Identification, cloning and expression analysis of the pluripotency promoting Nanog genes in mouse and human

Research progress of nanog gene in fish

Nanog is a crucial regulatory factor in maintaining the self-renewal and pluripotency of embryonic stem cells. It is involved in various biological processes, such as early embryonic development, cell reprogramming, cell cycle regulation, the proliferation and migration of primordial germ cells. While research on this gene has primarily focused on mammals, there has been a growing interest in studying nanog in fish. However, there is a notable lack of comprehensive reviews regarding this gene in fish, which is essential for guiding future research. This review aims to provide a thorough summary of the gene's structure, expression patterns, functions and regulatory mechanisms in fish. The findings suggest that nanog probably has both conserved and divergent functions in regulating cell pluripotency, early embryonic development, and germ cell development in teleosts compared to other species, including mammals. These insights lay the foundation for future research and applications of the nanog gene, providing a new perspective for understanding the evolution and conserved charactristics of teleost nanog.

Gastrulation-stage gene expression in Nipbl+/- mouse embryos foreshadows the development of syndromic birth defects

In animal models, Nipbl deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange syndrome, the most common cause of which is Nipbl haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA sequencing on wild-type and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than wild-type and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and Cornelia de Lange syndrome.

Gastrulation-stage gene expression in Nipbl +/- mouse embryos foreshadows the development of syndromic birth defects

In animal models, Nipbl-deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange Syndrome (CdLS), the most common cause of which is Nipbl-haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA-sequencing on wildtype (WT) and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than WT and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl-deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and CdLS.

Teaser

Gene expression changes during gastrulation of Nipbl-deficient mice shed light on early origins of structural birth defects.

A short history of pluripotent stem cells markers

The expression of one or more of a small number of molecules, typically cell surface-associated antigens, or transcription factors, is widely used for identifying pluripotent stem cells (PSCs) or for monitoring their differentiation. However, none of these marker molecules are uniquely expressed by PSCs and all are expressed by stem cells that have lost the ability to differentiate. Consequently, none are indicators of pluripotency, per se. Here we summarize the nature and characteristics of several markers that are in wide use, including the cell surface antigens, stage-specific embryonic antigen (SSEA)-1, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, GCTM2, and the transcription factors POUF5/OCT4, NANOG, and SOX2, highlighting issues that must be considered when interpreting data about their expression on putative PSCs.

Different Types of Pluripotent Stem Cells Represent Different Developmental Stages

Pluripotent stem cell lines established from early-stage embryos of mammals or other species represent the embryonic stages before the initiation of somatic development. In these stem cell lines, cell proliferation capacity is maintained while developmental progression is arrested at a specific developmental stage that is determined by the combination of culture conditions, cell state, and species. All of these pluripotent stem cell lines express the transcription factors (TFs) Sox2 and Pou5f1 (Oct3/4); hence, these TFs are often regarded as pluripotency factors. However, the regulatory roles of these TFs vary depending on the cell line type. The cell lines representing preimplantation stage embryonic cells (mouse embryonic stem cells, mESCs) are regulated principally by the combined action of Sox2 and Pou5f1. Human ESCs and mouse epiblast stem cells (EpiSCs) represent immature and mature epiblast cells, respectively, where Otx2 and Zic2 progressively take over the preimplantation stage's regulatory roles of Sox2 and Pou5f1. This transition of the core TFs occurs to prepare for the initiation of somatic development.

Multimodal characterization of murine gastruloid development

Gastruloids are 3D structures generated from pluripotent stem cells recapitulating fundamental principles of embryonic pattern formation. Using single-cell genomic analysis, we provide a resource mapping cell states and types during gastruloid development and compare them with the in vivo embryo. We developed a high-throughput handling and imaging pipeline to spatially monitor symmetry breaking during gastruloid development and report an early spatial variability in pluripotency determining a binary response to Wnt activation. Although cells in the gastruloid-core revert to pluripotency, peripheral cells become primitive streak-like. These two populations subsequently break radial symmetry and initiate axial elongation. By performing a compound screen, perturbing thousands of gastruloids, we derive a phenotypic landscape and infer networks of genetic interactions. Finally, using a dual Wnt modulation, we improve the formation of anterior structures in the existing gastruloid model. This work provides a resource to understand how gastruloids develop and generate complex patterns in vitro.

The role of embryonic stem cells, transcription and growth factors in mammals: A review

Mammals represent a relevant species in worldwide cultures with significant commercial value. These animals are considered an attractive large animal model for biomedical and biotechnology research. The development of large animal experimental models may open alternative strategies for investigating stem cells (SCs) physiology and potential application in the veterinary field. The embryonic stem cells (ESCs) are known to possess natural pluripotency that confers the ability to differentiate into various tissues in vivo and in vitro. These notable characteristics can be useful for research and innovative applications, including biomedicine, agriculture and industry. Transcription factors play a crucial role in preserving stem cell self-renewal, whereas growth factors are involved in both growth and differentiation. However, to date, many questions concerning pluripotency, cellular differentiation regulator genes, and other molecules such as growth factors and their interactions in many mammalian species remain unresolved. The purpose of this review is to provide an overall review regarding the study of ESCs in mammals and briefly discuss the role of transcription and growth factors.

NANOGP1, a tandem duplicate of NANOG, exhibits partial functional conservation in human naïve pluripotent stem cells

Gene duplication events can drive evolution by providing genetic material for new gene functions, and they create opportunities for diverse developmental strategies to emerge between species. To study the contribution of duplicated genes to human early development, we examined the evolution and function of NANOGP1, a tandem duplicate of the transcription factor NANOG. We found that NANOGP1 and NANOG have overlapping but distinct expression profiles, with high NANOGP1 expression restricted to early epiblast cells and naïve-state pluripotent stem cells. Sequence analysis and epitope-tagging revealed that NANOGP1 is protein coding with an intact homeobox domain. The duplication that created NANOGP1 occurred earlier in primate evolution than previously thought and has been retained only in great apes, whereas Old World monkeys have disabled the gene in different ways, including homeodomain point mutations. NANOGP1 is a strong inducer of naïve pluripotency; however, unlike NANOG, it is not required to maintain the undifferentiated status of human naïve pluripotent cells. By retaining expression, sequence and partial functional conservation with its ancestral copy, NANOGP1 exemplifies how gene duplication and subfunctionalisation can contribute to transcription factor activity in human pluripotency and development.

The Divergent and Conserved Expression Profile of Turtle Nanog Gene Comparing with Fish and Mammals

Nanog is a homeodomain-containing transcription factor, and it plays a vital role in maintaining the pluripotency of embryonic stem cells. Nanog’s function has been well studied in many species. However, there is lack of reporting on the Nanog gene in reptile. Here, we identified a 1032 bp cDNA sequence of a Nanog gene in Pelidiscus sinensis, known as PsNanog. PsNanog has a highly conserved HD domain and shares a high identity with that of Chelonia mydas and the lowest identity with Oryzias latipes. Similarly, PsNanog presented a tight cluster with C. mydas Nanog, but was far from those of teleosts. Additionally, we cloned a length of 1870 bp PsNanog promoter. Dual luciferase assay showed that the DNA fragment of −1560 to +1 exhibited a high promoter activity. The RT-PCR and RT-qPCR results showed that PsNanog was predominantly expressed in ovary, and then in testis. The in situ hybridization and immunohistochemical analysis showed that PsNanog was expressed in the early primary oocytes and the cytoplasm of the cortical region of stage VIII oocytes in ovary, and distributed in most stages of germ cells in testis. Collectively, the results imply that PsNanog probably has the conserved function in regulating germ cell development across phyla and is also a pluripotent cell gene and expressed in germ cells, which is similar to that in teleosts and mammals.

Stepwise pluripotency transitions in mouse stem cells

Pluripotent cells in mouse embryos, which first emerge in the inner cell mass of the blastocyst, undergo gradual transition marked by changes in gene expression, developmental potential, polarity, and morphology as they develop from the pre-implantation until post-implantation gastrula stage. Recent studies of cultured mouse pluripotent stem cells (PSCs) have clarified the presence of intermediate pluripotent stages between the naïve pluripotent state represented by embryonic stem cells (ESCs-equivalent to the pre-implantation epiblast) and the primed pluripotent state represented by epiblast stem cells (EpiSCs-equivalent to the late post-implantation gastrula epiblast). In this review, we discuss these recent findings in light of our knowledge on peri-implantation mouse development and consider the implications of these new PSCs to understand their temporal sequence and the feasibility of using them as model system for pluripotency.

Pluripotency factors regulate the onset of Hox cluster activation in the early embryo

Pluripotent cells are a transient population of the mammalian embryo dependent on transcription factors, such as OCT4 and NANOG, which maintain pluripotency while suppressing lineage specification. However, these factors are also expressed during early phases of differentiation, and their role in the transition from pluripotency to lineage specification is largely unknown. We found that pluripotency factors play a dual role in regulating key lineage specifiers, initially repressing their expression and later being required for their proper activation. We show that Oct4 is necessary for activation of HoxB genes during differentiation of embryonic stem cells and in the embryo. In addition, we show that the HoxB cluster is coordinately regulated by OCT4 binding sites located at the 3' end of the cluster. Our results show that core pluripotency factors are not limited to maintaining the precommitted epiblast but are also necessary for the proper deployment of subsequent developmental programs.

Sox2 levels regulate the chromatin occupancy of WNT mediators in epiblast progenitors responsible for vertebrate body formation

WNT signalling has multiple roles. It maintains pluripotency of embryonic stem cells, assigns posterior identity in the epiblast and induces mesodermal tissue. Here we provide evidence that these distinct functions are conducted by the transcription factor SOX2, which adopts different modes of chromatin interaction and regulatory element selection depending on its level of expression. At high levels, SOX2 displaces nucleosomes from regulatory elements with high-affinity SOX2 binding sites, recruiting the WNT effector TCF/β-catenin and maintaining pluripotent gene expression. Reducing SOX2 levels destabilizes pluripotency and reconfigures SOX2/TCF/β-catenin occupancy to caudal epiblast expressed genes. These contain low-affinity SOX2 sites and are co-occupied by T/Bra and CDX. The loss of SOX2 allows WNT-induced mesodermal differentiation. These findings define a role for Sox2 levels in dictating the chromatin occupancy of TCF/β-catenin and reveal how context-specific responses to a signal are configured by the level of a transcription factor.

Characterization of the Nanog gene involved in the gonadal development in pearlscale angelfish (Centropyge vrolikii)

The homeodomain transcription factor Nanog plays a crucial role in the embryonic and gonadal development and the maintenance of embryonic stem cells (ESCs), interacting with transcription factors such as Oct4 and Sox2 in mammals. Nevertheless, its pathways to molecular mechanisms remain unclear as to teleosts. This study investigates the role of the Nanog gene in gonadal development and sex reversal of pearlscale angelfish (Centropyge vrolikii). To understand the expression pattern of gonadal development, we identified the Nanog gene of C. vrolikii, which we named Cv-Nanog. The full-length cDNA sequence of Cv-Nanog was 2,136 bp in length and encoded a homeodomain protein of 436 amino acid residues. The gene structure and western blot prove results that Cv-Nanog was homologous to the Nanog gene of mammalians. The protein sequence comparison demonstrates that the Cv-Nanog shared a high degree of similarity with orthologs from other vertebrates in the conserved homeodomain. The Cv-Nanog gene was substantially expressed in gonads, and the expression was significantly higher in the ovaries than in the testis, according to quantitative real-time PCR (qRT-PCR) and western blot analyses. In situ hybridization reveals that the transcripts were located in the cytoplasm and membrane of the oocytes in the ovaries and testes. The expression of Cv-Nanog mRNA was weak in Sertoli cells but strong in germ cells. After overexpression of Cv-Nanog, the expression levels of pluripotent factors Sox2 and Oct4 increased significantly with 21.5-fold and 12.2-fold, respectively. Simultaneously, the TGF-beta signaling pathway was activated, and the gonadal cell growth was promoted. The expression of ovary-bias genes Cyp19a and Foxl2 was upregulated, and the expression of testis-bias genes Sox9 and Dmrt1 was downregulated to promote ovarian development. These results imply that the Nanog gene might play a crucial role in the process of gonadal development and sexual reversion in C. vrolikii. This study provides new insight to understand the molecular regulatory mechanism of the Nanog gene further and important clues for the future studies in gonadal development.

Heterozygous loss of Zbtb38 leads to early embryonic lethality via the suppression of Nanog and Sox2 expression

OBJECTIVES

Mammalian DNA methyltransferases are essential to re-establish global DNA methylation patterns during implantation, which is critical for transmitting epigenetic information to the next generation. In contrast, the significance of methyl-CpG binding proteins (MBPs) that bind methylated CpG remains almost unknown at this stage. We previously demonstrated that Zbtb38 (also known as CIBZ)-a zinc finger type of MBP-is required for mouse embryonic stem (ES) cell proliferation by positively regulating Nanog expression. However, the physiological function of Zbtb38 in vivo remains unclear.

MATERIALS AND METHODS

This study used the Cre-loxP system to generate conditional Zbtb38 knockout mice. Cell proliferation and apoptosis were studied by immunofluorescence staining. Quantitative real-time PCR, immunoblotting and immunofluorescence were performed to investigate the molecular mechanisms.

RESULTS

Germline loss of the Zbtb38 single allele resulted in decreased epiblast cell proliferation and increased apoptosis shortly after implantation, leading to early embryonic lethality. Heterozygous loss of Zbtb38 reduced the expression of Nanog, Sox2, and the genes responsible for epiblast proliferation, differentiation, and cell viability. Although this early lethal phenotype, Zbtb38 is dispensable for ES cell establishment and identity.

CONCLUSIONS

These findings indicate that Zbtb38 is essential for early embryonic development via the suppression of Nanog and Sox2 expression.

Characterization of nanog in Nile tilapia (Oreochromis niloticus) and its spatiotemporal expression patterns during embryonic and gonadal development

Nanog is one of the well-characterized core transcription factors in pluripotency maintenance network. So far, studies on fishes indicate that the Nanog expression occurs from embryonic 1-cell stage to blastula stage, and is restricted to the gonadal germline cells in adult tissues, which is strikingly different from that in mammals. However, whether this expression profile is conservative in fishes remains to be investigated. Here Nile tilapia (Oreochromis niloticus) nanog (named as Ong) was identified and its spatiotemporal expression patterns during embryonic and gonadal development were investigated. The Ong cDNA contains an open reading frame of 678 bp, encoding 226 amino acids. The anti-Ong antibody was prepared through prokaryotic protein expression and its specificity was validated. The Ong expression in embryonic 1-cell stage did not appear until the early stage of blastocyst and continued to the late stage of blastocyst. In adult tissues, its expression was limited to gonads. Its expression patterns during gonadal development were further investigated by in situ hybridization and immunohistochemical staining. In testis, Ong was not expressed at 30 dah (days after hatching), but highly expressed in spermatogonia and spermatocytes at 150 dah; in ovaries at 30 and 150 dah, it was not expressed in germline cells but in all somatic cells. This expression profile is strikingly different from reports in fishes to date. Our study firstly indicates that the Nanog expression profile is not conservative in fishes. This study is valuable for further functional and evolutionary study of this gene.

Epithelium-specific ETS transcription factor-1 regulates NANOG expression and inhibits NANOG-induced proliferation of human embryonic carcinoma cells

The epithelium-specific ETS transcription factor-1 (ESE-1) plays multiple roles in pathogenesis and normal development of epithelial tissues. NANOG, a key mediator of stem cell self-renewal and pluripotency, is also expressed in various cancers and pluripotent cells. In this study, we investigated how ESE-1 influences NANOG expression and NANOG-induced proliferation in human germ cell-derived embryonic carcinoma NCCIT cells. Endogenous ESE-1 expression in NCCIT cells significantly increased during differentiation, whereas NANOG expression decreased. In addition, NANOG expression was downregulated by exogenous overexpression of ESE-1, and increased by shRNA-mediated knockdown of ESE-1. NANOG transcriptional activity was reduced by dose-dependent ESE-1 overexpression and a putative ESE-1 binding site (EBS) was mapped within conserved region 2. Site-directed mutagenesis of the putative EBS abrogated the repressive effect of ESE-1 on NANOG promoter activity. ESE-1 directly interacted with the putative EBS to regulate transcriptional activity of NANOG. Furthermore, NANOG-induced proliferation and colony formation of NCCIT cells were inhibited by ESE-1 overexpression and stimulated by ESE-1 shRNA-mediated knockdown. Altogether, our results suggest that ESE-1 exerts an anti-proliferative effect on NCCIT cells by acting as a novel transcriptional repressor of NANOG.

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells (PSCs) from farm animals opens new approaches not only for reproduction, genetic engineering, treatment and conservation of these species, but also for screening novel drugs for their efficacy and toxicity, and modelling of human diseases. Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages, or lost their cellular potency; indicating that the protocols which allowed the derivation of murine or human embryonic stem (ES) cells were not sufficient to support the maintenance of ES cells from farm animals. This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support naïve pluripotency in ES cells from livestock species. However, the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging, and requires further refinements. Here, we review the current achievements in the derivation of PSCs from farm animals, and discuss the potential application areas.

The Role of E3s in Regulating Pluripotency of Embryonic Stem Cells and Induced Pluripotent Stem Cells

Pluripotent embryonic stem cells (ESCs) are derived from early embryos and can differentiate into any type of cells in living organisms. Induced pluripotent stem cells (iPSCs) resemble ESCs, both of which serve as excellent sources to study early embryonic development and realize cell replacement therapies for age-related degenerative diseases and other cell dysfunction-related illnesses. To achieve these valuable applications, comprehensively understanding of the mechanisms underlying pluripotency maintenance and acquisition is critical. Ubiquitination modifies proteins with Ubiquitin (Ub) at the post-translational level to monitor protein stability and activity. It is extensively involved in pluripotency-specific regulatory networks in ESCs and iPSCs. Ubiquitination is achieved by sequential actions of the Ub-activating enzyme E1, Ub-conjugating enzyme E2, and Ub ligase E3. Compared with E1s and E2s, E3s are most abundant, responsible for substrate selectivity and functional diversity. In this review, we focus on E3 ligases to discuss recent progresses in understanding how they regulate pluripotency and somatic cell reprogramming through ubiquitinating core ESC regulators.

Embryonic stem cell-like subpopulations are present within Schwannoma

BACKGROUND

There is accumulating evidence of the presence of embryonic stem cell (ESC)-like cells in benign tumors.

AIM

This study aimed to identify ESC-like cells in Schwannoma using the induced-pluripotent stem cell (iPSC) markers OCT4, SOX2, NANOG, KLF4 and c-MYC.

METHODS

Immunohistochemical (IHC) staining (n = 20) and RT-qPCR (n = 6) were performed on Schwannoma tissue samples (STS) to investigate protein and mRNA expression of these iPSC markers, respectively. Immunofluorescence (IF) staining was performed to investigate co-localization of the iPSC markers with CD34, α-SMA and CD133.

RESULTS

IHC staining and RT-qPCR demonstrated protein and mRNA expression of all five iPSC markers, respectively. IF staining showed expression of SOX2, KLF4 and c-MYC on the tumor cells and the endothelium of the tumor microvessels which also expressed OCT4, while NANOG was exclusively expressed on the endothelium of the tumor microvessels. The OCT4+/CD34+ endothelium expressed CD133.

CONCLUSION

We have identified a putative OCT4+/SOX2+/NANOG+/KLF4+/c-MYC+/CD133+ ESC-like subpopulation on the endothelium of tumor microvessels and an OCT4-/SOX2+/NANOG-/KLF4+/c-MYC+/CD133+ ESC-like subpopulation, within Schwannoma.

TET1 Interacts Directly with NANOG via Independent Domains Containing Hydrophobic and Aromatic Residues

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TET1 and NANOG interact via multiple independent binding regions.

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TET1 and NANOG interactions are mediated by aromatic and hydrophobic residues.

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TET1 residues that bind NANOG are highly conserved in mammals.

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Co-localisation of TET1 and NANOG on chromatin is enriched at NANOG target genes.

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NANOG and TET1 have regulatory roles in maintaining and reprogramming pluripotency.

The DNA demethylase TET1 is highly expressed in embryonic stem cells and is important both for lineage commitment, and reprogramming to naïve pluripotency. TET1 interacts with the pluripotency transcription factor NANOG which may contribute to its biological activity in pluripotent cells. However, how TET1 interacts with other proteins is largely unknown. Here, we characterise the physical interaction between TET1 and NANOG using embryonic stem cells and bacterial expression systems. TET1 and NANOG interact through multiple binding sites that act independently. Critically, mutating conserved hydrophobic and aromatic residues within TET1 and NANOG abolishes the interaction. On chromatin, NANOG is predominantly localised at ESC enhancers. While TET1 binds to CpG dinucleotides in promoters using its CXXC domain, TET1 also binds to enhancers, though the mechanism involved is unknown. Comparative ChIP-seq analysis identifies genomic loci bound by both TET1 and NANOG, that correspond predominantly to pluripotency enhancers. Importantly, around half of NANOG transcriptional target genes are associated with TET1-NANOG co-bound sites. These results indicate a mechanism by which TET1 protein may be targeted to specific sites of action at enhancers by direct interaction with a transcription factor.

Low-Level Nanog Expression in the Regulation of Quiescent Endothelium

Supplemental Digital Content is available in the text.

Nanog is expressed in adult endothelial cells (ECs) at a low-level, however, its functional significance is not known. The goal of our study was to elucidate the role of Nanog in adult ECs using a genetically engineered mouse model system.

Improving the safety of human pluripotent stem cell therapies using genome-edited orthogonal safeguards

Despite their rapidly-expanding therapeutic potential, human pluripotent stem cell (hPSC)-derived cell therapies continue to have serious safety risks. Transplantation of hPSC-derived cell populations into preclinical models has generated teratomas (tumors arising from undifferentiated hPSCs), unwanted tissues, and other types of adverse events. Mitigating these risks is important to increase the safety of such therapies. Here we use genome editing to engineer a general platform to improve the safety of future hPSC-derived cell transplantation therapies. Specifically, we develop hPSC lines bearing two drug-inducible safeguards, which have distinct functionalities and address separate safety concerns. In vitro administration of one small molecule depletes undifferentiated hPSCs >10⁶-fold, thus preventing teratoma formation in vivo. Administration of a second small molecule kills all hPSC-derived cell-types, thus providing an option to eliminate the entire hPSC-derived cell product in vivo if adverse events arise. These orthogonal safety switches address major safety concerns with pluripotent cell-derived therapies.

Human pluripotent stem cell derived therapies can have serious safety risks. Here the authors design two drug inducible genetic safeguards to deplete undifferentiated hPSCs and hPSC-derived cell types.

The DNA methylation profile of human spermatogonia at single-cell- and single-allele-resolution refutes its role in spermatogonial stem cell function and germ cell differentiation

Human spermatogonial stem cells (hSSCs) have potential in fertility preservation of prepubertal boys or in treatment of male adults suffering from meiotic arrest. Prior to therapeutic application, in vitro propagation of rare hSSCs is mandatory. As the published data points to epigenetic alterations in long-term cell culture of spermatogonia (SPG), an initial characterisation of their DNA methylation state is important. Testicular biopsies from five adult normogonadotropic patients were converted into aggregate-free cell suspensions. FGFR3-positive (FGFR3+) SPG, resembling a very early stem cell state, were labelled with magnetic beads and isolated in addition to unlabelled SPG (FGFR3-). DNA methylation was assessed by limiting dilution bisulfite pyrosequencing for paternally imprinted (H19 and MEG3), maternally imprinted (KCNQ1OT1, PEG3, and SNRPN), pluripotency (POU5F1/OCT4 and NANOG), and spermatogonial/hSSC marker (FGFR3, GFRA1, PLZF, and L1TD1) genes on either single cells or pools of 10 cells. Both spermatogonial subpopulations exhibited a methylation pattern largely equivalent to sperm, with hypomethylation of hSSC marker and maternally imprinted genes and hypermethylation of pluripotency and paternally imprinted genes. Interestingly, we detected fine differences between the two spermatogonial subpopulations, which were reflected by an inverse methylation pattern of imprinted genes, i.e. decreasing methylation in hypomethylated genes and increasing methylation in hypermethylated genes, from FGFR3+ through FGFR3- SPG to sperm. Limitations of this study are due to it not being performed on a genome-wide level and being based on previously published regulatory gene regions. However, the concordance of DNA methylation between SPG and sperm implies that hSSC regulation and germ cell differentiation do not occur at the DNA methylation level.

The NANOG Transcription Factor Induces Type 2 Deiodinase Expression and Regulates the Intracellular Activation of Thyroid Hormone in Keratinocyte Carcinomas

Type 2 deiodinase (D2), the principal activator of thyroid hormone (TH) signaling in target tissues, is expressed in cutaneous squamous cell carcinomas (SCCs) during late tumorigenesis, and its repression attenuates the invasiveness and metastatic spread of SCC. Although D2 plays multiple roles in cancer progression, nothing is known about the mechanisms regulating D2 in cancer. To address this issue, we investigated putative upstream regulators of D2 in keratinocyte carcinomas. We found that the expression of D2 in SCC cells is positively regulated by the NANOG transcription factor, whose expression, besides being causally linked to embryonic stemness, is associated with many human cancers. We also found that NANOG binds to the D2 promoter and enhances D2 transcription. Notably, blockage of D2 activity reduced NANOG-induced cell migration as well as the expression of key genes involved in epithelial-mesenchymal transition in SCC cells. In conclusion, our study reveals a link among endogenous endocrine regulators of cancer, thyroid hormone and its activating enzyme, and the NANOG regulator of cancer biology. These findings could provide the basis for the development of TH inhibitors as context-dependent anti-tumor agents.

Ratio of the zygote cytoplasm to the paternal genome affects the reprogramming and developmental efficiency of androgenetic embryos

Uniparental embryos have uniparental genomes and are very useful models for studying the specific gene expression of parents or for exploring the biological significance of genomic imprinting in mammals. However, the early developmental efficiency of androgenetic embryos is significantly lower than that of parthenogenetic embryos. In addition, oocytes are able to reprogram sperm nuclei after fertilization to guarantee embryonic development by maternally derived reprogramming factors, which accumulate during oogenesis. However, the importance of maternal material in the efficiency of reprogramming the pronucleus of androgenetic embryos is not known. In this study, androgenetic embryos were constructed artificially by pronucleus transfer (PT) or double sperm injection (DS). Compared with DS embryos, PT embryos that were derived from two zygotes contained more maternal material, like 10-11 translocation methylcytosine deoxygenase 3 (Tet3) and histone variant 3.3 (H3.3). Our experiments confirmed the better developmental potential of PT embryos, which had higher blastocyst rates, a stronger expression of pluripotent genes, a lower expression of apoptotic genes, and superior blastocyst quality. Our findings indicate that the aggregation of more maternal materials in the paternal pronucleus facilitate the reprogramming of the paternal genome, improving embryonic development in PT androgenesis.

Nanog regulates Pou3f1 expression at the exit from pluripotency during gastrulation

Pluripotency is regulated by a network of transcription factors that maintain early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a critical factor for maintaining pluripotency and its role in primordial germ cell differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development is its expression restricted to primordial germ cells. In this work, we unveiled a previously unknown mechanism by which Nanog specifically represses genes involved in anterior epiblast lineage. Analysis of transcriptional data from both embryonic stem cells and gastrulating mouse embryos revealed Pou3f1 expression to be negatively correlated with that of Nanog during the early stages of differentiation. We have functionally demonstrated Pou3f1 to be a direct target of NANOG by using a dual transgene system for the controlled expression of Nanog Use of Nanog null ES cells further demonstrated a role for Nanog in repressing a subset of anterior neural genes. Deletion of a NANOG binding site (BS) located nine kilobases downstream of the transcription start site of Pou3f1 revealed this BS to have a specific role in the regionalization of the expression of this gene in the embryo. Our results indicate an active role of Nanog inhibiting neural regulatory networks by repressing Pou3f1 at the onset of gastrulation.This article has an associated First Person interview with the joint first authors of the paper.

Mapping cell migrations and fates in a gastruloid model to the human primitive streak

Although fate maps of early embryos exist for nearly all model organisms, a fate map of the gastrulating human embryo remains elusive. Here, we use human gastruloids to piece together a rudimentary fate map for the human primitive streak (PS). This is possible because differing levels of BMP, WNT and NODAL lead to self-organization of gastruloids into homogenous subpopulations of endoderm and mesoderm, and comparative analysis of these gastruloids, together with the fate map of the mouse embryo, allows the organization of these subpopulations along an anterior-posterior axis. We also developed a novel cell tracking technique that detected robust fate-dependent cell migrations in our gastruloids comparable with those found in the mouse embryo. Taken together, our fate map and recording of cell migrations provides a first coarse view of what the human PS may resemble in vivo.

Genetic basis for primordial germ cells specification in mouse and human: Conserved and divergent roles of PRDM and SOX transcription factors

Primordial germ cells (PGCs) are embryonic precursors of sperm and egg that pass on genetic and epigenetic information from one generation to the next. In mammals, they are induced from a subset of cells in peri-implantation epiblast by BMP signaling from the surrounding tissues. PGCs then initiate a unique developmental program that involves comprehensive epigenetic resetting and repression of somatic genes. This is orchestrated by a set of signaling molecules and transcription factors that promote germ cell identity. Here we review significant findings on mammalian PGC biology, in particular, the genetic basis for PGC specification in mice and human, which has revealed an evolutionary divergence between the two species. We discuss the importance and potential basis for these differences and focus on several examples to illustrate the conserved and divergent roles of critical transcription factors in mouse and human germline.

Retinoic Acid Induces Differentiation of Mouse F9 Embryonic Carcinoma Cell by Modulating the miR-485 Targeting of Abhd2

Retinoic acid (RA) plays a key role in pluripotent cell differentiation. In F9 embryonic carcinoma cells, RA can induce differentiation towards somatic lineages via the Ras-extracellular signal-regulated kinase (Ras/Erk) pathway, but the mechanism through which it induces the Erk1/2 phosphorylation is unclear. Here, we show that miR-485 is a positive regulator that targets α/β-hydrolase domain-containing protein 2 (Abhd2), which can result in Erk1/2 phosphorylation and triggers differentiation. RA up-regulates miR-485 and concurrently down-regulates Abhd2. We verified that Abhd2 is targeted by miR-485 and they both can influence the phosphorylation of Erk1/2. In summary, RA can mediate cell differentiation by phosphorylating Erk1/2 via miR-485 and Abhd2.

The pluripotency factor NANOG controls primitive hematopoiesis and directly regulates Tal1

Progenitors of the first hematopoietic cells in the mouse arise in the early embryo from Brachyury-positive multipotent cells in the posterior-proximal region of the epiblast, but the mechanisms that specify primitive blood cells are still largely unknown. Pluripotency factors maintain uncommitted cells of the blastocyst and embryonic stem cells in the pluripotent state. However, little is known about the role played by these factors during later development, despite being expressed in the postimplantation epiblast. Using a dual transgene system for controlled expression at postimplantation stages, we found that Nanog blocks primitive hematopoiesis in the gastrulating embryo, resulting in a loss of red blood cells and downregulation of erythropoietic genes. Accordingly, Nanog-deficient embryonic stem cells are prone to erythropoietic differentiation. Moreover, Nanog expression in adults prevents the maturation of erythroid cells. By analysis of previous data for NANOG binding during stem cell differentiation and CRISPR/Cas9 genome editing, we found that Tal1 is a direct NANOG target. Our results show that Nanog regulates primitive hematopoiesis by directly repressing critical erythroid lineage specifiers.

Chimeric NANOG repressors inhibit glioblastoma growth in vivo in a context-dependent manner

Targeting stemness promises new therapeutic strategies against highly invasive tumors. While a number of approaches are being tested, inhibiting the core transcription regulatory network of cancer stem cells is an attractive yet challenging possibility. Here we have aimed to provide the proof of principle for a strategy, previously used in developmental studies, to directly repress the targets of a salient stemness and pluripotency factor: NANOG. In doing so we expected to inhibit the expression of so far unknown mediators of pro-tumorigenic NANOG function. We chose NANOG since previous work showed the essential requirement for NANOG activity for human glioblastoma (GBM) growth in orthotopic xenografts, and it is apparently absent from many adult human tissues thus likely minimizing unwanted effects on normal cells. NANOG repressor chimeras, which we name NANEPs, bear the DNA-binding specificity of NANOG through its homeodomain (HD), and this is linked to transposable human repressor domains. We show that in vitro and in vivo, NANEP5, our most active NANEP with a HES1 repressor domain, mimics knock-down (kd) of NANOG function in GBM cells. Competition orthotopic xenografts also reveal the effectiveness of NANEP5 in a brain tumor context, as well as the specificity of NANEP activity through the abrogation of its function via the introduction of specific mutations in the HD. The transcriptomes of cells expressing NANEP5 reveal multiple potential mediators of pro-tumorigenic NANEP/NANOG action including intercellular signaling components. The present results encourage further studies on the regulation of context-dependent NANEP abundance and function, and the development of NANEP-based anti-cancer therapies.

Genetic dissection of Nodal and Bmp signalling requirements during primordial germ cell development in mouse

The essential roles played by Nodal and Bmp signalling during early mouse development have been extensively documented. Here we use conditional deletion strategies to investigate functional contributions made by Nodal, Bmp and Smad downstream effectors during primordial germ cell (PGC) development. We demonstrate that Nodal and its target gene Eomes provide early instructions during formation of the PGC lineage. We discover that Smad2 inactivation in the visceral endoderm results in increased numbers of PGCs due to an expansion of the PGC niche. Smad1 is required for specification, whereas in contrast Smad4 controls the maintenance and migration of PGCs. Additionally we find that beside Blimp1, down-regulated phospho-Smad159 levels also distinguishes PGCs from their somatic neighbours so that emerging PGCs become refractory to Bmp signalling that otherwise promotes mesodermal development in the posterior epiblast. Thus balanced Nodal/Bmp signalling cues regulate germ cell versus somatic cell fate decisions in the early posterior epiblast.

A comparative in vitro study of the osteogenic and adipogenic potential of human dental pulp stem cells, gingival fibroblasts and foreskin fibroblasts

Human teeth contain a variety of mesenchymal stem cell populations that could be used for cell-based regenerative therapies. However, the isolation and potential use of these cells in the clinics require the extraction of functional teeth, a process that may represent a significant barrier to such treatments. Fibroblasts are highly accessible and might represent a viable alternative to dental stem cells. We thus investigated and compared the in vitro differentiation potential of human dental pulp stem cells (hDPSCs), gingival fibroblasts (hGFs) and foreskin fibroblasts (hFFs). These cell populations were cultured in osteogenic and adipogenic differentiation media, followed by Alizarin Red S and Oil Red O staining to visualize cytodifferentiation. Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) was performed to assess the expression of markers specific for stem cells (NANOG, OCT-4), osteogenic (RUNX2, ALP, SP7/OSX) and adipogenic (PPAR-γ2, LPL) differentiation. While fibroblasts are more prone towards adipogenic differentiation, hDPSCs exhibit a higher osteogenic potential. These results indicate that although fibroblasts possess a certain mineralization capability, hDPSCs represent the most appropriate cell population for regenerative purposes involving bone and dental tissues.

Esrrb extinction triggers dismantling of naïve pluripotency and marks commitment to differentiation

Self-renewal of embryonic stem cells (ESCs) cultured in LIF/fetal calf serum (FCS) is incomplete with some cells initiating differentiation. While this is reflected in heterogeneous expression of naive pluripotency transcription factors (TFs), the link between TF heterogeneity and differentiation is not fully understood. Here, we purify ESCs with distinct TF expression levels from LIF/FCS cultures to uncover early events during commitment from naïve pluripotency. ESCs carrying fluorescent Nanog and Esrrb reporters show Esrrb downregulation only in Nanoglow cells. Independent Esrrb reporter lines demonstrate that Esrrbnegative ESCs cannot effectively self-renew. Upon Esrrb loss, pre-implantation pluripotency gene expression collapses. ChIP-Seq identifies different regulatory element classes that bind both OCT4 and NANOG in Esrrbpositive cells. Class I elements lose NANOG and OCT4 binding in Esrrbnegative ESCs and associate with genes expressed preferentially in naïve ESCs. In contrast, Class II elements retain OCT4 but not NANOG binding in ESRRB-negative cells and associate with more broadly expressed genes. Therefore, mechanistic differences in TF function act cumulatively to restrict potency during exit from naïve pluripotency.

Somatic Pluripotent Genes in Tissue Repair, Developmental Disease, and Cancer

Embryonic stem cells possess the ability to differentiate into all cell types of the body. This pliable developmental state is achieved by the function of a series of pluripotency factors, classically identified as OCT4, SOX2, and NANOG. These pluripotency factors are responsible for activating the larger pluripotency networks and the self-renewal programs which give ES cells their unique characteristics. However, during differentiation pluripotency networks become downregulated as cells achieve greater lineage specification and exit the cell cycle. Typically the repression of pluripotency is viewed as a positive factor to ensure the fidelity of cellular identity by restricting cellular pliancy. Consistent with this view, the expression of pluripotency factors is greatly restricted in somatic cells. However, there are examples whereby cells either maintain or reactivate pluripotency factors to preserve the increased potential for the healing of wounds or tissue homeostasis. Additionally there are many examples where these pluripotency factors become reactivated in a variety of human pathologies, particularly cancer. In this review, we will summarize the somatic repression of pluripotency factors, their role in tissue homeostasis and wound repair, and the human diseases that are associated with pluripotency factor misregulation with an emphasis on their role in the etiology of multiple cancers.

Functional characterization of NANOG in goat pre-implantation embryonic development

Nanog as a novel pluripotent cell-specific gene plays important roles in regulation of signaling pathways for maintenance and induction of pluripotency in inner cell mass (ICM) and embryonic stem cells (ESC) in mouse. The molecular features and transcription regulation of NANOG gene in domestic animals are not well defined. In this study, we performed knockdown of NANOG mRNA in goat embryos and examined its effect on early embryonic development. Presumptive zygotes were injected with a volume of 8-10 pl NANOG or scrambled (SCR) siRNA, and subsequently cleavage and blastocyst formation rate were assessed. Furthermore, gene expression analysis was carried out in 6-8 cell and blastocyst derived embryos from non-injected controls, SCR - and siRNA-injected presumptive zygotes. Cleavage and blastocyst rates in siRNA groups were insignificantly lower than the control and SCR groups. Embryos with reduced expression of NANOG showed decrease in number of trophectoderm (TE) and total cells in blastocysts. Analysis of expression of developmentally important genes (SOX2, OCT4 and NANOG), which work as a network, showed that NANOG knockdown results in significant increase in expression of SOX2 and OCT4 and among the possible target genes (CDX2, REX1 and GATA4) of this network, only GATA4 showed increased expression. Our results suggest that NANOG is likely to be required for proliferation of trophoblastic cells.

Oct4 regulates the embryonic axis and coordinates exit from pluripotency and germ layer specification in the mouse embryo

Lineage segregation in the mouse embryo is a finely controlled process dependent upon coordination of signalling pathways and transcriptional responses. Here we employ a conditional deletion system to investigate embryonic patterning and lineage specification in response to loss of Oct4. We first observe ectopic expression of Nanog in Oct4-negative postimplantation epiblast cells. The expression domains of lineage markers are subsequently disrupted. Definitive endoderm expands at the expense of mesoderm; the anterior-posterior axis is positioned more distally and an ectopic posterior-like domain appears anteriorly, suggesting a role for Oct4 in maintaining the embryonic axis. Although primitive streak forms in the presumptive proximal-posterior region, epithelial-to-mesenchymal transition is impeded by an increase of E-cadherin, leading to complete tissue disorganisation and failure to generate germ layers. In explant and in vitro differentiation assays, Oct4 mutants also show upregulation of E-cadherin and Foxa2, suggesting a cell-autonomous phenotype. We confirm requirement for Oct4 in self-renewal of postimplantation epiblast ex vivo Our results indicate a role for Oct4 in orchestrating multiple fates and enabling expansion, correct patterning and lineage choice in the postimplantation epiblast.

Molecular characterization and expression patterns of Nanog gene validating its involvement in the embryonic development and maintenance of spermatogonial stem cells of farmed carp, Labeo rohita

Background

The homeobox containing transcription factor Nanog plays crucial roles in embryonic development/proliferation and/or maintenance of spermatogonial stem cells (SSCs) via interacting with transcription factors such as Oct4 and Sox2 in mammals. However, knowledge of its exact mechanistic pathways remains unexploited. Very little is known about teleost Nanog. Information on the Nanog gene of farmed rohu carp (Labeo rohita) is lacking. We cloned and characterized the Nanog gene of rohu carp to understand the expression pattern in early developmental stages and also deduced the genomic organization including promoter elements.

Results

Rohu Nanog (LrNanog) cDNA comprised an open reading frame of 1,161 nucleotides bearing a structural homeodomain; whereas, the genomic structure contained four exons and three introns suggesting that it is homologous to mammalian counterparts. Phylogenetically, it was closely related to freshwater counterparts. Protein sequence (386 AA of 42.65 kDa) comparison revealed its low similarity with other vertebrate counterparts except that of the conserved homeodomain. Tissue distribution analysis revealed the existence of LrNanog transcripts only in adult gonads. The heightened abundances in the ovary and proliferating spermatogonia suggested its participations in maternal inheritance and male germ cell development. The potentiating abundances from fertilized egg onwards peaking at blastula stage vis- à-vis decreasing levels from gastrula stage onwards demonstrated its role in embryonic stem cell development. We also provided evidence of its presence in SSCs by western blotting analysis. Further, the promoter region was characterized, predicting a basal core promoter and other consensus elements.

Conclusion

The molecular characterization of LrNanog and its documented expression profiling at transcript and protein levels are indicative of its functional linkage with embryonic/spermatogonial stem cell maintenance. This is the first report of LrNanog genomic organization including its promoter sequence information with predicted regulatory elements of a large-bodied carp species. This will be useful for elucidating its mechanism expression in future. Nanog could be used as a potential biomarker for proliferating carp SSCs.

Micropattern differentiation of mouse pluripotent stem cells recapitulates embryo regionalized cell fate patterning

During gastrulation epiblast cells exit pluripotency as they specify and spatially arrange the three germ layers of the embryo. Similarly, human pluripotent stem cells (PSCs) undergo spatially organized fate specification on micropatterned surfaces. Since in vivo validation is not possible for the human, we developed a mouse PSC micropattern system and, with direct comparisons to mouse embryos, reveal the robust specification of distinct regional identities. BMP, WNT, ACTIVIN and FGF directed mouse epiblast-like cells to undergo an epithelial-to-mesenchymal transition and radially pattern posterior mesoderm fates. Conversely, WNT, ACTIVIN and FGF patterned anterior identities, including definitive endoderm. By contrast, epiblast stem cells, a developmentally advanced state, only specified anterior identities, but without patterning. The mouse micropattern system offers a robust scalable method to generate regionalized cell types present in vivo, resolve how signals promote distinct identities and generate patterns, and compare mechanisms operating in vivo and in vitro and across species.

Pre-gastrula Development of Non-eutherian Mammals

Marsupials and monotremes differ from eutherian mammals in many features of their reproduction and development. Some features appear to be representative of transitional stages in evolution from therapsid reptiles to humans and mice, particularly with respect to the extraembryonic tissues that have undergone remarkable modifications to accommodate reduced egg size and quantity of yolk/deutoplasm, and increasing emphasis on viviparity and placentation. Trophoblast and hypoblast contribute the epithelial layers in most of the extraembryonic membranes and are the first two lineages to differentiate from the embryonic lineage. How they are specified varies greatly among mammals, perhaps largely due to heterochrony in the stage at which they must function. Differences probably also exist in the stage at which lineages are specified relative to the stage at which they fully commit to differentiation. The dogma of sequential commitment to trophoblast and hypoblast with progressive loss of potency may not be a fundamental feature of early mammalian development, but merely a recently acquired developmental pattern in eutherians, or at least mice.

Antagonism between the transcription factors NANOG and OTX2 specifies rostral or caudal cell fate during neural patterning transition

During neurogenesis, neural patterning is a critical step during which neural progenitor cells differentiate into neurons with distinct functions. However, the molecular determinants that regulate neural patterning remain poorly understood. Here we optimized the "dual SMAD inhibition" method to specifically promote differentiation of human pluripotent stem cells (hPSCs) into forebrain and hindbrain neural progenitor cells along the rostral-caudal axis. We report that neural patterning determination occurs at the very early stage in this differentiation. Undifferentiated hPSCs expressed basal levels of the transcription factor orthodenticle homeobox 2 (OTX2) that dominantly drove hPSCs into the "default" rostral fate at the beginning of differentiation. Inhibition of glycogen synthase kinase 3β (GSK3β) through CHIR99021 application sustained transient expression of the transcription factor NANOG at early differentiation stages through Wnt signaling. Wnt signaling and NANOG antagonized OTX2 and, in the later stages of differentiation, switched the default rostral cell fate to the caudal one. Our findings have uncovered a mutual antagonism between NANOG and OTX2 underlying cell fate decisions during neural patterning, critical for the regulation of early neural development in humans.

A sister of NANOG regulates genes expressed in pre-implantation human development

The NANOG homeobox gene plays a pivotal role in self-renewal and maintenance of pluripotency in human, mouse and other vertebrate embryonic stem cells, and in pluripotent cells of the blastocyst inner cell mass. There is a poorly studied and atypical homeobox locus close to the Nanog gene in some mammals which could conceivably be a cryptic paralogue of NANOG, even though the loci share only 20% homeodomain identity. Here we argue that this gene, NANOGNB (NANOG Neighbour), is an extremely divergent duplicate of NANOG that underwent radical sequence change in the mammalian lineage. Like NANOG, the NANOGNB gene is expressed in pre-implantation embryos of human and cow; unlike NANOG, NANOGNB expression is restricted to 8-cell and morula stages, preceding blastocyst formation. When expressed ectopically in adult cells, human NANOGNB elicits gene expression changes, including downregulation of a set of genes that have an expression pulse at the 8-cell stage of pre-implantation development. We conclude that gene duplication and massive sequence divergence in mammals generated a novel homeobox gene that acquired new developmental roles complementary to those of Nanog.

Zfp281 is essential for mouse epiblast maturation through transcriptional and epigenetic control of Nodal signaling

Pluripotency is defined by a cell's potential to differentiate into any somatic cell type. How pluripotency is transited during embryo implantation, followed by cell lineage specification and establishment of the basic body plan, is poorly understood. Here we report the transcription factor Zfp281 functions in the exit from naive pluripotency occurring coincident with pre-to-post-implantation mouse embryonic development. By characterizing Zfp281 mutant phenotypes and identifying Zfp281 gene targets and protein partners in developing embryos and cultured pluripotent stem cells, we establish critical roles for Zfp281 in activating components of the Nodal signaling pathway and lineage-specific genes. Mechanistically, Zfp281 cooperates with histone acetylation and methylation complexes at target gene enhancers and promoters to exert transcriptional activation and repression, as well as epigenetic control of epiblast maturation leading up to anterior-posterior axis specification. Our study provides a comprehensive molecular model for understanding pluripotent state progressions in vivo during mammalian embryonic development.

Formative pluripotency: the executive phase in a developmental continuum

The regulative capability of single cells to give rise to all primary embryonic lineages is termed pluripotency. Observations of fluctuating gene expression and phenotypic heterogeneity in vitro have fostered a conception of pluripotency as an intrinsically metastable and precarious state. However, in the embryo and in defined culture environments the properties of pluripotent cells change in an orderly sequence. Two phases of pluripotency, called naïve and primed, have previously been described. In this Hypothesis article, a third phase, called formative pluripotency, is proposed to exist as part of a developmental continuum between the naïve and primed phases. The formative phase is hypothesised to be enabling for the execution of pluripotency, entailing remodelling of transcriptional, epigenetic, signalling and metabolic networks to constitute multi-lineage competence and responsiveness to specification cues.

Summary: This Hypothesis article poses that a third state of pluripotency, called formative pluripotency, exists between the naïve and primed states, and is enabling for the execution of pluripotency.

Maternal inheritance of Nanog ortholog in blunt-snout bream

The homeodomain transcription factor Nanog plays an essential role in maintaining pluripotency and self-renewal of embryonic stem cells in mammals. However, the evolutionary conservation of its ortholog in teleosts remains elusive. Here we isolated and characterized a Nanog homolog named as Ma-Nanog in blunt-snout bream (Megalobrama amblycephala). The full-length genomic sequence is 3,326 bp in length and consists of four exons encoding a homeodomain protein of 386 amino acid residues. Comparison of protein sequences revealed that Ma-Nanog is highly homologous to those in other teleosts, particularly in the homeodomain region. During embryogenesis, RNA expression of Nanog was only detected in early developmental embryos, predominantly at the blastula stage, which suggested the transcripts were mainly present in pluripotent stem cells. RNA fluorescence in situ hybridization verified that the signal of the transcripts is present in the germ cells. RNA expression was observed in the oogonia and early stage of oocytes in the ovary, or in the spermatogonia, spermatocytes, and spermatids in the testis. Surprisingly, the transcripts were also detected in adult tissues such as in liver by RT-PCR or qRT-PCR. Subcellular localization of the Nanog protein was also verified in nuclei. Taken together, these results suggested that Ma-Nanog is maternally inherited with conserved features, thus can be potentially used as a marker for stem cells in blunt-snout bream.

Characterization of the porcine Nanog 5'-flanking region

Objective

Nanog, a homeodomain protein, has been investigated in humans and mice using embryonic stem cells (ESCs). Because of the limited availability of ESCs, few studies have reported the function and role of Nanog in porcine ESCs. Therefore, in this study, we investigated the location of the porcine Nanog chromosome and its basal promoter activity, which might have potential applications in development of ESCs specific marker as well as understanding its operating systems in the porcine.

Methods

To characterize the porcine Nanog promoter, the 5′-flanking region of Nanog was isolated from cells of mini-pig ears. BLAST database search showed that there are two porcine Nanog genomic loci, chromosome 1 and 5, both of which contain an exon with a start codon. Deletion mutants from the 5′-flanking region of both loci were measured using the Dual-Luciferase Reporter Assay System, and a fluorescence marker, green fluorescence protein.

Results

Promoter activity was detected in the sequences of chromosome 5, but not in those of chromosome 1. We identified the sequences from –99 to +194 that possessed promoter activity and contained transcription factor binding sites from deletion fragment analysis. Among the transcription factor binding sites, a Sp1 was found to play a crucial role in basal promoter activity, and point mutation of this site abolished its activity, confirming its role in promoter activity. Furthermore, gel shift analysis and chromatin immunoprecipitation analysis confirmed that Sp1 transcription factor binds to the Sp1 binding site in the porcine Nanog promoter. Taken together, these results show that Sp1 transcription factor is an essential element for porcine Nanog basal activity the same as in human and mouse.

Conclusion

We showed that the porcine Nanog gene is located on porcine chromosome 5 and its basal transcriptional activity is controlled by Sp1 transcription factor.

Pluri-IQ: Quantification of Embryonic Stem Cell Pluripotency through an Image-Based Analysis Software

Image-based assays, such as alkaline phosphatase staining or immunocytochemistry for pluripotent markers, are common methods used in the stem cell field to assess pluripotency. Although an increased number of image-analysis approaches have been described, there is still a lack of software availability to automatically quantify pluripotency in large images after pluripotency staining. To address this need, we developed a robust and rapid image processing software, Pluri-IQ, which allows the automatic evaluation of pluripotency in large low-magnification images. Using mouse embryonic stem cells (mESC) as a model, we combined an automated segmentation algorithm with a supervised machine-learning platform to classify colonies as pluripotent, mixed, or differentiated. In addition, Pluri-IQ allows the automatic comparison between different culture conditions. This efficient user-friendly open-source software can be easily implemented in images derived from pluripotent cells or cells that express pluripotent markers (e.g., OCT4-GFP) and can be routinely used, decreasing image assessment bias.

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Open-source software to evaluate pluripotency in low-magnification images

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Automatic colony detection and segmentation

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Supervised machine-learning platform with high characterization accuracy

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Software tools for easy data validation, visualization, and data analysis comparison