Bmi-1 regulates self-renewal, proliferation and senescence of human fetal neural stem cells in vitro

The Senescence Markers p16INK4A, p14ARF/p19ARF, and p21 in Organ Development and Homeostasis

It is widely accepted that senescent cells accumulate with aging. They are characterized by replicative arrest and the release of a myriad of factors commonly called the senescence-associated secretory phenotype. Despite the replicative cell cycle arrest, these cells are metabolically active and functional. The release of SASP factors is mostly thought to cause tissue dysfunction and to induce senescence in surrounding cells. As major markers for aging and senescence, p16INK4, p14ARF/p19ARF, and p21 are established. Importantly, senescence is also implicated in development, cancer, and tissue homeostasis. While many markers of senescence have been identified, none are able to unambiguously identify all senescent cells. However, increased levels of the cyclin-dependent kinase inhibitors p16INK4A and p21 are often used to identify cells with senescence-associated phenotypes. We review here the knowledge of senescence, p16INK4A, p14ARF/p19ARF, and p21 in embryonic and postnatal development and potential functions in pathophysiology and homeostasis. The establishment of senolytic therapies with the ultimate goal to improve healthy aging requires care and detailed knowledge about the involvement of senescence and senescence-associated proteins in developmental processes and homeostatic mechanism. The review contributes to these topics, summarizes open questions, and provides some directions for future research.

The role and mechanisms of polycomb repressive complex 2 on the regulation of osteogenic and neurogenic differentiation of stem cells

The stem cells differentiate into osteoblasts or neurocytes is the key process for treatment of bone‐ or neural tissue‐related diseases which is caused by ageing, fracture, injury, inflammation, etc Polycomb group complexes (PcGs), especially the polycomb repressive complex 2 (PRC2), act as pivotal epigenetic regulators by modifying key developmental regulatory genes during stem cells differentiation. In this review, we summarize the core subunits, the variants and the potential functions of PRC2. We also highlight the underlying mechanisms of PRC2 associated with the osteogenic and neurogenic differentiation of stem cells, including its interaction with non‐coding RNAs, histone acetyltransferases, histone demethylase, DNA methyltransferase and polycomb repressive complex 1. This review provided a substantial information of epigenetic regulation mediated by PRC2 which leads to the osteogenic and neurogenic differentiation of stem cells.

Role of Nrf2 and mitochondria in cancer stem cells; in carcinogenesis, tumor progression, and chemoresistance

Cancer stem cells (CSCs) are rare sub-population in tumor mass with self-renewal and differentiation abilities; CSCs are considered as the main cells which are responsible for tumor metastasis, cancer recurrence, and chemo/radio-resistance. CSCs are believed to contain low mitochondria in quantity, high concentration of nuclear factor erythroid 2-related factor 2 (Nrf2), and low reactive oxygen species (ROS) levels. Mitochondria regulate certain cellular functions, including controlling of cellular energetics, calcium signaling, cell growth and cell differentiation, cell cycle regulation, and cell death. Also, mitochondria are the main sources of intrinsic ROS production. Dysfunction of CSCs mitochondria due to oxidative phosphorylation is reported in several pathological conditions, including metabolic disorders, age-related diseases, and various types of cancers. ROS levels play a significant role in cellular signal transduction and CSCs' identity and differentiation capability. Nrf2 is a master transcription factor that plays critical functions in maintaining cellular redox hemostasis by regulating several antioxidant and detoxification pathways. Recently, the critical function of Nrf2 in CSCs has been revealed by several studies. Nrf2 is an essential molecule in the maintenance of CSCs' stemness and self-renewal in response to different oxidative stresses such as chemotherapy-induced elevation of ROS. Nrf2 enables these cells to recover from chemotherapy damages, and promotes establishment of invasion and dissemination. In this study, we have summarized the role of Nrf2 and mitochondria function CSCs, which promote cancer development. The significant role of Nrf2 in the regulation of mitochondrial function and ROS levels suggests this molecule as a potential target to eradicate CSCs.

Targeting EGFR Enriches Stem Cell-Like Properties in Salivary Adenoid Cystic Carcinoma by Activating the Notch1 Pathway

Background

Salivary adenoid cystic carcinoma (SACC), a rare cancer arising in the salivary glands, is characterized by high rates of relapse and distant metastasis. Epidermal growth factor receptor (EGFR) has been implicated in SACC carcinogenesis. However, prospective trials of EGFR-targeting therapies in SACC are limited, and the optimum regimen is unclear.

Methods

The effects of erlotinib on cell proliferation, colony formation, ALDH enzymatic activity and tumorsphere formation were investigated in SACC cells. Expression of the cancer stem cell markers Bmi-1 and Oct4 was evaluated using Western blotting.

Results

We found that while it robustly inhibited cell growth, targeting EGFR with erlotinib enriched the ALDH⁺ cell population and elevated the clonogenicity of SACC cells, suggesting an increase in stem cell-like potential. In addition, we found that suppression of EGFR kinase activity with erlotinib led to the activation of Notch1 signaling, leading to an increase in stem cell-like properties. Moreover, the γ-secretase inhibitor GSI treatment eliminated the erlotinib-induced increase in stem cell-like properties by decreasing Notch activity.

Conclusion

Our results provide an explanation for the worsened survival observed in some studies of erlotinib therapy in SACC and provide potential therapeutic strategies by combined blockade of the EGFR and Notch1 pathways.

Polycomb repressive complex 1: Regulators of neurogenesis from embryonic to adult stage

Development of vertebrate nervous system is a complex process which involves differential gene expression and disruptions in this process or in the mature brain, may lead to neurological disorders and diseases. Extensive work that spanned several decades using rodent models and recent work on stem cells have helped uncover the intricate process of neuronal differentiation and maturation. There are various morphological changes, genetic and epigenetic modifications which occur during normal mammalian neural development, one of the chromatin modifications that controls vital gene expression are the posttranslational modifications on histone proteins, that controls accessibility of translational machinery. Among the histone modifiers, polycomb group proteins (PcGs), such as Ezh2, Eed and Suz12 form large protein complexes-polycomb repressive complex 2 (PRC2); while Ring1b and Bmi1 proteins form core of PRC1 along with accessory proteins such as Cbx, Hph, Rybp and Pcgfs catalyse histone modifications such as H3K27me3 and H2AK119ub1. PRC1 proteins are known to play critical role in X chromosome inactivation in females but they also repress the expression of key developmental genes and tightly regulate the mammalian neuronal development. In this review we have discussed the signalling pathways, morphogens and nuclear factors that initiate, regulate and maintain cells of the nervous system. Further, we have extensively reviewed the recent literature on the role of Ring1b and Bmi1 in mammalian neuronal development and differentiation; as well as highlighted questions that are still unanswered.

Implications of Epigenetic Mechanisms and their Targets in Cerebral Ischemia Models

BACKGROUND

Understanding the complexities associated with the ischemic condition and identifying therapeutic targets in ischemia is a continued challenge in stroke biology. Emerging evidence reveals the potential involvement of epigenetic mechanisms in the incident and outcome of stroke, suggesting novel therapeutic options of targeting different molecules related to epigenetic regulation.

OBJECTIVE

This review summarizes our current understanding of ischemic pathophysiology, describes various in vivo and in vitro models of ischemia, and examines epigenetic modifications associated with the ischemic condition.

METHOD

We focus on microRNAs, DNA methylation, and histone modifying enzymes, and present how epigenetic studies are revealing novel drug target candidates in stroke.

CONCLUSION

Finally, we discuss emerging approaches for the prevention and treatment of stroke and post-stroke effects using pharmacological interventions with a wide therapeutic window.

Epigenetic Reprogramming of Pericentromeric Satellite DNA in Premalignant and Malignant Lesions

Repression of repetitive DNA is important for maintaining genomic stability, but is often perturbed in cancer. For instance, the megabase satellite domain at chromosome 1q12 is a common site of genetic rearrangements, such as translocations and deletions. Polycomb-group proteins can be observed as large subnuclear domains called polycomb bodies, the composition and cellular function of which has remained elusive. This study demonstrates that polycomb bodies are canonical subunits of the multiprotein polycomb repressive complex 1 deposited on 1q12 pericentromeric satellite DNA, which are normally maintained as constitutive heterochromatin by other mechanisms. Furthermore, the data reveal that polycomb bodies are exclusive to premalignant and malignant cells, being absent in normal cells. For instance, polycomb bodies are present in melanocytic cells of nevi and conserved in primary and metastatic melanomas. Deposition of polycomb on the 1q12 satellite DNA in melanoma development correlated with reduced DNA methylation levels. In agreement with this, inhibition of DNA methyltransferases, with the hypomethylating agent guadecitabine (SGI-110), was sufficient for polycomb body formation on pericentromeric satellites in primary melanocytes. This suggests that polycomb bodies form in cancer cells with global DNA demethylation to control the stability of pericentromeric satellite DNA. These results reveal a novel epigenetic perturbation specific to premalignant and malignant cells that may be used as an early diagnostic marker for detection of precancerous changes and a new therapeutic entry point.Implications: Pericentromeric satellite DNA is epigenetically reprogrammed into polycomb bodies as a premalignant event with implications for transcriptional activity and genomic stability. Mol Cancer Res; 16(3); 417-27. ©2018 AACR.

Reduction of gastric cancer proliferation and invasion by miR-15a mediated suppression of Bmi-1 translation

B-cell specific moloney leukemia virus insertion site 1 (Bmi-1) gene plays important roles in gastric cancer, but the epigenetic regulatory mechanism by microRNA (miRNA) and the functional significance of Bmi-1 inhibition in gastric cancer remains elusive. In this study, we systematically investigated the functional roles of miRNA mediated Bmi-1 suppression in gastric cancer. Our results show that the expression of miR-15a is significantly reduced in gastric cancer and the protein expression levels of Bmi-1 are inversely correlated with miR-15a (P = 0.034) in gastric cancer patient samples. Functional studies revealed that ectopic expression of miR-15a decreased Bmi-1 in gastric cancer cell lines with reduced proliferation and tumor invasion. High levels of Bmi-1 in gastric cancer patients are significantly associated with better overall survival (P = 0.024) based on the Kaplan-Meier survival analysis.

Antitumor activity and inhibitory effects on cancer stem cell-like properties of Adeno-associated virus (AAV) -mediated Bmi-1 interference driven by Bmi-1 promoter for gastric cancer

Bmi-1 is aberrantly activated in various cancers and plays a vital role in maintaining the self-renewal of stem cells. Our previous research revealed that Bmi-1 was overexpressed in gastric cancer (GC) and it's overexpression was an independent negative prognostic factor, suggesting it can be a therapeutic target. The main purpose of this investigation was to explore the antitumor activity of Bmi-1 interference driven by its own promoter (Ad-Bmi-1i) for GC. In this study, we used adenoviral vector to deliver Bmi-1 shRNA driven by its own promoter to treat GC. Our results revealed that Ad-Bmi-1i could selectively silence Bmi-1 in GC cells which overexpress Bmi-1 and suppress the malignant phenotypes and stem-like properties of GC cells in vitro and in vivo. Moreover, direct injection of Ad-Bmi-1i into xenografts suppressed tumor growth and destroyed cancer cells in vivo. Ad-Bmi-1i inhibited the proliferation of GC cells mainly via inducing senescence in vitro, but it suppressed tumor through inducing senescence and apoptosis, and inhibiting angiogenesis in vivo. Bmi-1 knockdown by Ad-Bmi-1i downregulated VEGF via inhibiting AKT activity. These results suggest that Ad-Bmi-1i not only inhibits tumor growth and stem cell-like phenotype by inducing cellular senescence directly, but also has an indirect anti-tumor activity by anti-angiogenesis effects via regulating PTEN/AKT/VEGF pathway. Transfer of gene interference guided by its own promoter by an adeno-associated virus (AAV) vector might be a potent antitumor approach for cancer therapy.

Expression of microRNA-452 via adenoviral vector inhibits non-small cell lung cancer cells proliferation and metastasis

The microRNA miR-452 has been shown to function as a tumor suppressor. However, the cellular mechanism and potential application of miR-452-mediated cancer suppression remain great unknown. This study aims to identify how miR-452 acts in regulating non-small cell lung cancer (NSCLC) proliferation and metastasis. Expression of miR-452 via adenoviral (Ad) vector inhibits the proliferation, invasion, and migration of NSCLC cells A549 or H460. Our data also shows that miR-452 down-regulates the expression of Bmi-1 as well as pro-survival or anti-apoptosis regulators Survivin, cIAP-1, and cIAP-2. By such gene interference, miR-452 modulates NSCLC cell epithelial-mesenchymal transition (EMT) and further disrupts their migration and invasion. Moreover, miR-452 blocks the activation of PI3K/AKT pathway, which is also required for EMT process. These data reveal that miR-452 treatment could be a novel target or strategy for NSCLC treatment.

Nanoparticle siRNA against BMI-1 with a Polyethylenimine-Laminarin Conjugate for Gene Therapy in Human Breast Cancer

The B-cell-specific Moloney leukemia virus inset site 1 gene (BMI-1) has attracted considerable attention in recent years because of its key role in breast cancer development and metastasis. The downregulation of BMI-1 expression via small interfering RNA (siRNA) effectively inhibits tumor growth. However, the successful application of this therapy is limited by the unavailability of an appropriate vector for siRNA transfer. Therefore, this study aimed to construct a novel laminarin-based nonviral gene transfer vector to carry a constructed BMI-1-targeting siRNA and to investigate the in vitro and in vivo antitumor effects of this siRNA on breast cancer cells. To enhance the siRNA-carrying capacity, we introduced polyethylenimine (PEI) to laminarin's surface via N,N'-carbonyldiimidazole, which produced the cationic PEI-modified laminarin conjugate nLP. Subsequent in vitro experiments indicated that nLP not only formed a nanoparticle with a diameter of 200 nm through electrostatic interactions with siRNA but also showed high efficiency (95.0%) in the delivery siRNA to MCF-7 cells. The nanoparticle targeting BMI-1 (nLP/siBMI-2) reduced BMI-1 expression in breast MCF-7 cells by 90.9% reduction. An in vivo tumor suppression experiment demonstrated that the nLP/siBMI-2 nanoparticle had relatively low toxicity and good gene-therapeutic efficacy, with a tumor inhibition rate of 46.6%.

Senescence suppressors: their practical importance in replicative lifespan extension in stem cells

Recent animal and clinical studies report promising results for the therapeutic utilization of stem cells in regenerative medicine. Mesenchymal stem cells (MSCs), with their pluripotent nature, have advantages over embryonic stem cells in terms of their availability and feasibility. However, their proliferative activity is destined to slow by replicative senescence, and the limited proliferative potential of MSCs not only hinders the preparation of sufficient cells for in vivo application, but also draws a limitation on their potential for differentiation. This calls for the development of safe and efficient means to increase the proliferative as well as differentiation potential of MSCs. Recent advances have led to a better understanding of the underlying mechanisms and significance of cellular senescence, facilitating ways to manipulate the replicative lifespan of a variety of primary cells, including MSCs. This paper introduces a class of proteins that function as senescence suppressors. Like tumor suppressors, these proteins are lost in senescence, while their forced expression delays the onset of senescence. Moreover, treatments that increase the expression or the activity of senescence suppressors, therefore, cause expansion of the replicative and differentiation potential of MSCs. The nature of the activities and putative underlying mechanisms of the senescence suppressors will be discussed to facilitate their evaluation.

Deregulation of Bmi-1 is associated with enhanced migration, invasion and poor prognosis in salivary adenoid cystic carcinoma

BACKGROUND

Bmi-1 had been found to involve in self renewal of stem cells and tumorigenesis in various malignancies. In this study, we investigated the role of Bmi-1 in the development of salivary adenoid cystic carcinoma (SACC).

METHODS

At first, we confirmed that the deregulation of Bmi-1 was a frequent event in SACC; up-regulation of Bmi-1 was correlated with clinical stages, vital status and distant metastasis and associated with reduced overall survival and disease free survival. SACC-LM cells, higher migration and invasion abilities, elevated the expression of Bmi-1 protein, epithelial-mesenchymal transition (EMT) related proteins (Snail, Slug and Vimentin) and cancer stem cells (CSCs) related proteins (ABCG2, Notch, ALDH-1, Oct-4, Nanog and Epcam) compared to the SACC-83 cells (lower migration and invasion abilities). The migration and invasion abilities were inhibited in SACC-LM cells upon Bmi-1 knockdown. Meanwhile, Bmi-1 knockdown resulted in simultaneous loss of stem cell markers and EMT markers in SACC-LM cells.

CONCLUSION

Our studies confirm that Bmi-1 deregulation plays an important role in the development of SACC and contributes to the migration and the invasion abilities of SACC, which is involved in EMT and CSCs.

GENERAL SIGNIFICANCE

To our knowledge, this is the first study revealing that Bmi-1 deregulation is associated with enhanced migration, invasion and poor prognosis in salivary adenoid cystic carcinoma.

Silencing Bmi-1 enhances the senescence and decreases the metastasis of human gastric cancer cells

AIM: To evaluate the impact of Bmi-1 on cell senescence and metastasis of human gastric cancer cell line BGC823.

METHODS: Two pairs of complementary small hairpin RNA (shRNA) oligonucleotides targeting the Bmi-1 gene were designed, synthesized, annealed and cloned into the pRNAT-U6.2 vector. After DNA sequencing to verify the correct insertion of the shRNA sequences, the recombinant plasmids were transfected into BGC823 cells. The expression of Bmi-1 mRNA and protein was examined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. The effects of Bmi-1 knockdown on cell senescence and metastasis were determined by the β-Gal activity assay and Boyden chamber assay, respectively.

RESULTS: The double-stranded oligonucleotide fragments of Bmi-1 short interfering RNA (siRNA) cloned into pRNAT-U6.2 vector conformed to the inserted sequence. RT-PCR and Western blotting indicated that the expression levels of Bmi-1 gene mRNA and protein were markedly decreased in transfected BGC823 cells with pRNAT-U6.2-si1104 and pRNAT-U6.2-si1356, especially in transfected BGC823 cells with pRNAT-U6.2-si1104, compared with two control groups (empty vector and blank group). In particular, Bmi-1 protein expression was almost completely abolished in cells transfected with the recombinant vector harboring shRNA targeting the sequence GGAGGAGGTGAATGATAAA (nt1104-1122). Compared with untransfected cells and cells transfected with the empty vector, the mean percentage of senescent cells increased and the number of cells passing through the Matrigel decreased in cells transfected with the recombinant vectors.

CONCLUSION: Silencing Bmi-1 by RNA interference can increase the senescent cell rate and effectively reduce the metastasis of gastric cancer cells.

Chromatin-modifying agents for epigenetic reprogramming and endogenous neural stem cell-mediated repair in stroke

The recent explosion of interest in epigenetics and chromatin biology has made a significant impact on our understanding of the pathophysiology of cerebral ischemia and led to the identification of new treatment strategies for stroke, such as those that employ histone deacetylase inhibitors. These are key advances; however, the rapid pace of discovery in chromatin biology and innovation in the development of chromatin-modifying agents implies there are emerging classes of drugs that may also have potential benefits in stroke. Herein, we discuss how various chromatin regulatory factors and their recently identified inhibitors may serve as drug targets and therapeutic agents for stroke, respectively. These factors primarily include members of the repressor element-1 silencing transcription factor (REST)/neuron-restrictive silencer factor macromolecular complex, polycomb group (PcG) proteins, and associated chromatin remodeling factors, which have been linked to the pathophysiology of cerebral ischemia. Further, we suggest that, because of the key roles played by REST, PcG proteins and other chromatin remodeling factors in neural stem and progenitor cell (NSPC) biology, chromatin-modifying agents can be utilized not only to mitigate ischemic injury directly but also potentially to promote endogenous NSPC-mediated brain repair mechanisms.

Nrf2 is required to maintain the self-renewal of glioma stem cells

Background

Glioblastomas are deadly cancers that display a functional cellular hierarchy maintained by self-renewing glioma stem cells (GSCs). Self-renewal is a complex biological process necessary for maintaining the glioma stem cells. Nuclear factor rythroid 2-related factor 2(Nrf2) plays a significant role in protecting cells from endogenous and exogenous stresses. Nrf2 is a key nuclear transcription factor that regulates antioxidant response element (ARE)-containing genes. Previous studies have demonstrated the significant role of Nrf2 in the proliferation of glioblastoma, and in their resistance to radioactive therapies. We examined the effect of knocking down Nrf2 in GSCs.

Methods

Nrf2 expression was down-regulated by shRNA transinfected with lentivirus. Expression levels of Nestin, Nrf2, BMI-1, Sox2 and Cyclin E were assessed by western blotting, quantitative polymerase chain reaction (qPCR) and immunohistochemistry analysis. The capacity for self-renewal in vitro was assessed by genesis of colonies. The capacity for self-renewal in vivo was analyzed by tumor genesis of xenografts in nude mice.

Results

Knockdown of Nrf2 inhibited the proliferation of GSCs, and significantly reduced the expression of BMI-1, Sox2 and CyclinE. Knocking down of Nrf2 changed the cell cycle distribution of GSCs by causing an uncharacteristic increase in the proportion of cells in the G2 phase and a decrease in the proportion of cells in the S phase of the cell cycle.

Conclusions

Nrf2 is required to maintain the self-renewal of GSCs, and its down-regulation can attenuate the self-renewal of GSCs significantly.

The dynamics of polycomb group proteins in early embryonic nervous system in mouse and human

Polycomb group (PcG) proteins are transcription regulatory proteins that control the expression of a variety of genes and the antero-posterior neural patterning from early embryogenesis. Although expression of PcG genes in the nervous system has been noticed, but the expression pattern of PcG proteins in early embryonic nervous system is still unclear. In this study, we analyzed the expression pattern of PRC1 complex members (BMI-1 and RING1B) and PRC2 complex members (EED, SUZ12 and EZH2) in early embryonic nervous system in mouse and human by Western blot and Immunohistochemistry. The results of Western blot showed that EED protein was significantly up-regulated with the increase of the day of pregnancy during the early embryogenesis in mouse. BMI-1 protein level was significantly increased from the day 10 of pregnancy, when compared with the day 9 of pregnancy. But the SUZ12, EZH2 and RING1B protein level did not change significantly. From the results of Immunohistochemistry, we found that the four PcG proteins were all expressed in the fetal brain and fetal spinal cord in mouse. In human, the expression of EED, SUZ12, and EZH2 was not significantly different in cerebral cortex and sacral spinal cord, but BMI-1 and RING1B expression was enhanced with the development of embryos in early pregnancy. Collectively, our findings showed that PRC1 and PRC2 were spatiotemporally expressed in brain and spinal cord of early embryos.

Long-lasting neurotoxic effects of exposure to methylmercury during development

Amongst environmental chemical contaminants, methylmercury (MeHg) remains a major concern because of its detrimental effects on developing organisms, which appear to be particularly susceptible to its toxicity. Here, we investigated the effects of low MeHg levels on the development of the nervous system using both in vitro and in vivo experimental models. In neural stem cells (NSCs), MeHg decreased proliferation and neuronal differentiation and induced cellular senescence associated with impairment in mitochondrial function and a concomitant decrease in global DNA methylation. Interestingly, the effects were heritable and could be observed in daughter NSCs never directly exposed to MeHg. By chronically exposing pregnant/lactating mice to MeHg, we found persistent behavioural changes in the male offspring, which exhibited depression-like behaviour that could be reversed by chronic treatment with the antidepressant fluoxetine. The behavioural alterations were associated with a decreased number of proliferating cells and lower expression of brain-derived neurotrophic factor (Bdnf) mRNA in the hippocampal dentate gyrus. MeHg exposure also induced long-lasting DNA hypermethylation, increased histone H3-K27 tri-methylation and decreased H3 acetylation at the Bdnf promoter IV, indicating that epigenetic mechanisms play a critical role in mediating the long-lasting effects of perinatal exposure to MeHg. Fluoxetine treatment restored the Bdnf mRNA expression levels, as well as the number of proliferating cells in the granule cell layer of the dentate gyrus, which further supports the hypothesis that links depression to impaired neurogenesis. Altogether, our findings have shown that low concentrations of MeHg induce long-lasting effects in NSCs that can potentially predispose individuals to depression, which we have reported earlier to occur in experimental animals exposed to MeHg during prenatal and early postnatal development.

HemaExplorer: a database of mRNA expression profiles in normal and malignant haematopoiesis

The HemaExplorer (http://servers.binf.ku.dk/hemaexplorer) is a curated database of processed mRNA Gene expression profiles (GEPs) that provides an easy display of gene expression in haematopoietic cells. HemaExplorer contains GEPs derived from mouse/human haematopoietic stem and progenitor cells as well as from more differentiated cell types. Moreover, data from distinct subtypes of human acute myeloid leukemia is included in the database allowing researchers to directly compare gene expression of leukemic cells with those of their closest normal counterpart. Normalization and batch correction lead to full integrity of the data in the database. The HemaExplorer has comprehensive visualization interface that can make it useful as a daily tool for biologists and cancer researchers to assess the expression patterns of genes encountered in research or literature. HemaExplorer is relevant for all research within the fields of leukemia, immunology, cell differentiation and the biology of the haematopoietic system.

Inherited effects of low-dose exposure to methylmercury in neural stem cells

Methylmercury (MeHg) is an environmental contaminant with recognized neurotoxic effects, particularly to the developing nervous system. In the present study, we show that nanomolar concentrations of MeHg can induce long-lasting effects in neural stem cells (NSCs). We investigated short-term direct and long-term inherited effects of exposure to MeHg (2.5 or 5.0 nM) using primary cultures of rat embryonic cortical NSCs. We found that MeHg had no adverse effect on cell viability but reduced NSC proliferation and altered the expression of cell cycle regulators (p16 and p21) and senescence-associated markers. In addition, we demonstrated a decrease in global DNA methylation in the exposed cells, indicating that epigenetic changes may be involved in the mechanisms underlying the MeHg-induced effects. These changes were observed in cells directly exposed to MeHg (parent cells) and in their daughter cells cultured under MeHg-free conditions. In agreement with our in vitro data, a trend was found for decreased cell proliferation in the subgranular zone in the hippocampi of adult mice exposed to low doses of MeHg during the perinatal period. Interestingly, this impaired proliferation had a measurable impact on the total number of neurons in the hippocampal dentate gyrus. Importantly, this effect could be reversed by chronic antidepressant treatment. Our study provides novel evidence for programming effects induced by MeHg in NSCs and supports the idea that developmental exposure to low levels of MeHg may result in long-term consequences predisposing to neurodevelopmental disorders and/or neurodegeneration.

Protoplasmic astrocytes enhance the ability of neural stem cells to differentiate into neurons in vitro

Protoplasmic astrocytes have been reported to exhibit neuroprotective effects on neurons, but there has been no direct evidence for a functional relationship between protoplasmic astrocytes and neural stem cells (NSCs). In this study, we examined neuronal differentiation of NSCs induced by protoplasmic astrocytes in a co-culture model. Protoplasmic astrocytes were isolated from new-born and NSCs from the E13-15 cortex of rats respectively. The differentiated cells labeled with neuron-specific marker β-tubulin III, were dramatically increased at 7 days in the co-culture condition. Blocking the effects of brain-derived neurotrophic factor (BDNF) with an anti-BDNF antibody reduced the number of neurons differentiated from NSCs when co-cultured with protoplasmic astrocytes. In fact, the content of BDNF in the supernatant obtained from protoplasmic astrocytes and NSCs co-culture media was significantly greater than that from control media conditions. These results indicate that protoplasmic astrocytes promote neuronal differentiation of NSCs, which is driven, at least in part, by BDNF.

REST and CoREST are transcriptional and epigenetic regulators of seminal neural fate decisions

Complementary transcriptional and epigenetic regulatory factors (e.g., histone and chromatin modifying enzymes and non-coding RNAs) regulate genes responsible for mediating neural stem cell maintenance and lineage restriction, neuronal and glial lineage specification, and progressive stages of lineage maturation. However, an overall understanding of the mechanisms that sense and integrate developmental signals at the genomic level and control cell type-specific gene network deployment has not emerged. REST and CoREST are central players in the transcriptional and epigenetic regulatory circuitry that is responsible for modulating neural genes, and they have been implicated in establishing cell identity and function, both within the nervous system and beyond it. Herein, we discuss the emerging context-specific roles of REST and CoREST and highlight our recent studies aimed at elucidating their neural developmental cell type- and stage-specific actions. These observations support the conclusion that REST and CoREST act as master regulators of key neural cell fate decisions.

Expression patterns of ABCG2, Bmi-1, Oct-3/4, and Yap in the developing mouse incisor

Recent studies have demonstrated the existence of dental stem cells in the continuously growing tooth. However, much remains to be learned about the complex mechanism involving stem cells during tooth development. We determined the expression patterns of four stem cell markers ABCG2, Bmi-1, Oct-3/4, and Yap in the developing mouse incisors between embryonic day (E) 11 and postnatal day (PN) 20. ABCG2 was localized strongly in the perivascular region of the incisor mesenchyme from E11 to PN20, and in the odontoblasts from E18 to PN20. Bmi-1 was expressed in both the dental epithelium and mesenchyme from E11 to E14. The expression of Bmi-1 was noticeably reduced at E16, and was restricted to the apical bud from E16 to PN20. Oct-3/4 was localized in the nucleus of the cells in the superficial layer and stellate reticulum within the dental epithelium from E11 to E14 and in the apical bud from E16 to PN20. Meanwhile, once the ameloblasts and odontoblasts began to appear at E16, they expressed Oct-3/4 in the cytoplasm. Yap was expressed in most of the basal cells of the incisor dental epithelium from E11 to E14, but was expressed mainly in the transit-amplifying (TA) cells within the basal cell layer from E16 to PN20. The unique and overlapping expression patterns of ABCG2, Bmi-1, Oct-3/4, and Yap suggest the independent and interactive functions of the four stem cell markers in the developing mouse incisor.