技术资料

Acute monocytic leukemia (AML-M5),a subtype of acute myeloid leukemia (AML),affects mostly young children and has poor prognosis. The mechanisms of treatment failure of AML-M5 are still unclear. In this study,we generated iPSC from THP-1 cells from a patient with AML-M5,using retroviruses encoding the pluripotency-associated genes (OCT3/4,SOX2,KLF4 and c-MYC). These AML-M5-derived iPSC showed features similar with those of human embryonic stem cells in terms of the morphology,gene expression,protein/antigen expression and differentiation capability. Parental-specific markers were down-regulated in these AML-M5-derived iPSCs. Expression of MLL-AF9 fusion gene (previously identified to be associated with pathogenesis of AML-M5) was observed in all iPSC clones as well as parental cells. We conclude that AML-M5-specific iPSC clones have been successfully developed. This disease model may provide a novel approach for future study of pathogenesis and therapeutic intervention of AML-M5. View Publication

The unique mental abilities of humans are rooted in the immensely expanded and folded neocortex,which reflects the expansion of neural progenitors,especially basal progenitors including basal radial glia (bRGs) and intermediate progenitor cells (IPCs). We found that constitutively active Sonic hedgehog (Shh) signaling expanded bRGs and IPCs and induced folding in the otherwise smooth mouse neocortex,whereas the loss of Shh signaling decreased the number of bRGs and IPCs and the size of the neocortex. SHH signaling was strongly active in the human fetal neocortex but Shh signaling was not strongly active in the mouse embryonic neocortex,and blocking SHH signaling in human cerebral organoids decreased the number of bRGs. Mechanistically,Shh signaling increased the initial generation and self-renewal of bRGs and IPC proliferation in mice and the initial generation of bRGs in human cerebral organoids. Thus,robust SHH signaling in the human fetal neocortex may contribute to bRG and IPC expansion and neocortical growth and folding. View Publication

Loss-of-function studies are fundamental for dissecting gene function. Yet,methods to rapidly and effectively perturb genes in mammalian cells,and particularly in stem cells,are scarce. Here we present a system for simultaneous conditional regulation of two different proteins in the same mammalian cell. This system harnesses the plant auxin and jasmonate hormone-induced degradation pathways,and is deliverable with only two lentiviral vectors. It combines RNAi-mediated silencing of two endogenous proteins with the expression of two exogenous proteins whose degradation is induced by external ligands in a rapid,reversible,titratable and independent manner. By engineering molecular tuners for NANOG,CHK1,p53 and NOTCH1 in mammalian stem cells,we have validated the applicability of the system and demonstrated its potential to unravel complex biological processes. View Publication

Directed differentiation of stem cells offers a scalable solution to the need for human cell models recapitulating islet biology and T2D pathogenesis. We profiled mRNA expression at 6 stages of an induced pluripotent stem cell (iPSC) model of endocrine pancreas development from 2 donors,and characterized the distinct transcriptomic profiles associated with each stage. Established regulators of endodermal lineage commitment,such as SOX17 (log2 fold change [FC] compared to iPSCs = 14.2,p-value = 4.9 × 10(-5)) and the pancreatic agenesis gene GATA6 (log2 FC = 12.1,p-value = 8.6 × 10(-5)),showed transcriptional variation consistent with their known developmental roles. However,these analyses highlighted many other genes with stage-specific expression patterns,some of which may be novel drivers or markers of islet development. For example,the leptin receptor gene,LEPR,was most highly expressed in published data from in vivo-matured cells compared to our endocrine pancreas-like cells (log2 FC = 5.5,p-value = 2.0 × 10(-12)),suggesting a role for the leptin pathway in the maturation process. Endocrine pancreas-like cells showed significant stage-selective expression of adult islet genes,including INS,ABCC8,and GLP1R,and enrichment of relevant GO-terms (e.g. insulin secretion"; odds ratio = 4.2� View Publication

Fibrodysplasia ossificans progressiva (FOP) syndrome is caused by mutation of the gene ACVR1,encoding a constitutive active bone morphogenetic protein type I receptor (also called ALK2) to induce heterotopic ossification in the patient. To genetically correct it,we attempted to generate the mutant ALK2-iPSCs (mALK2-iPSCs) from FOP-human dermal fibroblasts. However,the mALK2 leads to inhibitory pluripotency maintenance,or impaired clonogenic potential after single-cell dissociation as an inevitable step,which applies gene-correction tools to induced pluripotent stem cells (iPSCs). Thus,current iPSC-based gene therapy approach reveals a limitation that is not readily applicable to iPSCs with ALK2 mutation. Here we developed a simplified one-step procedure by simultaneously introducing reprogramming and gene-editing components into human fibroblasts derived from patient with FOP syndrome,and genetically treated it. The mixtures of reprogramming and gene-editing components are composed of reprogramming episomal vectors,CRISPR/Cas9-expressing vectors and single-stranded oligodeoxynucleotide harboring normal base to correct ALK2 c.617GtextgreaterA. The one-step-mediated ALK2 gene-corrected iPSCs restored global gene expression pattern,as well as mineralization to the extent of normal iPSCs. This procedure not only helps save time,labor and costs but also opens up a new paradigm that is beyond the current application of gene-editing methodologies,which is hampered by inhibitory pluripotency-maintenance requirements,or vulnerability of single-cell-dissociated iPSCs. View Publication

It has become increasingly clear that proper cellular control of pluripotency and differentiation is related to the regulation of rRNA synthesis. To further our understanding of the role that the regulation of rRNA synthesis has in pluripotency we monitored rRNA synthesis during the directed differentiation of human embryonic stem cells (hESCs). We discovered that the rRNA synthesis rate is reduced ˜50% within 6 hours of ACTIVIN A treatment. This precedes reductions in expression of specific stem cell markers and increases in expression of specific germ layer markers. The reduction in rRNA synthesis is concomitant with dissociation of the Pol I transcription factor,UBTF,from the rRNA gene promoter and precedes any increase to heterochromatin throughout the rRNA gene. To directly investigate the role of rRNA synthesis in pluripotency,hESCs were treated with the Pol I inhibitor,CX-5461. The direct reduction of rRNA synthesis by CX-5461 induces the expression of markers for all three germ layers,reduces the expression of pluripotency markers,and is overall similar to the ACTIVIN A induced changes. This work indicates that the dissociation of UBTF from the rRNA gene,and corresponding reduction in transcription,represent early regulatory events during the directed differentiation of pluripotent stem cells. View Publication

In most human somatic cells,the lack of telomerase activity results in progressive telomere shortening during each cell division. Eventually,DNA damage responses triggered by critically short telomeres induce an irreversible cell cycle arrest termed replicative senescence. However,the cellular responses of human pluripotent stem cells to telomere uncapping remain unknown. We generated telomerase knockout human embryonic stem (ES) cells through gene targeting. Telomerase inactivation in ES cells results in progressive telomere shortening. Telomere DNA damage in ES cells and neural progenitor cells induces rapid apoptosis when telomeres are uncapped,in contrast to fibroblast cells that enter a state of replicative senescence. Significantly,telomerase inactivation limits the proliferation capacity of human ES cells without affecting their pluripotency. By targeting telomerase activity,we can functionally separate the two unique properties of human pluripotent stem cells,namely unlimited self-renewal and pluripotency. We show that the potential of ES cells to form teratomas in vivo is dictated by their telomere length. By controlling telomere length of ES cells through telomerase inactivation,we can inhibit teratoma formation and potentially improve the safety of cell therapies involving terminally differentiated cells as well as specific progenitor cells that do not require sustained cellular proliferation in vivo,and thus sustained telomerase activity. This article is protected by copyright. All rights reserved. View Publication

Human somatic stem cells such as mesenchymal stem cells (hMSCs) have the capacity to differentiate into mesenchymal tissue lineages and to alter immune regulatory functions. As such,they hold promise for use in stem cell-based therapies. However,no method is currently available to evaluate the actual differentiation capacity of hMSCs prior to cell transplantation. Previously,we performed a comprehensive glycan profiling of adipose-derived hMSCs using high-density lectin microarray and demonstrated that $$2-6-sialylation is a marker of the differentiation potential of these cells. Nevertheless,no information was available about the structural details of these of $$2-6-sialylated glycans. Here we used high performance liquid chromatography (HPLC) analysis combined with mass spectrometry (MS) to perform a structural and quantitative glycome analysis targeting both N- and O-glycans derived from early (with differentiation ability) and late (without differentiation ability) passages of adipose tissue-derived hMSCs. Findings in these cells were compared with those from human induced pluripotent stem cells (hiPSCs),human dermal fibroblasts (hFibs) and cartilage tissue-derived chondrocytes. A higher percentage of $$2-6-sialylated N-glycans was detected in early passage cells (24-28 % of sialylated N-glycans) compared with late passage cells (13-15 %). A major $$2-6-sialylated N-glycan structure detected in adipose-derived hMSCs was that of mono-sialylated biantennary N-glycan. Similar results were obtained for the cartilage tissue-derived chondrocytes,Yub621c (28 % for passage 7 and 5 % for passage 28). In contrast,no significant differences were observed between early and late passage hMSCs with respect to $$2-6-sialylated O-glycan percentages. These results demonstrate that levels of $$2-6-sialylated N-glycans,but not O-glycans,could be used as markers of the differential potential of hMSCs. View Publication

Helper-dependent adenoviral vectors (HDAd) that express certain transgene products are impossible to produce because the transgene product is toxic to the producer cells,especially when made in large amounts during vector production. Downregulating transgene expression from the HDAd during vector production is a way to solve this problem. In this report,we show that this can be accomplished by inserting the target sequence for the adenoviral VA RNAI into the 3' untranslated region of the expression cassette in the HDAd. Thus during vector production,when the producer cells are coinfected with both the helper virus (HV) and the HDAd,the VA RNAI produced by the HV will target the transgene mRNA from the HDAd via the endogenous cellular RNAi pathway. Once the HDAd is produced and purified,transduction of the target cells results in unimpeded transgene expression because of the absence of HV. This simple and universal strategy permits for the robust production of otherwise recalcitrant HDAds. View Publication

Spinocerebellar ataxia type 3 (SCA3) is a dominantly inherited neurodegenerative disease caused by an expansion of the CAG-repeat in ATXN3. In this study,induced pluripotent stem cells (iPSCs) were generated from SCA3 patient dermal fibroblasts by electroporation with episomal plasmids encoding L-MYC,LIN28,SOX2,KLF4,OCT4 and short hairpin RNA targeting P53. The resulting iPSCs had normal karyotype,were free of integrated episomal plasmids,expressed pluripotency markers,could differentiate into the three germ layers in vitro and retained the disease-causing ATXN3 mutation. Potentially,this iPSC line could be a useful tool for the investigation of SCA3 disease mechanisms. View Publication

Recent studies have suggested that human pluripotent stem cells (hPSCs) depend primarily on glycolysis and only increase oxidative metabolism during differentiation. Here,we demonstrate that both glycolytic and oxidative metabolism can support hPSC growth and that the metabolic phenotype of hPSCs is largely driven by nutrient availability. We comprehensively characterized hPSC metabolism by using 13C/2H stable isotope tracing and flux analysis to define the metabolic pathways supporting hPSC bioenergetics and biosynthesis. Although glycolytic flux consistently supported hPSC growth,chemically defined media strongly influenced the state of mitochondrial respiration and fatty acid metabolism. Lipid deficiency dramatically reprogramed pathways associated with fatty acid biosynthesis and NADPH regeneration,altering the mitochondrial function of cells and driving flux through the oxidative pentose phosphate pathway. Lipid supplementation mitigates this metabolic reprogramming and increases oxidative metabolism. These results demonstrate that self-renewing hPSCs can present distinct metabolic states and highlight the importance of medium nutrients on mitochondrial function and development. Zhang et al. apply metabolic flux analysis to comprehensively characterize the metabolism of human pluripotent stem cells cultured in different media. Cells maintained in chemically defined media significantly upregulate lipid biosynthesis and redox pathways to compensate for medium lipid deficiency while downregulating oxidative mitochondrial metabolism. View Publication

Genomic imprinting is an epigenetic phenomenon resulting in parent-of-origin-specific gene expression that is regulated by a differentially methylated region. Gene mutations or failures in the imprinting process lead to the development of imprinting disorders,such as Angelman syndrome. The symptoms of Angelman syndrome are caused by the absence of functional UBE3A protein in neurons of the brain. To create a human neuronal model for Angelman syndrome,we reprogrammed dermal fibroblasts of a patient carrying a defined three-base pair deletion in UBE3A into induced pluripotent stem cells (iPSCs). In these iPSCs,both parental alleles are present,distinguishable by the mutation,and express UBE3A. Detailed characterization of these iPSCs demonstrated their pluripotency and exceptional stability of the differentially methylated region regulating imprinted UBE3A expression. We observed strong induction of SNHG14 and silencing of paternal UBE3A expression only late during neuronal differentiation,in vitro. This new Angelman syndrome iPSC line allows to study imprinted gene regulation on both parental alleles and to dissect molecular pathways affected by the absence of UBE3A protein. View Publication