Endogenous Pluripotency Genes Research Articles

Molecular characterization of an iPSC line derived from a patient with cone‐rod dystrophy related to a mutation in the PROM1 gene

Aims/Purpose: The PROM1 gene encodes the protein Prominin‐1, which plays a crucial role in the morphogenesis of photoreceptor outer segments. The c.1354dupT mutation, associated with various inherited retinal diseases (IRD) phenotypes, leads to a premature stop codon. This study aimed to assess the silencing efficiency of reprogramming vectors and the expression of endogenous pluripotency genes in the iPSC line [DCB]‐FiPSC1‐Ep5F‐2.Methods: The iPSC line [DCB]‐FiPSC1‐Ep5F‐2 was generated from a patient with Cone‐rod dystrophy (CRD) linked to the c.1354dupT mutation in the PROM1 gene. iPSC colonies were stained using alkaline phosphatase (AP) blue membrane substrate. The c.1354dupT mutation was Sanger sequenced. To confirm the absence of episomal vector integration, quantitative PCR (qPCR) targeting a region common to all reprogramming vectors (within the EBNA1 gene) was conducted. Vector‐specific primer‐based quantitative reverse transcription PCR (qRT‐PCR) was used to assess the expression of reprogramming genes from the episomal vectors. Additionally, qRT‐PCR with gene‐specific primers was utilized to evaluate the expression of endogenous pluripotency genes. Untransfected fibroblasts served as the negative control, while fibroblasts transfected with the episomal vectors 72 h earlier were used as the positive control.Results: The iPSC line [DCB]‐FiPSC1‐Ep5F‐2 exhibited positive AP activity. The presence of the c.1354dupT mutation was confirmed. Furthermore, the number of copies of the EBNA1 gene was significantly lower in the generated iPSC line compared to the control. The relative mRNA expression of the reprogramming vectors was also significantly lower in the iPSC line, while the relative mRNA expression of the endogenous pluripotency genes was significantly higher than in the control.Conclusions: While further immunocytochemical characterization is necessary to fully ascertain iPSC pluripotency, the patient‐derived iPSC line [DCB]‐FiPSC1‐Ep5F‐2 shows promise as a disease model for personalized therapy development.

Establishment of Capra hircus somatic cells and induction of pluripotent stem-like cells.

Capra hircus (goat) induced pluripotent stem cells (giPSCs) harbor enormous scientific value and contribute to cellular agriculture, animal cloning, etc. Conventional approaches to giPSC generation suffer from complexity and low preparation efficiency. In the present study, we introduced the episomal vectors carrying the human pluripotent genes in goat somatic cells to generate the giPSC-like colonies. Initially, a simple non-enzymatic method was used to isolate the goat dermal fibroblast cells and, further, a cell line was established. Later, goat fibroblast cells were transfected with commercially available episomal vectors carrying the human pluripotent genes and successfully generated the iPSC-like colonies which exhibited the expression of goat endogenous pluripotent genes and positive staining with alkaline phosphatase. Moreover, giPS-like cells formed embryoid bodies (EBs)-like aggregates and weekly expressed the marker genes of two germ layers. Reprogramming of goat fibroblast using episomal vectors carrying human pluripotent genes could lead to the development of an efficient and time- and cost-effective approach to giPSC generation.

Reprogramming efficiency and pluripotency of mule iPSCs over its parents†.

The mule is the interspecific hybrid of horse and donkey and has hybrid vigour in muscular endurance, disease resistance and longevity over its parents. Here, we examined adult fibroblasts of mule (MAFs) compared with the cells from their parents (DAFs and HAFs) (each species have repeated three independent individuals) in proliferation, apoptosis and glycolysis and found significant differences. We subsequently derived mule, donkey and horse induced pluripotent stem cells (miPSCs, diPSCs and hiPSCs) from three independent individuals of each species and found the reprogramming efficiency of MAFs were significantly higher than that of cells of donkey and horse. miPSCs, diPSCs and hiPSCs all expressed high levels of crucial endogenous pluripotency genes such as POU class 5 homeobox 1 (POU5F1, OCT4), SRY-box 2 (SOX2) and Nanog homeobox (NANOG) and propagated robustly in single cell passaging. miPSCs exhibited faster proliferation and higher pluripotency and differentiation than diPSCs and hiPSCs, which were reflected in co-cultures and separate-cultures, teratoma formation and chimera contribution. The establishment of miPSCs provide unique research material for investigation of "heterosis" and perhaps is more significant to study hybrid gamete formation.

The Defects of Epigenetic Reprogramming in Dox-Dependent Porcine-iPSCs.

Porcine-induced pluripotent stem cells (piPSCs) are of great significance to animal breeding and human medicine; however, an important problem is that the maintenance of piPSCs mainly depends on exogenous expression of pluripotent transcription factors (TFs), and germline transmission-competent piPSCs have not yet been successfully established. In this study, we explore the defect of epigenetic reprogramming during piPSCs formation, including chromatin accessibility, DNA methylation, and imprinted gene expression, with high-throughput sequencing (ATAC-seq, WGBS, RNA-seq, and Re-seq) methods. We found the somatic features were successfully silenced by connecting closed chromatin loci with downregulated genes, while DNA methylation has limited effects on somatic silence. However, the incomplete chromatin remodeling and DNA demethylation in pluripotency genes hinder pluripotent activation, resulting in the low expression of endogenous pluripotency genes. In addition, the expression of potential imprinted genes was abnormal, and many allelic-biased expressed genes in porcine embryonic fibroblasts (PEFs) were erased, accompanied by establishment of new allelic-biased expressed genes in piPSCs. This study reveals the aberrant epigenetic reprogramming during dox-dependent piPSCs formation, which lays the foundation for research of porcine-iPSC reprogramming and genome imprinting.

A One-step strategy to target essential factors with auxin-inducible degron system in mouse embryonic stem cells.

The self-renewal and pluripotency of embryonic stem cells (ESCs) are conferred by networks including transcription factors and histone modifiers. The Auxin-inducible degron (AID) system can rapidly and reversibly degrade its target proteins and is becoming a powerful tool to explore novel function of key pluripotent and histone modifier genes in ESCs. However, the low biallelic tagging efficiency and a basal degradation level of the current AID systems deem it unsuitable to target key pluripotent genes with tightly controlled expression levels. Here, we develop a one-step strategy to successfully target and repress the endogenous pluripotent genes in mouse ESCs and replace their expression with AID fused transgenes. Therefore, this work provides an efficient way for employing the AID system to uncover novel function of essential pluripotent and chromatin modifier genes in ESCs.

Exogenous LIN28 Is Required for the Maintenance of Self-Renewal and Pluripotency in Presumptive Porcine-Induced Pluripotent Stem Cells

Porcine species have been used in preclinical transplantation models for assessing the efficiency and safety of transplants before their application in human trials. Porcine-induced pluripotent stem cells (piPSCs) are traditionally established using four transcription factors (4TF): OCT4, SOX2, KLF4, and C-MYC. However, the inefficiencies in the reprogramming of piPSCs and the maintenance of their self-renewal and pluripotency remain challenges to be resolved. LIN28 was demonstrated to play a vital role in the induction of pluripotency in humans. To investigate whether this factor is similarly required by piPSCs, the effects of adding LIN28 to the 4TF induction method (5F approach) on the efficiency of piPSC reprogramming and maintenance of self-renewal and pluripotency were examined. Using a retroviral vector, porcine fetal fibroblasts were transfected with human OCT4, SOX2, KLF4, and C-MYC with or without LIN28. The colony morphology and chromosomal stability of these piPSC lines were examined and their pluripotency properties were characterized by investigating both their expression of pluripotency-associated genes and proteins and in vitro and in vivo differentiation capabilities. Alkaline phosphatase assay revealed the reprogramming efficiencies to be 0.33 and 0.17% for the 4TF and 5TF approaches, respectively, but the maintenance of self-renewal and pluripotency until passage 40 was 6.67 and 100%, respectively. Most of the 4TF-piPSC colonies were flat in shape, showed weak positivity for alkaline phosphatase, and expressed a significantly high level of SSEA-4 protein, except for one cell line (VSMUi001-A) whose properties were similar to those of the 5TF-piPSCs; that is, tightly packed and dome-like in shape, markedly positive for alkaline phosphatase, and expressing endogenous pluripotency genes (pOCT4, pSOX2, pNANOG, and pLIN28), significantly high levels of pluripotent proteins (OCT4, SOX2, NANOG, LIN28, and SSEA-1), and a significantly low level of SSEA-4 protein. VSMUi001-A and all 5F-piPSC lines formed embryoid bodies, underwent spontaneous cardiogenic differentiation with cardiac beating, expressed cardiomyocyte markers, and developed teratomas. In conclusion, in addition to the 4TF, LIN28 is required for the effective induction of piPSCs and the maintenance of their long-term self-renewal and pluripotency toward the development of all germ layers. These piPSCs have the potential applicability for veterinary science.

Generation of two iPS cell lines (HIHDNDi001-A and HIHDNDi001-B) from a Parkinson's disease patient carrying the heterozygous p.A30P mutation in SNCA.

Dermal fibroblasts from a patient carrying a heterozygous c.88G>C mutation in the SNCA gene that encodes alpha-synuclein were reprogrammed to pluripotency by retroviruses. This pathogenic mutation generates the p.A30P form of the alpha-synuclein protein leading to autosomal dominantly inherited Parkinson's disease (PD). Two clonal iPS cell lines were generated (A30P-3 and A30P-4) and characterised by validating the silencing of viral transgenes, the expression of endogenous pluripotency genes, directed differentiation into three germ layers in-vitro and a stable molecular genotype. These iPSC lines will serve as a valuable resource in determining the role of the p.A30P SNCA mutation in PD pathogenesis.

Regulatory Dynamics of Tet1 and Oct4 Resolve Stages of Global DNA Demethylation and Transcriptomic Changes in Reprogramming

Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) involves the reactivation of endogenous pluripotency genes and global DNA demethylation, but temporal resolution of these events using existing markers is limited. Here, we generate murine transgenic lines harboring reporters for the 5-methylcytosine dioxygenase Tet1 and for Oct4. By monitoring dual reporter fluorescence during pluripotency entry, we identify a sequential order of Tet1 and Oct4 activation by proximal and distal regulatory elements. Full Tet1 activation marks an intermediate stage that accompanies predominantly repression of somatic genes, preceding full Oct4 activation, and distinguishes two waves of global DNA demethylation that target distinct genomic features but are uncoupled from transcriptional changes. Tet1 knockout shows that TET1 contributes to both waves of demethylation and activates germline regulatory genes inreprogramming intermediates but is dispensable for Oct4 reactivation. Our dual reporter system for time-resolving pluripotency entry thus refines the molecular roadmap of iPSC maturation.

Osblr8 orchestrates intrachromosomal loop structure required for maintaining stem cell pluripotency.

Induced pluripotent stem cells (iPSCs), derived from reprogramming of somatic cells by a cocktail of transcription factors, have the capacity for unlimited self-renewal and the ability to differentiate into all of cell types present in the body. iPSCs may have therapeutic potential in regenerative medicine, replacing injured tissues or even whole organs. In this study, we examine epigenetic factors embedded in the specific 3-dimensional intrachromosomal architecture required for the activation of endogenous pluripotency genes. Using chromatin RNA in situ reverse transcription sequencing (CRIST-seq), we identified an Oct4-Sox2 binding long noncoding RNA, referred as to Osblr8, that is present in association with pluripotency status. Osblr8 was highly expressed in iPSCs and E14 embryonic stem cells, but it was silenced in fibroblasts. By using shRNA to knock down Osblr8, we found that this lncRNA was required for the maintenance of pluripotency. Overexpression of Osblr8 activated endogenous stem cell core factor genes. Mechanistically, Osblr8 participated in the formation of an intrachromosomal looping structure that is required to activate stem cell core factors during reprogramming. In summary, we have demonstrated that lncRNA Osblr8 is a chromatin architecture modulator of pluripotency-associated master gene promoters, highlighting its critical epigenetic role in reprogramming.

219 Invitro culture environment influences the ability to generate porcine primordial germ cell-like from induced pluripotent stem cells

The ability to generate primordial germ cell-like (PGCLs) from induced pluripotent stem cells (iPSCs) in swine could greatly contribute to regenerative medicine. Herein, we aimed to generate porcine PGCLs (ipPGCLs) from iPSCs derived from different culture systems. Porcine (p)iPSCs from fibroblasts of stillborn animals (n=3) were transduced with lentiviral vectors containing murine OCT4, SOX2, c-MYC, and KLF4 cDNAs and maintained in iPSC medium on mouse embryonic fibroblasts (MEFs). The cells were divided into three groups: (1) supplemented with 10ngmL−1 basic fibroblast growth factor (bFGF) and murine leukemia inhibitory factor (LIF), (2) only bFGF, or (3) only LIF. The piPSC colonies were generated and characterised for pluripotency. To induce piPSCs into ipPGCLs, three or more cell lines from each culture condition (after passage 20) were differentiated into epiblast stem cell-like cells (EpiLCs) by culture with 20ngmL−1 Activin A, 12ngmL−1 bFGF, and 1% knockout serum replacement (KSR) for 2 days. Then, cells were further induced to differentiate by nonadherent culture and supplementation with 500ngmL−1 bone morphogenetic protein (BMP)4, 500ngmL−1 BMP8a, LIF, 100ngmL−1 stem cell factor (SCF), and 50ngmL−1 epidermal growth factor for 4 days. The ipPGCLs were characterised by cell morphology and detection of germ cell markers by immunofluorescence and gene expression. Statistical analysis was determined by one-way ANOVA (Prism Software). Co-location quantification was determined using the plugin Colocalization Threshold in Image J software (National Institutes of Health). On average, the efficiency rate of iPSC generation was 71% for the iPSCs-bFGF group, 17% for the LIF group, and 85% for the bFGF+LIF group. All iPSCs colonies were positive for alkaline phosphatase and OCT4, SOX2, NANOG, TRA1-60, TRA1-81, SSEA1, and SSEA4 by immunofluorescence. Embryoid body assay revealed that the piPSCs were able to differentiate into three germ layers. The culture condition did not influence the expression of OCT4, NANOG, and KLF4 based on qRT-PCR, however; SOX2 was upregulated in the LIF group (P<0.05). The ipPGCLs generated showed a round morphology. Analysis of endogenous pluripotent genes OCT4, SOX2, and NANOG throughout differentiation (fibroblasts, iPSCs, EpiLCs, and PGCLs) revealed a mild upregulation in ipPGCLs, while OCT4 was slightly downregulated in ipPGCLs from iPSCs-LIF group. PRDM14 and STELLA were not observed in ipPGCLs, although BLIMP1 was present; DAZL and VASA were mildly upregulated. The STELLA, VASA, OCT4, and SOX2 proteins were detected in ipPGCLs, and DAZL was detected only in ipPGCLs from the iPSCs-FGF group. Protein co-localization analysis showed that ipPGCLs from the iPSCs-FGF group were 100% OCT4+STELLA-positive, 55% positive for DAZL+SOX2, and 66% positive for VASA+NANOG; for the LIF group: 99.3% were OCT4+STELLA positive, DAZL was not detected, 95.2% were positive for SOX2 and 85.6% for VASA+NANOG. In the bFGF+LIF group, 95.8% were positive for OCT4+STELLA, DAZL and SOX2 were not observed, and 70% were positive for VASA+NANOG. Exogenous reprogramming factors were still expressed and did not differ between groups. These results indicate that, under our conditions, the iPSCs-FGF group may represent the best culture condition for induction into ipPGCLs. Financial support for this study was provided by FAPESP (2015/25564-0 and 2015/26818-5).

Generation of induced pluripotent stem cells using elastin like polypeptides as a non-viral gene delivery system

Induced pluripotent stem cells (iPSCs) have been generated from various somatic cells using different approaches; however, a major restriction of reprogramming methods is the use of viral vectors, which have the risk of causing genome-integration of viral DNA. Here, without a viral vector, we generated iPSCs from mouse fibroblasts using an elastin-like polypeptide (ELP)-based transfection method. Our findings support the possible use of ELPs for delivery of the reprogramming genes in to somatic cells for generation of iPSCs. Results of gel retardation assay demonstrated efficient complexation of ELPs with a plasmid containing the four Yamanaka stem cell factors, Oct-4, Klf4, c-myc, and Sox2. After transfection, the iPSCs showed embryonic stem cell-like characteristics, including expression of endogenous pluripotency genes, differentiation into three germ layer lineages, and formation of teratomas in vivo. Our results demonstrate that ELP-based gene delivery may provide a safe method for use in generation of virus-free and exogenous DNA-free iPSCs, which will be crucial for future applications in stem cell-based therapies.

Generation of porcine induced-pluripotent stem cells from Sertoli cells

Induced pluripotent stem cells (iPSCs) are generated by reprogramming of somatic cells using four transcription factors: OCT4, SOX2, KLF-4, and c-MYC (OSKM). However, reprogramming efficiency of iPSCs is currently poor. In this study, we used the Sertoli line as a novel cell source for somatic cell reprogramming. Neonatal testes were collected from 1-week-old piglets. The testes were digested by a two-step enzymatic method to isolate Sertoli cells. The latter were transfected with retroviral vectors expressing OSKM. The Sertoli iPSC-like colonies were subjected to morphological analysis, alkaline phosphatase staining, RT-PCR, G-banding karyotyping, in vitro differentiation, and in vivo differentiation. Primary Sertoli cells had polygon-shaped morphology and manifested phagocytic activity as determined by a fluorescent bead assay. Sertoli cells also expressed the anti-Müllerian hormone protein in the cytoplasm. According to RT-PCR results, these cells expressed Sertoli cell markers (FSHR, KRT18, and GATA6) and endogenous transcription factors genes (KLF4 and c-MYC). A total of 240 colonies (0.3% efficiency) were detected by day 7 after viral transduction of 72500 cells. The Sertoli iPSC-like colonies contained small cells with a high nucleus-to-cytoplasm ratio. These colonies tested positive for alkaline phosphatase staining, expressed endogenous pluripotency genes, and had a normal karyotype. All these cell lines could form in vitro three-dimensional aggregates that represented three germ layers of embryonic-like cells. A total of two cell lines used for in vivo differentiation produced high-efficiency teratoma. In conclusion, Sertoli cells can efficiently serve as a novel cell source for iPSC reprogramming.

209 Overexpression of WAVE1 activates pluripotency-related genes in porcine somatic cells

Despite extensive efforts, cellular reprogramming in livestock species has had limited success. Induced pluripotent stem cells (iPSC) have been established; however, these cells often show incomplete reprogramming status, and constitutive expression of exogenous reprogramming factors is required due to inactivation of endogenous pluripotency-related genes. A previous study reported that overexpression of the Xenopus egg-derived WAVE1 gene assists reprogramming of murine somatic cells into the pluripotent state. The WAVE1 gene is also required for oocyte-mediated reprogramming by transcriptional activation of embryonic genes. In this study, we investigated the role of porcine WAVE1 in cellular reprogramming by inducing overexpression of WAVE1 in porcine fetal fibroblasts (PFF). Previously, we cloned the coding sequences (CDS) of porcine WAVE1 using porcine expressed sequence tags (EST) and predicted porcine WAVE1 sequences. The WAVE1 CDS, derived from porcine mature oocytes, was overexpressed in PFF by transfection using the Neon system. Then, G418-based antibiotic selection was performed to enrich cells constitutively overexpressing WAVE1. After cell culture for 4 weeks, RNA was extracted from the WAVE1 transfected and control PFF, and cDNA was synthesised from the RNA using random hexamers. The cDNAs were used for quantitative reverse transcription PCR to analyse the expression pattern of pluripotency- and reprogramming-related genes: POU5F1, NANOG, KLF2, SOX2, DPPA3, ZFP42, ESRRB, TET1, TET2, and TET3. The expression of target genes were normalized to GAPDH level and the ΔΔCt algorithm was used for analysis. Three technical replications and 4 biological replications were performed. Student’s t-test was used for the comparison and P-values<0.05 were considered significant. On average, a 20-fold increase of WAVE1 was observed in the transfected cells compared with control cells. Interestingly, overexpression of WAVE1 activated some of the pluripotency-related genes in porcine PFF. Specifically, transcript levels of NANOG, KLF2, and SOX2 were increased compared with those in the control cells (P<0.05). In addition, levels of POU5F1 and DPPA3 tended to be higher in WAVE1-overexpressing cells compared with those in the control cells (P<0.1). However, transcript levels of other pluripotency-related genes (ZFP42, DPPA3, and ESRRB) did not change in WAVE1-overexpressing cells. The expression level of TET family (TET1, TET2, and TET3), which is enriched in pluripotent stem cells and a key regulator of DNA methylation, was not changed in WAVE1-overexpressing cells. These results indicate that WAVE1 can be a novel factor in porcine cellular reprogramming. Considering that a key defect of current porcine iPSC generation is insufficient expression of endogenous pluripotency genes, application of WAVE1 may enhance quality of porcine iPSC. We intend to evaluate expression of pluripotency markers at the protein level in WAVE1-overexpressing cells and investigate mechanisms underpinning WAVE1-mediated reprogramming process in future studies.

Mitochondrial Dysfunctions Contribute to Hypertrophic Cardiomyopathy in Patient iPSC-Derived Cardiomyocytes with MT-RNR2 Mutation.

SummaryHypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young individuals. A potential role of mtDNA mutations in HCM is known. However, the underlying molecular mechanisms linking mtDNA mutations to HCM remain poorly understood due to lack of cell and animal models. Here, we generated induced pluripotent stem cell-derived cardiomyocytes (HCM-iPSC-CMs) from human patients in a maternally inherited HCM family who carry the m.2336T>C mutation in the mitochondrial 16S rRNA gene (MT-RNR2). The results showed that the m.2336T>C mutation resulted in mitochondrial dysfunctions and ultrastructure defects by decreasing the stability of 16S rRNA, which led to reduced levels of mitochondrial proteins. The ATP/ADP ratio and mitochondrial membrane potential were also reduced, thereby elevating the intracellular Ca2+ concentration, which was associated with numerous HCM-specific electrophysiological abnormalities. Our findings therefore provide an innovative insight into the pathogenesis of maternally inherited HCM.

Preserving self-renewal of porcine pluripotent stem cells in serum-free 3i culture condition and independent of LIF and b-FGF cytokines

Derivation of bona fide porcine pluripotent stem cells is still a critical issue because porcine embryonic stem cells (ESCs) are not available yet, and most of the culture conditions to maintain porcine induced pluripotent stem cells (piPSCs) are based on conditions for mouse and human iPS cells. In this study, we generated a doxycycline-inducible porcine iPS cell line (DOX-iPSCs) and used it to screen the optimal culture condition to sustain the self-renewal of piPSCs. We found that LIF and b-FGF were required for porcine cell reprogramming, but were not essential cytokines for maintaining the self-renewal and pluripotency of piPSCs. A serum-free 3i medium, which includes three inhibitors CHIR99021, SB431542, and PD0325901, three cytokines BMP4, SCF, and IL-6, and human platelet lysates (PL), was made through serious selections. In 3i condition, the doxycycline-inducible iPSCs could be passaged for a long term without the addition of doxycycline, and the flattened morphology of intermediate state piPSCs could convert to the naïve-like morphology with the increase in endogenous pluripotent gene expressions. Additionally, pPSC cell line isolated from 5.5 days blastocysts could be sustained in 3i medium and the expression of endogenous pluripotent genes OCT4, ESRRB, and STELLA was significantly increased. Our finding directed a new reprogramming strategy by using 3i condition to maintain and convert primed piPSCs into naïve-like pluripotent state. A combination of traditional LIF/b-FGF conditions and 3i condition may help us to find out an appropriate reprogramming approach to generate the naïve state of porcine iPSCs.

186 Improving Success Rate of Establishment and Maintenance of Porcine Induced Pluripotent Stem Cells by Investigation of Colony Morphology

Induced pluripotent stem cells (iPS cells) are generated by reprogramming of somatic cells using ectopic introduction of 4 transcription factors, including OCT4, SOX2, KLF4, and c-MYC (OSKM). Fibroblast cells are the most commonly used as a primary cell source for iPS cells because they are easy to harvest and culture. However, reprogramming efficiency of porcine fibroblasts is poor (~0.1%). During reprogramming process, mixed populations of primary colonies become the major obstacle in iPS establishment. In this study, we characterised 2 different colony morphologies at colony pick-up (compact and loose iPS morphology). We hypothesised that compact colonies will proceed to long-term culture and pluripotency. The fibroblast cells were isolated from tails of piglets and transfected with retroviral vectors expressing OSKM. The primary colonies were counted on Day 7 after gene transduction. The iPS-like colonies were divided into compact (n = 10) and loose (n = 10) morphology at colony pick-up. The characteristics of iPS-like cell lines were analysed by morphology, alkaline phosphatase staining, G-banding karyotype, immunofluorescence staining (OCT4), pluripotent gene expression (RT-PCR), and embryoid body formation. A total of 1,697 iPS-like colonies (2.34%) were observed. The compact colonies contained with tightly packed cells with distinct border between iPS colony and feeder cells, while colonies with irregular shape and border were classified as loose colonies. These 2 types of iPS-like colonies expressed alkaline phosphatase and OCT4. A total 5 of 10 (50%) compact morphology cell lines could be maintained in the undifferentiated state for more than 50 passages. But only 3 of 10 (30%) loose morphology cell lines demonstrated pluripotent characteristics. G-Banding karyotype analysis revealed normal chromosome number (n = 38). All of the cell lines also expressed endogenous pluripotent genes, including OSKM and NANOG and formed three-dimensional aggregating masses. In this study, we found that the cell lines from compact morphology could be maintained for longer than those of the loose morphology. A high rate of differentiation of loose iPS colony may also indicate that this type of colony has different pluripotency signals or incomplete reprogramming compared with compact colony. In conclusion, selection of compact colony morphology at colony pick-up is simple and reflects long-term propagation of porcine iPS cell lines. This information is important for improving the success rate of establishment and maintenance of porcine iPS cells.

RNA-Guided Activation of Pluripotency Genes in Human Fibroblasts.

Specific activation of endogenous genes can be achieved by programmable artificial transcription factors (ATFs). In this study, we compared two artificial, programmable, clustered regularly interspaced short palindromic repeats (CRISPR)-based, ubiquitous transcription factors: deficient CRISPR-associated protein 9 (dCas9)-VP64 (CRISPRa) alone, or a combination of dCas9-VP64 and MS2-P65-HSF1 [synergistic activation mediator (SAM) system] mediated activation of five pluripotency genes: KLF4 (K), LIN28 (L), MYC (M), OCT4 (O), and SOX2 (S) in human cells (HEK293T, HeLa, HepG2, and primary fibroblasts). Activation potential was monitored using a luciferase reporter system and we found that both CRISPRa and SAM can efficiently activate the proximal promoter of all five genes. We also observed that the guide RNA (gRNA) target sites and number of gRNAs have a major effect on gRNA-guided activation efficiency. Furthermore, increased activation efficiency (>3-folds) could be achieved by the SAM system compared to CRISPRa. In addition, we discovered that only the SAM system could efficiently activate LIN28, OCT4, and SOX2 expression (up to 100-folds compared to coexpression with a scrambled gRNA) in primary human fibroblasts. This SAM-mediated activation of LOS can be stably maintained for over 20 days in fibroblasts cultured in either fibroblasts or stem cell medium. However, when attempting to use the SAM-LOS activation as an approach for induced pluripotent stem cells-reprogramming, no embryonic stem-like colonies could be obtained from these SAM fibroblasts. In conclusion, our study showed that CRISPR/Cas9-based ATFs are potent to activate and maintain transcription of endogenous human pluripotent genes. However, future improvements of the system are still required to improve activation efficiency and cellular reprogramming using ATFs.

Mouse iPSC generated with porcine reprogramming factors as a model for studying the effects of non-silenced heterologous transgenes on pluripotency

Mouse somatic cells can be reprogrammed to pluripotency by the ectopic expression of four pluripotency transcription factors, Oct4, Sox2, cmyc, and Klf4. Usually, silencing of the exogenous reprogramming factors is considered to be essential for complete reprogramming and differentiation. In the vast majority of studies, murine pluripotency transcription factor sequences have been used for the reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPSC). The effectiveness of xenogeneic transcription factors in miPSC generation has not yet been investigated in detail. Here, we evaluated transposon-based vectors with four porcine pluripotency factors for their ability to reprogram mouse fetal fibroblasts (MEFs) harboring an Oct4-EGFP reporter construct to pluripotency. Additionally, we examined the effects of the non-silenced heterologous transgenes on the expression levels of key endogenous pluripotency markers and the differentiation capacities of the miPSC. Within 8 days of transfection with porcine reprogramming transcription factors the MEFs acquired typical compact miPSC morphology and upregulated expression of endogenous Oct4 and other critical pluripotency genes. Consequently, the transgenes under the control of the TetO promoter became silenced, while the CAG-controlled constructs were expressed throughout the period of culture. Despite the continuous transgene expression, the CAG-miPSC showed normal morphology and were capable of differentiation into the three primary germ layers in vitro and in vivo. However, the expression levels of important endogenous pluripotency markers, Klf4, c-myc, Rex1, and Utf1, were significantly lower in CAG-miPSC compared with TetO-miPSC with silenced reprogramming cassettes. Surprisingly, the endogenous Oct4 and Sox2 expression levels were not affected by the residual transgene expression. Our results suggest that porcine reprogramming transcription factors are suitable for production of miPSC, but silencing of the heterologous transgenes may be necessary for complete reprogramming to pluripotency.

In vitro effects of reprogramming factors on the expressions of pluripotent genes and CD34 gene in human acute promyelocytic leukemia HL-60 cells

ObjectiveOur study aims to explore the in vitro effects of reprogramming factors on the expressions of pluripotent genes and CD34 gene in HL-60 cells. MethodsAccording to the construction of lentiviral vector LV-OSCK of reprogramming factors (Oct-4, Sox2, Klf4, c-Myc), 293T cells were transfected to detect virus titer. The endogenous pluripotent genes (Oct4, SOX2, c-Myc and Klf4) and CD34 mRNA and protein expressions were detected by AP staining, immunofluorescence staining, qRT-PCR and flow cytometry. ResultsExpressions of Oct4, SOX2, c-Myc and Klf4 were 0.220±0.013, 0.186±0.009, 0.287±0.015 and 0.153±0.007. These levels were significantly higher in the experimental group than the control and blank groups. CD34 protein expression in the experimental group was also discovered to be significantly higher than the other two groups. ConclusionThe reprogramming factors could increase the expressions of pluripotent genes and CD34 gene in HL-60 cells.

EpCAM Intracellular Domain Promotes Porcine Cell Reprogramming by Upregulation of Pluripotent Gene Expression via Beta-catenin Signaling

Previous study showed that expression of epithelial cell adhesion molecule (EpCAM) was significantly upregulated in porcine induced pluripotent stem cells (piPSCs). However, the regulatory mechanism and the downstream target genes of EpCAM were not well investigated. In this study, we found that EpCAM was undetectable in fibroblasts, but highly expressed in piPSCs. Promoter of EpCAM was upregulated by zygotic activated factors LIN28, and ESRRB, but repressed by maternal factors OCT4 and SOX2. Knocking down EpCAM by shRNA significantly reduced the pluripotent gene expression. Conversely, overexpression of EpCAM significantly increased the number of alkaline phosphatase positive colonies and elevated the expression of endogenous pluripotent genes. As a key surface-to-nucleus factor, EpCAM releases its intercellular domain (EpICD) by a two-step proteolytic processing sequentially. Blocking the proteolytic processing by inhibitors TAPI-1 and DAPT could reduce the intracellular level of EpICD and lower expressions of OCT4, SOX2, LIN28, and ESRRB. We noticed that increasing intracellular EpICD only was unable to improve activity of EpCAM targeted genes, but by blocking GSK-3 signaling and stabilizing beta-catenin signaling, EpICD could then significantly stimulate the promoter activity. These results showed that EpCAM intracellular domain required beta-catenin signaling to enhance porcine cell reprogramming.