Manganese Superoxide Dismutase Gene Expression Is Induced by Nanog and Oct4, Essential Pluripotent Stem Cells' Transcription Factors

Maternal exposure to hyperbaric oxygen at the preimplantation stages increases apoptosis and ectopic Cdx2 expression and decreases Oct4 expression in mouse blastocysts via Nrf2-Notch1 upregulation and Nf2 downregulation

BACKGROUND

The environmental oxygen tension has been reported to impact the blastocyst quality and cell numbers in the inner cell mass (ICM) during human and murine embryogenesis. While the molecular mechanisms leading to increased ICM cell numbers and pluripotency gene expression under hypoxia have been deciphered, it remains unknown which regulatory pathways caused the underweight fetal body and overweight placenta after maternal exposure to hyperbaric oxygen (HBO).

RESULTS

The blastocysts from the HBO-exposed pregnant mice revealed significantly increased signals of reactive oxygen species (ROS) and nuclear Nrf2 staining, decreased Nf2 and Oct4 expression, increased nuclear Tp53bp1 and active caspase-3 staining, and ectopic nuclear signals of Cdx2, Yap, and the Notch1 intracellular domain (N1ICD) in the ICM. In the ICM of the HBO-exposed blastocysts, both Nf2 cDNA microinjection and Nrf2 shRNA microinjection significantly decreased the ectopic nuclear expression of Cdx2, Tp53bp1, and Yap whereas increased Oct4 expression, while Nrf2 shRNA microinjection also significantly decreased Notch1 mRNA levels and nuclear expression of N1ICD and active caspase-3.

CONCLUSION

We show for the first time that maternal exposure to HBO at the preimplantation stage induces apoptosis and impairs ICM cell specification via upregulating Nrf2-Notch1-Cdx2 expression and downregulating Nf2-Oct4 expression.

AKT1 induces Nanog promoter in a SUMOylation-dependent manner in different pluripotent contexts

AKT/PKB is a kinase crucial for pluripotency maintenance in pluripotent stem cells. Multiple post-translational modifications modulate its activity. We have previously demonstrated that AKT1 induces the expression of the pluripotency transcription factor Nanog in a SUMOylation-dependent manner in mouse embryonic stem cells. Here, we studied different cellular contexts and main candidates that could mediate this induction. Our results strongly suggest the pluripotency transcription factors OCT4 and SOX2 are not essential mediators. Additionally, we concluded that this induction takes place in different pluripotent contexts but not in terminally differentiated cells. Finally, the cross-matching analysis of ESCs, iPSCs and MEFs transcriptomes and AKT1 phosphorylation targets provided new clues about possible factors that could be involved in the SUMOylation-dependent Nanog induction by AKT.

Self-transfecting GMO-PMO chimera targeting Nanog enable gene silencing in vitro and suppresses tumor growth in 4T1 allografts in mouse

Phosphorodiamidate morpholino oligonucleotide (PMO)-based antisense reagents cannot enter cells without the help of a delivery technique, which limits their clinical applications. To overcome this problem, self-transfecting guanidinium-linked morpholino (GMO)-PMO or PMO-GMO chimeras have been explored as antisense agents. GMO facilitates cellular internalization and participates in Watson-Crick base pairing. Targeting NANOG in MCF7 cells resulted in decline of the whole epithelial to mesenchymal transition (EMT) and stemness pathway, evident through its phenotypic manifestations, all of which were promulgated in combination with Taxol due to downregulation of MDR1 and ABCG2. GMO-PMO-mediated knockdown of no tail gene resulted in desired phenotypes in zebrafish even upon delivery after 16-cell stages. In BALB/c mice, 4T1 allografts were found to regress via intra-tumoral administration of NANOG GMO-PMO antisense oligonucleotides (ASOs), which was associated with occurrence of necrotic regions. GMO-PMO-mediated tumor regression restored histopathological damage in liver, kidney, and spleen caused by 4T1 mammary carcinoma. Serum parameters of systemic toxicity indicated that GMO-PMO chimeras are safe. To the best of our knowledge, self-transfecting antisense reagent is the first report since the discovery of guanidinium-linked DNA (DNG), which could be useful as a combination cancer therapy and, in principle, can render inhibition of any target gene without using any delivery vehicle.

Profiling of mature-stage human breast milk cells identifies six unique lactocyte subpopulations

Breast milk is chock-full of nutrients, immunological factors, and cells that aid infant development. Maternal cells are the least studied breast milk component, and their unique properties are difficult to identify using traditional techniques. Here, we characterized the cells in mature-stage breast milk from healthy donors at the protein, gene, and transcriptome levels. Holistic analysis of flow cytometry, quantitative polymerase chain reaction, and single-cell RNA sequencing data identified the predominant cell population as epithelial with smaller populations of macrophages and T cells. Two percent of epithelial cells expressed four stem cell markers: SOX2, TRA-1-60, NANOG, and SSEA4. Furthermore, milk contained six distinct epithelial lactocyte subpopulations, including three previously unidentified subpopulations programmed toward mucosal defense and intestinal development. Pseudotime analysis delineated the differentiation pathways of epithelial progenitors. Together, these data define healthy human maternal breast milk cells and provide a basis for their application in maternal and infant medicine.

Surgical outcomes and quality of life in Rathke's cleft cysts undergoing endoscopic transsphenoidal resection: a multicentre study and systematic review of the literature

OBJECTIVE

To establish the effect of endoscopic endonasal surgery (EES) on quality-of-life (QoL) in symptomatic Rathke cleft cyst (RCC).

METHODS

Analysis of 38 patients with RCC treated by EES, with regular overall (ASBQ-35) and sinonasal-specific (SNOT-22) QoL assessment during the first postoperative year. A systematic literature review of large case series was performed with pooled analysis.

RESULTS

In our series, mean age was 53.6 years with a female predominance (73.7%). Larger cysts were seen in males (p < 0.01), those with hypogonadism (p = 0.04), and visual dysfunction (p = 0.04). Complete normalisation of vision was seen in 83.3%. Persistence of visual dysfunction postoperatively was associated with diabetes (p = 0.005), hypertension (p = 0.02), suprasellar only location (p = 0.001), and monocular field cut (p = 0.02). Surgery did not significantly effect hormonal function. Sinonasal QoL transiently worsened after surgery, resolving within 3 weeks. A parallel transient worsening of overall QoL normalised by 6 weeks, and remained at preoperative baseline thereafter. These results were comparable to the literature, where 76.4% demonstrated improvement of vision and 13.1% had recurrence after treatment. There was no significant difference in outcomes between EES and microscopic approaches.

CONCLUSIONS

We report longitudinal QoL outcomes in RCC for the first time. Vision commonly improves with surgery, but endocrinopathy is likely to persist. Microvascular risk-factors may compromise visual improvement. Surgery causes a transient worsening of sinonasal symptoms that resolves within 3-6 weeks, but patients may not experience significant improvement in QoL within the first postoperative year.

SUMO conjugation susceptibility of Akt/protein kinase B affects the expression of the pluripotency transcription factor Nanog in embryonic stem cells

Akt/PKB is a kinase involved in the regulation of a wide variety of cell processes. Its activity is modulated by diverse post-translational modifications (PTMs). Particularly, conjugation of the small ubiquitin-related modifier (SUMO) to this kinase impacts on multiple cellular functions, such as proliferation and splicing. In embryonic stem (ES) cells, this kinase is key for pluripotency maintenance. Among other functions, Akt is known to promote the expression of Nanog, a central pluripotency transcription factor (TF). However, the relevance of this specific PTM of Akt has not been previously analyzed in this context. In this work, we study the effect of Akt1 variants with differential SUMOylation susceptibility on the expression of Nanog. Our results demonstrate that both, the Akt1 capability of being modified by SUMO conjugation and a functional SUMO conjugase activity are required to induce Nanog gene expression. Likewise, we found that the common oncogenic E17K Akt1 mutant affected Nanog expression in ES cells also in a SUMOylatability dependent manner. Interestingly, this outcome takes places in ES cells but not in a non-pluripotent heterologous system, suggesting the presence of a crucial factor for this induction in ES cells. Remarkably, the two major candidate factors to mediate this induction, GSK3-β and Tbx3, are non-essential players of this effect, suggesting a complex mechanism probably involving non-canonical pathways. Furthermore, we found that Akt1 subcellular distribution does not depend on its SUMOylatability, indicating that Akt localization has no influence on the effect on Nanog, and that besides the membrane localization of E17K Akt mutant, SUMOylation is also required for its hyperactivity. Our results highlight the impact of SUMO conjugation in the function of a kinase relevant for a plethora of cellular processes, including the control of a key pluripotency TF.

The pluripotency transcription factor OCT4 represses heme oxygenase-1 gene expression

In embryonic stem (ES) cells, oxidative stress control is crucial for genomic stability, self-renewal, and cell differentiation. Heme oxygenase-1 (HO-1) is a key player of the antioxidant system and is also involved in stem cell differentiation and pluripotency acquisition. We found that the HO-1 gene is expressed in ES cells and induced after promoting differentiation. Moreover, downregulation of the pluripotency transcription factor (TF) OCT4 increased HO-1 mRNA levels in ES cells, and analysis of ChIP-seq public data revealed that this TF binds to the HO-1 gene locus in pluripotent cells. Finally, ectopic expression of OCT4 in heterologous systems repressed a reporter carrying the HO-1 gene promoter and the endogenous gene. Hence, this work highlights the connection between pluripotency and redox homeostasis.

Promoter hypermethylation of early B cell factor 1 (EBF1) is associated with cholangiocarcinoma progression

DNA hypermethylation in a promoter region causes gene silencing via epigenetic changes. We have previously reported that early B cell factor 1 (EBF1) was down-regulated in cholangiocarcinoma (CCA) tissues and related to tumor progression. Thus, we hypothesized that the DNA hypermethylation of EBF1 promoter would suppress EBF1 expression in CCA and induce its progression. In this study, the DNA methylation status of EBF1 and mRNA expression levels were analyzed in CCA and normal bile duct (NBD) tissues using a publicly available database of genome-wide association data. The results showed that the DNA methylation of EBF1 promoter region was significantly increased in CCA tissues compared with those of NBD. The degree of methylation was negatively correlated with EBF1 mRNA expression levels. Using methylation-specific PCR technique, the DNA methylation rates of EBF1 promoter region were investigated in CCA tissues (n=72). CCA patients with high methylation rates of EBF1 promoter region in the tumor tissues (54/72) had a poor prognosis. Higher methylation rates of EBF1 promoter region have shown in all CCA cell lines than that of an immortal cholangiocyte cell line (MMNK1). Upon treatment with the DNA methyltransferase inhibitor 5-Aza-dC, increased EBF1 expression levels and reduced DNA methylation rates were observed in CCA cells. Moreover, restoration of EBF1 expression in CCA cells led to inhibition of cell growth, migration and invasion. In addition, RNA sequencing analysis suggested that EBF1 is involved in suppression of numerous pathways in cancer. Taken together, DNA hypermethylation in the EBF1 promoter region suppresses EBF1 expression and induces CCA progression with aggressive clinical outcomes.

Novel Interplay between p53 and HO-1 in Embryonic Stem Cells

Stem cells genome safeguarding requires strict oxidative stress control. Heme oxygenase-1 (HO-1) and p53 are relevant components of the cellular defense system. p53 controls cellular response to multiple types of harmful stimulus, including oxidative stress. Otherwise, besides having a protective role, HO-1 is also involved in embryo development and in embryonic stem (ES) cells differentiation. Although both proteins have been extensively studied, little is known about their relationship in stem cells. The aim of this work is to explore HO-1-p53 interplay in ES cells. We studied HO-1 expression in p53 knockout (KO) ES cells and we found that they have higher HO-1 protein levels but similar HO-1 mRNA levels than the wild type (WT) ES cell line. Furthermore, cycloheximide treatment increased HO-1 abundance in p53 KO cells suggesting that p53 modulates HO-1 protein stability. Notably, H₂O₂ treatment did not induce HO-1 expression in p53 KO ES cells. Finally, SOD2 protein levels are also increased while Sod2 transcripts are not in KO cells, further suggesting that the p53 null phenotype is associated with a reinforcement of the antioxidant machinery. Our results demonstrate the existence of a connection between p53 and HO-1 in ES cells, highlighting the relationship between these stress defense pathways.

Mitochondrial Superoxide Dismutase Specifies Early Neural Commitment by Modulating Mitochondrial Dynamics

Studies revealing molecular mechanisms underlying neural specification have majorly focused on the role played by different transcription factors, but less on non-nuclear components. Earlier, we reported mitochondrial superoxide dismutase (SOD2) to be essential for self-renewal and pluripotency of mouse embryonic stem cells (mESCs). In the present study, we found SOD2 to be specifically required for neural lineage, but not the meso- or endoderm specification. Temporally, SOD2 regulated early neural genes, but not the matured genes, by modulating mitochondrial dynamics—specifically by enhancing the mitochondrial fusion protein Mitofusin 2 (MFN2). Bio-complementation strategy further confirmed SOD2 to enhance mitochondrial fusion process independent of its antioxidant activity. Over-expression of SOD2 along with OCT4, but neither alone, transdifferentiated mouse fibroblasts to neural progenitor-like colonies, conclusively proving the neurogenic potential of SOD2. In conclusion, our findings accredit a novel role for SOD2 in early neural lineage specification.

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SOD2 is essential for early neural differentiation of mESCs

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Up-regulation of MFN2, but not MFN1, underlies SOD2-mediated neurogenesis

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Antioxidant enzymatic activity of SOD2 is dispensable for mitochondrial fusion

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Overexpression of SOD2 with OCT4 transdifferentiate MEFs to iNPLCs

Interaction of apoptosis and pluripotency related transcripts for developmental potential of ovine embryos produced in vitro at different oxygen concentrations

The present study in sheep model was to find out the interaction of apoptotic transcripts, that is, Bcl2, Bax, Casp3, PCNA and p53 and pluripotency related transcripts, that is, Sox2, Nanog and Oct4 in ovine embryos produced in vitro at different O₂ concentrations (20% and 5% O₂) to compare their developmental potential. Oxygen concentrations did not influence the maturation and cleavage rate but the percentage of morula and blastocysts was significantly more at 5% as compared to 20% O₂. A significant upregulated expression of Bcl2 and PCNA genes and significantly downregulated expression of Casp3 and p53 were observed in the blastocysts at 5% than those at 20% O₂. The expression of Bax was not influenced by the O₂ concentration. Among the pluripotency related transcripts, the expression of Oct4 was significantly upregulated and the expression of Sox2 and Nanog was significantly downregulated in embryos at 5% than at 20% O₂. The study concluded that the embryos produced in vitro at low O₂ (5%) concentration regulate the expression of developmental genes related to apoptosis and pluripotency to improve the developmental potential of embryos as compared to high O₂ (20%) concentration.

The pluripotency transcription factor Nanog represses glutathione reductase gene expression in mouse embryonic stem cells

OBJECTIVE

Redox homeostasis maintenance is essential to bring about cellular functions. Particularly, embryonic stem cells (ESCs) have high fidelity mechanisms for DNA repair, high activity of different antioxidant enzymes and low levels of oxidative stress. Although the expression and activity of antioxidant enzymes are reduced throughout the differentiation, the knowledge about the transcriptional regulation of genes involved in defense against oxidative stress is yet restricted. Since glutathione is a central component of a complex system involved in preserving cellular redox status, we aimed to study whether the expression of the glutathione reductase (Gsr) gene, which encodes an essential enzyme for cellular redox homeostasis, is modulated by the transcription factors critical for self-renewal and pluripotency of ESCs.

RESULTS

We found that Gsr gene is expressed in ESCs during the pluripotent state and it was upregulated when these cells were induced to differentiate, concomitantly with Nanog decreased expression. Moreover, we found an increase in Gsr mRNA levels when Nanog was downregulated by a specific shRNA targeting this transcription factor in ESCs. Our results suggest that Nanog represses Gsr gene expression in ESCs, evidencing a role of this crucial pluripotency transcription factor in preservation of redox homeostasis in stem cells.

Superoxide dismutase 1 expression is modulated by the core pluripotency transcription factors Oct4, Sox2 and Nanog in embryonic stem cells

Redox homeostasis is vital for cellular functions and to prevent the detrimental consequences of oxidative stress. Pluripotent stem cells (PSCs) have an enhanced antioxidant system which supports the preservation of their genome. Besides, reactive oxygen species (ROS) are proposed to be involved in both self-renewal maintenance and in differentiation in embryonic stem cells (ESCs). Increasing evidence shows that cellular systems related to the oxidative stress defense decline along differentiation of PSCs. Although redox homeostasis has been extensively studied for many years, the knowledge about the transcriptional regulation of the genes involved in these systems is still limited. In this work, we studied Sod1 gene modulation by the PSCs fundamental transcription factors Oct4, Sox2 and Nanog. We found that this gene, which is expressed in mouse ESCs (mESCs), was repressed when they were induced to differentiate. Accordingly, these factors induced Sod1 promoter activity in a trans-activation assay. Finally, Sod1 mRNA levels were reduced when Oct4, Sox2 and Nanog were down-regulated by a shRNA approach in mESCs. Taken together, we found that PSCs' key transcription factors are involved in the modulation of Sod1 gene, suggesting a relationship between the pluripotency core and redox homeostasis in these cells.

Insights into the Dichotomous Regulation of SOD2 in Cancer

While loss of antioxidant expression and the resultant oxidant-dependent damage to cellular macromolecules is key to tumorigenesis, it has become evident that effective oxidant scavenging is conversely necessary for successful metastatic spread. This dichotomous role of antioxidant enzymes in cancer highlights their context-dependent regulation during different stages of tumor development. A prominent example of an antioxidant enzyme with such a dichotomous role and regulation is the mitochondria-localized manganese superoxide dismutase SOD2 (MnSOD). SOD2 has both tumor suppressive and promoting functions, which are primarily related to its role as a mitochondrial superoxide scavenger and H₂O₂ regulator. However, unlike true tumor suppressor- or onco-genes, the SOD2 gene is not frequently lost, or rarely mutated or amplified in cancer. This allows SOD2 to be either repressed or activated contingent on context-dependent stimuli, leading to its dichotomous function in cancer. Here, we describe some of the mechanisms that underlie SOD2 regulation in tumor cells. While much is known about the transcriptional regulation of the SOD2 gene, including downregulation by epigenetics and activation by stress response transcription factors, further research is required to understand the post-translational modifications that regulate SOD2 activity in cancer cells. Moreover, future work examining the spatio-temporal nature of SOD2 regulation in the context of changing tumor microenvironments is necessary to allows us to better design oxidant- or antioxidant-based therapeutic strategies that target the adaptable antioxidant repertoire of tumor cells.

Inhibition of Cell Division and DNA Replication Impair Mouse-Naïve Pluripotency Exit

The cell cycle has gained attention as a key determinant for cell fate decisions, but the contribution of DNA replication and mitosis in stem cell differentiation has not been extensively studied. To understand if these processes act as "windows of opportunity" for changes in cell identity, we established synchronized cultures of mouse embryonic stem cells as they exit the ground state of pluripotency. We show that initial transcriptional changes in this transition do not require passage through mitosis and that conversion to primed pluripotency is linked to lineage priming in the G1 phase. Importantly, we demonstrate that impairment of DNA replication severely blocks transcriptional switch to primed pluripotency, even in the absence of p53 activity induced by the DNA damage response. Our data suggest an important role for DNA replication during mouse embryonic stem cell differentiation, which could shed light on why pluripotent cells are only receptive to differentiation signals during G1, that is, before the S phase.