Mechanisms of OCT4 on 3,5,3'-Tri-iodothyronine and FSH-induced Granulosa Cell Development in Female Mice

Octamer-binding transcription factor 4 (OCT4) regulates the pluripotency of stem cells and also plays important roles in granulosa cells growth, which is regulated by follicle-stimulating hormone (FSH). Thyroid hormone (TH) is important for the development and maturation of follicles and the maintenance of various endocrine functions. Although 3,5,3'-triiodothyronine (T3) enhances the effects of FSH on the regulation of the growth of granulosa cells and development of follicles, it is unclear whether and, if so, how TH combines with FSH to regulate OCT4 expression in granulosa cells during the preantral to early antral transition stage. Our results showed that T3 enhanced FSH-induced OCT4 expression. However, T3/FSH-induced cellular growth was reduced by OCT4 small interfering RNA. OCT4 knockdown significantly increased the number of apoptotic cell. Moreover, T3 combined with FSH to increase estrogen receptor β (ERβ) expression but did not significantly affect estrogen receptor α expression. ERβ knockdown dramatically decreased T3/FSH-induced OCT4 expression and cell development and increased cell apoptosis. The phosphoinositide 3-kinases/protein kinase B pathway was involved in hormones inducing OCT4 and ERβ expressions. Furthermore, the hormones regulating OCT4 and ERβ expressions were regulated by cytochrome P450 lanosterol 14a-demethylase (CYP51), a key enzyme in sterol and steroid biosynthesis. T3 and FSH cotreatment potentiated cellular development by upregulating OCT4 expression, which is mediated by CYP51 and ERβ. These regulatory processes are mediated by the phosphoinositide 3-kinase/protein kinase B signaling pathway. These findings suggest that OCT4 mediates the T3 and FSH-induced development of follicles.

Dissecting OCT4 defines the role of nucleosome binding in pluripotency

Pioneer transcription factors such as OCT4 can target silent genes embedded in nucleosome-dense regions. How nucleosome interaction enables transcription factors to target chromatin and determine cell identity remains elusive. Here, we systematically dissect OCT4 to show that nucleosome binding is encoded within the DNA-binding domain and yet can be uncoupled from free-DNA binding. Furthermore, accelerating the binding kinetics of OCT4 to DNA enhances nucleosome binding. In cells, uncoupling nucleosome binding diminishes the ability of OCT4 to individually access closed chromatin, while more dynamic nucleosome binding results in expansive genome scanning within closed chromatin. However, both uncoupling and enhancing nucleosome binding are detrimental to inducing pluripotency from differentiated cells. Remarkably, stable interactions between OCT4 and nucleosomes are continuously required for maintaining the accessibility of pluripotency enhancers in stem cells. Our findings reveal how the affinity and residence time of OCT4-nucleosome complexes modulate chromatin accessibility during cell fate changes and maintenance.

Chaperone-mediated autophagy regulates the pluripotency of embryonic stem cells

Embryonic stem cells can propagate indefinitely in a pluripotent state, able to differentiate into all types of specialized cells when restored to the embryo. What sustains their pluripotency during propagation remains unclear. Here, we show that core pluripotency factors OCT4 and SOX2 suppress chaperone-mediated autophagy (CMA), a selective form of autophagy, until the initiation of differentiation. Low CMA activity promotes embryonic stem cell self-renewal, whereas its up-regulation enhances differentiation. CMA degrades isocitrate dehydrogenases IDH1 and IDH2 and reduces levels of intracellular α-ketoglutarate, an obligatory cofactor for various histone and DNA demethylases involved in pluripotency. These findings suggest that CMA mediates the effect of core pluripotency factors on metabolism, shaping the epigenetic landscape of stem cells and governing the balance between self-renewal and differentiation.

Stimulation of atypical cannabinoid receptor GPR55 abolishes the symptoms of detrusor overactivity in spontaneously hypertensive rats

Overactive bladder is a troublesome disease that affects 15% of the population in developed countries. Since pharmacotherapy of this condition is frequently associated with side effects, the better tolerated drugs are being searched for. The main objective of our study was to check whether activation of the atypical cannabinoid receptor GPR55 would normalize the changes in cystometric, cardiovascular and biochemical parameters in the hypertensive female Wistar-Kyoto rats presenting the symptoms of overactive bladder accompanied by inflammation and oxidative damage in the urinary tracts. A 14-day intra-arterial administration of O-1602 (0.25 mg/kg/day), a potent agonist of GRP55 receptors, was able to abolish the signs of detrusor overactivity, inflammation and oxidative damage in the urinary bladder of the spontaneously hypertensive animals. Moreover, it increased their heart rate, reduced the mean blood pressure, and normalized the levels of several proteins that play a significant role in the proper functioning of the urinary bladder (i.e., calcitonin gene related peptide, organic cation transporter 3, extracellular signal-regulated kinase 1/2, vesicular acetylcholine transporter, RhoA). Based on the outcomes of our experiments, the atypical cannabinoid receptor GPR55 has emerged as a potential drug target for the treatment of overactive bladder in female subjects. It could be particularly attractive in the cases in which this condition is accompanied with elevated blood pressure, though further studies on this subject are needed.

OCT4 Silencing Triggers Its Epigenetic Repression and Impairs the Osteogenic and Adipogenic Differentiation of Mesenchymal Stromal Cells

Mechanisms mediating mesenchymal stromal/stem cells’ (MSCs) multipotency are unclear. Although the expression of the pluripotency factor OCT4 has been detected in MSCs, whether it has a functional role in adult stem cells is still controversial. We hypothesized that a physiological expression level of OCT4 is important to regulate MSCs’ multipotency and trigger differentiation in response to environmental signals. Here, we specifically suppressed OCT4 in MSCs by using siRNA technology before directed differentiation. OCT4 expression levels were reduced by 82% in siOCT4-MSCs, compared with controls. Interestingly, siOCT4-MSCs also presented a hypermethylated OCT4 promoter. OCT4 silencing significantly impaired the ability of MSCs to differentiate into osteoblasts. Histologic and macroscopic analysis showed a lower degree of mineralization in siOCT4-MSCs than in controls. Moreover, OCT4 silencing prevented the up-regulation of osteoblast lineage-associated genes during differentiation. Similarly, OCT4 silencing resulted in decreased MSC differentiation potential towards the adipogenic lineage. The accumulation of lipids was reduced 3.0-fold in siOCT4-MSCs, compared with controls. The up-regulation of genes engaged in the early stages of adipogenesis was also suppressed in siOCT4-MSCs. Our findings provide evidence of a functional role for OCT4 in MSCs and indicate that a basal expression of this transcription factor is essential for their multipotent capacity.

Revealing cellular and molecular transitions in neonatal germ cell differentiation using single cell RNA sequencing

Neonatal germ cell development provides the foundation of spermatogenesis. However, a systematic understanding of this process is still limited. To resolve cellular and molecular heterogeneity in this process, we profiled single cell transcriptomes of undifferentiated germ cells from neonatal mouse testes and employed unbiased clustering and pseudotime ordering analysis to assign cells to distinct cell states in the developmental continuum. We defined the unique transcriptional programs underlying migratory capacity, resting cellular states and apoptosis regulation in transitional gonocytes. We also identified a subpopulation of primitive spermatogonia marked by CD87 (plasminogen activator, urokinase receptor), which exhibited a higher level of self-renewal gene expression and migration potential. We further revealed a differentiation-primed state within the undifferentiated compartment, in which elevated Oct4 expression correlates with lower expression of self-renewal pathway factors, higher Rarg expression, and enhanced retinoic acid responsiveness. Lastly, a knockdown experiment revealed the role of Oct4 in the regulation of gene expression related to the MAPK pathway and cell adhesion, which may contribute to stem cell differentiation. Our study thus provides novel insights into cellular and molecular regulation during early germ cell development.

Rabbit induced pluripotent stem cells retain capability of in vitro cardiac differentiation

Stem cells are promising cell source for treatment of multiple diseases as well as myocardial infarction. Rabbit model has essentially used for cardiovascular diseases and regeneration but information on establishment of induced pluripotent stem cells (iPSCs) and differentiation potential is fairly limited. In addition, there is no report of cardiac differentiation from iPSCs in the rabbit model. In this study, we generated rabbit iPSCs by reprogramming rabbit fibroblasts using the 4 transcription factors (OCT3/4, SOX2, KLF4, and c-Myc). Three iPSC lines were established. The iPSCs from all cell lines expressed genes (OCT3/4, SOX2, KLF4 and NANOG) and proteins (alkaline phosphatase, OCT-3/4 and SSEA-4) essentially described for pluripotency (in vivo and in vitro differentiation). Furthermore, they also had ability to form embryoid body (EB) resulting in three-germ layer differentiation. However, ability of particular cell lines and cell numbers at seeding markedly influenced on EB formation and also their diameters. The cell density at 20,000 cells per EB was selected for cardiac differentiation. After plating, the EBs attached and cardiac-like beating areas were seen as soon as 11 days of culture. The differentiated cells expressed cardiac progenitor marker FLK1 (51 ± 1.48%) on day 5 and cardiac troponin-T protein (10.29 ± 1.37%) on day 14. Other cardiac marker genes (cardiac ryanodine receptors (RYR2), α-actinin and PECAM1) were also expressed. This study concluded that rabbit iPSCs remained their in vitro pluripotency with capability of differentiation into mature-phenotype cardiomyocytes. However, the efficiency of cardiac differentiation is still restricted.

Generation of high quality of hepatocyte-like cells from induced pluripotent stem cells with Parp1 but lacking c-Myc

BACKGROUND

Induced pluripotent stem cells (iPSCs) have a great potential for application in patient-specific therapy. The reprogramming method that does not involve c-Myc reduces tumorigenic risk, but also largely reduces the efficiency of generation of iPSCs, especially for those reprogrammed from damaged cells. Poly(ADP-ribose) polymerase 1 (Parp1) catalyzes a reaction of poly(ADP-ribosylation) and has been reported to enhance cell reprogramming.

METHODS

Using Oct-4/Sox2/Klf4/Parp1 (OSKP) reprogramming method, reprogramming factors plus Parp1 were capable of generation of iPSCs from adult fibroblasts and further toward to differentiate from iPSCs status into hepatocyte-like cells.

RESULTS

Our results showed that Oct-4/Sox2/Klf4/Parp1 (OSKP)-derived iPSC exhibited regular pluripotent properties, long-term passages and more stable cellular-divided period. These OSKP-derived iPSCs can effectively differentiate into hepatocyte-like cells (OSKP-iPSC-Heps), and present high mRNA levels of Sox17, HNF3b, and HNF4a in OSKP-iPSC-Heps. The mature hepatic functions, including CYP3A4, LDL uptake, glycogen synthesis and urea secretion were analyzed and well detected in OSKP-iPSC-Heps on day 14 post-differentiation.

CONCLUSION

In conclusion, we demonstrated that Parp1 promoted reprogramming process to generate the high quality of iPSCs, which could be used as a high quality source of hepatocytes.

Glutamine Metabolism Regulates the Pluripotency Transcription Factor OCT4

The molecular mechanisms underlying the regulation of pluripotency by cellular metabolism in human embryonic stem cells (hESCs) are not fully understood. We found that high levels of glutamine metabolism are essential to prevent degradation of OCT4, a key transcription factor regulating hESC pluripotency. Glutamine withdrawal depletes the endogenous antioxidant glutathione (GSH), which results in the oxidation of OCT4 cysteine residues required for its DNA binding and enhanced OCT4 degradation. The emergence of the OCT4(lo) cell population following glutamine withdrawal did not result in greater propensity for cell death. Instead, glutamine withdrawal during vascular differentiation of hESCs generated cells with greater angiogenic capacity, thus indicating that modulating glutamine metabolism enhances the differentiation and functional maturation of cells. These findings demonstrate that the pluripotency transcription factor OCT4 can serve as a metabolic-redox sensor in hESCs and that metabolic cues can act in concert with growth factor signaling to orchestrate stem cell differentiation.

Oct4 plays a crucial role in the maintenance of gefitinib-resistant lung cancer stem cells

Several recent studies have suggested that cancer stem cells (CSCs) are involved in resistance to gefitinib in non-small cell lung cancer (NSCLC). Oct4, a member of the POU-domain transcription factor family, has been shown to be involved in CSC properties of various cancers. We previously reported that Oct4 and the putative lung CSC marker CD133 were highly expressed in gefitinib-resistant persisters (GRPs) in NSCLC cells, and GRPs exhibited characteristic features of the CSCs phenotype. The aim of this study was to elucidate the role of Oct4 in the resistance to gefitinib in NSCLC cells with an activating epidermal growth factor receptor (EGFR) mutation. NSCLC cell lines, PC9, which express the EGFR exon 19 deletion mutation, were transplanted into NOG mice, and were treated with gefitinib in vivo. After 14-17 days of gefitinib treatment, the tumors still remained; these tumors were referred to as gefitinib-resistant tumors (GRTs). PC9-GRTs showed higher expression of Oct4 and CD133. To investigate the role of Oct4 in the maintenance of gefitinib-resistant lung CSCs, we introduced the Oct4 gene into PC9 and HCC827 cells carrying an activating EGFR mutation by lentiviral infection. Transfection of Oct4 significantly increased CD133-positive GRPs and the number of sphere formation, reflecting the self-renewal activity, of PC9 and HCC827 cells under the high concentration of gefitinib in vitro. Furthermore, Oct4-overexpressing PC9 cells (PC9-Oct4) significantly formed tumors at 1 × 10 cells/injection in NOG mice as compared to control cells. In addition, PC9-Oct4 tumors were more resistant to gefitinib treatment as compared to control cells in vivo. Finally, immunohistochemical analysis revealed that Oct4 was highly expressed in tumor specimens of EGFR-mutant NSCLC patients with acquired resistance to gefitinib. Collectively, these findings suggest that Oct4 plays a pivotal role in the maintenance of lung CSCs resistant to gefitinib in EGFR mutation-positive NSCLC.

Generation of Induced Pluripotent Stem Cells in Rabbits

We describe a procedure for generating induced pluripotent stem cell lines in rabbits, using retroviral vectors expressing Oct4, Sox2, Klf4, and c-Myc of human origin to reprogram rabbit fibroblasts prepared from an ear skin biopsy. We also provide detailed procedures for characterizing the resulting iPSC lines, including the analysis of pluripotency marker expression by RT-qPCR, immunolabeling, and fluorescent-associated cell sorting, the evaluation of pluripotency by teratoma production and genetic stability by karyotyping.

Very Rapid and Efficient Generation of Induced Pluripotent Stem Cells from Mouse Pre-B Cells

One of the major obstacles in generating induced pluripotent stem (iPS) cells suitable for therapeutic application is the low efficiency of the process and the long time required, with many iPS lines acquiring genomic aberrations. In this chapter we describe a highly efficient iPS reprogramming system based on the transient expression in pre-B cells of the transcription factor C/EBPα, followed by the induction of the four Yamanaka factors (OSKM). In addition, the process is very rapid, yielding Oct4 positive cells within 2 days and Nanog-positive iPS cell colonies within a week.

Generation of Human Induced Pluripotent Stem Cells from Peripheral Blood Mononuclear Cells Using Sendai Virus

This protocol describes the efficient isolation of peripheral blood mononuclear cells from circulating blood via density gradient centrifugation and subsequent generation of integration-free human induced pluripotent stem cells. Peripheral blood mononuclear cells are cultured for 9 days to allow expansion of the erythroblast population. The erythroblasts are then used to derive human induced pluripotent stem cells using Sendai viral vectors, each expressing one of the four reprogramming factors Oct4, Sox2, Klf4, and c-Myc.

Generation of Partially Reprogrammed Cells and Fully Reprogrammed iPS Cells by Plasmid Transfection

Induced pluripotent stem (iPS) cells can be directly generated from somatic cells by overexpression of defined transcription factors. iPS cells can perpetually self-renew and differentiate into all cell types of an organism. iPS cells were first generated through infection with retroviruses that contain reprogramming factors. However, development of an exogene-free iPS cell generation method is crucial for future therapeutic applications, because integrated exogenes result in the formation of tumors in chimeras and regain pluripotency after differentiation in vitro. Here, we describe a method to generate iPS cells by transfection of plasmid vectors and to convert partially reprogrammed cells into fully reprogrammed iPS cells by switching from mouse ESC culture conditions to KOSR-based media with bFGF. We also describe basic methods used to characterize fully reprogrammed iPS cells.

Using Oct4:MerCreMer Lineage Tracing to Monitor Endogenous Oct4 Expression During the Reprogramming of Fibroblasts into Induced Pluripotent Stem Cells (iPSCs)

The reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) using a combination of defined transcription factors has become one of the most widely used techniques in stem cell biology. A critical, early event in iPSC reprogramming is the induction of the endogenous transcription factor network that maintains pluripotency in iPSCs. Here we describe using a transgenic, conditional Oct4-Cre construct to investigate the spatial and temporal induction of endogenous Oct4 expression during the reprogramming of mouse fibroblasts into iPS cells.

Induced Pluripotent Stem Cells from Nonhuman Primates

Induced pluripotent stem cells from nonhuman primates (NHPs) have unique roles in cell biology and regenerative medicine. Because of the relatedness of NHPs to humans, NHP iPS cells can serve as a source of differentiated derivatives that can be used to address important questions in the comparative biology of primates. Additionally, when used as a source of cells for regenerative medicine, NHP iPS cells serve an invaluable role in translational experiments in cell therapy. Reprogramming of NHP somatic cells requires the same conditions as previously established for human cells. However, throughout the process, a variety of modifications to the human cell protocols must be made to accommodate significant species differences.

Characterization of Oct4-GFP transgenic mice as a model to study the effect of environmental estrogens on the maturation of male germ cells by using flow cytometry

Oct4 is involved in regulation of pluripotency during normal development and is down-regulated during formation of postnatal reservoir of germ cells. We propose thatOct4/GFP transgenic mouse, which mimics the endogenous expression pattern of Oct4, could be used as a mammalian model to study the effects of environmental estrogens on the development of male germ cells. Oct4/GFP maturation profile was assessed during postnatal days -PND- 3, 5, 7, 10, 14 and 80, using flow cytometry. Then, we exposed pregnant mothers to 17α-ethinylestradiol (EE2) from day post coitum (dpc) 5 to PND7. Percentage of Oct4/GFP-expressing cells and levels of expression of Oct4/GPF were increased in PND7 after EE2 exposure. These observations were confirmed by analysis of GFP and endogenous Oct4 protein in the seminiferous tubules and by a reduction in epididymal sperm count in adult mice. We introduced Oct4/GFP mouse together with flow cytometry as a tool to evaluate changes in male germ cells development.

ZIC2-dependent OCT4 activation drives self-renewal of human liver cancer stem cells

Liver cancer stem cells (CSCs) have been identified and shown to have self-renewal and differentiation properties; however, the biology of these hepatic CSCs remains largely unknown. Here, we analyzed transcriptome gene expression profiles of liver CSCs and non-CSCs from hepatocellular carcinoma (HCC) cells lines and found that the transcription factor (TF) ZIC2 is highly expressed in liver CSCs. ZIC2 was required for the self-renewal maintenance of liver CSCs, as ZIC2 depletion reduced sphere formation and xenograft tumor growth in mice. We determined that ZIC2 acts upstream of the TF OCT4 and that ZIC2 recruits the nuclear remodeling factor (NURF) complex to the OCT4 promoter, thereby initiating OCT4 activation. In HCC patients, expression levels of the NURF complex were consistent with clinical severity and prognosis. Moreover, ZIC2 and OCT4 levels positively correlated to the clinicopathological stages of HCC patients. Altogether, our results indicate that levels of ZIC2, OCT4, and the NURF complex can be detected and used for diagnosis and prognosis prediction of HCC patients. Moreover, these factors may be potential therapeutic targets for eradicating liver CSCs.

Oct-3/4: Not Just a Gatekeeper of Pluripotency for Embryonic Stem Cell, a Cell Fate Instructor through a Gene Dosage Effect

Oct-3/4 encoded by Pou5f1 has been longwise recognised as a gatekeeper for embryonic stem (ES) cell pluripotency. Recently, it was suggested that Oct-3/4 one of the earliest transcription factor of the embryo might feature some functions in differentiation of cell lineages. We recently uncovered a key role of Oct-3/4 in both ES cell specification toward a cardiac lineage and in mesodermal commitment of the embryonic epiblast. Our findings demonstrated a gene dosage effect of Oct-3/4, a factor at the cross-road between cell self-renewal and cell lineage specification. What is the genetic and/or epigenetic mechanism underlying this process is still questionable. The extraview presents some hypotheses that might account for the pleiotropic dose-dependent functions of Oct-3/4.

Pou5f1/Oct4 promotes cell survival via direct activation of mych expression during zebrafish gastrulation

Myc proteins control cell proliferation, cell cycle progression, and apoptosis, and play important roles in cancer as well in establishment of pluripotency. Here we investigated the control of myc gene expression by the Pou5f1/Oct4 pluripotency factor in the early zebrafish embryo. We analyzed the expression of all known zebrafish Myc family members, myca, mycb, mych, mycl1a, mycl1b, and mycn, by whole mount in situ hybridization during blastula and gastrula stages in wildtype and maternal plus zygotic pou5f1 mutant (MZspg) embryos, as well as by quantitative PCR and in time series microarray data. We found that the broad blastula and gastrula stage mych expression, as well as late gastrula stage mycl1b expression, both depend on Pou5f1 activity. We analyzed ChIP-Seq data and found that both Pou5f1 and Sox2 bind to mych and mycl1b control regions. The regulation of mych by Pou5f1 appears to be direct transcriptional activation, as overexpression of a Pou5f1 activator fusion protein in MZspg embryos induced strong mych expression even when translation of zygotically expressed mRNAs was suppressed. We further showed that MZspg embryos develop enhanced apoptosis already during early gastrula stages, when apoptosis was not be detected in wildtype embryos. However, Mych knockdown alone did not induce early apoptosis, suggesting potentially redundant action of several early expressed myc genes, or combination of several pathways affected in MZspg. Experimental mych overexpression in MZspg embryos did significantly, but not completely suppress the apoptosis phenotype. Similarly, p53 knockdown only partially suppressed apoptosis in MZspg gastrula embryos. However, combined knockdown of p53 and overexpression of Mych completely rescued the MZspg apoptosis phenotype. These results reveal that Mych has anti-apoptotic activity in the early zebrafish embryo, and that p53-dependent and Myc pathways are likely to act in parallel to control apoptosis at these stages.

Oct4: the final frontier, differentiation defining pluripotency

The transcription factor OCT4 is a cornerstone of pluripotency, and yet OCT4 has also been associated with differentiation in a number of contexts. Reporting in this issue of Developmental Cell, Frum et al. (2013) show that OCT4's major early activity in the blastocyst is to support primitive endoderm differentiation.

Nanog suppresses cell migration by downregulating thymosin β4 and Rnd3

Nanog, Sox2, and Oct4 are key transcription factors critical for the pluripotency and self-renewal of embryonic stem (ES) cells. Their downregulations lead to differentiation, accompanied with changes in cell motility. Whether these factors impact cell motility directly, however, is not clear. Here we addressed this question by initially assessing their effect in non-stem cells. We found that the ectopic expression of Nanog, Sox2, or Oct4 markedly inhibited ECV304 cell migration. Detailed examinations revealed that Nanog induced disorganizations of the actin cytoskeleton and peripheral localizations of focal adhesions. These effects required its DNA-binding domain and are thus transcription dependent. Furthermore, thymosin β4 and Rnd3 were identified as its downstream targets. Their depletions in ECV304 cells by RNAi phenocopied the ectopic expression of Nanog in both cell motility and actin organization, whereas their ectopic expressions rescued the migration defect of Nanog overexpression. Both proteins were upregulated during mouse ES cell differentiation. Their levels in the pluripotent mouse P19 cells also increased upon Nanog ablation, coincident with an increase in cell motility. Moreover, persistent expression of Nanog in zebrafish embryos suppressed gastrulation and cell migration. These results indeed suggest a dual role of certain transcription factors in the orchestration of differentiation and motility.

Embryonic transcription factors CDX2 and Oct4 are overexpressed in neuroendocrine tumors of the ileum: a pilot study

BACKGROUND

Neuroendocrine tumors (NETs) of the ileum are rare submucosal tumors that are often diagnosed at advanced stages with metastatic spread to the liver causing a carcinoid syndrome. They present as solitary or multiple tumors. In NETs, loss of sequences on chromosomes 11, 16, 18 and 22 or gain of sequences on chromosomes 17 and 19 has been described. In this study we explored the expression of two novel candidate genes, CDX2 and Oct4, in NETs of the ileum and analyzed whether the molecular expression pattern correlates with the clinical phenotype (solitary/multiple tumors).

METHODS

Data from all patients who underwent surgery for a NET of the ileum between 2000 and 2010 were retrieved from a prospective database. For each patient, frozen normal and tumor tissue was used for the comparison of gene expression levels of two putative cancer stem cell markers, CDX2 and Oct4, using real-time PCR (rtPCR). Serial slides from paraffin blocks were used for immunohistochemistry. Gene expression was compared between normal and tumor tissue as well as between solitary and multiple tumors.

RESULTS

78 patients were identified. In rtPCR, a statistically significant higher expression of CDX2 in tumor tissue (p < 0.001) compared to normal tissue was found. The expression of Oct4 was elevated in the tumors, but did not reach the level of significance (p = 0.155). The expression of both candidate genes was confirmed immunohistochemically and showed a nuclear expression pattern. There was no difference in expression between solitary and multiple tumors or between tumors that had already spread to the liver.

CONCLUSION

CDX2 is overexpressed in ileum NETs, thus playing a role in the tumorigenesis of these rare tumors. Since expression does not correlate with clinical stage or phenotype, it might be an early event in tumor development.

Intercellular transport of Oct4 in mammalian cells: a basic principle to expand a stem cell niche?

Background

The octamer-binding transcription factor 4 (Oct4) was originally described as a marker of embryonic stem cells. Recently, the role of Oct4 as a key regulator in pluripotency was shown by its ability to reprogram somatic cells in vitro, either alone or in concert with other factors. While artificial induction of pluripotency using transcription factors is possible in mammalian cell culture, it remains unknown whether a potential natural transfer mechanism might be of functional relevance in vivo. The stem cell based regeneration of deer antlers is a unique model for rapid and complete tissue regeneration in mammals and therefore most suitable to study such mechanisms. Here, the transfer of pluripotency factors from resident stem cell niche cells to differentiated cells could recruit more stem cells and start rapid tissue regeneration.

Methodology/Principal Findings

We report on the ability of STRO-1⁺ deer antlerogenic mesenchymal stem cells (DaMSCs) to transport Oct4 via direct cell-to-cell connections. Upon cultivation in stem cell expansion medium, we observed nuclear Oct4 expression in nearly all cells. A number of these cells exhibit Oct4 expression not only in the nucleus, but also with perinuclear localisation and within far-ranging intercellular connections. Furthermore, many cells showed intercellular connections containing both F-actin and α-tubulin and through which transport could be observed. To proof that intercellular Oct4-transfer has functional consequences in recipient cells we used a co-culture approach with STRO-1⁺ DaMSCs and a murine embryonic fibroblast indicator cell line (Oct4-GFP MEF). In this cell line a reporter gene (GFP) under the control of an Oct4 responsive element is only expressed in the presence of Oct4. GFP expression in Oct4-GFP cells started after 24 hours of co-culture providing evidence of Oct4 transfer from STRO-1⁺ DaMSCs to Oct4-GFP MEF target cells.

Conclusions

Our findings indicate a possible mechanism for the expansion of a resident stem cell niche by induction of pluripotency in surrounding non-niche cells via transfer of transcription factors through intercellular connections. This provides a new approach to explain the rapid annual antler regrowth.

Simple generation of human induced pluripotent stem cells using poly-beta-amino esters as the non-viral gene delivery system

Reprogramming of somatic cells to induced pluripotent stem (iPS) cells can be achieved by the delivery of a combination of transcription factors, including Oct4, Sox2, Klf4, and c-Myc. Retroviral and lentiviral vectors are commonly used to express these four reprogramming factors separately and obtain reprogrammed iPS cells. Although efficient and reproducible, these approaches involve the time-consuming and labor-intensive production of retroviral or lentiviral particles together with a high risk of working with potentially harmful viruses overexpressing potent oncogenes, such as c-Myc. Here, we describe a simple method to produce bona fide iPS cells from human fibroblasts using poly-β-amino esters as the transfection reagent for the delivery of a single CAG-driven polycistronic plasmid expressing Oct4, Sox2, Klf4, c-Myc, and a GFP reporter gene (OSKMG). We demonstrate for the first time that poly-β-amino esters can be used to deliver a single polycistronic reprogramming vector into human fibroblasts, achieving significantly higher transfection efficiency than with conventional transfection reagents. After a protocol of serial transfections using poly-β-amino esters, we report a simple methodology to generate human iPS cells from human fibroblasts avoiding the use of viral vectors.

Role of the stemness factors sox2, oct3/4, and nanog in gastric carcinoma

BACKGROUND

Cancer stem cells have been proposed to be responsible for cancer tumorigenicity, and then to persist in tumors as a distinct population and cause relapse and metastasis. Recently, the stemness factors Sox2, Oct3/4, and Nanog were associated with induced pluripotent stem cells, suggesting a correlation between these stemness factors and cancer stem cells. We therefore investigated the role of stemness factors in the tumorigenesis of human gastric cancer.

MATERIALS AND METHODS

A total of 290 patients who had undergone resection of a primary gastric cancer at our institute were enrolled. A curative R0 resection was performed for 253 of 290 patients, and the remaining 37 patients were treated with a palliative resection. The expression levels of Sox2, Oct3/4, and Nanog were analyzed by immunohistochemistry.

RESULTS

Sox2, Oct3/4, and Nanog expression were positive in 159 (55%), 129 (44%), and 28 (10%) of 290 gastric cancers, respectively. There was a statistically significant correlation between Sox2-positive or Oct3/4-negative expression and invasion depth, lymph node metastasis, or lymphatic invasion. In 253 patients with a curative resection, the prognosis of patients with Sox2-positive tumors or Oct3/4-negative tumors was significantly (P < 0.01 or P = 0.04, log-rank) worse than that of patients with Sox2-negative or Oct3/4-positive tumors, respectively. A multivariate analysis revealed the expression of Sox2 or Oct3/4 to be an independent prognostic factor (P = 0.01 or P = 0.04).

CONCLUSIONS

Sox2-positive expression or Oct3/4-negative expression might be associated with invasion of gastric cancer. Sox2 and Oct3/4 might be independent prognostic factors for patients with gastric cancer.

Epigenetic regulation of reprogramming factors towards pluripotency in mouse preimplantation development

PURPOSE OF REVIEW

Pluripotency is the ability of a cell to give rise to all the tissues of the adult body. During development, both genetic and epigenetic mechanisms are proposed to be involved in the establishment of the pluripotent state in the cells of the epiblast. Here, we review recent findings on the biological function and epigenetic regulation of reprogramming factors with a particular focus on the early mouse embryo.

RECENT FINDINGS

A number of functional studies have identified a group of transcription factors required for reprogramming during mouse preimplantation development. Among these transcription factors, Oct4, Sox2, and Nanog are also crucial for establishment and/or maintenance of pluripotency in vivo. Genome-wide studies with ES cells have highlighted the colocalization of these factors onto ES cell chromatin and the existence of a transcriptional network that might direct pluripotency. Furthermore, recent studies on transcription factor-mediated induced reprogramming to induced pluripotent stem cells have revealed roles of these transcription factors on reprogramming.

SUMMARY

Oct4, Sox2, and Nanog seem to work at different times of the reprogramming process in vivo. Elucidating the regulatory mechanisms of these factors provides not only insights into the reprogramming mechanisms but also in the regulation of mouse preimplantation development.

Loss of a cohesin-linked suppressor APRIN (Pds5b) disrupts stem cell programs in embryonal carcinoma: an emerging cohesin role in tumor suppression

Cohesins appear to have critical functions beyond mitotic cohesion. Our data on a cohesin-associated Pds5-paralog, APRIN, indicate a novel cohesin role in stem cell differentiation. APRIN/Pds5B is lost in many cancers and it is a putative tumor suppressor. Its mutations in the germ line, however, generate birth defects. We reasoned that as both cancer and birth defects share disrupted stem cell differentiation, the data suggest an APRIN/Pds5B cohesin function in stem cells. We used an embryonal carcinoma stem cell model and show here that (i) APRIN expression is precisely coordinated with stem cell differentiation; (ii) this coordination involves surface-contact and endocrine pathways; and (iii) APRIN/Pds5b coordination is critical in stem/progenitor exit decisions. APRIN knockdown disrupted Oct4, Nanog and SOX2 patterns, differentiation failed and the resulting immature proliferative cells did not progress beyond proneural progenitor phase. Furthermore, the phenotype-blocked progenitor exit (Mash-1(+)); failed E-cadherin exit (E-Cadh(low+)); incomplete N-cadherin transition (N-Cadh(low+)); retained proliferative capacity (c-myc(+)); irregular stemness (SOX2(late++)) and lost response to contact and hormonal cues-shares similarities with cancer-initiating cells. The data suggest novel APRIN/Pds5B-linked cohesin roles in stem/progenitor programs and a new mechanism in tumor suppression.

Targeting of de novo DNA methylation throughout the Oct-4 gene regulatory region in differentiating embryonic stem cells

Differentiation of embryonic stem (ES) cells is accompanied by silencing of the Oct-4 gene and de novo DNA methylation of its regulatory region. Previous studies have focused on the requirements for promoter region methylation. We therefore undertook to analyse the progression of DNA methylation of the ∼2000 base pair regulatory region of Oct-4 in ES cells that are wildtype or deficient for key proteins. We find that de novo methylation is initially seeded at two discrete sites, the proximal enhancer and distal promoter, spreading later to neighboring regions, including the remainder of the promoter. De novo methyltransferases Dnmt3a and Dnmt3b cooperate in the initial targeted stage of de novo methylation. Efficient completion of the pattern requires Dnmt3a and Dnmt1, but not Dnmt3b. Methylation of the Oct-4 promoter depends on the histone H3 lysine 9 methyltransferase G9a, as shown previously, but CpG methylation throughout most of the regulatory region accumulates even in the absence of G9a. Analysis of the Oct-4 regulatory domain as a whole has allowed us to detect targeted de novo methylation and to refine our understanding the roles of key protein components in this process.

Induced pluripotent stem cell generation using a single lentiviral stem cell cassette

Induced pluripotent stem (iPS) cells can be generated using retroviral vectors expressing Oct4, Klf4, Sox2, and cMyc. Most prior studies have required multiple retroviral vectors for reprogramming, resulting in high numbers of genomic integrations in iPS cells and limiting their use for therapeutic applications. Here we describe the use of a single lentiviral vector expressing a "stem cell cassette" composed of the four transcription factors and a combination of 2A peptide and internal ribosome entry site technology, generating iPS cells from postnatal fibroblasts. iPS cells generated in this manner display embryonic stem cell-like morphology, express stem cell markers, and exhibit in vivo pluripotency, as evidenced by their ability to differentiate in teratoma assays and their robust contribution to mouse chimeras. Combining all factors into a single transcript achieves the most efficient reprogramming system to date and allows derivation of iPS cells with a single viral integration. The use of a single lentiviral vector for reprogramming represents a powerful laboratory tool and a significant step toward the application of iPS technology for clinical purposes.

Genetic analysis of the role of the reprogramming gene LIN-28 in human embryonic stem cells

LIN-28 is a gene recently shown to be involved in the conversion of somatic cells to induced pluripotent stem cells. We have previously shown that LIN-28 is highly expressed in human embryonic stem cells (HESCs); however, its role in these cells has not been investigated. We now show that, like OCT4, SOX2, and NANOG, LIN-28 is downregulated during differentiation of HESCs into embryoid bodies. In addition, we investigate the role of LIN-28 in HESCs by manipulation of its expression levels. LIN-28 overexpression impairs the ability of cells to grow at clonal densities, due to increased differentiation and decreased cell division. Analysis of cell differentiation under these conditions revealed that it is mostly towards the extraembryonic endoderm lineage. Moreover, we show that, during early mouse development, high levels of Lin-28 are also observed in the extraembryonic endoderm, and therefore it seems that, both in vitro and in vivo, high levels of LIN-28 may specify an extraembryonic endoderm fate. However, LIN-28 seems dispensable for self-renewal of HESCs; its downregulation neither impairs HESC proliferation nor leads to their differentiation. Thus, LIN-28 does not seem to be involved in the self-renewal of HESCs, but rather seems to be involved in their decision to switch from self-renewal to differentiation.

Cloning and characterization of the rabbitPOU5F1gene

The product of the POUSF1 gene, Oct4, plays an important role both in embryonic development and in the self-renewal and differentiation of totipotent cells. To understand the function of Oct4 in rabbit ES cells, we cloned and sequenced the rabbit POU5F1 gene, as well as the cDNA encoded by the gene. The Oct4 cDNA contains a 1083 bp ORF encoding a 360 aa protein and a 241 bp 3' UTR sequence. Oct4 mRNA was expressed at a high level in rabbit ES cells and was barely detectable in the adult spleen, kidney, brain and muscle tissues. The POU5F1 gene is approximately 6 kb in length and includes five exons and four introns. Gene organization is similar to that of the mouse, human and bovine orthologs. Sequencing of the gene revealed an 82% (mouse), 90% (human) and 89% (bovine) overall identity at the protein level. The rabbit POUSF1 gene was mapped to chromosome 12q1.1 by PCR amplification of DNA from two putative POU5F1-containing BAC clones, which were previously mapped to chromosome 12q1.1. The cloning of the rabbit POU5F1 gene will facilitate studies on its roles in rabbit embryogenesis and ES cells.

Functional similarities among genes regulated by OCT4 in human mesenchymal and embryonic stem cells

OCT4 is a master transcriptional regulator, which mediates pluripotency in ESCs through inhibition of tissue-specific and promotion of stem cell-specific genes. Suppression of OCT4, along with other regulators of pluripotency, such as SOX2 and NANOG, has been correlated with cell-fate specification and lineage-specific differentiation. Recent reports have shown the expression of OCT4 in adult MSCs but have not ascribed functional homology with ESCs. MSCs are mesoderm-derived cells, primarily resident in adult bone marrow, that undergo lineage-specific differentiation to generate specialized cells such as stroma, fat, bone, and cartilage. We have previously demonstrated the plasticity of MSCs through their ability to generate neuronal cells. Here, we show that OCT4 provides similar regulatory circuitries in human MSCs and ESCs, using chromatin immunoprecipitation-DNA selection and ligation technology and loss-of-function studies. MSCs were found to express the embryonic transcription factors OCT4, NANOG, and SOX2. In addition, OCT4 was found to (a) target similar genes in MSCs and ESCs, (b) promote the expression of MSC-specific genes, and (c) regulate MSC cell cycle progression. The results suggest similar regulatory mechanisms for OCT4 in MSCs and ESCs and have implications regarding MSC plasticity. Disclosure of potential conflicts of interest is found at the end of this article.

Oct4 targets regulatory nodes to modulate stem cell function

Stem cells are characterized by two defining features, the ability to self-renew and to differentiate into highly specialized cell types. The POU homeodomain transcription factor Oct4 (Pou5f1) is an essential mediator of the embryonic stem cell state and has been implicated in lineage specific differentiation, adult stem cell identity, and cancer. Recent description of the regulatory networks which maintain ‘ES’ have highlighted a dual role for Oct4 in the transcriptional activation of genes required to maintain self-renewal and pluripotency while concomitantly repressing genes which facilitate lineage specific differentiation. However, the molecular mechanism by which Oct4 mediates differential activation or repression at these loci to either maintain stem cell identity or facilitate the emergence of alternate transcriptional programs required for the realization of lineage remains to be elucidated. To further investigate Oct4 function, we employed gene expression profiling together with a robust statistical analysis to identify genes highly correlated to Oct4. Gene Ontology analysis to categorize overrepresented genes has led to the identification of themes which may prove essential to stem cell identity, including chromatin structure, nuclear architecture, cell cycle control, DNA repair, and apoptosis. Our experiments have identified previously unappreciated roles for Oct4 for firstly, regulating chromatin structure in a state consistent with self-renewal and pluripotency, and secondly, facilitating the expression of genes that keeps the cell poised to respond to cues that lead to differentiation. Together, these data define the mechanism by which Oct4 orchestrates cellular regulatory pathways to enforce the stem cell state and provides important insight into stem cell function and cancer.

Sumoylation of Oct4 enhances its stability, DNA binding, and transactivation

Transcription factor Oct4 is a master regulator affecting the fate of pluripotent stem cells and germ cell precursors. Oct4 expression is tightly regulated, and small changes in expression level can have dramatic effects on differentiation or oncogenesis. Post-translational modifications including phosphorylation and ubiquitination have been reported to regulate Oct4 transcriptional activity. Here we show that Oct4 is a target for small ubiquitin-related modifier (SUMO)-1 modification in vivo and in vitro. Sumoylation of Oct4 occurs at a single lysine, Lys(118), located at the end of the amino-terminal transactivation domain and next to the Pit1-Oct-Unc86 (POU) DNA binding domain. SUMO-1 and Oct4 colocalize at several promoter sequences in vivo, and a fraction of Oct4 molecules colocalized with SUMO-1 in nuclear aggregates. Sumoylation of Oct4 led to significantly increased Oct4 stability and increased DNA binding. In addition, SUMO-1 cotransfection led to augmented Oct4 transactivation potential that was reduced when the Oct4 sumoylation target site was mutated. Therefore, sumoylation of Oct4 results in increased stability, DNA binding, and transactivation and provides an important mechanism to regulate Oct4 activity.

Conserved POU/OCT- and GATA-binding sites in 5'-flanking promoter region of mammalian WNT8B orthologs

WNT family members are secreted-type glycoproteins regulating cell fate, planar cell polarity, cell adhesion, and cell movement. WNT signals are context-dependently transduced to the canonical pathway for the transcriptional up-regulation of MYC, CCND1, FGF20, JAG1, WISP1 and DKK1 genes, and also to the non-canonical pathway for the activation of RHOA, JNK, PKC, NFAT and NLK signaling cascades. We cloned and characterized the wild-type human WNT8B, while another group the aberrant human WNT8B with Gly230Ala and Arg284Leu amino-acid substitutions. Although WNT8B is undetectable in normal adult tissues by using Northern blot analyses, WNT8B is expressed in gastric cancer, pancreatic cancer, colorectal cancer, breast cancer, and embryonal tumors. Here, comparative integromics on WNT8B orthologs were investigated by using bioinformatics (Techint) and human intelligence (Humint). Cow Wnt8b gene was identified within NW_001494361.1 genome sequence. Predicted sequence XM_582222.3 was an artificial cow Wnt8b with aberrant prediction for the first exon. Cow Wnt8b complete coding sequence was found to encode a 350-amino-acid protein, which showed 96.9% total-amino-acid identity with human WNT8B. Comparative proteomics revealed that N-terminal signal peptide, 22 Cys residues, two Asn-linked glycosylation sites, Gly230, and Arg284 of human WNT8B were conserved among mammalian WNT8B orthologs. Comparative genomics revealed that POU/OCT- and GATA-binding sites in the 5'-flanking promoter region were conserved among human, chimpanzee, cow, mouse, and rat WNT8B orthologs. In silico expression analyses revealed that human WNT8B was expressed in embryoid body derived from embryonic stem (ES) cells, hepatocyte progenitors derived from ES cells, fetal brain, diffuse-type gastric cancer, colorectal cancer, prostate cancer, and ovarian fibrotheoma. Based on the expression profiles of POU and GATA family transcription factors, it was revealed that WNT8B expression in hepatocyte progenitors derived from human ES cells is due to POU5F1 (OCT3/OCT4) and GATA3, and also that WNT8B expression in diffuse-type gastric cancer is due to POU5F1 and GATA6.

OCT4: biological functions and clinical applications as a marker of germ cell neoplasia

Germ cell tumours (GCTs) are a heterogeneous group of neoplasms, which develop in the gonads as well as in extragonadal sites, that share morphological patterns and an overall good prognosis, owing to their responsiveness to current surgical, chemotherapeutic, and radiotherapeutic measures. GCTs demonstrate extremely interesting biological features because of their close relationships with normal embryonal development as demonstrated by the pluripotentiality of some undifferentiated GCT variants. The similarities between GCTs and normal germ cell development have made it possible to identify possible pathogenetic pathways in neoplastic transformation and progression of GCTs. Genotypic and immunophenotypic profiles of these tumours are also useful in establishing and narrowing the differential diagnosis in cases of suspected GCTs. Recently, OCT4 (also known as OCT3 or POU5F1), a transcription factor that has been recognized as fundamental in the maintenance of pluripotency in embryonic stem cells and primordial germ cells, has been proposed as a useful marker for GCTs that exhibit features of pluripotentiality, specifically seminoma/dysgerminoma/germinoma and embryonal carcinoma. The development of commercially available OCT4-specific antibodies suitable for immunohistochemistry on paraffin-embedded specimens has generated increasing numbers of reports of OCT4 expression in a wide variety of gonadal and extragonadal GCTs. OCT4 immunostaining has been shown to be a sensitive and specific marker for seminomatous/(dys)germinomatous tumours and in embryonal carcinoma variants of non-seminomatous GCTs, whether in primary gonadal or extragonadal sites or in metastatic lesions. Therefore, OCT4 immunohistochemistry is an additional helpful marker both in the differential diagnosis of specific histological subtypes of GCTs and in establishing a germ cell origin for some metastatic tumours of uncertain primary. OCT4 expression has also been reported in pre-invasive conditions such as intratubular germ cell neoplasia, unclassified (IGCNU) and the germ cell component of gonadoblastoma. Additionally, OCT4 immunostaining shows promise as a useful tool in managing patients known to be at high risk for the development of invasive GCTs.

LIF-mediated control of embryonic stem cell self-renewal emerges due to an autoregulatory loop

Stem cells convert graded stimuli into all-or-nothing cell-fate responses. We investigated how embryonic stem cells (ESCs) convert leukemia inhibitory factor (LIF) concentration into an all-or-nothing cell-fate decision (self-renewal). Using a combined experimental/computational approach we demonstrate unexpected switch-like (on/off) signaling in response to LIF. This behavior emerges over time due to a positive feedback loop controlling transcriptional expression of LIF signaling pathway components. The autoregulatory loop maintains robust pathway responsiveness ("on") at sufficient concentrations of exogenous LIF, while autocrine signaling and low concentrations of exogenous LIF cause ESCs to adopt the weakly responsive ("off") state of differentiated cells. We demonstrate that loss of ligand responsiveness is reversible and precedes loss of the ESC transcription factors Oct4 and Nanog, suggesting an early step in the hierarchical control of differentiation. While endogenously produced ligands were insufficient to sustain the "on" state, they buffer it, influencing the timing of differentiation. These results demonstrate a novel switch-like behavior, which establishes the LIF threshold for ESC self-renewal.

From adult stem cells to cancer stem cells: Oct-4 Gene, cell-cell communication, and hormones during tumor promotion

Carcinogenesis is characterized by "initiation," "promotion," and "progression" phases. The "stem cell theory" and "de-differentiation" theories are used to explain the origin of cancer. Growth control for stem cells, which lack functional gap junctional intercellular communication (GJIC), involves negative soluble or niche factors, while for progenitor cells, it involves GJIC. Tumor promoters, hormones, and growth factors inhibit GJIC reversibly. Oncogenes stably inhibit GJIC. Cancer cells, which lack growth control and the ability to terminally differentiate and to apoptose, lack GJIC. The Oct3/4 gene, a POU (Pit-Oct-Unc) family of transcription factors was thought to be expressed only in embryonic stem cells and in tumor cells. With the availability of normal adult human stem cells, tests for the expression of Oct3/4 gene and the stem cell theory in human carcinogenesis became possible. Human breast, liver, pancreas, kidney, mesenchyme, and gastric stem cells, HeLa and MCF-7 cells, and canine tumors were tested with antibodies and polymerase chain reaction (PCR) primers for Oct3/4. Adult human breast stem cells, immortalized nontumorigenic and tumor cell lines, but not the normal differentiated cells, expressed Oct3/4. Adult human differentiated cells lose their Oct-4 expression. Oct3/4 is expressed in a few cells found in the basal layer of human skin epidermis. The data demonstrate that normal adult stem cells and cancer stem cells maintain expression of Oct3/4, consistent with the stem cell hypothesis of carcinogenesis. These Oct-4 positive cells might represent the "cancer stem cells." A strategy to target "cancer stem cells" is to suppress the Oct-4 gene in order to cause the cells to differentiate.

Conserved POU-binding site linked to SP1-binding site within FZD5 promoter: Transcriptional mechanisms of FZD5 in undifferentiated human ES cells, fetal liver/spleen, adult colon, pancreatic islet, and diffuse-type gastric cancer

Canonical WNT signals are transduced through Frizzled (FZD) family receptor and LRP5/LRP6 co-receptor to upregulate FGF20, JAG1, DKK1, WISP1, CCND1 and MYC genes for cell-fate determination, while non-canonical WNT signals are transduced through FZD family receptor and ROR2/PTK7/RYK co-receptor to activate RHOA/RHOU/RAC/CDC42, JNK, PKC, NLK and NFAT signaling cascades for the regulation of tissue polarity, cell movement, and adhesion. We previously reported molecular cloning and characterization of human FZD5, which showed six amino-acid substitutions with human Hfz5. FZD5, functioning as WNT5A receptor, is the key molecule in the fields of oncology, regenerative medicine, cardiology, rheumatology, diabetology, and gastroenterology. Here, comparative integromics analyses on FZD5 orthologs were performed by using bioinformatics (Techint) and human intelligence (Humint). Chimpanzee FZD5 and cow Fzd5 genes were identified within NW_104292.1 and AC166656.2 genome sequences, respectively. FZD5 orthologs were seven-transmembrane proteins with extracellular Frizzled domain, leucine zipper motif around the 5th transmembrane domain, and cytoplasmic DVL- and PDZ-binding motifs. Ser523 and Ser529 around the DVL-binding motif of FZD5 orthologs were putative aPKC phosphorylation sites. POU5F1 (OCT4)-binding site linked to SP1-binding site within the 5'-promoter region of human FZD5 gene was evolutionarily conserved among mammalian FZD5 orthologs. POU5F1 was more related to POU2F and POU3F subfamily members. POU5F1 was preferentially expressed in undifferentiated human embryonic stem (ES) cells, pancreatic islet, and diffuse-type gastric cancer. POU2F1 (OCT1) was expressed in ES cells, fetal liver/spleen, adult colon, POU2F2 in ES cells, fetal liver/spleen, and POU2F3 in diffuse-type gastric cancer. Multiple SP1/KLF family members, other than KLF2 or KLF4, were expressed in undifferentiated human ES cells. Together, these facts indicate that POU5F1 and POU2F subfamily members play a pivotal role for the FZD5 expression in undifferentiated human ES cells, fetal liver/spleen, adult colon, pancreatic islet, and diffuse-type gastric cancer.

Oct-4: The Almighty POUripotent Regulator?

Oct-4 plays an essential role as a central regulator of the undifferentiated state. Grinnell et al. demonstrate for the first time that Oct-4 by itself has the ability to reprogram committed somatic cells, inducing their dedifferentiation by reverting them to a more developmentally potent state. This study provides evidence that Oct-4 might be the master regulator of the pluripotent state in mammalian cells.

Unraveling the transcriptional network controlling ES cell pluripotency

Separate transcriptional pathways have been delineated for the maintenance of the undifferentiated state and for self-renewal in embryonic stem cells.

Embryonic stem cells (ES cells) are powerful tools for genetic engineering and hold significant potential for regenerative medicine. Recent work provides new insights into ES cell pluripotency and delineates separate transcriptional pathways in ES cells for maintenance of the undifferentiated state and for self-renewal.

Beta-catenin up-regulates Nanog expression through interaction with Oct-3/4 in embryonic stem cells

It is well known that mouse embryonic stem (ES) cells can be maintained by the presence of leukemia inhibitory factor (LIF). Recent studies have revealed that Wnt also exhibits activity similar to LIF. The molecular mechanism behind the maintenance of ES cells by these factors, however, is not fully understood. In this study, we found that LIF enhances level of nuclear beta-catenin, a component of the Wnt signaling pathway. Expression of an activated mutant of beta-catenin led to the long-term proliferation of ES cells, even in the absence of LIF. Furthermore, it was found that beta-catenin up-regulates Nanog in an Oct-3/4-dependent manner and that beta-catenin physically associates with Oct-3/4. These results suggest that up-regulating Nanog through interaction with Oct-3/4 involves beta-catenin in the LIF- and Wnt-mediated maintenance of ES cell self-renewal.

Characterization of NOBOX DNA Binding Specificity and Its Regulation of Gdf9 and Pou5f1 Promoters

Nobox (newborn ovary homeobox gene) deficiency disrupts early folliculogenesis and the expression of oocyte-specific genes in mice. Here, we identified several cis-acting sites, TAATTG, TAGTTG, and TAATTA as NOBOX DNA binding elements (NBEs) using a library of randomly generated oligonucleotides by cyclic amplification of sequence target assay and mutation analyses. We show that NOBOX preferentially binds to the NOBOX binding elements with high affinity. In addition, we found that promoter regions of mouse Pou5f1 and Gdf9 contain one (-426) and three NOBOX binding elements (-786, -967, and -1259), respectively. NOBOX binds to these putative NOBOX binding elements with high affinity and augmented transcriptional activity of luciferase reporter driven by mouse Pou5f1 and Gdf9 promoters containing the NOBOX binding elements. In chromatin immunoprecipitation assays, DNA sequences from Pou5f1 and Gdf9 promoters co-precipitated with anti-NOBOX antibody. These results suggest that NOBOX directly regulates the transcription of Pou5f1 and Gdf9 in oocytes during early folliculogenesis.