p53 regulates cell cycle and microRNAs to promote differentiation of human embryonic stem cells. PLoS Biol. 2012;10:e1001268. [PMID: 22389628 PMCID: PMC3289600 DOI: 10.1371/journal.pbio.1001268]

Cell Competition Eliminates Aneuploid Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) maintain diploid populations for generations despite a persistently high rate of mitotic errors that cause aneuploidy, or chromosome imbalances. Consequently, to maintain genome stability, aneuploidy must inhibit hPSC proliferation, but the mechanisms are unknown. Here, we surprisingly find that homogeneous aneuploid populations of hPSCs proliferate unlike aneuploid non-transformed somatic cells. Instead, in mosaic populations, cell non-autonomous competition between neighboring diploid and aneuploid hPSCs eliminates less fit aneuploid cells. Aneuploid hPSCs with lower Myc or higher p53 levels relative to diploid neighbors are outcompeted but conversely gain a selective advantage when Myc and p53 relative abundance switches. Thus, although hPSCs frequently missegregate chromosomes and inherently tolerate aneuploidy, Myc- and p53-driven cell competition preserves their genome integrity. These findings have important implications for the use of hPSCs in regenerative medicine and for how diploid human embryos are established despite the prevalence of aneuploidy during early development.

P53 and BCL-2 family proteins PUMA and NOXA define competitive fitness in pluripotent cell competition

Cell Competition is a process by which neighboring cells compare their fitness. As a result, viable but suboptimal cells are selectively eliminated in the presence of fitter cells. In the early mammalian embryo, epiblast pluripotent cells undergo extensive Cell Competition, which prevents suboptimal cells from contributing to the newly forming organism. While competitive ability is regulated by MYC in the epiblast, the mechanisms that contribute to competitive fitness in this context are largely unknown. Here, we report that P53 and its pro-apoptotic targets PUMA and NOXA regulate apoptosis susceptibility and competitive fitness in pluripotent cells. PUMA is widely expressed specifically in pluripotent cells in vitro and in vivo. We found that P53 regulates MYC levels in pluripotent cells, which connects these two Cell Competition pathways, however, MYC and PUMA/NOXA levels are independently regulated by P53. We propose a model that integrates a bifurcated P53 pathway regulating both MYC and PUMA/NOXA levels and determines competitive fitness.

Transcriptome Analysis of Key Genes Involved in the Initiation of Spermatogonial Stem Cell Differentiation

PURPOSE

The purpose of this study was to screen the genes and pathways that are involved in spermatogonia stem cell (SSC) differentiation regulation during the transition from Aundiff to A1. Methods: RNA sequencing was performed to screen differentially expressed genes at 1 d and 2 d after SSC differentiation culture. KEGG pathway enrichment and GO function analysis were performed to reveal the genes and pathways related to the initiation of early SSC differentiation.

RESULTS

The GO analysis showed that Rpl21, which regulates cell differentiation initiation, significantly increased after 1 day of SSC differentiation. The expressions of Fn1, Cd9, Fgf2, Itgb1, Epha2, Ctgf, Cttn, Timp2 and Fgfr1, which are related to promoting differentiation, were up-regulated after 2 days of SSC differentiation. The analysis of the KEGG pathway revealed that RNA transport is the most enriched pathway 1 day after SSC differentiation. Hspa2, which promotes the differentiation of male reproductive cells, and Cdkn2a, which participates in the cell cycle, were significantly up-regulated. The p53 pathway and MAPK pathway were the most enriched pathways 2 days after SSC differentiation. Cdkn1a, Hmga2, Thbs1 and Cdkn2a, microRNAs that promote cell differentiation, were also significantly up-regulated.

CONCLUSIONS

RNA transport, the MAPK pathway and the p53 pathway may play vital roles in early SSC differentiation, and Rpl21, Fn1, Cd9, Fgf2, Itgb1, Epha2, Ctgf, Cttn, Timp2, Fgfr1, Hspa2, Cdkn2a, Cdkn1a, Hmga2 and Thbs1 are involved in the initiation of SSC differentiation. The findings of this study provide a reference for further revelations of the regulatory mechanism of SSC differentiation.

Expanding Roles of the E2F-RB-p53 Pathway in Tumor Suppression

The transcription factor E2F links the RB pathway to the p53 pathway upon loss of function of pRB, thereby playing a pivotal role in the suppression of tumorigenesis. E2F fulfills a major role in cell proliferation by controlling a variety of growth-associated genes. The activity of E2F is controlled by the tumor suppressor pRB, which binds to E2F and actively suppresses target gene expression, thereby restraining cell proliferation. Signaling pathways originating from growth stimulative and growth suppressive signals converge on pRB (the RB pathway) to regulate E2F activity. In most cancers, the function of pRB is compromised by oncogenic mutations, and E2F activity is enhanced, thereby facilitating cell proliferation to promote tumorigenesis. Upon such events, E2F activates the Arf tumor suppressor gene, leading to activation of the tumor suppressor p53 to protect cells from tumorigenesis. ARF inactivates MDM2, which facilitates degradation of p53 through proteasome by ubiquitination (the p53 pathway). P53 suppresses tumorigenesis by inducing cellular senescence or apoptosis. Hence, in almost all cancers, the p53 pathway is also disabled. Here we will introduce the canonical functions of the RB-E2F-p53 pathway first and then the non-classical functions of each component, which may be relevant to cancer biology.

Time-resolved Small-RNA Sequencing Identifies MicroRNAs Critical for Formation of Embryonic Stem Cells from the Inner Cell Mass of Mouse Embryos

Cells of the inner cell mass (ICM) acquire a unique ability for unlimited self-renewal during transition into embryonic stem cells (ESCs) in vitro, while preserving their natural multi-lineage differentiation potential. Several different pathways have been identified to play roles in ESC formation but the function of non-coding RNAs in this process is poorly understood. Here, we describe several microRNAs (miRNAs) that are crucial for efficient generation of mouse ESCs from ICMs. Using small-RNA sequencing, we characterize dynamic changes in miRNA expression profiles during outgrowth of ICMs in a high-resolution, time-course dependent manner. We report several waves of miRNA transcription during ESC formation, to which miRNAs from the imprinted Dlk1-Dio3 locus contribute extensively. In silico analyses followed by functional investigations reveal that Dlk1-Dio3 locus-embedded miRNAs (miR-541-5p, miR-410-3p, and miR-381-3p), miR-183-5p, and miR-302b-3p promote, while miR-212-5p and let-7d-3p inhibit ESC formation. Collectively, these findings offer new mechanistic insights into the role of miRNAs during ESC derivation.

Activation of AMPK promotes cardiac differentiation by stimulating the autophagy pathway

Autophagy, a critical catabolic process for cell survival against different types of stress, has a role in the differentiation of various cells, such as cardiomyocytes. Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) is an energy-sensing protein kinase involved in the regulation of autophagy. In addition to its direct role in regulating autophagy, AMPK can also influence other cellular processes by regulating mitochondrial function, posttranslational acetylation, cardiomyocyte metabolism, mitochondrial autophagy, endoplasmic reticulum stress, and apoptosis. As AMPK is involved in the control of various cellular processes, it can influence the health and survival of cardiomyocytes. This study investigated the effects of an AMPK inducer (Metformin) and an autophagy inhibitor (Hydroxychloroquine) on the differentiation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). The results showed that autophagy was upregulated during cardiac differentiation. Furthermore, AMPK activation increased the expression of CM-specific markers in hPSC-CMs. Additionally, autophagy inhibition impaired cardiomyocyte differentiation by targeting autophagosome-lysosome fusion. These results indicate the significance of autophagy in cardiomyocyte differentiation. In conclusion, AMPK might be a promising target for the regulation of cardiomyocyte generation by in vitro differentiation of pluripotent stem cells.

p53 isoform expression promotes a stemness phenotype and inhibits doxorubicin sensitivity in breast cancer

In breast cancer, dysregulated TP53 expression signatures are a better predictor of chemotherapy response and survival outcomes than TP53 mutations. Our previous studies have shown that high levels of Δ40p53 are associated with worse disease-free survival and disruption of p53-induced DNA damage response in breast cancers. Here, we further investigated the in vitro and in vivo implications of Δ40p53 expression in breast cancer. We have shown that genes associated with cell differentiation are downregulated while those associated with stem cell regulation are upregulated in invasive ductal carcinomas expressing high levels of Δ40p53. In contrast to p53, endogenous ∆40p53 co-localised with the stem cell markers Sox2, Oct4, and Nanog in MCF-7 and ZR75-1 cell lines. ∆40p53 and Sox2 co-localisation was also detected in breast cancer specimens. Further, in cells expressing a high ∆40p53:p53 ratio, increased expression of stem cell markers, greater mammosphere and colony formation capacities, and downregulation of miR-145 and miR-200 (p53-target microRNAs that repress stemness) were observed compared to the control subline. In vivo, a high ∆40p53:p53 ratio led to increased tumour growth, Ki67 and Sox2 expression, and blood microvessel areas in the vehicle-treated mice. High expression of ∆40p53 also reduced tumour sensitivity to doxorubicin compared to control tumours. Enhanced therapeutic efficacy of doxorubicin was observed when transiently targeting Δ40p53 or when treating cells with OTSSP167 with concomitant chemotherapy. Taken together, high Δ40p53 levels induce tumour growth and may promote chemoresistance by inducing a stemness phenotype in breast cancer; thus, targeting Δ40p53 in tumours that have a high Δ40p53:p53 ratio could enhance the efficacy of standard-of-care therapies such as doxorubicin.

PRPF8 controls alternative splicing of PIRH2 to modulate the p53 pathway and survival of human ESCs

Human embryonic stem cells (hESCs) have great potential for developmental biology and regenerative medicine. However, extensive apoptosis often occurs when hESCs respond to various stresses or injuries. Understanding the molecular control and identifying new factors associated with hESC survival are fundamental to ensure the high quality of hESCs. In this study, we report that PRPF8, an RNA spliceosome component, is essential for hESC survival. PRPF8 knockdown (KD) induces p53 protein accumulation and activates the p53 pathway, leading to apoptosis in hESCs. Strikingly, silencing of p53 rescues PRPF8 KD-induced apoptosis, indicating that PRPF8 KD triggers hESC apoptosis through activating the p53 pathway. In search for the mechanism by which p53 pathway is activated by PRPF8 KD, we find that PRPF8 KD alters alternative splicing of many genes, including PIRH2 which encodes an E3 ubiquitin ligase of p53. PIRH2 has several isoforms such as PIRH2A, PIRH2B, and PIRH2C. Intriguingly, PRPF8 KD specifically increases the transcript level of the PIRH2B isoform, which lacks a RING domain and E3 ligase activity. Functionally, PIRH2B KD partially rescues the reduction in cell numbers and upregulation of P21 caused by PRPF8 KD in hESCs. The finding suggests that PRPF8 controls alternative splicing of PIRH2 to maintain the balance of p53 pathway activity and survival of hESCs. The PRPF8/PIRH2/p53 axis identified here provides new insights into how p53 pathway and hESC survival are precisely regulated at multiple layers, highlighting an important role of posttranscriptional machinery in supporting hESC survival.

Placental microRNA methylome signatures may serve as biomarkers and therapeutic targets for prenatally opioid-exposed infants with neonatal opioid withdrawal syndrome

Introduction: The neonate exposed to opioids in utero faces a constellation of withdrawal symptoms postpartum commonly called neonatal opioid withdrawal syndrome (NOWS). The incidence of NOWS has increased in recent years due to the opioid epidemic. MicroRNAs (miRNAs) are small non-coding RNA molecules that play a crucial role in gene regulation. Epigenetic variations in microRNAs (miRNAs) and their impact on addiction-related processes is a rapidly evolving area of research. Methods: The Illumina Infinium Methylation EPIC BeadChip was used to analyze DNA methylation levels of miRNA-encoding genes in 96 human placental tissues to identify miRNA gene methylation profiles as-sociated with NOWS: 32 from mothers whose prenatally opioid-exposed infants required pharmacologic management for NOWS, 32 from mothers whose prenatally opioid-exposed infants did not require treat-ment for NOWS, and 32 unexposed controls. Results: The study identified 46 significantly differentially methylated (FDR p-value ≤ 0.05) CpGs associated with 47 unique miRNAs, with a receiver operating characteristic (ROC) area under the curve (AUC) ≥0.75 including 28 hypomethylated and 18 hypermethylated CpGs as potentially associated with NOWS. These dysregulated microRNA methylation patterns may be a contributing factor to NOWS pathogenesis. Conclusion: This is the first study to analyze miRNA methylation profiles in NOWS infants and illustrates the unique role miRNAs might have in diagnosing and treating the disease. Furthermore, these data may provide a step toward feasible precision medicine for NOWS babies as well.

Role of p53 in promoting BMP9‑induced osteogenic differentiation of mesenchymal stem cells through TGF‑β1

Known as a tumour suppressor gene, p53 also plays a key role in controlling the differentiation of mesenchymal stem cells (MSCs). Bone morphogenetic protein 9 (BMP9) has been identified as a potent factor in inducing osteogenic differentiation of MSCs, but its relationship with p53 remains unclear. The present study revealed that TP53 was expressed at higher levels in MSCs from patients with osteoporosis and was associated with the top 10 core central genes found in the current osteoporosis genetic screen. p53 was expressed in C2C12, C3H10T1/2, 3T3-L1, MEFs, and MG-63 cell lines, and could be upregulated by BMP9, as measured by western blotting and reverse-transcription quantitative PCR (RT-qPCR). Furthermore, overexpression of p53 increased the mRNA and protein levels of osteogenic marker Runx2 and osteopontin, as evaluated by western blotting and RT-qPCR in BMP9-induced MSCs, whereas the p53 inhibitor pifithrin (PFT)-α attenuated these effects. The same trend was found in alkaline phosphatase activities and matrix mineralization, as measured by alkaline phosphatase staining and alizarin red S staining. Moreover, p53 overexpression reduced adipo-differentiation markers of PPARγ and lipid droplet formation, as measured by western blotting, RT-qPCR and oil red O staining, respectively, whereas PFT-α facilitated adipo-differentiation in MSCs. In addition, p53 promoted TGF-β1 expression and inhibition of TGF-β1 by LY364947 partially attenuated the effects of p53 on promoting BMP9-induced MSC osteo-differentiation and inhibiting adipo-differentiation. The inhibitory effect of PFT-α on osteogenic markers and the promoting effect on adipogenic markers can be reversed when combined with TGF-β1. TGF-β1 may enhance the promotion of osteo-differentiation of MSCs by p53 through inhibition of adipo-differentiation. Collectively, by promoting BMP9-induced MSCs bone differentiation and inhibiting adipose differentiation, p53 may be a novel therapeutic target for bone-related diseases.

Supplementing culture medium with the weak acid, 5,5-dimethyl-2,4-oxazolidinedione (DMO) limits the development of aneuploid mouse embryos through a Trp53-dependent mechanism

PURPOSE

This study was designed to determine if DMO limits in vitro development of aneuploid-enriched mouse embryos by activating a Trp53-dependent mechanism.

METHODS

Mouse cleavage-stage embryos were treated with reversine to induce aneuploidy or vehicle to generate controls, and then cultured in media supplemented with DMO to reduce the pH of the culture media. Embryo morphology was assessed by phase microscopy. Cell number, mitotic figures, and apoptotic bodies were revealed by staining fixed embryos with DAPI. mRNA levels of Trp53, Oct-4, and Cdx2 were monitored by quantitative polymerase chain reactions (qPCRs). The effect of Trp53 on the expression of Oct-4 and Cdx2 was assessed by depleting Trp53 using Trp53 siRNA.

RESULTS

Aneuploid-enriched late-stage blastocysts were morphologically indistinguishable from control blastocysts but had fewer cells and reduced mRNA levels of Oct-4 and Cdx2. Adding 1 mM DMO to the culture media during the 8-cell to blastocyst transition reduced the formation of aneuploid-enriched late-stage blastocysts but not control blastocysts and further suppressed the levels of Oct-4 and Cdx2 mRNA. Trp53 RNA levels in aneuploid-enriched embryos that were exposed to DMO were > twofold higher than controls, and Trp53 siRNA levels reduced the levels of Trp53 and increased levels of Oct-4 and Cdx2 mRNA by > twofold.

CONCLUSION

These studies suggest that the development of morphologically normal aneuploid-enriched mouse blastocysts can be inhibited by adding low amounts of DMO to the culture media, which results in elevated levels of Trp53 mRNA that suppresses Oct-4 and Cdx2 expression.

A pluripotent developmental state confers a low fidelity of chromosome segregation

During in vitro propagation, human pluripotent stem cells (hPSCs) frequently become aneuploid with incorrect chromosome numbers due to mitotic chromosome segregation errors. Yet, it is not understood why hPSCs exhibit a low mitotic fidelity. Here, we investigate the mechanisms responsible for mitotic errors in hPSCs and show that the primary cause is lagging chromosomes in anaphase with improper merotelic microtubule attachments. Accordingly, short-term treatment (<24 h) with small molecules that prolong mitotic duration or destabilize chromosome microtubule attachments reduces merotelic errors and lagging chromosome rates, although hPSCs adapt and lagging chromosome rates rebound upon long-term (>24 h) microtubule destabilization. Strikingly, we also demonstrate that mitotic error rates correlate with developmental potential decreasing or increasing upon loss or gain of pluripotency, respectively. Thus, a low mitotic fidelity is an inherent and conserved phenotype of hPSCs. Moreover, chromosome segregation fidelity depends on developmental state in normal human cells.

Specialized Circuitry of Embryonic Stem Cells Promotes Genomic Integrity

Embryonic stem cells (ESCs) give rise to all cell types of the organism. Given the importance of these cells in this process, ESCs must employ robust mechanisms to protect genomic integrity or risk catastrophic propagation of mutations throughout the organism. Should such an event occur in daughter cells that will eventually contribute to the germline, the overall species health could dramatically decline. This review describes several key mechanisms employed by ESCs that are unique to these cells, in order to maintain their genomic integrity. Additionally, the contributions of cell cycle regulators in modulating ESC differentiation, after DNA damage exposure, are also examined. Where data are available, findings reported in ESCs are extended to include observations described in induced pluripotent stem cells (IPSCs).

Transcriptome analysis reveals synergistic modulation of E-cadherin/N-cadherin in hMSC aggregates chondrogenesis

BACKGROUND

N-cadherin-mediated cell adhesion is a vital inductor for mesenchymal condensation in chondrogenesis. Recent studies have revealed the involvement of E-cadherin in enhancing the multipotency of mesenchymal stem cells (MSCs) and limb development; however, the signaling crosstalk of E/N-cadherin remains unclear.

OBJECTIVE

This study aimed to explore the synergistic modulation of E/N-cadherin in the chondrogenic differentiation of MSC aggregates.

METHODS

Human E/N-cadherin-functionalized (hE/N-cad-Fc) poly (lactic-co-glycolic acid) (PLGA) microparticles (hE/N-cad-PLGA) were incorporated into the human MSC (hMSC) aggregates to upregulate the expression of the corresponding endogenous cadherin. The chondrogenic differentiation of the hMSC aggregates was initiated by hE/N-cad-PLGA, controlling the release of transforming growth factor-β (TGF-β). A transcriptome analysis was used to assess differentially expressed genes (DEGs) modulated by hE/N-cad-Fc in hMSC aggregate chondrogenesis. Gene functions and signaling pathways were assessed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The associated biological pathways were assessed by a protein-protein interaction (PPI) network analysis, and the results were further confirmed by real-time quantitative PCR (qPCR) and western blotting.

RESULTS

A total of 1083 DEGs, comprising 111 upregulated and 972 downregulated genes, were discovered to be related to the enhanced chondrogenic differentiation modulated by hE/N-cad-Fc. The GO and KEGG functional enrichment analyses revealed that hE/N-cad-Fc synergistically regulated the p53-related survival signaling pathway. PPI analysis revealed that mitogen-activated protein kinases (MAPK) caspase regulation is a core aspect of the chondrogenic differentiation process, confirmed by western blotting.

CONCLUSION

To the best of our knowledge, our study is the first to reveal that the synergistic modulation of E/N-cadherin enhances the chondrogenic differentiation of hMSCs via the ERK1/2-p53 signaling axis.

ESRG is critical to maintain the cell survival and self-renewal/pluripotency of hPSCs by collaborating with MCM2 to suppress p53 pathway

The mechanisms of self-renewal and pluripotency maintenance of human pluripotent stem cells (hPSCs) have not been fully elucidated, especially for the role of those poorly characterized long noncoding RNAs (lncRNAs). ESRG is a lncRNA highly expressed in hPSCs, and its functional roles are being extensively explored in the field. Here, we identified that the transcription of ESRG can be directly regulated by OCT4, a key self-renewal factor in hPSCs. Knockdown of ESRG induces hPSC differentiation, cell cycle arrest, and apoptosis. ESRG binds to MCM2, a replication-licensing factor, to sustain its steady-state level and nuclear location, safeguarding error-free DNA replication. Further study showed that ESRG knockdown leads to MCM2 abnormalities, resulting in DNA damage and activation of the p53 pathway, ultimately impairs hPSC self-renewal and pluripotency, and induces cell apoptosis. In summary, our study suggests that ESRG, as a novel target of OCT4, plays an essential role in maintaining the cell survival and self-renewal/pluripotency of hPSCs in collaboration with MCM2 to suppress p53 signaling. These findings provide critical insights into the mechanisms underlying the maintenance of self-renewal and pluripotency in hPSCs by lncRNAs.

Transition of amyloid/mutant p53 from tumor suppressor to an oncogene and therapeutic approaches to ameliorate metastasis and cancer stemness

The tumor suppressor p53 when undergoes amyloid formation confers several gain-of-function (GOF) activities that affect molecular pathways crucial for tumorigenesis and progression like some of the p53 mutants. Even after successful cancer treatment, metastasis and recurrence can result in poor survival rates. The major cause of recurrence is mainly the remnant cancer cells with stem cell-like properties, which are resistant to any chemotherapy treatment. Several studies have demonstrated the role of p53 mutants in exacerbating cancer stemness properties and epithelial-mesenchymal transition in these remnant cancer cells. Analyzing the amyloid/mutant p53-mediated signaling pathways that trigger metastasis, relapse or chemoresistance may be helpful for the development of novel or improved individualized treatment plans. In this review, we discuss the changes in the metabolic pathways such as mevalonate pathway and different signaling pathways such as TGF-β, PI3K/AKT/mTOR, NF-κB and Wnt due to p53 amyloid formation, or mutation. In addition to this, we have discussed the role of the regulatory microRNAs and lncRNAs linked with the mutant or amyloid p53 in human malignancies. Such changes promote tumor spread, potential recurrence, and stemness. Importantly, this review discusses the cancer therapies that target either mutant or amyloid p53, restore wild-type functions, and exploit the synthetic lethal interactions with mutant p53.

BISC: accurate inference of transcriptional bursting kinetics from single-cell transcriptomic data

Gene expression in mammalian cells is inherently stochastic and mRNAs are synthesized in discrete bursts. Single-cell transcriptomics provides an unprecedented opportunity to explore the transcriptome-wide kinetics of transcriptional bursting. However, current analysis methods provide limited accuracy in bursting inference due to substantial noise inherent to single-cell transcriptomic data. In this study, we developed BISC, a Bayesian method for inferring bursting parameters from single cell transcriptomic data. Based on a beta-gamma-Poisson model, BISC modeled the mean-variance dependency to achieve accurate estimation of bursting parameters from noisy data. Evaluation based on both simulation and real intron sequential RNA fluorescence in situ hybridization data showed improved accuracy and reliability of BISC over existing methods, especially for genes with low expression values. Further application of BISC found bursting frequency but not bursting size was strongly associated with gene expression regulation. Moreover, our analysis provided new mechanistic insights into the functional role of enhancer and superenhancer by modulating both bursting frequency and size. BISC also formulated a downstream framework to identify differential bursting (in frequency and size separately) genes in samples under different conditions. Applying to multiple datasets (a mouse embryonic cell and fibroblast dataset, a human immune cell dataset and a human pancreatic cell dataset), BISC identified known cell-type signature genes that were missed by differential expression analysis, providing additional insights in understanding the cell-specific stochastic gene transcription. Applying to datasets of human lung and colon cancers, BISC successfully detected tumor signature genes based on alterations in bursting kinetics, which illustrates its value in understanding disease development regarding transcriptional bursting. Collectively, BISC provides a new tool for accurately inferring bursting kinetics and detecting differential bursting genes. This study also produced new insights in the role of transcriptional bursting in regulating gene expression, cell identity and tumor progression.

Inhibiting DNA methylation as a strategy to enhance adipose-derived stem cells differentiation: Focus on the role of Akt/mTOR and Wnt/β-catenin pathways on adipogenesis

Adipose-derived mesenchymal stem cells (ASCs) represent a valid therapeutic option for clinical application in several diseases, due to their ability to repair damaged tissues and to mitigate the inflammatory/immune response. A better understanding of the underlying mechanisms regulating ASC biology might represent the chance to modulate their in vitro characteristics and differentiation potential for regenerative medicine purposes. Herein, we investigated the effects of the demethylating agent 5-azacytidine (5-aza) on proliferation, clonogenicity, migration, adipogenic differentiation and senescence of ASCs, to identify the molecular pathways involved. Through functional assays, we observed a detrimental effect of 5-aza on ASC self-renewal capacity and migration, accompanied by actin cytoskeleton reorganization, with decreased stress fibers. Conversely, 5-aza treatment enhanced ASC adipogenic differentiation, as assessed by lipid accumulation and expression of lineage-specific markers. We analyzed the involvement of the Akt/mTOR, MAPK and Wnt/β-catenin pathways in these processes. Our results indicated impairment of Akt and ERK phosphorylation, potentially explaining the reduced cell proliferation and migration. We observed a 5-aza-mediated inhibition of the Wnt signaling pathway, this potentially explaining the pro-adipogenic effect of the drug. Finally, 5-aza treatment significantly induced ASC senescence, through upregulation of the p53/p21 axis. Our data may have important translational implications, by helping in clarifying the potential risks and advantages of using epigenetic treatment to improve ASC characteristics for cell-based clinical approaches.

MiR-34a-5p promotes hepatic gluconeogenesis by suppressing SIRT1 expression

Elevated hepatic gluconeogenesis is a major contributor of fasting hyperglycemia in diabetes. MicroRNAs (miRNAs) are tightly linked to glucose metabolism, but their role in hepatic gluconeogenesis remains largely unkown. In this current study, miR-34a-5p expression was significantly increased in liver tissues of db/db mice. Overexpression of miR-34a-5p promoted hepatic glucose production in mouse primary hepatocytes with increased expressions of gluconeogenic genes while miR-34a-5p inhibition displayed a contrary action. MiR-34a-5p overexpression in mouse primary hepatocytes repressed SIRT1 expression. SIRT1 inhibition by EX527 blocked phosphoenolpyruvate carboxykinase (PEPCK) protein degradation and enhanced hepatic gluconeogenesis. Treatment of A485 (a CBP/p300 inhibitor) decreased miR-34a-5p and PEPCK expressions in the livers of db/db mice, but elevated SIRT1 protein expression. In mouse primary hepatocytes, A485 exhibited a similar result. Overexpression of miR-34a-5p attenuated A485-inhibited gluconeogenic gene expressions and A485-induced SIRT1 protein expression. Finally, after miR-34a-5p was inhibited in the livers of db/db mice, hepatic glucose production and gluconeogenic gene expressions were markedly lowered. Our findings highlight a critical role of miR-34a-5p in the regulation of hepatic gluconeogenesis and miR-34a-5p may be a potential target in the treatment of type 2 diabetes.

An Updated View of the Roles of p53 in Embryonic Stem Cells

The TP53 gene is unarguably one of the most studied human genes. Its encoded protein, p53, is a tumor suppressor and is often called the "guardian of the genome" due to its pivotal role in maintaining genome stability. Historically, most studies of p53 have focused on its roles in somatic cells and tissues, but in the last two decades, its functions in embryonic stem cells (ESCs) and induced pluripotent stem cells have attracted increasing attention. Recent studies have identified p53 as a critical regulator of pluripotency, self-renewal, differentiation, proliferation, and genome stability in mouse and human embryonic stem cells. In this article, we systematically review the studies on the functions of p53 in ESCs, provide an updated overview, attempt to reconcile controversial results described in the literature, and discuss the relevance of these cellular functions of p53 to its roles in tumor suppression.

WDR36 Safeguards Self-Renewal and Pluripotency of Human Extended Pluripotent Stem Cells

Extended pluripotent stem cells (EPS cells) have unlimited self-renewal ability and the potential to differentiate into mesodermal, ectodermal, and endodermal cells. Notably, in addition to developing the embryonic (Em) lineages, it can also make an effective contribution to extraembryonic (ExEm) lineages both in vitro and in vivo. However, multiple mysteries still remain about the underlying molecular mechanism of EPS cells’ maintenance and developmental potential. WDR36 (WD Repeat Domain 36), a protein of 105 kDa with 14 WD40 repeats, which may fold into two β-propellers, participates in 18sRNA synthesis and P53 stress response. Though WDR36 safeguards mouse early embryonic development, that is, homozygous knockout of WDR36 can result in embryonic lethality, what role does WDR36 plays in self-renewal and differentiation developmental potential of human EPS cells is still a subject of concern. Here, our findings suggested that the expression of WDR36 was downregulated during human hEPS cells lost self-renewal. Through constructing inducible knockdown or overexpressing WDR36-human EPS cell lines, we found that WDR36 knockdown disrupted self-renewal but promoted the mesodermal differentiation of human EPS cells; however, overexpressing of WDR36 had little effect. Additionally, P53 inhibition could reverse the effects of WDR36 knockdown, on both self-renewal maintenance and differentiation potential of human EPS cells. These data implied that WDR36 safeguards self-renewal and pluripotency of human EPS cells, which would extend our understanding of the molecular mechanisms of human EPS cells’ self-renewal and differentiation.

The Complete Loss of p53 Expression Uniquely Predicts Worse Prognosis in Colorectal Cancer

p53 immunohistochemistry is considered an accurate surrogate marker reflecting the underlying TP53 mutation status and has utility in tumor diagnostics. In the present study, 269 primary CRCs were immunohistochemically evaluated for p53 expression to assess its utility in diagnostic pathology and prognostication. p53 expression was wild-type in 59 cases (23%), overexpressed in 143 cases (55%), completely lost in 50 cases (19%), and cytoplasmic in 10 cases (4%). p53 immunoreactivity was associated with tumor size (p = 0.0056), mucus production (p = 0.0015), and mismatch repair (MMR) system status (p < 0.0001). Furthermore, among CRCs with wild-type p53 expression, a significantly higher number of cases had decreased CDX2 than those with p53 overexpression (p = 0.012) or complete p53 loss (p = 0.043). In contrast, among CRCs with p53 overexpression, there were significantly fewer ALCAM-positive cases than p53 wild-type cases (p = 0.0045). However, no significant association was detected between p53 immunoreactivity and the “stem-like” immunophenotype defined by CDX2 downregulation and ALCAM-positivity. Multivariate Cox hazards regression analysis identified tubular-forming histology (hazard ratio [HR] = 0.17, p < 0.0001), younger age (HR = 0.52, p = 0.021), and female sex (HR = 0.55, p = 0.046) as potential favorable factors. The analysis also revealed complete p53 loss (HR = 2.16, p = 0.0087), incomplete resection (HR = 2.65, p = 0.0068), and peritoneal metastasis (HR = 5.32, p < 0.0001) as potential independent risk factors for patients with CRC. The sub-cohort survival analyses classified according to chemotherapy after surgery revealed that CRC patients with wild-type p53 expression tended to have better survival than those with overexpression or complete loss after chemotherapy. Thus, immunohistochemistry for p53 could be used for the prognostication and chemotherapy target selection of patients with CRC.

BEND3 safeguards pluripotency by repressing differentiation-associated genes

The molecular basis of how the BEN domain–containing gene family regulates chromatin function and transcription remains to be elucidated. We report that BEND3 is highly expressed in pluripotent cells and binds to promoters of genes involved in differentiation. BEND3 regulates the expression of differentiation-associated genes by modulating the chromatin architecture at promoters. We propose that transcription repression mediated by BEND3 is essential for normal development and maintenance of pluripotency.

BEN domain–containing proteins are emerging rapidly as an important class of factors involved in modulating gene expression, yet the molecular basis of how they regulate chromatin function and transcription remains to be established. BEND3 is a quadruple BEN domain–containing protein that associates with heterochromatin and functions as a transcriptional repressor. We find that BEND3 is highly expressed in pluripotent cells, and the induction of differentiation results in the down-regulation of BEND3. The removal of BEND3 from pluripotent cells results in cells exhibiting upregulation of the differentiation-inducing gene expression signature. We find that BEND3 binds to the promoters of differentiation-associated factors and key cell cycle regulators, including CDKN1A, encoding the cell cycle inhibitor p21, and represses the expression of differentiation-associated genes by enhancing H3K27me3 decoration at these promoters. Our results support a model in which transcription repression mediated by BEND3 is essential for normal development and to prevent differentiation.

Noncanonical roles of p53 in cancer stemness and their implications in sarcomas

Impairment of the prominent tumor suppressor p53, well known for its canonical role as the "guardian of the genome", is found in almost half of human cancers. More recently, p53 has been suggested to be a crucial regulator of stemness, orchestrating the differentiation of embryonal and adult stem cells, suppressing reprogramming into induced pluripotent stem cells, or inhibiting cancer stemness (i.e., cancer stem cells, CSCs), which underlies the development of therapy-resistant tumors. This review addresses these noncanonical roles of p53 and their implications in sarcoma initiation and progression. Indeed, dysregulation of p53 family proteins is a common event in sarcomas and is associated with poor survival. Additionally, emerging studies have demonstrated that loss of wild-type p53 activity hinders the terminal differentiation of mesenchymal stem cells and leads to the development of aggressive sarcomas. This review summarizes recent findings on the roles of aberrant p53 in sarcoma development and stemness and further describes therapeutic approaches to restore normal p53 activity as a promising anti-CSC strategy to treat refractory sarcomas.

p57 Suppresses the Pluripotency and Proliferation of Mouse Embryonic Stem Cells by Positively Regulating p53 Activation

Embryonic stem cells (ESCs) are pluripotent stem cells that have indefinite self-renewal capacities under appropriate culture conditions in vitro. The pluripotency maintenance and proliferation of these cells are delicately governed by the concert effect of a complex transcriptional regulatory network. Herein, we discovered that p57^Kip2 (p57), a cyclin-dependent kinase inhibitor canonically inhibiting cell proliferation, played a role in suppressing the pluripotency state of mouse ESCs (mESCs). p57 knockdown significantly stimulated the expressions of core pluripotency factors NANOG, OCT4, and SOX2, while p57 overexpression inhibited the expressions of these factors in mESCs. In addition, consistent with its function in somatic cells, p57 suppressed mESC proliferation. Further analysis showed that p57 could interact with and contribute to the activation of p53 in mESCs. In conclusion, the present study showed that p57 could antagonize the pluripotency state and the proliferation process of mESCs. This finding uncovers a novel function of p57 and provides new evidence for elucidating the complex regulatory of network of mESC fate.

Infection by High-Risk Human Papillomaviruses, Epithelial-to-Mesenchymal Transition and Squamous Pre-Malignant or Malignant Lesions of the Uterine Cervix: A Series of Chained Events?

Wound healing requires static epithelial cells to gradually assume a mobile phenotype through a multi-step process termed epithelial-to-mesenchymal transition (EMT). Although it is inherently transient and reversible, EMT perdures and is abnormally activated when the epithelium is chronically exposed to pathogens: this event deeply alters the tissue and eventually contributes to the development of diseases. Among the many of them is uterine cervical squamous cell carcinoma (SCC), the most frequent malignancy of the female genital system. SCC, whose onset is associated with the persistent infection of the uterine cervix by high-risk human papillomaviruses (HR-HPVs), often relapses and/or metastasizes, being resistant to conventional chemo- or radiotherapy. Given that these fearsome clinical features may stem, at least in part, from the exacerbated and long-lasting EMT occurring in the HPV-infected cervix; here we have reviewed published studies concerning the impact that HPV oncoproteins, cellular tumor suppressors, regulators of gene expression, inflammatory cytokines or growth factors, and the interactions among these effectors have on EMT induction and cervical carcinogenesis. It is predictable and desirable that a broader comprehension of the role that EMT inducers play in SCC pathogenesis will provide indications to flourish new strategies directed against this aggressive tumor.

The Basally Expressed p53-Mediated Homeostatic Function

Apart from mutations in the p53 gene, p53 functions can be alternatively compromised by a decrease in nuclear p53 protein levels or activities. In accordance, enhanced p53 protein turnover due to elevated expression of the critical p53 E3 ligase MDM2 or MDM2/MDMX is found in many human cancers. Likewise, the HPV viral E6 protein-mediated p53 degradation critically contributes to the tumorigenesis of cervical cancer. In addition, growth-promoting signaling-induced cell proliferation is accompanied by p53 downregulation. Animal studies have also shown that loss of p53 is essential for oncogenes to drive malignant transformation. The close association between p53 downregulation and carcinogenesis implicates a critical role of basally expressed p53. In accordance, available evidence indicates that a reduced level of basal p53 is usually associated with disruption of homeostasis, suggesting a homeostatic function mediated by basal p53. However, basally expressed p53 under non-stress conditions is maintained at a relatively low abundance with little transcriptional activity, raising the question of how basal p53 could protect homeostasis. In this review, we summarize the findings pertinent to basal p53-mediated activities in the hope of developing a model in which basally expressed p53 functions as a barrier to anabolic metabolism to preserve homeostasis. Future investigation is necessary to characterize basal p53 functionally and to obtain an improved understanding of p53 homeostatic function, which would offer novel insight into the role of p53 in tumor suppression.

Transplantation of human embryonic stem cells alleviates motor dysfunction in AAV2-Htt171-82Q transfected rat model of Huntington's disease

BACKGROUND

Human embryonic stem cells (hESCs) transplantation had shown to provide a potential source of cells in neurodegenerative disease studies and lead to behavioral recovery in lentivirus transfected or, toxin-induced Huntington's disease (HD) rodent model. Here, we aimed to observe if transplantation of superparamagnetic iron oxide nanoparticle (SPION)-labeled hESCs could migrate in the neural degenerated area and improve motor dysfunction in an AAV2-Htt171-82Q transfected Huntington rat model.

METHODS

All animals were randomly allocated into three groups at first: HD group, sham group, and control group. After six weeks, the animals of the HD group and sham group were again divided into two subgroups depending on animals receiving either ipsilateral or contralateral hESCs transplantation. We performed cylinder test and stepping test every two weeks after AAV2-Htt171-82Q injection and hESCs transplantation. Stem cell tracking was performed once per two weeks using T2 and T2*-weighted images at 4.7 Tesla MRI. We also performed immunohistochemistry and immunofluorescence staining to detect the presence of hESCs markers, huntingtin protein aggregations, and iron in the striatum.

RESULTS

After hESCs transplantation, the Htt virus-injected rats exhibited significant behavioral improvement in behavioral tests. SPION labeled hESCs showed migration with hypointense signal in MRI. The cells were positive with βIII-tubulin, GABA, and DARPP32.

CONCLUSION

Collectively, our results suggested that hESCs transplantation can be a potential treatment for motor dysfunction of Huntington's disease.

A Balancing Act: p53 Activity from Tumor Suppression to Pathology and Therapeutic Implications

TP53, encoding the p53 transcription factor, is the most frequently mutated tumor suppressor gene across all human cancer types. While p53 has long been appreciated to induce antiproliferative cell cycle arrest, apoptosis, and senescence programs in response to diverse stress signals, various studies in recent years have revealed additional important functions for p53 that likely also contribute to tumor suppression, including roles in regulating tumor metabolism, ferroptosis, signaling in the tumor microenvironment, and stem cell self-renewal/differentiation. Not only does p53 loss or mutation cause cancer, but hyperactive p53 also drives various pathologies, including developmental phenotypes, premature aging, neurodegeneration, and side effects of cancer therapies. These findings underscore the importance of balanced p53 activity and influence our thinking of how to best develop cancer therapies based on modulating the p53 pathway. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Developmental Acquisition of p53 Functions

Remarkably, the p53 transcription factor, referred to as “the guardian of the genome”, is not essential for mammalian development. Moreover, efforts to identify p53-dependent developmental events have produced contradictory conclusions. Given the importance of pluripotent stem cells as models of mammalian development, and their applications in regenerative medicine and disease, resolving these conflicts is essential. Here we attempt to reconcile disparate data into justifiable conclusions predicated on reports that p53-dependent transcription is first detected in late mouse blastocysts, that p53 activity first becomes potentially lethal during gastrulation, and that apoptosis does not depend on p53. Furthermore, p53 does not regulate expression of genes required for pluripotency in embryonic stem cells (ESCs); it contributes to ESC genomic stability and differentiation. Depending on conditions, p53 accelerates initiation of apoptosis in ESCs in response to DNA damage, but cell cycle arrest as well as the rate and extent of apoptosis in ESCs are p53-independent. In embryonic fibroblasts, p53 induces cell cycle arrest to allow repair of DNA damage, and cell senescence to prevent proliferation of cells with extensive damage.

Palmitic Acid Methyl Ester Enhances Adipogenic Differentiation in Rat Adipose Tissue-Derived Mesenchymal Stem Cells through a G Protein-Coupled Receptor-Mediated Pathway

Adipogenic differentiation from stem cells has become a research target due to the increasing interest in obesity. It has been indicated that adipocytes can secrete palmitic acid methyl ester (PAME), which is able to regulate stem cell proliferation. However, the effects of PAME on adipogenic differentiation in stem cell remain unclear. Here, we present that the adipogenic differentiation medium supplemented with PAME induced the differentiation of rat adipose tissue-derived mesenchymal stem cells (rAD-MSCs) into adipocyte. rAD-MSCs were treated with PAME for 12 days and then subjected to various analyses. The results from the present study show that PAME significantly increased the levels of adipogenic differentiation markers, PPARγ and Gpd1, and enhanced adipogenic differentiation in rAD-MSCs. Furthermore, the level of GPR40/120 protein increased during induction of adipocyte differentiation in rAD-MSCs. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced adipogenic differentiation. Moreover, PAME significantly increased phosphorylation of extracellular signal-regulated kinases (ERK), but not AKT and mTOR. Cotreatment with PAME and a GPR40/120 antagonist together inhibited the PAME-enhanced ERK phosphorylation and adipogenic differentiation. PAME also increased the intracellular Ca²⁺ levels. Cotreatment with PAME and a Ca²⁺ chelator or a phospholipase C (PLC) inhibitor prevented the PAME-enhanced ERK phosphorylation and adipogenic differentiation. Our data suggest that PAME activated the GPR40/120/PLC-mediated pathway, which in turn increased the intracellular Ca²⁺ levels, thereby activating the ERK, and eventually enhanced adipogenic differentiation in rAD-MSCs. The findings from the present study might help get insight into the physiological roles and molecular mechanism of PAME in regulating stem cell differentiation.

Effects of 2,2',4,4'-tetrabromodiphenyl ether on the development of mouse embryonic stem cells

2,2',4,4'-Tetrabromodiphenyl ether (BDE47) poses potential risks to reproduction and development, but the mechanism of its toxicity has not yet been elucidated. To explore the developmental toxicity of BDE47, mouse embryonic stem cells (mESCs), which are ideal models for testing the developmental toxicity of environmental contaminants in vitro, were exposed to BDE47 (0.04 μM, 1 μM, 25 μM, or 100 μM) for 24 h or 48 h in this study. Our results indicated that BDE47 treatment changed the morphology of mESCs, inhibited cell viability and increased apoptosis. In addition, alkaline phosphatase (AP) staining in mESCs was significantly decreased after BDE47 treatment (25 μM and 100 μM), indicating that BDE47 treatment affected the pluripotency of mESCs. Through a cell immunofluorescence assay, we found that the fluorescence intensities of Oct4, Sox2 and Nanog were all significantly lower in the group treated with the highest BDE47 concentration (100 μM) than in the control group, consistent with the qRT-PCR and Western blot results. The levels of miR-145 and miR-34a, which regulate genes related to cell differentiation, were significantly increased in BDE47-treated mESCs, further clarifying the potential mechanism. Overall, our findings demonstrate that BDE47 exposure upregulates the expression of miR-145 and miR-34a and in turn downregulates the expression of Oct4, Sox2 and Nanog, thereby affecting apoptosis and pluripotency and causing toxicity during embryonic development.

MiR-200c-3p maintains stemness and proliferative potential in adipose-derived stem cells by counteracting senescence mechanisms

Adipose-derived mesenchymal stem cells (ASCs) are promising therapeutic tools in regenerative medicine because they possess self-renewal, differentiation and immunomodulatory capacities. After isolation, ASCs are passaged multiple times in vitro passages to obtain a sufficient amount of cells for clinical applications. During this time-consuming procedure, ASCs become senescent and less proliferative, compromising their clinical efficacy. Here, we sought to investigate how in vitro passages impact ASC proliferation/senescence and expression of immune regulatory proteins. MicroRNAs are pivotal regulators of ASC physiology. Particularly, miR-200c is known to maintain pluripotency and targets the immune checkpoint Programmed death-ligand 1 (PD-L1). We therefore investigated its involvement in these critical characteristics of ASCs during in vitro passages. We found that when transiently expressed, miR-200c-3p promotes proliferation, maintains stemness, and contrasts senescence in late passaged ASCs. Additionally, this miRNA modulates PD-L1 and Indoleamine 2,3-Dioxygenase (IDO1) expression, thus most likely interfering with the immunoregulatory capacity of ASCs. Based on our results, we suggest that expression of miR-200c-3p may prime ASC towards a self-renewing phenotype by improving their in vitro expansion. Contrarily, its inhibition is associated with senescence, reduced proliferation and induction of immune regulators. Our data underline the potential use of miR-200c-3p as a switch for ASCs reprogramming and their clinical application.

Mutations of p53 associated with pancreatic cancer and therapeutic implications

Pancreatic adenocarcinoma is a malignancy with rising incidence and grim prognosis. Despite improvements in therapeutics for treating metastatic pancreatic cancer, this disease is invariably fatal with survival time less than a few years. New molecular understanding of the pathogenesis of pancreatic adenocarcinoma based on efforts led by The Cancer Genome Atlas and other groups has elucidated the landscape of this disease and started to produce therapeutic results, leading to the first introduction of targeted therapies for subsets of pancreatic cancers bearing specific molecular lesions such as BRCA mutations. These efforts have highlighted that subsets of pancreatic cancers are particularly sensitive to chemotherapy. The most common molecular lesions in pancreatic adenocarcinomas are mutations in an oncogene KRAS and the TP53 gene that encodes for tumor suppressor protein p53. This paper will review the landscape of pancreatic cancers, focusing on mutations of p53, a major tumor suppressor protein, in pancreatic cancers and possible therapeutic repercussions.

Impact of the interplay between stemness features, p53 and pol iota on replication pathway choices

Using human embryonic, adult and cancer stem cells/stem cell-like cells (SCs), we demonstrate that DNA replication speed differs in SCs and their differentiated counterparts. While SCs decelerate DNA replication, differentiated cells synthesize DNA faster and accumulate DNA damage. Notably, both replication phenotypes depend on p53 and polymerase iota (POLι). By exploring protein interactions and newly synthesized DNA, we show that SCs promote complex formation of p53 and POLι at replication sites. Intriguingly, in SCs the translocase ZRANB3 is recruited to POLι and required for slow-down of DNA replication. The known role of ZRANB3 in fork reversal suggests that the p53–POLι complex mediates slow but safe bypass of replication barriers in SCs. In differentiated cells, POLι localizes more transiently to sites of DNA synthesis and no longer interacts with p53 facilitating fast POLι-dependent DNA replication. In this alternative scenario, POLι associates with the p53 target p21, which antagonizes PCNA poly-ubiquitination and, thereby potentially disfavors the recruitment of translocases. Altogether, we provide evidence for diametrically opposed DNA replication phenotypes in SCs and their differentiated counterparts putting DNA replication-based strategies in the spotlight for the creation of therapeutic opportunities targeting SCs.

Deletion of Nrip1 delays skin aging by reducing adipose-derived mesenchymal stem cells (ADMSCs) senescence, and maintaining ADMSCs quiescence

Our previous studies found that deletion of nuclear receptor interacting protein 1 (Nrip1) extended longevity in female mice and delayed cell senescence. The current study investigates the role of NRIP1 in regulating functions of adipose-derived mesenchymal stem cells (ADMSCs) and explores the mechanisms of NRIP1 in skin aging. We first verified the skin aging phenotypes in young (6 months) and old (20 months) C57BL/6J (B6) mice and found deletion of Nrip1 can delay skin aging phenotypes, including reduced thickness of dermis and subcutaneous white adipose tissue (sWAT), as well as the accumulation of senescent cells in sWAT. In ADMSCs isolated from sWAT, we found that deletion of Nrip1 could decrease cell proliferation, prevent cell apoptosis, and suppress adipogenesis. Interestingly, deletion of Nrip1 also reduced cell senescence and maintain cell quiescence of ADMSCs. Moreover, the expressions of genes associated with senescence (p21, and p53), inflammation (p65, IL6, and IL1a), and growth factor (mTOR, Igf1) were reduced in Nrip1 knockout ADMSCs, as well as in siNrip1-treated ADMSCs. Suppression of Nrip1 by siNrip1 also decreased the expressions of mTOR, p-mTOR, p65, and p-p65 in ADMSCs. Reduced expressions of p65 and p-p65 were also confirmed in the skin of Nrip1 knockout mice. These findings suggest that NRIP1 plays an important role in delaying skin aging by reducing ADMSCs senescence and maintaining ADMSCs quiescence.

p53 Promotes Differentiation of Cardiomyocytes from hiPSC through Wnt Signaling-Mediated Mesendodermal Differentiation

Background and Objectives

Manipulating different signaling pathways via small molecules could efficiently induce cardiomyocytes from human induced pluripotent stem cells (hiPSC). However, the effect of transcription factors on the hiPSC-directed cardiomyocytes differentiation remains unclear. Transcription factor, p53 has been demonstrated indispensable for the early embryonic development and mesendodermal differentiation of embryonic stem cells (ESC). We tested the hypothesis that p53 promotes cardiomyocytes differentiation from human hiPSC.

Methods and Results

Using the well-characterized GiWi protocol that cardiomyocytes are generated from hiPSC via temporal modulation of Wnt signaling pathway by small molecules, we demonstrated that forced expression of p53 in hiPSC remarkably improved the differentiation efficiency of cardiomyocytes from hiPSC, whereas knockdown endogenous p53 decreased the yield of cardiomyocytes. This p53-mediated increased cardiomyocyte differentiation was mediated through WNT3, as evidenced by that overexpression of p53 upregulated the expression of WNT3, and knockdown of p53 decreased the WNT3 expression. Mechanistic analysis showed that the increased cardiomyocyte differentiation partially depended on the amplified mesendodermal specification resulted from p53-mediated activation of WNT3-mediated Wnt signaling. Consistently, endogenous WNT3 knockdown significantly ameliorated mesendodermal specification and subsequent cardiomyocyte differentiation.

Conclusions

These results provide a novel insight into the potential effect of p53 on the development and differentiation of cardiomyocyte during embryogenesis.

G1-phase progression in pluripotent stem cells

During early embryonic development both the rapid increase in cell number and the expression of genes that control developmental decisions are tightly regulated. Accumulating evidence has indicated that these two seemingly independent processes are mechanistically intertwined. The picture that emerges from studies on the cell cycle of embryonic stem cells is one in which proteins that promote cell cycle progression prevent differentiation and vice versa. Here, we review which transcription factors and signalling pathways play a role in both maintenance of pluripotency as well as cell cycle progression. We will not only describe the mechanism behind their function but also discuss the role of these regulators in different states of mouse pluripotency. Finally, we elaborate on how canonical cell cycle regulators impact on the molecular networks that control the maintenance of pluripotency and lineage specification.

TRIM24 promotes stemness and invasiveness of glioblastoma cells via activating Sox2 expression

BACKGROUND

Glioblastoma stem cells (GSCs) are a subpopulation of glioblastoma (GBM) cells that are critical for tumor invasion and treatment resistance. However, little is known about the function and mechanism of tripartite motif-containing 24 (TRIM24) in GSCs.

METHODS

Immunofluorescence, flow cytometry, and western blot analyses were used to evaluate TRIM24 and cluster of differentiation (CD)133 expression profiles in GBM surgical specimens and GSC tumorspheres. Different TRIM24 expression levels in patients' tumors, as measured by both immunohistochemistry and western blot, were related to their corresponding MRI data. Wound healing, Matrigel invasion, and xenograft immunohistochemistry were conducted to determine GBM cell invasion.

RESULTS

We identified that TRIM24 was coexpressed with CD133 and Nestin in GBM tissues and tumorsphere cells. Limiting dilution assays and xenotransplantation experiments illustrated that knockdown of TRIM24 expression reduced GSC self-renewal capacity and invasive growth. TRIM24 expression levels were positively associated with the volumes of peritumoral T2 weighted image abnormality. Rescue experiments indicated TRIM24 participation in GBM infiltrative dissemination. Chromatin immunoprecipitation, reporter gene assay, PCR, western blot, and immunohistochemistry demonstrated that TRIM24 activated the expression of the pluripotency transcription factor sex determining region Y-box 2 (Sox2) to regulate GBM stemness and invasion in vitro and in vivo. Finally, the close relationship between TRIM24 and Sox2 was validated by testing samples enrolled in our study and exploring external databases.

CONCLUSIONS

Our findings uncover essential roles of the TRIM24-Sox2 axis in GBM stemness and invasiveness, suggesting TRIM24 as a potential target for effective GBM management.

Fragmentation of Small-Cell Lung Cancer Regulatory States in Heterotypic Microenvironments

Small-cell lung cancers derive from pulmonary neuroendocrine cells, which have stem-like properties to reprogram into other cell types upon lung injury. It is difficult to uncouple transcriptional plasticity of these transformed cells from genetic changes that evolve in primary tumors or secondary metastases. Profiling of single cells is also problematic if the required sample dissociation activates injury-like signaling and reprogramming. Here we defined cell-state heterogeneities in situ through laser capture microdissection-based 10-cell transcriptomics coupled with stochastic-profiling fluctuation analysis. In labeled cells from a small-cell lung cancer mouse model initiated by neuroendocrine deletion of Rb1-Trp53, variations in transcript abundance revealed cell-to-cell differences in regulatory state in vitro and in vivo. Fluctuating transcripts in spheroid culture were partly shared among Rb1-Trp53-null models, and heterogeneities increased considerably when cells were delivered intravenously to colonize the liver. Colonization of immunocompromised animals drove a fractional appearance of alveolar type II-like markers and poised cells for paracrine stimulation from immune cells and hepatocytes. Immunocompetency further exaggerated the fragmentation of tumor states in the liver, yielding mixed stromal signatures evident in bulk sequencing from autochthonous tumors and metastases. Dozens of transcript heterogeneities recurred irrespective of biological context; their mapped orthologs brought together observations of murine and human small-cell lung cancer. Candidate heterogeneities recurrent in the liver also stratified primary human tumors into discrete groups not readily explained by molecular subtype but with prognostic relevance. These data suggest that heterotypic interactions in the liver and lung are an accelerant for intratumor heterogeneity in small-cell lung cancer. SIGNIFICANCE: These findings demonstrate that the single-cell regulatory heterogeneity of small-cell lung cancer becomes increasingly elaborate in the liver, a common metastatic site for the disease.See related articles by Singh and colleagues, p. 1840 and Sutcliffe and colleagues, p. 1868.

CREB-binding protein (CBP) gene family regulates planarian survival and stem cell differentiation

In developmental biology, the regulation of stem cell plasticity and differentiation remains an open question. CBP(CREB-binding protein)/p300 is a conserved gene family that functions as a transcriptional co-activator and plays important roles in a wide range of cellular processes, including cell death, the DNA damage response, and tumorigenesis. The acetyl transferase activity of CBPs is particularly important, as histone and non-histone acetylation results in changes in chromatin architecture and protein activity that affect gene expression. Many studies have described the conserved functions of CBP/p300 in stem cell proliferation and differentiation. The planarian Schmidtea mediterranea is an excellent model for the in vivo study of the molecular mechanisms underlying stem cell differentiation during regeneration. However, how this process is regulated genetically and epigenetically is not well-understood yet. We identified 5 distinct Smed-cbp genes in S. mediterranea that show different expression patterns. Functional analyses revealed that Smed-cbp-2 appears to be essential for stem cell maintenance. On the other hand, the silencing of Smed-cbp-3 resulted in the growth of blastemas that were apparently normal, but remained largely unpigmented and undifferentiated. Smed-cbp-3 silencing also affected the differentiation of several cell lineages including neural, epidermal, digestive, and excretory cell types. Finally, we analysed the predicted interactomes of CBP-2 and CBP-3 as an initial step to better understand their functions in planarian stem cell biology. Our results indicate that planarian cbp genes play key roles in stem cell maintenance and differentiation.

Activation of P53 Via Nutlin-3a Reveals Role for P53 In ROS Signaling During Cardiac Differentiation of hiPSCs

Activation of the transcription factor P53 within cancer cells is a well-characterized pathway, whereas the effects of P53 activation during development remain largely unexplored. Previous research has indicated that increased levels of P53 protein during key murine developmental stages cause defects in multiple embryonic tissues, including the heart. These findings were confirmed in several different mouse models of congenital heart defects, but P53 activation in a human system of cardiovascular development is not available. Utilizing human induced pluripotent stem cells (hiPSCs), we characterized the normal levels of P53 during cardiac differentiation and showed that levels of P53 are high in hiPSCs and decrease upon cardiac lineage commitment. We also observed P53 localization changed from mainly cytoplasmic in iPS colonies to the nucleus in the Nkx2-5 + cardiac progenitor stage. Pharmacological-mediated increase of P53 protein levels with the Mdm2 inhibitor Nutlin-3a during early (mesoderm to cardiac mesoderm) stages of cardiogenesis resulted in a sizeable loss of cardiomyocytes due to increased apoptosis and cell cycle arrest. Interestingly, increasing P53 levels did not result in apoptosis at later (cardiac progenitor to beating cardiomyocytes) stages of the cardiac differentiation. These results illustrate the temporal sensitivity to increased P53 levels during cardiogenesis. We conducted RNA-Seq on these cells with or without Nutlin-3a to ascertain transcriptional differences due to increased P53 at the different stages during the differentiation. Our results from the RNA-Seq revealed up-regulation of Sestrins after Nutlin-3a treatment suggesting a new role for P53 in the metabolism of cardiac regeneration.

The Association between TIF1 Family Members and Cancer Stemness in Solid Tumors

Simple Summary

Stem cell-associated molecular features of solid tumors, collectively known as cancer stemness, are of great importance in the development, progression, and reoccurrence of cancer. Transcriptional and epigenetic dysregulation is significantly associated with cancer stemness. Here, we investigated the association between the Transcriptional Intermediary Factor 1 (TIF1) family members and cancer stemness in solid tumors. We aimed to evaluate the potential value of TIF1 members in predicting a stem-like cancer phenotype. Our results indicate that only TIF1β (also known as Tripartite Motif protein 28, TRIM28) high expression is consequently associated with a “stemness high” phenotype, regardless of the tumor type, resulting in a worse prognosis for cancer patients. The oncogenic signature of TRIM28^HIGH tumors significantly reflects the enrichment of “stemness high” cancers with targets for c-Myc (MYC Proto-Oncogene). TRIM28-associated gene expression profiles are also robustly enriched with stemness markers. Our results demonstrate that the association between high TRIM28 expression and an enriched cancer stem cell-like phenotype is a common phenomenon across solid tumors.

Abstract

Cancer progression entails a gradual loss of a differentiated phenotype in parallel with the acquisition of stem cell-like features. Cancer de-differentiation and the acquisition of stemness features are mediated by the transcriptional and epigenetic dysregulation of cancer cells. Here, using publicly available data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases and harnessing several bioinformatic tools, we characterized the association between Transcriptional Intermediary Factor 1 (TIF1) family members and cancer stemness in 27 distinct types of solid tumors. We aimed to define the prognostic value for TIF1 members in predicting a stem cell-like cancer phenotype and patient outcome. Our results demonstrate that high expression of only one member of the TIF1 family, namely TIF1β (also known as Tripartite Motif protein 28, TRIM28) is consequently associated with enriched cancer stemness across the tested solid tumor types, resulting in a worse prognosis for cancer patients. TRIM28 is highly expressed in higher grade tumors that exhibit stem cell-like traits. In contrast to other TIF1 members, only TIF1β/TRIM28-associated gene expression profiles were robustly enriched with stemness markers regardless of the tumor type. Our work demonstrates that TIF1 family members exhibit distinct expression patterns in stem cell-like tumors, despite their structural and functional similarity. Among other TIF1 members, only TRIM28 might serve as a marker of cancer stemness features.

Non-Coding RNAs in Retinoic Acid as Differentiation and Disease Drivers

All-trans retinoic acid (RA) is the most active metabolite of vitamin A. Several studies have described a pivotal role for RA signalling in different biological processes such as cell growth and differentiation, embryonic development and organogenesis. Since RA signalling is highly dose-dependent, a fine-tuning regulatory mechanism is required. Thus, RA signalling deregulation has a major impact, both in development and disease, related in many cases to oncogenic processes. In this review, we focus on the impact of ncRNA post-transcriptional regulatory mechanisms, especially those of microRNAs and lncRNAs, in RA signalling pathways during differentiation and disease.

p53 and Tumor Suppression: It Takes a Network

The TP53 tumor suppressor is the most frequently mutated gene in human cancer. p53 suppresses tumorigenesis by transcriptionally regulating a network of target genes that play roles in various cellular processes. Though originally characterized as a critical regulator for responses to acute DNA damage (activation of apoptosis and cell cycle arrest), recent studies have highlighted new pathways and transcriptional targets downstream of p53 regulating genomic integrity, metabolism, redox biology, stemness, and non-cell autonomous signaling in tumor suppression. Here, we summarize our current understanding of p53-mediated tumor suppression, situating recent findings from mouse models and unbiased screens in the context of previous studies and arguing for the importance of the pleiotropic effects of the p53 transcriptional network in inhibiting cancer.

Cancer Stemness: p53 at the Wheel

The tumor suppressor p53 maintains an equilibrium between self-renewal and differentiation to sustain a limited repertoire of stem cells for proper development and maintenance of tissue homeostasis. Inactivation of p53 disrupts this balance and promotes pluripotency and somatic cell reprogramming. A few reports in recent years have indicated that prevalent TP53 oncogenic gain-of-function (GOF) mutations further boosts the stemness properties of cancer cells. In this review, we discuss the role of wild type p53 in regulating pluripotency of normal stem cells and various mechanisms that control the balance between self-renewal and differentiation in embryonic and adult stem cells. We also highlight how inactivating and GOF mutations in p53 stimulate stemness in cancer cells. Further, we have explored the various mechanisms of mutant p53-driven cancer stemness, particularly emphasizing on the non-coding RNA mediated epigenetic regulation. We have also analyzed the association of cancer stemness with other crucial gain-of-function properties of mutant p53 such as epithelial to mesenchymal transition phenotypes and chemoresistance to understand how activation of one affects the other. Given the critical role of cancer stem-like cells in tumor maintenance, cancer progression, and therapy resistance of mutant p53 tumors, targeting them might improve therapeutic efficacy in human cancers with TP53 mutations.

MicroRNA-34a: the bad guy in age-related vascular diseases

The age-related vasculature alteration is the prominent risk factor for vascular diseases (VD), namely, atherosclerosis, abdominal aortic aneurysm, vascular calcification (VC) and pulmonary arterial hypertension (PAH). The chronic sterile low-grade inflammation state, alias inflammaging, characterizes elderly people and participates in VD development. MicroRNA34-a (miR-34a) is emerging as an important mediator of inflammaging and VD. miR-34a increases with aging in vessels and induces senescence and the acquisition of the senescence-associated secretory phenotype (SASP) in vascular smooth muscle (VSMCs) and endothelial (ECs) cells. Similarly, other VD risk factors, including dyslipidemia, hyperglycemia and hypertension, modify miR-34a expression to promote vascular senescence and inflammation. miR-34a upregulation causes endothelial dysfunction by affecting ECs nitric oxide bioavailability, adhesion molecules expression and inflammatory cells recruitment. miR-34a-induced senescence facilitates VSMCs osteoblastic switch and VC development in hyperphosphatemia conditions. Conversely, atherogenic and hypoxic stimuli downregulate miR-34a levels and promote VSMCs proliferation and migration during atherosclerosis and PAH. MiR34a genetic ablation or miR-34a inhibition by anti-miR-34a molecules in different experimental models of VD reduce vascular inflammation, senescence and apoptosis through sirtuin 1 Notch1, and B-cell lymphoma 2 modulation. Notably, pleiotropic drugs, like statins, liraglutide and metformin, affect miR-34a expression. Finally, human studies report that miR-34a levels associate to atherosclerosis and diabetes and correlate with inflammatory factors during aging. Herein, we comprehensively review the current knowledge about miR-34a-dependent molecular and cellular mechanisms activated by VD risk factors and highlight the diagnostic and therapeutic potential of modulating its expression in order to reduce inflammaging and VD burn and extend healthy lifespan.

Transcriptomic Analysis of Naïve Human Embryonic Stem Cells Cultured in Three-Dimensional PEG Scaffolds

Naïve human embryonic stem cells (ESCs) are characterized by improved viability, proliferation, and differentiation capacity in comparison to traditionally derived primed human ESCs. However, currently used two-dimensional (2-D) cell culture techniques fail to mimic the three-dimensional (3-D) in vivo microenvironment, altering morphological and molecular characteristics of ESCs. Here, we describe the use of 3-D self-assembling scaffolds that support growth and maintenance of the naïve state characteristics of ESC line, Elf1. Scaffolds were formed via a Michael addition reaction upon the combination of two 8-arm polyethylene glycol (PEG) polymers functionalized with thiol (PEG-8-SH) and acrylate (PEG-8-Acr) end groups. 3-D scaffold environment maintained the naïve state and supported the long-term growth of ESCs. RNA-sequencing demonstrated significant changes in gene expression profiles between 2-D and 3-D grown cells. Gene ontology analysis revealed upregulation of biological processes involved in the regulation of transcription and translation, extracellular matrix organization, and chromatin remodeling in 3-D grown cells. 3-D culture conditions also induced upregulation of genes associated with Wnt and focal adhesion signaling, while p53 signaling pathway associated genes were downregulated. Our findings, for the first time, provide insight into the possible mechanisms of self-renewal of naïve ESCs stimulated by the transduction of mechanical signals from the 3-D microenvironment.