Role of retinoic acid in the differentiation of embryonal carcinoma and embryonic stem cells

ALDH1A1 and ALDH1A3 paralogues of aldehyde dehydrogenase 1 control myogenic differentiation of skeletal muscle satellite cells by retinoic acid-dependent and -independent mechanisms

ALDH1A1 and ALDH1A3 paralogues of aldehyde dehydrogenase 1 (ALDH1) control myogenic differentiation of skeletal muscle satellite cells (SC) by formation of retinoic acid (RA) and subsequent cell cycle adjustments. The respective relevance of each paralogue for myogenic differentiation and the mechanistic interaction of each paralogue within RA-dependent and RA-independent pathways remain elusive.We analysed the impact of ALDH1A1 and ALDH1A3 activity on myogenesis of murine C2C12 myoblasts. Both paralogues are pivotal factors in myogenic differentiation, since CRISPR/Cas9-edited single paralogue knock-out impaired serum withdrawal-induced myogenic differentiation, while successive recombinant re-expression of ALDH1A1 or ALDH1A3, respectively, in the corresponding ALDH1 paralogue single knock-out cell lines, recovered the differentiation potential. Loss of differentiation in single knock-out cell lines was restored by treatment with RA-analogue TTNPB, while RA-receptor antagonization by AGN 193109 inhibited differentiation of wildtype cell lines, supporting the idea that RA-dependent pathway is pivotal for myogenic differentiation which is accomplished by both paralogues.However, overexpression of ALDH1-paralogues or disulfiram-mediated inhibition of ALDH1 enzymatic activity not only increased ALDH1A1 and ALDH1A3 protein levels but also induced subsequent differentiation of C2C12 myoblasts independently from serum withdrawal, indicating that ALDH1-dependent myogenic differentiation relies on different cellular conditions. Remarkably, ALDH1-paralogue knock-out impaired the autophagic flux, namely autophagosome cargo protein p62 formation and LC3B-I to LC3B-II conversion, demonstrating that ALDH1-paralogues interact with autophagy in myogenesis. Together, ALDH1 paralogues play a crucial role in myogenesis by orchestration of complex RA-dependent and RA-independent pathways.

Synergistic activation of RARβ and RARγ nuclear receptors restores cell specialization during stem cell differentiation by hijacking RARα-controlled programs

How cells respond to different external cues to develop along defined cell lineages to form complex tissues is a major question in systems biology. Here, we investigated the potential of retinoic acid receptor (RAR)-selective synthetic agonists to activate the gene regulatory programs driving cell specialization during nervous tissue formation from embryonic carcinoma (P19) and mouse embryonic (E14) stem cells. Specifically, we found that the synergistic activation of the RARβ and RARγ by selective ligands (BMS641 or BMS961) induces cell maturation to specialized neuronal subtypes, and to astrocytes and oligodendrocyte precursors. Using RAR isotype knockout lines exposed to RAR-specific agonists, interrogated by global transcriptome landscaping and in silico modeling of transcription regulatory signal propagation, revealed major RARα-driven gene programs essential for optimal neuronal cell specialization and hijacked by the synergistic activation of the RARβ and RARγ receptors. Overall, this study provides a systems biology view of the gene programs accounting for the previously observed redundancy between RARs, paving the way toward their potential use for directing cell specialization during nervous tissue formation.

The Beginning of Meiosis in Mammalian Female Germ Cells: A Never-Ending Story of Intrinsic and Extrinsic Factors

Meiosis is the unique division of germ cells resulting in the recombination of the maternal and paternal genomes and the production of haploid gametes. In mammals, it begins during the fetal life in females and during puberty in males. In both cases, entering meiosis requires a timely switch from the mitotic to the meiotic cell cycle and the transition from a potential pluripotent status to meiotic differentiation. Revealing the molecular mechanisms underlying these interrelated processes represents the essence in understanding the beginning of meiosis. Meiosis facilitates diversity across individuals and acts as a fundamental driver of evolution. Major differences between sexes and among species complicate the understanding of how meiosis begins. Basic meiotic research is further hindered by a current lack of meiotic cell lines. This has been recently partly overcome with the use of primordial-germ-cell-like cells (PGCLCs) generated from pluripotent stem cells. Much of what we know about this process depends on data from model organisms, namely, the mouse; in mice, the process, however, appears to differ in many aspects from that in humans. Identifying the mechanisms and molecules controlling germ cells to enter meiosis has represented and still represents a major challenge for reproductive medicine. In fact, the proper execution of meiosis is essential for fertility, for maintaining the integrity of the genome, and for ensuring the normal development of the offspring. The main clinical consequences of meiotic defects are infertility and, probably, increased susceptibility to some types of germ-cell tumors. In the present work, we report and discuss data mainly concerning the beginning of meiosis in mammalian female germ cells, referring to such process in males only when pertinent. After a brief account of this process in mice and humans and an historical chronicle of the major hypotheses and progress in this topic, the most recent results are reviewed and discussed.

HOX genes in stem cells: Maintaining cellular identity and regulation of differentiation

Stem cells display a unique cell type within the body that has the capacity to self-renew and differentiate into specialized cell types. Compared to pluripotent stem cells, adult stem cells (ASC) such as mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) exhibit restricted differentiation capabilities that are limited to cell types typically found in the tissue of origin, which implicates that there must be a certain code or priming determined by the tissue of origin. HOX genes, a subset of homeobox genes encoding transcription factors that are generally repressed in undifferentiated pluripotent stem cells, emerged here as master regulators of cell identity and cell fate during embryogenesis, and in maintaining this positional identity throughout life as well as specifying various regional properties of respective tissues. Concurrently, intricate molecular circuits regulated by diverse stem cell-typical signaling pathways, balance stem cell maintenance, proliferation and differentiation. However, it still needs to be unraveled how stem cell-related signaling pathways establish and regulate ASC-specific HOX expression pattern with different temporal-spatial topography, known as the HOX code. This comprehensive review therefore summarizes the current knowledge of specific ASC-related HOX expression patterns and how these were integrated into stem cell-related signaling pathways. Understanding the mechanism of HOX gene regulation in stem cells may provide new ways to manipulate stem cell fate and function leading to improved and new approaches in the field of regenerative medicine.

All models are wrong, but some are useful: Establishing standards for stem cell-based embryo models

Detailed studies of the embryo allow an increasingly mechanistic understanding of development, which has proved of profound relevance to human disease. The last decade has seen in vitro cultured stem cell-based models of embryo development flourish, which provide an alternative to the embryo for accessible experimentation. However, the usefulness of any stem cell-based embryo model will be determined by how accurately it reflects in vivo embryonic development, and/or the extent to which it facilitates new discoveries. Stringent benchmarking of embryo models is thus an important consideration for this growing field. Here we provide an overview of means to evaluate both the properties of stem cells, the building blocks of most embryo models, as well as the usefulness of current and future in vitro embryo models.

New insights into Vitamin C function: Vitamin C induces JAK2 activation through its receptor-like transporter SVCT2

Vitamin C (VitC) is a requisite nutrient for humans and other primates. Extensive research continuously illustrates the applications of VitC in promoting cell reprogramming, fine-tuning embryonic stem cell function, and fighting diseases. Given its chemical reduction property, VitC predominantly acts as an antioxidant to reduce reactive oxygen species (ROS) and as a cofactor for certain dioxygenases involved in epigenetic regulation. Here, we propose that VitC is also a bio-signaling molecule based on the finding that sodium-dependent VitC transporter (SVCT) 2 is a novel receptor-like transporter of VitC that possesses dual activities in mediating VitC uptake and Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 2 signaling pathway. Through interaction, SVCT2 induces JAK2 phosphorylation while transporting VitC into cells. Activated JAK2 phosphorylates the C-terminus of SVCT2, resulting in the recruitment and activation of STAT2. As a highlight, our results suggest that the activation of JAK2 synergistically promotes regulation of VitC in ROS scavenging and epigenetic modifications through phosphorylating pyruvate dehydrogenase kinase 1, ten-eleven translocation enzyme 3, and histone H3 Tyr⁴¹. Furthermore, VitC-activated JAK2 exhibits bidirectional effects in regulating cell pluripotency and differentiation. Our results thus reveal that the SVCT2-mediated JAK2 activation facilitates VitC functions in a previously unknown manner.

Negative Correlation Between Vitamin A and Positive Correlation Between Vitamin E and Inflammation Among Healthy Adults in Korea: Based on the Korea National Health and Nutrition Examination Survey (KNHANES) 2016-2018 7th Edition

PURPOSE

Vitamins exert its effect through different isoforms. The isoform conversion phases involved are affected outside factors. Here, we investigated the correlation between serum retinol, α-tocopherol, and serum inflammatory markers using stratified data acquired from 2016 to 2018 Korea National Health and Nutrition Examination Survey (KNHANES).

MATERIALS AND METHODS

This study was based on data acquired from the 7th edition (2016-2018) of the Korea National Health and Nutrition Examination Survey, consisting of survey data on smoking and alcohol drinking, serum retinol level, serum α-tocopherol level, high-sensitivity C-reactive protein (hs-CRP), and baseline characteristics.

RESULTS

There was a negative correlation between serum retinol and hs-CRP in alcohol drinking men. There was a negative correlation between serum retinol and hs-CRP in the alcohol-nonsmoking female group. There was a positive correlation between α-tocopherol and hs-CRP in the nonsmoking and alcohol-drinking group. There was a positive correlation between α-tocopherol and hs-CRP in the nonsmoking and alcohol-drinking female group. There was positive correlation between vitamin A and E and metabolic syndrome. The lowest vitamin A level was observed in subjects with all five metabolic syndrome criteria matched.

CONCLUSION

There was a negative correlation between serum retinol and hs-CRP and positive correlation between α-tocopherol and hs-CRP. Absorption and secretion of serum retinol are affected by inflammation status through retinol-binding protein. Alcohol acts as a competitive inhibitor of vitamin A oxidation through alcohol dehydrogenase and ALDH activity. Smoking causes inflammation and induces reactive oxygen species scavenging system and increases cytochrome p450 levels. These factors may have contributed to the observed findings. Metabolic syndrome subjects increased as the levels of vitamin A and vitamin E increased. Since obesity is inversely related to ALDH activity, we postulate that patients with metabolic syndrome may also have low ALDH activity, especially in the Asian population. Future studies are warranted to study the efficacy of ALDH or ALDH inducers in patients with vitamin A deficiency or metabolic syndrome.

Glioma Stem-Like Cells Can Be Targeted in Boron Neutron Capture Therapy with Boronophenylalanine

As glioma stem cells are chemo- and radio-resistant, they could be the origins of recurrent malignant glioma. Boron neutron capture therapy (BNCT) is a tumor-selective particle radiation therapy. ¹⁰B(n,α)⁷Li capture reaction produces alpha particles whose short paths (5-9 µm) lead to selective killing of tumor cells. P-boronophenylalanine (BPA) is a chemical compound used in clinical trials for BNCT. Here, we used mass cytometry (Cytof) to investigate whether glioma stem-like cells (GSLCs) take up BPA or not. We used GSLCs, and cells differentiated from GSLCs (DCs) by fetal bovine serum. After exposure to BPA for 24 h at 25 ppm in 5% CO₂ incubator, we immune-stained them with twenty stem cell markers, anti-Ki-67, anti-BPA and anti-CD98 (heterodimer that forms the large BPA transporter) antibodies and analyzed them with Cytof. The percentage of BPA⁺ or CD98⁺ cells with stem cell markers (Oct3/4, Nestin, SOX2, Musashi-1, PDGFRα, Notch2, Nanog, STAT3 and C-myc, among others) was 2-4 times larger among GSLCs than among DCs. Analyses of in vivo orthotopic tumor also indicated that 100% of SOX2⁺ or Nestin⁺ GSLCs were BPA⁺, whereas only 36.9% of glial fibrillary acidic protein (GFAP)⁺ DCs were BPA⁺. Therefore, GSLCs may take up BPA and could be targeted by BNCT.

ZGLP1 is a determinant for the oogenic fate in mice

Sex determination of germ cells is vital to creating the sexual dichotomy of germ cell development, thereby ensuring sexual reproduction. However, the underlying mechanisms remain unclear. Here, we show that ZGLP1, a conserved transcriptional regulator with GATA-like zinc fingers, determines the oogenic fate in mice. ZGLP1 acts downstream of bone morphogenetic protein, but not retinoic acid (RA), and is essential for the oogenic program and meiotic entry. ZGLP1 overexpression induces differentiation of in vitro primordial germ cell-like cells (PGCLCs) into fetal oocytes by activating the oogenic programs repressed by Polycomb activities, whereas RA signaling contributes to oogenic program maturation and PGC program repression. Our findings elucidate the mechanism for mammalian oogenic fate determination, providing a foundation for promoting in vitro gametogenesis and reproductive medicine.

The molecular aspects of absorption and metabolism of carotenoids and retinoids in vertebrates

Vitamin A is an essential nutrient necessary for numerous basic physiological functions, including reproduction and development, immune cell differentiation and communication, as well as the perception of light. To evade the dire consequences of vitamin A deficiency, vertebrates have evolved specialized metabolic pathways that enable the absorption, transport, and storage of vitamin A acquired from dietary sources as preformed retinoids or provitamin A carotenoids. This evolutionary advantage requires a complex interplay between numerous specialized retinoid-transport proteins, receptors, and enzymes. Recent advances in molecular and structural biology resulted in a rapid expansion of our understanding of these processes at the molecular level. This progress opened new avenues for the therapeutic manipulation of retinoid homeostasis. In this review, we summarize current research related to the biochemistry of carotenoid and retinoid-processing proteins with special emphasis on the structural aspects of their physiological actions. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Wnt Signaling Modulates Routes of Retinoic Acid-Induced Differentiation of Embryonic Stem Cells

Smooth muscle cells (SMCs) are important cell type for regenerative medicine. Previous studies showed that retinoic acid (RA) induces differentiation of SMCs from monolayer-cultured embryonic stem cells (ESCs) with high efficiency. However, the underlying mechanisms are still poorly defined. Here, we identified Wnt signaling as a primary regulator for RA-induced ESC differentiation. The activation of Wnt signaling inhibited the epithelial-mesenchymal transition during ESC differentiation, leading to inhibition of RA-induced SMC differentiation and promoting differentiation of ESCs toward primitive endoderm (PrE) lineage instead, while the inhibition of Wnt signaling promoted RA-induced SMC differentiation. Loss-of-function studies revealed that 7-like 2 (Tcf7l2) was the key transcription factor that Wnt operate through during RA-induced differentiation. Thus, this study revealed that the Tcf7l2-mediated Wnt signaling is a switch in determining the mesoderm/PrE fates in RA-induced ESC differentiation.

Differentiation of Urothelium from Mouse Embryonic Stem Cells in Chemically Defined Conditions

The urothelium of the bladder and urethra are derived from the definitive endoderm during development. Cellular signaling molecules important to the developmental specification of the urothelium are also implicated in the dysregulation of the tissue repair mechanism characteristic of bladder disease. Hence, a complete understanding of the regulation of urothelium development is central to understanding the processes of bladder disease, and in development of simple chemically defined methods for use in regenerative medicine. Key to this is a suitable in vitro model that readily allows for the prosecution of biologically pertinent questions. Here a method for differentiating urothelium from mouse embryonic stem cells in chemically defined conditions is described. The method includes a description of flow cytometry and RT-PCR analysis of definitive endoderm markers Cxcr4, c-Kit, and FoxA2, and of terminally differentiated urothelial cell markers Upk1b and Upk2.

E2F1 Mediates the Retinoic Acid-Induced Transcription of Tshz1 during Neuronal Differentiation in a Cell Division-Dependent Manner

The involvement of cell division in cellular differentiation has long been accepted. Cell division may be required not only for the expansion of a differentiated cell population but also for the execution of differentiation processes. Nonetheless, knowledge regarding how specific differentiation processes are controlled in a cell division-dependent manner is far from complete. Here, we determined the involvement of cell division in neuronal differentiation. We initially confirmed that cell division is an essential event for the neuronal differentiation of P19 embryonic carcinoma cells. We investigated the induction mechanisms of Tshz1, whose expression is induced by retinoic acid (RA) in a cell division-dependent manner. Promoter analysis of Tshz1 revealed a specific region required for RA-dependent transcription. A series of experiments was used to identify E2F1 as the induction factor for the RA-dependent transcription of Tshz1 We propose that E2F1 mediates neuronal differentiation in a cell division-dependent manner.

Combinatorial knockout of RARα, RARβ, and RARγ completely abrogates transcriptional responses to retinoic acid in murine embryonic stem cells

All-trans-retinoic acid (RA), a potent inducer of cellular differentiation, functions as a ligand for retinoic acid receptors (RARα, β, and γ). RARs are activated by ligand binding, which induces transcription of direct genomic targets. However, whether embryonic stem cells respond to RA through routes that do not involve RARs is unknown. Here, we used CRISPR technology to introduce biallelic frameshift mutations in RARα, RARβ, and RARγ, thereby abrogating all RAR functions in murine embryonic stem cells. We then evaluated RA-responsiveness of the RAR-null cells using RNA-Seq transcriptome analysis. We found that the RAR-null cells display no changes in transcripts in response to RA, demonstrating that the RARs are essential for the regulation of all transcripts in murine embryonic stem cells in response to RA. Our key finding, that in embryonic stem cells the transcriptional effects of RA all depend on RARs, addresses a long-standing topic of discussion in the field of retinoic acid signaling.

Development of biotin-retinoid conjugates as chemical probes for analysis of retinoid function

Herein, we report the rational design, synthesis and biological evaluation of conjugates consisting of the synthetic retinoid Am580 and biotin connected via a linker moiety. We found that the linking substructure between the retinoid part and the biotin part is critical for retaining the biological activity. Conjugate 4 with a shorter linker showed similar potency to endogenous retinoid ATRA (1) and the parent compound Am580 (2) for neural differentiation of mouse embryotic carcinoma P19 cells, and showed the same pattern of induction of gene expression. It is expected to be useful as a probe for investigations of retinoid function. The design rationale and structure-activity relationship of the linker moiety are expected to be helpful for developing biotin conjugates of other nuclear receptor ligands.

Retinoic acid and CTCF play key roles in inducing the collinear expression of the Hoxa cluster

During the development of an embryo, the initiation of the collinear expression of Hox genes is essential for the proper formation of the anteroposterior body axis. Retinoic acid (RA), a natural derivative of vitamin A, plays a role in vertebrate development by regulating Hox gene expression. CCCTC-binding factor (CTCF), an insulator protein that controls gene transcription, also regulates the expression of Hox genes by binding to the CTCF-binding sites (CBSs). It has been reported that upon RA signaling, retinoic acid response elements (RAREs) located in the Hox clusters become occupied. Interestingly, RAREs exist in close proximity with CBSs, and therefore when RA is bound, CTCF cannot bind. Without CTCF and its insulator activities, the repressive domain in the chromatin becomes open for gene transcription. Here, we examine the relationship between RA and CTCF during the RA-induced expression of the Hoxa cluster genes, using F9 murine embryonic teratocarcinoma cells as a model system. We treated F9 cells with RA for different time, confirmed the collinear expression of Hoxa genes, and validated CTCF-binding in F9 cells as well as in CTCF-overexpressing F9 cells, in the presence of RA. The present study suggests that RA and CTCF pose antagonistic effects on each other during vertebrate development to attain Hox gene collinearity.

A novel role of metal response element binding transcription factor 2 at the Hox gene cluster in the regulation of H3K27me3 by polycomb repressive complex 2

Polycomb repressive complex 2 (PRC2) is known to play an important role in the regulation of early embryonic development, differentiation, and cellular proliferation by introducing methyl groups onto lysine 27 of histone H3 (H3K27me3). PRC2 is tightly associated with silencing of Hox gene clusters and their sequential activation, leading to normal development and differentiation. To investigate epigenetic changes induced by PRC2 during differentiation, deposition of PRC2 components and levels of H3K27me3 were extensively examined using mouse F9 cells as a model system. Contrary to positive correlation between PRC2 deposition and H3K27me3 level, down-regulation of PRC2 components by shRNA and inhibition of EZH1/2 resulted in unexpected elevation of H3K27me3 level at the Hox gene cluster despite its global decrease. We found that metal response element binding transcriptional factor 2 (MTF2), one of sub-stoichiometric components of PRC2, was stably bound to Hox genes. Its binding capability was dependent on other core PRC2 components. A high level of H3K27me3 at Hox genes in Suz12-knock out cells was reversed by knockdown of Mtf2.This shows that MTF2 is necessary to consolidate PRC2-mediated histone methylation. Taken together, our results indicate that expression of Hox gene clusters during differentiation is strictly modulated by the activity of PRC2 secured by MTF2.

Gene expression signatures after ethanol exposure in differentiating embryoid bodies

During the differentiation process, various epigenetic factors regulate the precise expression of important genes and control cellular fate. During this stage, the differentiating cells become vulnerable to external stimuli. Here, we used an early neural differentiation model to observe ethanol-mediated transcriptional alterations. Our objective was to identify important molecular regulators of ethanol-related alterations in the genome during differentiation. A transcriptomic analysis was performed to profile the mRNA expression in differentiating embryoid bodies with or without ethanol treatment. In total, 147 differentially expressed genes were identified in response to 50mM ethanol. Of these differentially expressed genes, 78 genes were up-regulated and 69 genes were down-regulated. Our analysis revealed a strong association among the transcript signatures of the important modulators which were involved in protein modification, protein synthesis and gene expression. Additionally, ethanol-mediated activation of DNA transcription was observed. We also profiled ethanol-responsive transcription factors (TFs), upstream transcriptional regulators and TF-binding motifs in the differentiating embryoid bodies. In this study, we established a platform that we hope will help other researchers determine the ethanol-mediated changes that occur during cellular differentiation.

Retinoic acid-induced upregulation of miR-219 promotes the differentiation of embryonic stem cells into neural cells

MicroRNAs (miRNAs) regulate critical cell processes, such as apoptosis, proliferation, and development. However, the role of miRNAs in embryonic stem cell (ESC) neural differentiation induced by retinoic acid (RA) and factors that govern neural directional differentiation remain poorly understood. In this study, we demonstrated that miR-219 is sufficient in promoting mouse ESCs to undergo neural differentiation. We discovered that Foxj3 and Zbtb18, two target genes of miR-219, are not able to determine the process of RA-induced differentiation, however they prevent ESCs from differentiating into neural cells. We identified four downstream genes, namely, Olig1, Zic5, Erbb2, and Olig2, which are essential to the gene interaction networks for neural differentiation. These data explain the mechanism of RA-induced neural differentiation of mESCs on the basis of miRNAs and support the crucial role of miR-219 in neurodevelopment.

Tumorigenic and Differentiation Potentials of Embryonic Stem Cells Depend on TGFβ Family Signaling: Lessons from Teratocarcinoma Cells Stimulated to Differentiate with Retinoic Acid

A significant challenge for the development of safe pluripotent stem cell-based therapies is the incomplete in vitro differentiation of the pluripotent stem cells and the presence of residual undifferentiated cells initiating teratoma development after transplantation in recipients. To understand the mechanisms of incomplete differentiation, a comparative study of retinoic acid-induced differentiation of mouse embryonic stem (ES) and teratocarcinoma (EC) cells was conducted. The present study identified differences in proliferative activity, differentiation, and tumorigenic potentials between ES and EC cells. Higher expression of Nanog and Mvh, as well as Activin A and BMP4, was found in undifferentiated ES cells than in EC cells. However, the expression levels of Activin A and BMP4 increased more sharply in the EC cells during retinoic acid-induced differentiation. Stimulation of the Activin/Nodal and BMP signaling cascades and inhibition of the MEK/ERK and PI3K/Act signaling pathways resulted in a significant decrease in the number of Oct4-expressing ES cells and a loss of tumorigenicity, similar to retinoic acid-stimulated EC cells. Thus, this study demonstrates that a differentiation strategy that modulates prodifferentiation and antiproliferative signaling in ES cells may be effective for eliminating tumorigenic cells and may represent a valuable tool for the development of safe stem cell therapeutics.

Site-specific regulation of histone H1 phosphorylation in pluripotent cell differentiation

BACKGROUND

Structural variation among histone H1 variants confers distinct modes of chromatin binding that are important for differential regulation of chromatin condensation, gene expression and other processes. Changes in the expression and genomic distributions of H1 variants during cell differentiation appear to contribute to phenotypic differences between cell types, but few details are known about the roles of individual H1 variants and the significance of their disparate capacities for phosphorylation. In this study, we investigated the dynamics of interphase phosphorylation at specific sites in individual H1 variants during the differentiation of pluripotent NT2 and mouse embryonic stem cells and characterized the kinases involved in regulating specific H1 variant phosphorylations in NT2 and HeLa cells.

RESULTS

Here, we show that the global levels of phosphorylation at H1.5-Ser18 (pS18-H1.5), H1.2/H1.5-Ser173 (pS173-H1.2/5) and H1.4-Ser187 (pS187-H1.4) are regulated differentially during pluripotent cell differentiation. Enrichment of pS187-H1.4 near the transcription start site of pluripotency factor genes in pluripotent cells is markedly reduced upon differentiation, whereas pS187-H1.4 levels at housekeeping genes are largely unaltered. Selective inhibition of CDK7 or CDK9 rapidly diminishes pS187-H1.4 levels globally and its enrichment at housekeeping genes, and similar responses were observed following depletion of CDK9. These data suggest that H1.4-S187 is a bona fide substrate for CDK9, a notion that is further supported by the significant colocalization of CDK9 and pS187-H1.4 to gene promoters in reciprocal re-ChIP analyses. Moreover, treating cells with actinomycin D to inhibit transcription and trigger the release of active CDK9/P-TEFb from 7SK snRNA complexes induces the accumulation of pS187-H1.4 at promoters and gene bodies. Notably, the levels of pS187-H1.4 enrichment after actinomycin D treatment or cell differentiation reflect the extent of CDK9 recruitment at the same loci. Remarkably, the global levels of H1.5-S18 and H1.2/H1.5-S173 phosphorylation are not affected by these transcription inhibitor treatments, and selective inhibition of CDK2 does not affect the global levels of phosphorylation at H1.4-S187 or H1.5-S18.

CONCLUSIONS

Our data provide strong evidence that H1 variant interphase phosphorylation is dynamically regulated in a site-specific and gene-specific fashion during pluripotent cell differentiation, and that enrichment of pS187-H1.4 at genes is positively related to their transcription. H1.4-S187 is likely to be a direct target of CDK9 during interphase, suggesting the possibility that this particular phosphorylation may contribute to the release of paused RNA pol II. In contrast, the other H1 variant phosphorylations we investigated appear to be mediated by distinct kinases and further analyses are needed to determine their functional significance.

Retinoic acid combined with spermatogonial stem cell conditions facilitate the generation of mouse germ-like cells

Spermatogenic lineage has been directly generated in spermatogonial stem cell (SSC) conditions from human pluripotent stem cells (PSCs). However, it remains unknown whether mouse embryonic stem cells (ESCs) can directly differentiate into advanced male germ cell lineage in the same conditions. Here, we showed rather low efficiency of germ-like cell generation from mouse ESCs in SSC conditions. Interestingly, addition of retinoic acid (RA) into SSC conditions enabled efficient differentiation of mouse ESCs into germ-like cells, as shown by the activation of spermatogenesis-associated genes such as Mvh, Dazl, Prdm14, Stella, Scp1, Scp3, Stra8 and Rec8. In contrast, for cells cultured in control medium, the activation of the above genes barely occurred. In addition, RA with SSC conditions yielded colonies of Acrosin-expressing cells and the positive ratio reached a peak at day 6. Our work thus establishes a simple and cost-efficient approach for male germ like cell differentiation from mouse PSCs and may propose a useful strategy for studying spermatogenesis in vitro.

Mechanisms Regulating Stemness and Differentiation in Embryonal Carcinoma Cells

Just over ten years have passed since the seminal Takahashi-Yamanaka paper, and while most attention nowadays is on induced, embryonic, and cancer stem cells, much of the pioneering work arose from studies with embryonal carcinoma cells (ECCs) derived from teratocarcinomas. This original work was broad in scope, but eventually led the way for us to focus on the components involved in the gene regulation of stemness and differentiation. As the name implies, ECCs are malignant in nature, yet maintain the ability to differentiate into the 3 germ layers and extraembryonic tissues, as well as behave normally when reintroduced into a healthy blastocyst. Retinoic acid signaling has been thoroughly interrogated in ECCs, especially in the F9 and P19 murine cell models, and while we have touched on this aspect, this review purposely highlights how some key transcription factors regulate pluripotency and cell stemness prior to this signaling. Another major focus is on the epigenetic regulation of ECCs and stem cells, and, towards that end, this review closes on what we see as a new frontier in combating aging and human disease, namely, how cellular metabolism shapes the epigenetic landscape and hence the pluripotency of all stem cells.

Molecular cloning, expression analysis and transcript localization of testicular orphan nuclear receptor 2 in the male catfish, Clarias batrachus

Testicular receptor 2 (TR2; also known as Nr2c1) is one of the first orphan nuclear receptors identified and known to regulate various physiological process with or without any ligand. In this study, we report the cloning of full length nr2c1 and its expression analysis during gonadal development, seasonal testicular cycle and after human chorionic gonadotropin (hCG) induction. In addition, in situ hybridization (ISH) was performed to localize nr2c1 transcripts in adult testis and whole catfish (1day post hatch). Tissue distribution and gonadal ontogeny studies revealed high expression of nr2c1 in developing and adult testis. Early embryonic stage-wise expression of nr2c1 seems to emphasize its importance in cellular differentiation and development. Substantial expression of nr2c1 during pre-spawning phase and localization of nr2c1 transcripts in sperm/spermatids were observed. Significant upregulation after hCG induction indicate that nr2c1 is under the regulation of gonadotropins. Whole mount ISH analysis displayed nr2c1 expression in notochord indicating its role in normal vertebrate development. Taken together, our findings suggest that nr2c1 may have a plausible role in the testicular and embryonic development of catfish.

Medial Ganglionic Eminence Cells Freshly Obtained or Expanded as Neurospheres Show Distinct Cellular and Molecular Properties in Reducing Epileptic Seizures

AIMS

Medial ganglionic eminence (MGE) progenitors give rise to inhibitory interneurons and may serve as an alternative cell source for large-scale cell transplantation for epilepsy after in vitro expansion. We investigated whether modifications in the culture medium of MGE neurospheres affect neuronal differentiation and expression of MGE-specific genes. In vivo, we compared anticonvulsant effects and cell differentiation pattern among neurospheres grown in different culture media and compared them with freshly harvested MGE cells.

METHODS

We used four variations of cell culture: standard, containing growth factors (EGF/FGF-2) (GF); addition of retinoic acid (GF-RA); withdrawal of EGF/FGF-2 (WD); and addition of retinoic acid and withdrawal of EGF/FGF-2 (WD-RA). Based on in vitro results neurosphere-grown (WD-RA or GF conditions) or fresh MGE cells were transplanted into the hippocampus.

RESULTS

In vitro WD-RA showed increased neuronal population and higher expression of Dlx1, Nkx2.1, and Lhx6 genes in comparison with GF culture condition. After transplantation, fresh MGE cells and neurospheres (GF) showed anticonvulsant effects. However, fresh MGE cells differentiated preferentially into inhibitory neurons, while GF gave rise to glial cells.

CONCLUSION

We conclude that freshly isolated and neurosphere-grown MGE cells reduced seizures by different mechanisms (inhibitory interneurons vs. astrocytes). Fresh MGE cells appear more appropriate for cell therapies targeting inhibitory interneurons for conferring anticonvulsant outcomes.

Reconstructed cell fate-regulatory programs in stem cells reveal hierarchies and key factors of neurogenesis

Cell lineages, which shape the body architecture and specify cell functions, derive from the integration of a plethora of cell intrinsic and extrinsic signals. These signals trigger a multiplicity of decisions at several levels to modulate the activity of dynamic gene regulatory networks (GRNs), which ensure both general and cell-specific functions within a given lineage, thereby establishing cell fates. Significant knowledge about these events and the involved key drivers comes from homogeneous cell differentiation models. Even a single chemical trigger, such as the morphogen all-trans retinoic acid (RA), can induce the complex network of gene-regulatory decisions that matures a stem/precursor cell to a particular step within a given lineage. Here we have dissected the GRNs involved in the RA-induced neuronal or endodermal cell fate specification by integrating dynamic RXRA binding, chromatin accessibility, epigenetic promoter epigenetic status, and the transcriptional activity inferred from RNA polymerase II mapping and transcription profiling. Our data reveal how RA induces a network of transcription factors (TFs), which direct the temporal organization of cognate GRNs, thereby driving neuronal/endodermal cell fate specification. Modeling signal transduction propagation using the reconstructed GRNs indicated critical TFs for neuronal cell fate specification, which were confirmed by CRISPR/Cas9-mediated genome editing. Overall, this study demonstrates that a systems view of cell fate specification combined with computational signal transduction models provides the necessary insight in cellular plasticity for cell fate engineering. The present integrated approach can be used to monitor the in vitro capacity of (engineered) cells/tissues to establish cell lineages for regenerative medicine.

Meta-Analysis of EMT Datasets Reveals Different Types of EMT

As a critical process during embryonic development, cancer progression and cell fate conversions, epithelial-mesenchymal transition (EMT) has been extensively studied over the last several decades. To further understand the nature of EMT, we performed meta-analysis of multiple microarray datasets to identify the related generic signature. In this study, 24 human and 17 mouse microarray datasets were integrated to identify conserved gene expression changes in different types of EMT. Our integrative analysis revealed that there is low agreement among the list of the identified signature genes and three other lists in previous studies. Since removing the datasets with weakly-induced EMT from the analysis did not significantly improve the overlapping in the signature-gene lists, we hypothesized the existence of different types of EMT. This hypothesis was further supported by the grouping of 74 human EMT-induction samples into five distinct clusters, and the identification of distinct pathways in these different clusters of EMT samples. The five clusters of EMT-induction samples also improves the understanding of the characteristics of different EMT types. Therefore, we concluded the existence of different types of EMT was the possible reason for its complex role in multiple biological processes.

Effects of vitamin A deficiency in the postnatal mouse heart: role of hepatic retinoid stores

To determine whether hepatic depletion of vitamin A (VA) stores has an effect on the postnatal heart, studies were carried out with mice lacking liver retinyl ester stores fed either a VA-sufficient (LRVAS) or VA-deficient (LRVAD) diet (to deplete circulating retinol and extrahepatic stores of retinyl esters). There were no observable differences in the weights or gross morphology of hearts from LRVAS or LRVAD mice relative to sex-matched, age-matched, and genetically matched wild-type (WT) controls fed the VAS diet (WTVAS), but changes in the transcription of functionally relevant genes were consistent with a state of VAD in LRVAS and LRVAD ventricles. In silico analysis revealed that 58/67 differentially expressed transcripts identified in a microarray screen are products of genes that have DNA retinoic acid response elements. Flow cytometric analysis revealed a significant and cell-specific increase in the number of proliferating Sca-1 cardiac progenitor cells in LRVAS animals relative to WTVAS controls. Before myocardial infarction, LRVAS and WTVAS mice had similar cardiac systolic function and structure, as measured by echocardiography, but, unexpectedly, repeat echocardiography demonstrated that LRVAS mice had less adverse remodeling by 1 wk after myocardial infarction. Overall, the results demonstrate that the adult heart is responsive to retinoids, and, most notably, reducing hepatic VA stores (while maintaining circulating levels of VA) impacts ventricular gene expression profiles, progenitor cell numbers, and response to injury.

Capturing Identity and Fate Ex Vivo: Stem Cells from the Mouse Blastocyst

During mouse preimplantation development, three molecularly, morphologically, and spatially distinct lineages are formed, the embryonic epiblast, the extraembryonic primitive endoderm, and the trophectoderm. Stem cell lines representing each of these lineages have now been derived and can be indefinitely maintained and expanded in culture, providing an unlimited source of material to study the interplay of tissue-specific transcription factors and signaling pathways involved in these fundamental cell fate decisions. Here we outline our current understanding of the derivation, maintenance, and properties of these in vitro stem cell models representing the preimplantation embryonic lineages.

Fluorescence imaging of in vivo miR-124a-induced neurogenesis of neuronal progenitor cells using neuron-specific reporters

Background

Facilitation of the differentiation of the stem cells toward neuronal lineage is crucial for enhancing the differentiation efficacy of grafted stem cells for the possible treatment of neurodegenerative disorders. MicroRNA124a (miR-124a) has been considered as a neuronal lineage regulator, possessing the capability to activate neuronal differentiation. In this study, using a neuronal promoter-based reporter and live-cell fluorescence imaging, we visualized in vitro and in vivo the enhanced neuronal differentiation of neuronal progenitor cells with miR-124a overproduction.

Methods

The neuron specific alpha1 tubulin promoter-driven RFP reporter (pTa1-RFP) was used to trace the miR-124a-induced neuronal differentiation in live cell condition. MiR-124a or miR-scramble in 10 % glucose buffer was mixed with in vivo-jetPEITM and in vivo fluorescence images were obtained daily using Maestro spectral fluorescent imager.

Results

Neurite outgrowth was clearly seen in F11 cells after miR-124a transfection, and immunofluorescence staining showed increase of Tuj1 and NF at 48 hours. When pTa1-RFP-transfected F11 cells were implanted simultaneously with miR-124a into the nude mice, gradually increasing reporter signals and morphological changes indicated neuronal differentiation for 48 hours in live cells in vitro. The miR-124a-treated F11 cells showed higher reporter signals on in vivo fluorescence imaging than miR-scramble-treated cells, which were verified by ex vivo confirmation of Tuj1 and NF expression.

Conclusions

These results indicated that neuronal reporter-based neurogenesis imaging can be used for monitoring miR-124a acting as neuronal activator when miRNA was injected in in vivo PEI-coated form for miRNA-mediated regenerative therapy.

P53 Regulates Rapid Apoptosis in Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) are sensitive to DNA damage and undergo rapid apoptosis compared to their differentiated progeny cells. Here, we explore the underlying mechanisms for the increased apoptotic sensitivity of hPSCs that helps to determine pluripotent stem cell fate. Apoptosis was induced by exposure to actinomycin D, etoposide, or tunicamycin, with each agent triggering a distinct apoptotic pathway. We show that hPSCs are more sensitive to all three types of apoptosis induction than are lineage-non-specific, retinoic-acid-differentiated hPSCs. Also, Bax activation and pro-apoptotic mitochondrial intermembrane space protein release, which are required to initiate the mitochondria-mediated apoptosis pathway, are more rapid in hPSCs than in retinoic-acid-differentiated hPSCs. Surprisingly, Bak and not Bax is essential for actinomycin-D-induced apoptosis in human embryonic stem cells. Finally, P53 is degraded rapidly in an ubiquitin-proteasome-dependent pathway in hPSCs at steady state but quickly accumulates and induces apoptosis when Mdm2 function is impaired. Rapid degradation of P53 ensures the survival of healthy hPSCs but avails these cells for immediate apoptosis upon cellular damage by P53 stabilization. Altogether, we provide an underlying, interconnected molecular mechanism that primes hPSCs for quick clearance by apoptosis to eliminate hPSCs with unrepaired genome alterations and preserves organismal genomic integrity during the early critical stages of human embryonic development.

CRISPR/Cas9-Mediated Genomic Deletion of the Beta-1, 4 N-acetylgalactosaminyltransferase 1 Gene in Murine P19 Embryonal Carcinoma Cells Results in Low Sensitivity to Botulinum Neurotoxin Type C

Botulinum neurotoxins produced by Clostridium botulinum cause flaccid paralysis by inhibiting neurotransmitter release at peripheral nerve terminals. Previously, we found that neurons derived from the murine P19 embryonal carcinoma cell line exhibited high sensitivity to botulinum neurotoxin type C. In order to prove the utility of P19 cells for the study of the intracellular mechanism of botulinum neurotoxins, ganglioside-knockout neurons were generated by deletion of the gene encoding beta-1,4 N-acetylgalactosaminyltransferase 1 in P19 cells using the clustered regularly interspaced short palindromic repeats combined with Cas9 (CRISPR/Cas9) system. By using this system, knockout cells could be generated more easily than with previous methods. The sensitivity of the generated beta-1,4 N-acetylgalactosaminyltransferase 1-depleted P19 neurons to botulinum neurotoxin type C was decreased considerably, and the exogenous addition of the gangliosides GD1a, GD1b, and GT1b restored the susceptibility of P19 cells to botulinum neurotoxin type C. In particular, addition of a mixture of these three ganglioside more effectively recovered the sensitivity of knockout cells compared to independent addition of GD1a, GD1b, or GT1b. Consequently, the genome-edited P19 cells generated by the CRISPR/Cas9 system were useful for identifying and defining the intracellular molecules involved in the toxic action of botulinum neurotoxins.

Signalling Through Retinoic Acid Receptors is Required for Reprogramming of Both Mouse Embryonic Fibroblast Cells and Epiblast Stem Cells to Induced Pluripotent Stem Cells

We previously demonstrated that coexpressing retinoic acid (RA) receptor gamma and liver receptor homolog-1 (LRH1 or NR5A2) with OCT4, MYC, KLF4, and SOX2 (4F) rapidly reprograms mouse embryonic fibroblast cells (MEFs) into induced pluripotent stem cells (iPSCs). Here, we further explore the role of RA in reprogramming and report that the six factors (6F) efficiently and directly reprogram MEFs into integration-free iPSCs in defined medium (N2B27) in the absence of feeder cells. Through genetic and chemical approaches, we find that RA signalling is essential, in a highly dose-sensitive manner, for MEF reprogramming. The removal of exogenous RA from N2B27, the inhibition of endogenous RA synthesis or the expression of a dominant-negative form of RARA severely impedes reprogramming. By contrast, supplementing N2B27 with various retinoids substantially boosts reprogramming. In addition, when coexpressed with LRH1, RA receptors (RARs) can promote reprogramming in the absence of both exogenous and endogenously synthesized RA. Remarkably, the reprogramming of epiblast stem cells into embryonic stem cell-like cells also requires low levels of RA, which can modulate Wnt signalling through physical interactions of RARs with β-catenin. These results highlight the important functions of RA signalling in reprogramming somatic cells and primed stem cells to naïve pluripotency. Stem Cells 2015;33:1390-1404.

Addition of all-trans-retinoic acid to omeprazole and sucralfate therapy improves the prognosis of gastric dysplasia

OBJECTIVE

To investigate the efficacy of all-trans retinoic acid (ATRA) in human gastric dysplasia.

METHODS

In this double-blind study, patients with precancerous gastric dysplasia with or without intestinal metaplasia (IM) received either conventional treatment consisting of omeprazole and sucralfate (control group) or conventional treatment plus ATRA. Gastric mucosal biopsies were performed before and after drug treatment and were analysed histologically; expression of retinoblastoma (Rb) protein and HER2 protein in gastric mucosa were measured using immunohistochemistry.

RESULTS

A total of 122 patients were included in the study, 63 in the ATRA group and 59 in the control group. In the ATRA group, dysplasia was attenuated in 43 out of 63 patients (68%) compared with 22 out of 59 patients (37%) in the control group; however, IM was not affected by treatment in either group. ATRA treatment was associated with significantly increased Rb expression and decreased HER2 expression in gastric mucosa.

CONCLUSIONS

The use of conventional therapy plus ATRA for gastric dysplasia was associated with improved efficacy compared with conventional therapy alone. It was also accompanied by increased Rb expression and decreased HER2 expression in gastric mucosa. The addition of ATRA to conventional therapy for gastritis may improve the prognosis of gastric dysplasia.

Role of retinoic acid and platelet-derived growth factor receptor cross talk in the regulation of neonatal gonocyte and embryonal carcinoma cell differentiation

Neonatal gonocytes are direct precursors of spermatogonial stem cells, the cell pool that supports spermatogenesis. Although unipotent in vivo, gonocytes express pluripotency genes common with embryonic stem cells. Previously, we found that all-trans retinoic acid (RA) induced the expression of differentiation markers and a truncated form of platelet-derived growth factor receptor (PDGFR)β in rat gonocytes, as well as in F9 mouse embryonal carcinoma cells, an embryonic stem cell-surrogate that expresses somatic lineage markers in response to RA. The present study is focused on identifying the signaling pathways involved in RA-induced gonocyte and F9 cell differentiation. Mitogen-activated protein kinase kinase (MEK) 1/2 activation was required during F9 cell differentiation towards somatic lineage, whereas its inhibition potentiated RA-induced Stra8 expression, suggesting that MEK1/2 acts as a lineage specification switch in F9 cells. In both cell types, RA increased the expression of the spermatogonial/premeiotic marker Stra8, which is in line with F9 cells being at a stage before somatic-germline lineage specification. Inhibiting PDGFR kinase activity reduced RA-induced Stra8 expression. Interestingly, RA increased the expression of PDGFRα variant forms in both cell types. Together, these results suggest a potential cross talk between RA and PDGFR signaling pathways in cell differentiation. RA receptor-α inhibition partially reduced RA effects on Stra8 in gonocytes, indicating that RA acts in part via RA receptor-α. RA-induced gonocyte differentiation was significantly reduced by inhibiting SRC (v-src avian sarcoma [Schmidt-Ruppin A-2] viral oncogene) and JAK2/STAT5 (Janus kinase 2/signal transducer and activator of transcription 5) activities, implying that these signaling molecules play a role in gonocyte differentiation. These results suggest that gonocyte and F9 cell differentiation is regulated via cross talk between RA and PDGFRs using different downstream pathways.

Oxidative stress, redox regulation and diseases of cellular differentiation

BACKGROUND

Within cells, there is a narrow concentration threshold that governs whether reactive oxygen species (ROS) induce toxicity or act as second messengers.

SCOPE OF REVIEW

We discuss current understanding of how ROS arise, facilitate cell signaling, cause toxicities and disease related to abnormal cell differentiation and those (primarily) sulfur based pathways that provide nucleophilicity to offset these effects.

PRIMARY CONCLUSIONS

Cellular redox homeostasis mediates a plethora of cellular pathways that determine life and death events. For example, ROS intersect with GSH based enzyme pathways to influence cell differentiation, a process integral to normal hematopoiesis, but also affecting a number of diverse cell differentiation related human diseases. Recent attempts to manage such pathologies have focused on intervening in some of these pathways, with the consequence that differentiation therapy targeting redox homeostasis has provided a platform for drug discovery and development.

GENERAL SIGNIFICANCE

The balance between electrophilic oxidative stress and protective biomolecular nucleophiles predisposes the evolution of modern life forms. Imbalances of the two can produce aberrant redox homeostasis with resultant pathologies. Understanding the pathways involved provides opportunities to consider interventional strategies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

PI3K/Akt pathway regulates retinoic acid-induced Hox gene expression in F9 cells

Retinoic acid (RA), the most potent natural form of vitamin A, is a key morphogen in vertebrate development and a potent regulator of both adult and embryonic cell differentiation. Specifically, RA regulates clustered Hox gene expression during embryogenesis and is required to establish the anteroposterior body plan. The PI3K/Akt pathway was also reported to play an essential role in the process of RA-induced cell differentiation. Therefore, we tested whether the PI3K/Akt pathway is involved in RA-induced Hox gene expression in a F9 murine embryonic teratocarcinoma cells. To examine the effect of PI3K/Akt signaling on RA-induced initiation of collinear expression of Hox genes, F9 cells were treated with RA in the presence or absence of PI3K inhibitor LY294002, and time-course gene expression profiles for all 39 Hox genes located in four different clusters-Hoxa, Hoxb, Hoxc, and Hoxd-were analyzed. Collinear expression of Hoxa and -b cluster genes was initiated earlier than that of the -c and -d clusters upon RA treatment. When LY294002 was applied along with RA, collinear expression induced by RA was delayed, suggesting that the PI3K/Akt signaling pathway somehow regulates RA-induced collinear expression of Hox genes in F9 cells. The initiation of Hox collinear expression by RA and the delayed expression following LY294002 in F9 cells would provide a good model system to decipher the yet to be answered de novo collinear expression of Hox genes during gastrulation, which make the gastrulating cells to remember their positional address along the AP body axis in the developing embryo.

Vitamin A deficiency impairs spatial learning and memory: the mechanism of abnormal CBP-dependent histone acetylation regulated by retinoic acid receptor alpha

Vitamin A (VA) is an essential micronutrient. Numerous studies have confirmed that VA deficiency (VAD) leads to a decline in learning and memory function. Our previous studies have demonstrated that retinoic acid nuclear receptor α (RARα) in the hippocampus plays a crucial role in learning and memory, but the exact mechanism for this process is unclear. Epigenetic modifications, particularly histone acetylation, are involved in nervous system development, learning and memory function, and the pathogenesis of neurodegenerative diseases. Histone acetyltransferases (HATs), such as CREB-binding protein (CBP), E1A-binding protein p300 (p300), and p300/CBP-associated factor (PCAF), are critical for regulating memory function. The current study uses RARα and CBP as examples to study the connections between the RA signaling pathway and histone acetylation modification and to reveal the epigenetic mechanism in VAD-induced learning and memory impairment. This study examined the expression of RARα, HATs, acetylated histone H3/H4, and memory-related genes (Zif268, cFos, FosB), as well as the interaction of RARα and CBP in the hippocampus of 8-week-old rats. Additionally, the changes shown in vivo were further assessed in primary cultured neurons with the inhibition or overexpression of RARα. We found significantly lower levels of histone acetylation in the VAD rats. Furthermore, this downregulation, which impairs learning and memory, is induced by the dysregulation of CBP-dependent histone acetylation that is mediated by RARα. This work provides a solid theoretical foundation and experimental basis for the importance of ensuring sufficient nutritional VA during pregnancy and early life to prevent impairments of learning and memory in adulthood.

Labeling of neuronal differentiation and neuron cells with biocompatible fluorescent nanodiamonds

Nanodiamond is a promising carbon nanomaterial developed for biomedical applications. Here, we show fluorescent nanodiamond (FND) with the biocompatible properties that can be used for the labeling and tracking of neuronal differentiation and neuron cells derived from embryonal carcinoma stem (ECS) cells. The fluorescence intensities of FNDs were increased by treatment with FNDs in both the mouse P19 and human NT2/D1 ECS cells. FNDs were taken into ECS cells; however, FNDs did not alter the cellular morphology and growth ability. Moreover, FNDs did not change the protein expression of stem cell marker SSEA-1 of ECS cells. The neuronal differentiation of ECS cells could be induced by retinoic acid (RA). Interestingly, FNDs did not affect on the morphological alteration, cytotoxicity and apoptosis during the neuronal differentiation. Besides, FNDs did not alter the cell viability and the expression of neuron-specific marker β-III-tubulin in these differentiated neuron cells. The existence of FNDs in the neuron cells can be identified by confocal microscopy and flow cytometry. Together, FND is a biocompatible and readily detectable nanomaterial for the labeling and tracking of neuronal differentiation process and neuron cells from stem cells.

Foxa1 contributes to the repression of Nanog expression by recruiting Grg3 during the differentiation of pluripotent P19 embryonal carcinoma cells

Transcription factor Foxa1 plays a critical role during neural differentiation and is induced immediately after retinoic acid (RA)-initiated differentiation of pluripotent P19 embryonal carcinoma cells, correlated with the downregulated expression of pluripotency-related genes such as Nanog. To study whether Foxa1 participates in the repression of pluripotency factors, we expressed Foxa1 ectopically in P19 cells and identified that Nanog was repressed directly by Foxa1. We confirmed that Foxa1 was able to interact with Grg3, which is a transcriptional corepressor that expresses in P19 cells as well as during RA-induced P19 cell differentiation. Knockdown of Foxa1 or Grg3 delayed the downregulation of Nanog expression during RA-induced P19 cell differentiation. Furthermore, we found that Foxa1 recruited Grg3 to the Nanog promoter -2kb upstream region and switched the promoter to an inactive chromatin status represented by typical modifications in histone H3. Together, our results suggested a critical involvement of Foxa1 in the negative regulation of Nanog expression during the differentiation of pluripotent stem cells.

Headway and hurdles in the clinical development of dietary phytochemicals for cancer therapy and prevention: lessons learned from vitamin A derivatives

Accumulating epidemiologic and preclinical evidence support the pharmacologic use of a variety of dietary chemicals for the prevention and treatment of cancer. However, it will be challenging to translate these findings into routine clinical practice since phytochemicals have pleiotropic biological activities that have to be balanced for optimal efficacy without unacceptable and potentially unanticipated toxicities. Correctly matching patient populations and settings with optimal, natural product-based phytochemical therapies will require a greater understanding of the specific mechanisms underlying the efficacy, toxicity, and resistance of each agent in a variety of normal, premalignant, and malignant settings. This, in turn, necessitates continued commitment from the basic research community to guide carefully designed and informed clinical trials. The most developed class of anticancer phytochemicals consists of the derivatives of vitamin A called retinoids. Unlike other natural product chemicals currently under study, the retinoids have been extensively tested in humans. Over 30 years of clinical investigation has resulted in several disappointments, but there were some spectacular successes where certain retinoid-based protocols are now FDA-approved standard of care therapies to treat specific malignancies. Furthermore, retinoids are one of the most evaluated pharmacologic agents in the ultra-challenging setting of interventional cancer prevention. This review will summarize the development of retinoids in cancer therapy and prevention with an emphasis on currently proposed mechanisms mediating their efficacy, toxicity, and resistance.

The transcription factor FOXM1 (Forkhead box M1): proliferation-specific expression, transcription factor function, target genes, mouse models, and normal biological roles

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor, which stimulates cell proliferation and exhibits a proliferation-specific expression pattern. Accordingly, both the expression and the transcriptional activity of FOXM1 are increased by proliferation signals, but decreased by antiproliferation signals, including the positive and negative regulation by protooncoproteins or tumor suppressors, respectively. FOXM1 stimulates cell cycle progression by promoting the entry into S-phase and M-phase. Moreover, FOXM1 is required for proper execution of mitosis. Accordingly, FOXM1 regulates the expression of genes, whose products control G1/S-transition, S-phase progression, G2/M-transition, and M-phase progression. Additionally, FOXM1 target genes encode proteins with functions in the execution of DNA replication and mitosis. FOXM1 is a transcriptional activator with a forkhead domain as DNA binding domain and with a very strong acidic transactivation domain. However, wild-type FOXM1 is (almost) inactive because the transactivation domain is repressed by three inhibitory domains. Inactive FOXM1 can be converted into a very potent transactivator by activating signals, which release the transactivation domain from its inhibition by the inhibitory domains. FOXM1 is essential for embryonic development and the foxm1 knockout is embryonically lethal. In adults, FOXM1 is important for tissue repair after injury. FOXM1 prevents premature senescence and interferes with contact inhibition. FOXM1 plays a role for maintenance of stem cell pluripotency and for self-renewal capacity of stem cells. The functions of FOXM1 in prevention of polyploidy and aneuploidy and in homologous recombination repair of DNA-double-strand breaks suggest an importance of FOXM1 for the maintenance of genomic stability and chromosomal integrity.

Retinoid signaling in progenitors controls specification and regeneration of the urothelium

The urothelium is a multilayered epithelium that serves as a barrier between the urinary tract and blood, preventing the exchange of water and toxic substances. It consists of superficial cells specialized for synthesis and transport of uroplakins that assemble into a tough apical plaque, one or more layers of intermediate cells, and keratin 5-expressing basal cells (K5-BCs), which are considered to be progenitors in the urothelium and other specialized epithelia. Fate mapping, however, reveals that intermediate cells rather than K5-BCs are progenitors in the adult regenerating urothelium, that P cells, a transient population, are progenitors in the embryo, and that retinoids are critical in P cells and intermediate cells, respectively, for their specification during development and regeneration. These observations have important implications for tissue engineering and repair and, ultimately, may lead to treatments that prevent loss of the urothelial barrier, a major cause of voiding dysfunction and bladder pain syndrome.