Scientific Resources

Although modulation of protein levels is an important tool for study of protein function,it is difficult or impossible to knockdown or knockout genes that are critical for cell growth or viability. For such genes,a conditional knockdown approach would be valuable. The FKBP protein-based destabilization domain (DD)-tagging approach,which confers instability to the tagged protein in the absence of the compound Shield-1,has been shown to provide rapid control of protein levels determined by Shield-1 concentration. Although a strategy to knock-in DD-tagged protein at the endogenous loci has been employed in certain parasite studies,partly due to the relative ease of knock-in as a result of their mostly haploid lifecycles,this strategy has not been demonstrated in diploid or hyperploid mammalian cells due to the relative difficulty of achieving complete knock-in in all alleles. The recent advent of CRISPR/Cas9 homing endonuclease-mediated targeted genome cleavage has been shown to allow highly efficient homologous recombination at the targeted locus. We therefore assessed the feasibility of using CRISPR/Cas9 to achieve complete knock-in to DD-tag the essential gene Treacher Collins-Franceschetti syndrome 1 (TCOF1) in human 293T cells. Using a double antibiotic selection strategy to select clones with at least two knock-in alleles,we obtained numerous complete knock-in clones within three weeks of initial transfection. DD-TCOF1 expression in the knock-in cells was Shield-1 concentration-dependent,and removal of Shield-1 resulted in destabilization of DD-TCOF1 over the course of hours. We further confirmed that the tagged TCOF1 retained the nucleolar localization of the wild-type untagged protein,and that destabilization of DD-TCOF1 resulted in impaired cell growth,as expected for a gene implicated in ribosome biogenesis. CRISPR/Cas9-mediated homologous recombination to completely knock-in a DD tag likely represents a generalizable and efficient strategy to achieve rapid modulation of protein levels in mammalian cells. View Publication

BACKGROUND Although studies have shown that Oct4,Sox2,Klf4,and c-Myc (OKSM)-mediated induced pluripotent stem cell (iPSC) technology sensitizes cancer cells to drugs,the potential risk of inserting c-Myc and random insertions of exogenous sequences into the genome persists. Several authors,including us,have presented microRNA (miRNA)-mediated reprogramming as an alternative approach. Herein,we evaluated the efficacy of miRNA-mediated reprogramming on hepatocellular carcinoma (HCC) cells. METHODS Among three miRNAs (miR-200c,miR-302s,and miR-369s) that were previously presented for miRNA-mediated reprogramming,miR-302 was expressed at low levels in HCC cells. After transfecting three times with miR-302,the cells were incubated in ES medium for 3 weeks and then characterized. RESULTS iPSC-like spheres were obtained after the 3-week incubation. Spheres presented high NANOG and OCT4 expression,low proliferation,high apoptosis,low epithelial-mesenchymal transition marker expression (N-cadherin,TGFBR2),and sensitization to drugs. Several miRNAs were changed (e.g.,low oncomiR miR-21,high miR-29b). cMyc was decreased,and methylation was elevated on histone 3 at lysine 4 (H3K4). Differentiated cells expressed markers of each germ layer (GFAP,FABP4,and ALB). AOF2 (also known as LSD1 or KDM1),one of the targets for miR-302,was repressed in iPSC-like-spheres. Silencing of AOF2 resulted in similar features of iPSC-like-spheres,including cMyc down-regulation and H3K4 methylation. In drug-resistant cells,sensitization was achieved through miR-302-mediated reprogramming. CONCLUSIONS miR-302-mediated iPSC technology reprogrammed HCC cells and improved drug sensitivity through AOF2 down-regulation,which caused H3K4 methylation and c-Myc repression. View Publication

OBJECTIVES Kidney disease is emerging as a critical medical problem worldwide. Because of limited treatment options for the damaged kidney,stem cell treatment is becoming an alternative therapeutic approach. Of many possible human stem cell sources,pluripotent stem cells are most attractive due to their self-renewal and pluripotent capacity. However,little is known about the derivation of renal lineage cells from human pluripotent stem cells (hPSCs). In this study,we developed a novel protocol for differentiation of nephron progenitor cells (NPCs) from hPSCs in a serum- and feeder-free system. MATERIALS AND METHODS We designed step-wise protocols for differentiation of human pluripotent stem cells toward primitive streak,intermediate mesoderm and NPCs by recapitulating normal nephrogenesis. Expression of key marker genes was examined by RT-PCR,real time RT-PCR and immunocytochemistry. Each experiment was independently performed three times to confirm its reproducibility. RESULTS After modification of culture period and concentration of exogenous factors,hPSCs can differentiate into NPCs that markedly express specific marker genes such as SIX2,GDNF,HOXD11,WT1 and CITED1 in addition to OSR1,PAX2,SALL1 and EYA1. Moreover,NPCs possess the potential of bidirectional differentiation into both renal tubular epithelial cells and glomerular podocytes in defined culture conditions. In particular,approximately 70% of SYN-positive cells were obtained from hPSC-derived NPCs after podocytes induction. NPCs can also form in vitro tubule-like structures in three dimensional culture systems. CONCLUSIONS Our novel protocol for hPSCs differentiation into NPCs can be useful for producing alternative sources of cell replacement therapy and disease modeling for human kidney diseases. View Publication

We recently reported that chronic lymphocytic leukemia (CLL) subgroups with distinct clonotypic BCRs present discrete patterns of TLR expression,function,and/or tolerance. In this study,to explore whether specific types of BCR/TLR collaboration exist in CLL,we studied the effect of single versus concomitant BCR and/or TLR stimulation on CLL cells from mutated (M-CLL) and unmutated CLL (U-CLL) cases. We stimulated negatively isolated CLL cells by using anti-IgM,imiquimod,and CpG oligodeoxynucleotide for BCR,TLR7,and TLR9,respectively,alone or in combination for different time points. After in vitro culture in the absence of stimulation,differences in p-ERK were identified at any time point,with higher p-ERK levels in U-CLL versus M-CLL. Pronounced p-ERK induction was seen by single stimulation in U-CLL,whereas BCR/TLR synergism was required in View Publication

Data suggest that clinical applications of human induced pluripotent stem cells (hiPSCs) will be realized. Nonetheless,clinical applications will require hiPSCs that are free of exogenous DNA and that can be manufactured through Good Manufacturing Practice (GMP). Optimally,derivation of hiPSCs should be rapid and efficient in order to minimize manipulations,reduce potential for accumulation of mutations and minimize financial costs. Previous studies reported the use of modified synthetic mRNAs to reprogram fibroblasts to a pluripotent state. Here,we provide an optimized,fully chemically defined and feeder-free protocol for the derivation of hiPSCs using synthetic mRNAs. The protocol results in derivation of fully reprogrammed hiPSC lines from adult dermal fibroblasts in less than two weeks. The hiPSC lines were successfully tested for their identity,purity,stability and safety at a GMP facility and cryopreserved. To our knowledge,as a proof of principle,these are the first integration-free iPSCs lines that were reproducibly generated through synthetic mRNA reprogramming that could be putatively used for clinical purposes. View Publication

Antiserum to epithelial membrane antigen and three monoclonal antibodies (MAb) to milk-fat globule membranes immunocytochemically stain only epithelial cells,whereas a fourth reacts also with myoepithelial cells in inter- and intralobular ducts of human breast. Staining with peanut lectin shows a gradual increase for epithelial cells,from little or no staining in ducts through variable staining in ductules to intense staining in secretory alveoli. Antisera and MAb to vimentin,smooth-muscle actin,MAb to the common acute lymphoblastic leukemia antigen and to a glycoprotein of 135 KD stain myoepithelial cells in main ducts,but this staining is reduced in inter- and intralobular ducts and ductules. MAb to epithelial-specific keratin 18 stain a minor population of ductal epithelial cells,the major population of epithelial cells in interlobular (ILD) and extralobular terminal ducts (ETD),and epithelial cells in a minority of ductules. In lactating glands most epithelial cells in ductules are stained,but the alveolar and myoepithelial cells are unstained. Keratin MAb PKK2 and LP34 strongly stain myoepithelial cells,but only a minor population of epithelial cells in main ducts. However,these MAb stain principally the epithelial cells in ILD,ETD,and a minority of ductules. In lactating glands most epithelial cells are stained in ductules,but the myoepithelial and not the alveolar cells are stained intensely in secretory lobules. It is suggested that the unusual staining pattern of cells found principally in the ILD,ETD,and some ductules may represent regions of growth and/or subpopulation(s) of cells intermediate between epithelial and myoepithelial cells. View Publication

Human embryonic stem cells (hESC) and induced pluripotent stem cells (hiPSC) can differentiate into many cell types and are important for regenerative medicine; however,further work is needed to reliably differentiate hESC and hiPSC into neural-restricted multipotent derivatives or specialized cell types under conditions that are free from animal products. Toward this goal,we tested the transition of hESC and hiPSC lines onto xeno-free (XF) / feeder-free conditions and evaluated XF substrate preference,pluripotency,and karyotype. Critically,XF transitioned H9 hESC,Shef4 hESC,and iPS6-9 retained pluripotency (Oct-4 and NANOG),proliferation (MKI67 and PCNA),and normal karyotype. Subsequently,XF transitioned hESC and hiPSC were induced with epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) to generate neuralized spheres containing primitive neural precursors,which could differentiate into astrocytes and neurons,but not oligoprogenitors. Further neuralization of spheres via LIF supplementation and attachment selection on CELLstart substrate generated adherent human neural stem cells (hNSC) with normal karyotype and high proliferation potential under XF conditions. Interestingly,adherent hNSC derived from H9,Shef4,and iPS6-9 differentiated into significant numbers of O4+ oligoprogenitors (∼20-30%) with robust proliferation; however,very few GalC+ cells were observed (∼2-4%),indicative of early oligodendrocytic lineage commitment. Overall,these data demonstrate the transition of multiple hESC and hiPSC lines onto XF substrate and media conditions,and a reproducible neuralization method that generated neural derivatives with multipotent cell fate potential and normal karyotype. View Publication

Integrating viruses represent robust tools for cellular reprogramming; however,the presence of viral transgenes in induced pluripotent stem cells (iPSCs) is deleterious because it holds the risk of insertional mutagenesis leading to malignant transformation. Here,we combine the robustness of lentiviral reprogramming with the efficacy of Cre recombinase protein transduction to derive iPSCs devoid of transgenes. By genome-wide analysis and targeted differentiation towards the cardiomyocyte lineage,we show that transgene-free iPSCs are superior to iPSCs before Cre transduction. Our study provides a simple,rapid and robust protocol for the generation of clinical-grade iPSCs suitable for disease modeling,tissue engineering and cell replacement therapies. View Publication

Embryonic stem (ES) and induced-pluripotent stem (iPS) cells can be grown indefinitely under appropriate conditions whilst retaining the ability to differentiate to cells representative of the three primary germ layers. Such cells have the potential to revolutionize medicine by offering treatment options for a wide range of diseases and disorders as well as providing a model system for elucidating mechanisms involved in development and disease. In recent years,evidence for the function of E-cadherin in regulating pluripotent and self-renewal signaling pathways in ES and iPS cells has emerged. In this review,we discuss the function of E-cadherin and its interacting partners in the context of development and disease. We then describe relevant literature highlighting the function of E-cadherin in establishing and maintaining pluripotent and self-renewal properties of ES and iPS cells. In addition,we present experimental data demonstrating that exposure of human ES cells to the E-cadherin neutralizing antibody SHE78.7 allows culture of these cells in the absence of FGF2-supplemented medium. View Publication

Post-translational modification of histones is fundamental to the regulation of basic nuclear processes and subsequent cellular events,including differentiation. In this study,we analyzed acetylated forms of histones H2A,H2B,and H4 during induced differentiation in mouse (mESCs) and human (hESCs) embryonic stem cells and during induced enterocytic differentiation of colon cancer cells in vitro. Endoderm-like differentiation of mESCs induced by retinoic acid and enterocytic differentiation induced by histone deacetylase inhibitor sodium butyrate were accompanied by increased mono-,di-,and tri-acetylation of histone H2B and a pronounced increase in di- and tri-acetylation of histone H4. In enterocytes,mono-acetylation of histone H2A also increased and tetra-acetylation of histone H4 appeared only after induction of this differentiation pathway. During differentiation of hESCs,we observed increased mono-acetylation and decreased tri-acetylation of H2B. Mono-,di-,and tri-acetylation of H4 were reduced,manifested by a significant increase in nonacetylated H4 histones. Levels of acetylated histones increased during induced differentiation in mESCs and during histone deacetylase (HDAC) inhibitor-induced enterocytic differentiation,whereas differentiation of human ESCs was associated with reduced acetylation of histones H2B and H4. View Publication

GANT61 is a small-molecule inhibitor of glioma-associated oncogene 1 (GLI1)- and GLI2-mediated transcription at the nuclear level that exerts its effect by preventing DNA binding. It has been demonstrated to induce cell death against Ewing's sarcoma family tumor (ESFT) cell lines in a dose-dependent manner. The most sensitive cell line was SK-N-LO,which expresses the EWS-FLI1 fusion gene. SK-N-LO cells treated with GANT61 showed cellular and nuclear morphological changes,including cell shrinkage,chromatin condensation and nuclear fragmentation,in a concentration-dependent manner,as visualized by Hoechst 33342 staining. Furthermore,annexin V-propidium iodide (PI) double-staining revealed a significant increase in the number of late apoptotic cells. GANT61 induced a significant decrease in the proportion of cells in the S phase. Significant decrease of the protein levels of GLI2,survivin,cyclin A and claspin,and significant increase of p21 expression was also observed in the cells treated with GANT61. Moreover,poly (ADP-ribose) polymerase (PARP) cleavage was observed,but no cleavage of caspase-3 or -7,or any change in the expressions of Bcl-2 or p53 were observed. These findings suggest that GANT61 induces cell death of SK-N-LO cells in a caspase-independent manner,by inhibiting DNA replication in the S phase. View Publication

As a critical tumor suppressor,p53 is inactivated in human cancer cells by somatic gene mutation or disruption of pathways required for its activation. Therefore,it is critical to elucidate the mechanism underlying p53 activation after genotoxic and cellular stresses. Accumulating evidence has indicated the importance of posttranslational modifications such as acetylation in regulating p53 stability and activity. However,the physiological roles of the eight identified acetylation events in regulating p53 responses remain to be fully understood. By employing homologous recombination,we introduced various combinations of missense mutations (lysine to arginine) into eight acetylation sites of the endogenous p53 gene in human embryonic stem cells (hESCs). By determining the p53 responses to DNA damage in the p53 knock-in mutant hESCs and their derivatives,we demonstrate physiological importance of the acetylation events within the core domain (K120 and K164) and at the C-terminus (K370/372/373/381/382/386) in regulating human p53 responses to DNA damage. View Publication