrenia,brought potassium and zinc content back to control levels. These results expand the understanding of atomic element imbalance related to schizophrenia and may provide novel insights for the screening of drugs to treat mental disorders. ?? 2014 Elsevier B.V. View Publication

Human induced pluripotent stem cells (hiPSCs) offer the potential to study otherwise inaccessible cell types. Critical to this is the directed differentiation of hiPSCs into functional cell lineages. This is of particular relevance to research into neurological disease,such as Parkinson's disease (PD),in which midbrain dopaminergic neurons degenerate during disease progression but are unobtainable until post-mortem. Here we report a detailed study into the physiological maturation over time of human dopaminergic neurons in vitro. We first generated and differentiated hiPSC lines into midbrain dopaminergic neurons and performed a comprehensive characterisation to confirm dopaminergic functionality by demonstrating dopamine synthesis,release,and re-uptake. The neuronal cultures include cells positive for both tyrosine hydroxylase (TH) and G protein-activated inward rectifier potassium channel 2 (Kir3.2,henceforth referred to as GIRK2),representative of the A9 population of substantia nigra pars compacta (SNc) neurons vulnerable in PD. We observed for the first time the maturation of the slow autonomous pace-making (textless10 Hz) and spontaneous synaptic activity typical of mature SNc dopaminergic neurons using a combination of calcium imaging and electrophysiology. hiPSC-derived neurons exhibited inositol tri-phosphate (IP3) receptor-dependent release of intracellular calcium from the endoplasmic reticulum in neuronal processes as calcium waves propagating from apical and distal dendrites,and in the soma. Finally,neurons were susceptible to the dopamine neuron-specific toxin 1-methyl-4-phenylpyridinium (MPP+) which reduced mitochondrial membrane potential and altered mitochondrial morphology. Mature hiPSC-derived dopaminergic neurons provide a neurophysiologically-defined model of previously inaccessible vulnerable SNc dopaminergic neurons to bridge the gap between clinical PD and animal models. View Publication

Research in the embryo and in culture has resulted in a sophisticated understanding of many regulators of pluripotent cell differentiation. As a consequence,protocols for the differentiation of pluripotent cells generally rely on a combination of exogenous growth factors and endogenous signalling. Little consideration has been given to manipulating other pathways to achieve pluripotent cell differentiation. The integrity of cell:cell contacts has been shown to influence lineage choice during pluripotent cell differentiation,with disruption of cell:cell contacts promoting mesendoderm formation and maintenance of cell:cell contacts resulting in the preferential formation of neurectoderm. Staurosporine is a broad spectrum inhibitor of serine/threonine kinases which has several effects on cell function,including interruption of cell:cell contacts,decreasing focal contact size,inducing epithelial to mesenchyme transition (EMT) and promoting cell differentiation. The possibility that staurosporine could influence lineage choice from pluripotent cells in culture was investigated. The addition of staurosporine to differentiating mouse EPL resulted in preferential formation of mesendoderm and mesoderm populations,and inhibited the formation of neurectoderm. Addition of staurosporine to human ES cells similarly induced primitive streak marker gene expression. These data demonstrate the ability of staurosporine to influence lineage choice during pluripotent cell differentiation and to mimic the effect of disrupting cell:cell contacts. Staurosporine induced mesendoderm in the absence of known inducers of formation,such as serum and BMP4. Staurosporine induced the expression of mesendoderm markers,including markers that were not induced by BMP4,suggesting it acted as a broad spectrum inducer of molecular gastrulation. This approach has identified a small molecule regulator of lineage choice with potential applications in the commercial development of ES cell derivatives,specifically as a method for forming mesendoderm progenitors or as a culture adjunct to prevent the formation of ectoderm progenitors during pluripotent cell differentiation. ?? 2014. View Publication

Induced pluripotent stem (iPS) cells are somatic cells that have been reprogrammed to a pluripotent state via the introduction of defined transcription factors. Although iPS is a potentially valuable resource for regenerative medicine and drug development,several issues regarding their pluripotency,differentiation propensity and potential for tumorigenesis remain to be elucidated. Analysis of cell surface glycans has arisen as an interesting tool for the characterization of iPS. An appropriate characterization of glycan surface molecules of human embryonic stem (hES) cells and iPS cells might generate crucial data to highlight their role in the acquisition and maintenance of pluripotency. In this study,we characterized the surface glycans of iPS generated from menstrual blood-derived mesenchymal cells (iPS-MBMC). We demonstrated that,upon spontaneous differentiation,iPS-MBMC present high amounts of terminal $\$-galactopyranoside residues,pointing to an important role of terminal-linked sialic acids in pluripotency maintenance. The removal of sialic acids by neuraminidase induces iPS-MBMC and hES cells differentiation,prompting an ectoderm commitment. Exposed $\$-galactopyranose residues might be recognized by carbohydrate-binding molecules found on the cell surface,which could modulate intercellular or intracellular interactions. Together,our results point for the first time to the involvement of the presence of terminal sialic acid in the maintenance of embryonic stem cell pluripotency and,therefore,the modulation of sialic acid biosynthesis emerges as a mechanism that may govern stem cell differentiation. View Publication

The tumorigenicity of human pluripotent stem cells (hPSCs) is widely acknowledged as a major obstacle that withholds their application in regenerative medicine. This protocol describes two efficient and robust ways to chemically eliminate the tumor-initiating hPSCs from monolayer culture. The protocol details how to maintain and differentiate hPSCs,how to apply chemical inhibitors to cultures of hPSCs and their differentiated progeny,and how to assess the purity of the resultant cell cultures using in vitro and in vivo assays. It also describes how to rescue the cytotoxic effect. The elimination and the rescue assay can be completed within 3-5 d,the in vitro assessment requires another day,and the in vivo assessment requires up to 12 additional weeks. View Publication