Bmi-1 dependence distinguishes neural stem cell self-renewal from progenitor proliferation

Hedgehog-Gli1 signaling regelates differentiation of chicken (Gallus gallus) embryonic stem cells to male germ cells

Gli1 is an important signaling molecular in Hedgehog signaling pathway. In our study, we explored the adjustment effect of Hedgehog-Gli1 signaling pathway on chicken male germ cells differentiation based on the transcriptome-wide analyses of chicken ESCs, primordial germ cells (PGCs) and spermatogonia stem cells (SSCs) that were associated with male germ cell differentiation. We screened out Hedgehog signaling pathway and identified 8 candidated differentially expressed genes (DEGs), Wnt3a, Wnt16, Wnt8a, HHIPL1, Gli1, BMP6, BMP7 and TTLL4. These DEGs expression change trend among blastoderm, genital ridge and testes, from which ESCs, PGCs and SSCs were isolated was the same as RNA-Seq data with quantitative RT-PCR evaluation. Based on retinoic acid (RA) induction of ESCs to SSCs in vitro, Gli1 overexpression has the ability to induce ESCs differentiation and SSCs-like cells formation and high expression of related reproductive genes, like Cvh, C-kit, Blamp1, Prmd14, Stra8, Dazl, integrin α6 and integrin β1 and so on in vitro. While RNAi knockdown of Gli1 can protect ESCs from differentiating into SSCs and correspondingly reduce the expression of the associated reproductive gene in vivo and vitro. Immunochemistry results showed that Gli1 overexpression could increase the expression of PGCs markers Cvh and C-kit and SSCs markers integrin α6 and integrin β1 in vivo, while Gli1 knockdown can have the opposite effect in vivo and in vitro. PAS stain and flow cytometry (FCM) evaluation results indicated the quantity of germ cells is decrease or increase with Gli1 knockdown or overexpression. Collectively, these results uncovered a novel function of Gli1 and demonstrated Hedgehog-Gli1 signaling pathway involved in chicken male germ cell differentiation, where it acts as a facilitator.

Upregulation of the proto-oncogene Bmi-1 predicts a poor prognosis in pediatric acute lymphoblastic leukemia

BACKGROUND

Bmi-1, the B cell-specific moloney murine leukemia virus insertion site 1, is a member of the Polycomb-group (PcG) family and acts as an oncogene in various tumors; however, its expression related to the prognosis of pediatric patients with acute lymphoblastic leukemia (ALL) has not been well studied.

METHODS

The Bmi-1 expression levels in the bone marrow of 104 pediatric ALL patients and 18 normal control subjects were determined by using qRT-PCR. The association between the Bmi-1 expression and the clinicopathological characteristics of pediatric ALL patients was analyzed, and the correlation between Bmi-1 and the prognosis of pediatric ALL was calculated according to the Kaplan-Meier method. Furthermore, the association between Bmi-1 expression and its transcriptional regulator Sall4 was investigated.

RESULTS

Compared to normal control subjects, patients with primary pediatric ALL exhibited upregulated levels of Bmi-1. However, these levels were sharply decreased in patients who achieved complete remission. A significant positive association between elevated Bmi-1 levels and a poor response to prednisone as well as an increased clinical risk was observed. Patients who overexpressed Bmi-1 at the time of diagnosis had a lower relapse-free survival (RFS) rate (75.8%), whereas patients with lower Bmi-1 expression had an RFS of 94.1%. Furthermore, in ALL patients, the mRNA expression of Bmi-1 was positively correlated to the mRNA expression of Sall4a.

CONCLUSIONS

Taken together, these data suggest that Bmi-1 could serve as a novel prognostic biomarker in pediatric primary ALL and may be partially regulated by Sall4a. Our study also showed that Bmi-1 could serve as a new therapeutic target for the treatment of pediatric ALL.

MicroRNA-194 represses glioma cell epithelial‑to‑mesenchymal transition by targeting Bmi1

MicroRNA-194 (miR-194) is frequently dysregulated in many types of cancer. However, the function of miR-194 in glioma remains unknown. In the present study, we aimed to investigate the biological functions of miR-194 in glioma and the potential molecular mechanism of miR-194 involved in glioma progression. We found that miR-194 expression was significantly reduced in glioma specimens and cell lines, as detected by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The overexpression of miR-194 inhibited while the suppression of miR-194 promoted cell migration, invasion and epithelial mesenchymal transition (EMT) in glioma cells. Bioinformatics analysis showed that the B cell-specific moloney murine leukemia virus insertion site 1 (Bmi1) was a direct target of miR-194, which was validated by dual-luciferase reporter assay, RT-qPCR and western blot analysis. The restoration of Bmi1 expression significantly abrogated the suppressive effect of miR-194 on glioma cell EMT. Taken together, the present study suggests that miR-194 inhibits glioma cell EMT by targeting Bmi1 providing novel insights into understanding the pathogenesis of glioma. The restoration of miR-194 may be a potential therapeutic strategy for glioma treatment.

UbE2E1/UBCH6 Is a Critical in Vivo E2 for the PRC1-catalyzed Ubiquitination of H2A at Lys-119

UbE2E1/UbcH6 is an E2 ubiquitin-conjugating enzyme that is regulated by USP7. We identified UbE2E1 as a novel component of Polycomb repressive complex 1 (PRC1), the E3 ligase complex responsible for histone H2A ubiquitination and gene silencing. We demonstrate that UbE2E1 is critical for the monoubiquitination of H2A at residue Lys-119 (uH2AK119) through its association with the PRC1 complex. UbE2E1 interacts with PRC1 subunits including Ring1A and Ring1B. Overexpression of UbE2E1 results in increased levels of uH2AK119, whereas overexpression of catalytically inactive UbE2E1_C131A or UbE2E1 knockdown results in decreased levels of uH2AK119. The down-regulation of H2A ubiquitination by loss of function of UbE2E1 is correlated with alleviated p16^INK4a promoter repression and induced growth inhibition in HCT116 cells. These results are specific to UbE2E1 as knockdown of UbE2D E2s does not show any effect on uH2AK119. We extended the UbE2E1 regulation of uH2AK119 to USP7 and showed that USP7 is also a key regulator for monoubiquitination at H2A Lys-119 as both knockdown and deletion of USP7 results in decreased levels of uH2AK119. This study reveals that UbE2E1 is an in vivo E2 for the PRC1 ligase complex and thus plays an important role in the regulation of H2A Lys-119 monoubiquitination.

Human Corneal Endothelial Cells Expanded In Vitro Are a Powerful Resource for Tissue Engineering

Human corneal endothelial cells have two major functions: barrier function mediated by proteins such as ZO-1 and pump function mediated by Na-K-ATPase which help to maintain visual function. However, human corneal endothelial cells are notorious for their limited proliferative capability in vivo and are therefore prone to corneal endothelial dysfunction that eventually may lead to blindness. At present, the only method to cure corneal endothelial dysfunction is by transplantation of a cadaver donor cornea with normal corneal endothelial cells. Due to the global shortage of donor corneas, it is vital to engineer corneal tissue in vitro that could potentially be transplanted clinically. In this review, we summarize the advances in understanding the behavior of human corneal endothelial cells, their current engineering strategy in vitro and their potential applications.

Characterization and Prospective of Human Corneal Endothelial Progenitors

Corneal endothelial cells play a critical role in maintaining corneal transparency and dysfunction of these cells caused by aging, diseases (such as Fuch's dystrophy), injury or surgical trauma, which can lead to corneal edema and blindness. Due to their limited proliferative capacity in vivo, the only treatment method is via transplantation of a cadaver donor cornea. However, there is a severe global shortage of donor corneas. To circumvent such issues, tissue engineering of corneal tissue is a viable option thanks to the recent discoveries in this field. In this review, we summarize the recent advances in reprogramming adult human corneal endothelial cells into their progenitor status, the expansion methods and characteristics of human corneal endothelial progenitors, and their potential clinical applications as corneal endothelial cell grafts.

Targeting Stem Cells in Brain Tumors

Stem cells are commonly defined as undifferentiated cells capable of self-renewing and giving rise to a large number of differentiated progeny. It is becoming increasingly apparent that there exist cancer stem cells (CSCs) from which the cells of any given malignancy arise, whereby only a few cells out of a population of cancer cells are able to initiate tumor formation. These CSCs, like their normal counterparts, are characterized by self-renewal and the ability to “differentiate” into all of the cell types in the original tumor. Current chemotherapeutic strategies involve using non-specific cytotoxic agents that target rapidly cycling cells. Although this may reduce disease burden in many cases, these therapies may miss the rare, self-renewing population that truly gives rise to the malignancy (the CSC).

This review will focus on the recent discovery of stem cell-like cells in human brain tumors, putative “brain cancer stem cells,” which exhibit the properties of self-renewal and the ability to recapitulate the original tumor heterogeneity. Dissecting the molecular mechanisms that underlie the ability of these cells to self-renew and maintain quiescence may allow the development of novel therapeutic strategies that will allow for more efficacious and less toxic therapies for these devastating malignancies.

Compositional and functional diversity of canonical PRC1 complexes in mammals

The compositional complexity of Polycomb Repressive Complex 1 (PRC1) increased dramatically during vertebrate evolution. What is considered the "canonical" PRC1 complex consists of four subunits originally identified as regulators of body segmentation in Drosophila. In mammals, each of these four canonical subunits consists of two to six paralogs that associate in a combinatorial manner to produce over a hundred possible distinct PRC1 complexes with unknown function. Genetic studies have begun to define the phenotypic roles for different PRC1 paralogs; however, relating these phenotypes to unique biochemical and transcriptional function for the different paralogs has been challenging. In this review, we attempt to address how the compositional diversity of canonical PRC1 complexes relates to unique roles for individual PRC1 paralogs in transcriptional regulation. This review focuses primarily on PRC1 complex composition, genome targeting, and biochemical function.

An NAD+-dependent transcriptional program governs self-renewal and radiation resistance in glioblastoma

Accumulating evidence suggests cancer cells exhibit a dependency on metabolic pathways regulated by nicotinamide adenine dinucleotide (NAD⁺). Nevertheless, how the regulation of this metabolic cofactor interfaces with signal transduction networks remains poorly understood in glioblastoma. Here, we report nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting step in NAD⁺ synthesis, is highly expressed in glioblastoma tumors and patient-derived glioblastoma stem-like cells (GSCs). High NAMPT expression in tumors correlates with decreased patient survival. Pharmacological and genetic inhibition of NAMPT decreased NAD⁺ levels and GSC self-renewal capacity, and NAMPT knockdown inhibited the in vivo tumorigenicity of GSCs. Regulatory network analysis of RNA sequencing data using GSCs treated with NAMPT inhibitor identified transcription factor E2F2 as the center of a transcriptional hub in the NAD⁺-dependent network. Accordingly, we demonstrate E2F2 is required for GSC self-renewal. Downstream, E2F2 drives the transcription of members of the inhibitor of differentiation (ID) helix-loop-helix gene family. Finally, we find NAMPT mediates GSC radiation resistance. The identification of a NAMPT-E2F2-ID axis establishes a link between NAD⁺ metabolism and a self-renewal transcriptional program in glioblastoma, with therapeutic implications for this formidable cancer.

Combined Treatments with a Retinoid Receptor Agonist and Epigenetic Modulators in Human Neuroblastoma Cells

Neuroblastoma (NB) is the most common extracranial solid childhood tumor accounting for around 15% of pediatric cancer deaths and most probably originates from a failure in the development of embryonic neural crest cells. Retinoids can inhibit the proliferation and stimulate differentiation of NB cells. In addition, epigenetic events involving changes in chromatin structure and DNA methylation can mediate the effects of retinoids; hence, the scope of this study is to investigate the use of retinoids and epigenetic drugs in NB cell lines. Here, we demonstrate that the combination of retinoid all trans-retinoic acid (ATRA) with inhibitors of either histone deacetylases (HDACs) or DNA methyltransferase is more effective in impairing the proliferation of human SH-SY5Y and SK-N-BE(2) NB cells than any drug given alone. Treatments also induced differential changes on the messenger RNA (mRNA) expression of retinoid receptor subtypes and reduced the protein content of c-Myc, the neuronal markers NeuN and β-3 tubulin, and the oncoprotein Bmi1. These results suggest that the combination of retinoids with epigenetic modulators is more effective in reducing NB growth than treatment with single drugs.

Bmi1 Loss in the Organ of Corti Results in p16ink4a Upregulation and Reduced Cell Proliferation of Otic Progenitors In Vitro

The mature mammalian organ of Corti does not regenerate spontaneously after injury, mainly due to the absence of cell proliferation and the depletion of otic progenitors with age. The polycomb gene B lymphoma Mo-MLV insertion region 1 homolog (Bmi1) promotes proliferation and cell cycle progression in several stem cell populations. The cell cycle inhibitor p16^ink4a has been previously identified as a downstream target of Bmi1. In this study, we show that Bmi1 is expressed in the developing inner ear. In the organ of Corti, Bmi1 expression is temporally regulated during embryonic and postnatal development. In contrast, p16^ink4a expression is not detectable during the same period. Bmi1-deficient mice were used to investigate the role of Bmi1 in cochlear development and otosphere generation. In the absence of Bmi1, the postnatal organ of Corti displayed normal morphology at least until the end of the first postnatal week, suggesting that Bmi1 is not required for the embryonic or early postnatal development of the organ of Corti. However, Bmi1 loss resulted in the reduced sphere-forming capacity of the organ of Corti, accompanied by the decreased cell proliferation of otic progenitors in otosphere cultures. This reduced proliferative capacity was associated with the upregulation of p16^ink4ain vitro. Viral vector-mediated overexpression of p16^ink4a in wildtype otosphere cultures significantly reduced the number of generated otospheres in vitro. The findings strongly suggest a role for Bmi1 as a promoter of cell proliferation in otic progenitor cells, potentially through the repression of p16^ink4a.

Senescence Mediated by p16INK4a Impedes Reprogramming of Human Corneal Endothelial Cells into Neural Crest Progenitors

Human corneal endothelial cells (HCECs) have limited proliferative capacity due to “contact-inhibition” at G1 phase. Such contact-inhibition can be delayed from Day 21 to Day 42 by switching EGF-containing SHEM to LIF/bFGF-containing MESCM through transient activation of LIF-JAK1-STAT3 signaling that delays eventual nuclear translocation of p16^INK4a. Using the latter system, we have reported a novel tissue engineering technique by implementing 5 weekly knockdowns with p120 catenin (p120) and Kaiso siRNAs since Day 7 to achieve effective expansion of HCEC monolayers to a transplantable size with a normal HCEC density, through reprogramming of HCECs into neural crest progenitors by activating p120-Kaiso-RhoA-ROCK-canonical BMP signaling. Herein, we noted that a single knockdown with p120-Kaiso siRNAs at Day 42 failed to achieve such reprogramming when contact inhibition transitioned to senescence with nuclear translocation of p16^INK4a. In contrast, 5 weekly knockdowns with p120-Kaiso siRNAs since Day 7 precluded senescence mediated by p16^INK4a by inducing nuclear translocation of Bmi1 because of sustained activation of JAK2-STAT3 signaling downstream of p120-Kaiso-RhoA-ROCK signaling. STAT3 or Bmi1 siRNA impeded nuclear exclusion of p16^INK4a and suppressed the reprogramming induced by p120-Kaiso siRNAs, suggesting that another important engineering strategy of HCEC lies in prevention of senescence mediated by nuclear translocation of p16^INK4a.

miR-27b shapes the presynaptic transcriptome and influences neurotransmission by silencing the polycomb group protein Bmi1

Background

MicroRNAs (miRNAs) are short non-coding RNAs that are emerging as important post-transcriptional regulators of neuronal and synaptic development. The precise impact of miRNAs on presynaptic function and neurotransmission remains, however, poorly understood.

Results

Here, we identify miR-27b—an abundant neuronal miRNA implicated in neurological disorders—as a global regulator of the presynaptic transcriptome. miR-27b influences the expression of three quarters of genes associated with presynaptic function in cortical neurons. Contrary to expectation, a large majority of these genes are up-regulated by miR-27b. This stimulatory effect is mediated by miR-27b-directed silencing of several transcriptional repressors that cooperate to suppress the presynaptic transcriptome. The strongest repressive activity appears to be mediated by Bmi1, a component of the polycomb repressive complex implicated in self-renewal of neural stem cells. miR-27b knockdown leads to reduced synaptogenesis and to a marked decrease in neural network activity, which is fully restored by RNAi-mediated silencing of Bmi1.

Conclusions

We conclude that silencing of Bmi1 by miR-27b relieves repression of the presynaptic transcriptome and supports neurotransmission in cortical networks. These results expand the repressive activity of Bmi1 to genes involved in synaptic function and identify a unique post-transcriptional circuitry that stimulates expression of synaptic genes and promotes synapse differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3139-7) contains supplementary material, which is available to authorized users.

Bmi-1 promotes the invasion and migration of colon cancer stem cells through the downregulation of E-cadherin

Metastasis and recurrence are the challenges of cancer therapy. Recently, mounting evidence has suggested that cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) are critical factors in tumor metastasis and recurrence. The oncogene, Bmi-1, promotes the development of hematologic malignancies and many solid tumors. The aim of the present study was to elucidate the mechanisms through which Bmi-1 promotes the invasion and migration of colon CSCs (CCSCs) using the HCT116 colon cancer cell line. Sphere formation medium and magnetic‑activated cell sorting were used to enrich and screen the CCSCs. CD133 and CD44 were regarded as markers of CCSCs and they were found to be co-expressed in the HCT116 colon cancer cell line. Colony formation assay, cell proliferation assay and viability assay using the Cell Counting Kit-8, and transplantation assay using nude mice injected with CCSCs were used to examine the CCSCs. The CD133+CD44+ HCT116 cells exhibited greater cloning efficiency, an enhanced proliferative ability, increased cell viability and stronger tumorigenicity; these cells were used as the CCSCs for subsequent experiments. In addition, the invasive and migratory abilities of the CD133+CD44+ HCT116 cells were markedly decreased when Bmi-1 was silenced by small interfering RNA (siRNA). The results of RT-qPCR and western blot analysis suggested that Bmi-1 had a negative effect on E-cadherin expression. On the whole, our findings suggest that Bmi-1 promotes the invasion and migration of CCSCs through the downregulation of E-cadherin, possibly by inducing EMT. Our findings thus indicate that Bmi-1 may be a novel therapeutic target for the treatment of colon cancer.

The EMT transcription factor Zeb2 controls adult murine hematopoietic differentiation by regulating cytokine signaling

Epithelial-to-mesenchymal-transition (EMT) is critical for normal embryogenesis and effective postnatal wound healing, but is also associated with cancer metastasis. SNAIL, ZEB, and TWIST families of transcription factors are key modulators of the EMT process, but their precise roles in adult hematopoietic development and homeostasis remain unclear. Here we report that genetic inactivation of Zeb2 results in increased frequency of stem and progenitor subpopulations within the bone marrow (BM) and spleen and that these changes accompany differentiation defects in multiple hematopoietic cell lineages. We found no evidence that Zeb2 is critical for hematopoietic stem cell self-renewal capacity. However, knocking out Zeb2 in the BM promoted a phenotype with several features that resemble human myeloproliferative disorders, such as BM fibrosis, splenomegaly, and extramedullary hematopoiesis. Global gene expression and intracellular signal transduction analysis revealed perturbations in specific cytokine and cytokine receptor-related signaling pathways following Zeb2 loss, especially the JAK-STAT and extracellular signal-regulated kinase pathways. Moreover, we detected some previously unknown mutations within the human Zeb2 gene (ZFX1B locus) from patients with myeloid disease. Collectively, our results demonstrate that Zeb2 controls adult hematopoietic differentiation and lineage fidelity through widespread modulation of dominant signaling pathways that may contribute to blood disorders.

Role of IGF1R(+) MSCs in modulating neuroplasticity via CXCR4 cross-interaction

To guide the use of human mesenchymal stem cells (MSCs) toward clinical applications, identifying pluripotent-like-markers for selecting MSCs that retain potent self-renewal-ability should be addressed. Here, an insulin-like growth factor 1 receptor (IGF1R)–expressing sub-population in human dental pulp MSCs (hDSCs), displayed multipotent properties. IGF1R expression could be maintained in hDSCs when they were cultured in 2% human cord blood serum (hUCS) in contrast to that in 10% fetal calf serum (FCS). Cytokine array showed that hUCS contained higher amount of several growth factors compared to FCS, including IGF-1 and platelet-derived growth factor (PDGF-BB). These cytokines modulates the signaling events in the hDSCs and potentially enhances engraftment upon transplantation. Specifically, a bidirectional cross-talk between IGF1R/IGF1 and CXCR4/SDF-1α signaling pathways in hDSCs, as revealed by interaction of the two receptors and synergistic activation of both signaling pathways. In rat stroke model, animals receiving IGF1R⁺ hDSCs transplantation, interaction between IGF1R and CXCR4 was demonstrated to promote neuroplasticity, therefore improving neurological function through increasing glucose metabolic activity, enhancing angiogenesis and anti-inflammatiory effects. Therefore, PDGF in hUCS-culture system contributed to the maintenance of the expression of IGF1R in hDSCs. Furthermore, implantation of IGF1R⁺ hDSCs exerted enhanced neuroplasticity via integrating inputs from both CXCR4 and IGF1R signaling pathways.

Bmi1 (+) cardiac progenitor cells contribute to myocardial repair following acute injury

Background

The inability of the adult mammalian heart to replace cells lost after severe cardiac injury compromises organ function. Although the heart is one of the least regenerative organs in the body, evidence accumulated in recent decades indicates a certain degree of renewal after injury. We have evaluated the role of cardiac Bmi1⁺ progenitor cells (Bmi1-CPC) following acute myocardial infarction (AMI).

Methods

Bmi1^Cre/+;Rosa26^YFP/+ (Bmi1-YFP) mice were used for lineage tracing strategy. After tamoxifen (TM) induction, yellow fluorescent protein (YFP) is expressed under the control of Rosa26 regulatory sequences in Bmi1⁺ cells. YFP⁺ cells were tracked following myocardial infarction. Additionally, whole transcriptome analysis of isolated YFP⁺ cells was performed in unchallenged hearts and after myocardial infarction.

Results

Deep-sequencing analysis of Bmi1-CPC from unchallenged hearts suggests that this population expresses high levels of pluripotency markers. Conversely, transcriptome evaluation of Bmi1-CPC following AMI shows a rich representation of genes related to cell proliferation, movement, and cell cycle. Lineage-tracing studies after cardiac infarction show that the progeny of Bmi1-expressing cells contribute to de novo cardiomyocytes (CM) (13.8 ± 5 % new YFP⁺ CM compared to 4.7 ± 0.9 % in age-paired non-infarcted hearts). However, apical resection of TM-induced day 1 Bmi1-YFP pups indicated a very minor contribution of Bmi1-derived cells to de novo CM.

Conclusions

Cardiac Bmi1 progenitor cells respond to cardiac injury, contributing to the generation of de novo CM in the adult mouse heart.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0355-7) contains supplementary material, which is available to authorized users.

Control of stress signaling in stem cells: crossroads of stem cells and cancer

Tumorigenesis is a relatively rare event in the human body considering the enormous number of cells composing our body and the frequent occurrence of genetic mutations in each cell. Nevertheless, the cells that happen to meet the minimum requirements can be transformed when stressed by a variety of oncogenic stimulations, then progress to form tumors. The vigorous competition between oncogenic signaling and tumor-suppressor defense is a critical determinant of cellular fate, which can be either tumorigenic transformation or cellular senescence/apoptosis depending on "who wins the battle." Recently, a number of cancers have been reported to originate from stem cells, whose self-renewing properties are normally reduced by innate tumor suppressors. Therefore, exploring the innate mechanism by which stem cells modulate tumor suppressors to maintain their "stemness" may provide valuable clues to characterize the distinctive oncogenic susceptibility of stem cells. This review is focused on the recent advances in the field of tumorigenesis of stem cells and on the associated molecular mechanisms.

Nuclear receptor NR5A2 controls neural stem cell fate decisions during development

The enormous complexity of mammalian central nervous system (CNS) is generated by highly synchronized actions of diverse factors and signalling molecules in neural stem/progenitor cells (NSCs). However, the molecular mechanisms that integrate extrinsic and intrinsic signals to control proliferation versus differentiation decisions of NSCs are not well-understood. Here we identify nuclear receptor NR5A2 as a central node in these regulatory networks and key player in neural development. Overexpression and loss-of-function experiments in primary NSCs and mouse embryos suggest that NR5A2 synchronizes cell-cycle exit with induction of neurogenesis and inhibition of astrogliogenesis by direct regulatory effects on Ink4/Arf locus, Prox1, a downstream target of proneural genes, as well as Notch1 and JAK/STAT signalling pathways. Upstream of NR5a2, proneural genes, as well as Notch1 and JAK/STAT pathways control NR5a2 endogenous expression. Collectively, these observations render NR5A2 a critical regulator of neural development and target gene for NSC-based treatments of CNS-related diseases.

The molecular signals regulating the decision of neural stem cells (NSC) to proliferate versus differentiate are unclear. Here, the authors identify the nuclear receptor NR5A2 as coordinating cell-cycle exit with differentiation of NSCs via direct actions on Ink4, Prox1, Notch1 and JAK/STAT.

The Polycomb Group Protein Pcgf1 Is Dispensable in Zebrafish but Involved in Early Growth and Aging

Polycomb Repressive Complex (PRC) 1 regulates the control of gene expression programs via chromatin structure reorganization. Through mutual exclusion, different PCGF members generate a variety of PRC1 complexes with potentially distinct cellular functions. In this context, the molecular function of each of the PCGF family members remains elusive. The study of PCGF family member expression in zebrafish development and during caudal fin regeneration reveals that the zebrafish pcgf genes are subjected to different regulations and that all PRC1 complexes in terms of Pcgf subunit composition are not always present in the same tissues. To unveil the function of Pcgf1 in zebrafish, a mutant line was generated using the TALEN technology. Mutant pcgf1^-/- fish are viable and fertile, but the growth rate at early developmental stages is reduced in absence of pcgf1 gene function and a significant number of pcgf1^-/- fish show signs of premature aging. This first vertebrate model lacking Pcgf1 function shows that this Polycomb Group protein is involved in cell proliferation during early embryogenesis and establishes a link between epigenetics and aging.

Role of Geminin in cell fate determination of hematopoietic stem cells (HSCs)

Geminin exerts two distinct molecular roles. Geminin negatively regulates DNA replication licensing through the direct interaction with Cdt1 to prevent re-replication in proliferating cells. Geminin also regulates chromatin remodeling through the direct interaction with Brahma/Brg1 to maintain undifferentiated states of stem cells. We previously uncovered that Polycomb-group complex 1 and Hoxb4/Hoxa9, well-known intrinsic factors that are essential for maintaining the hematopoietic stem cell (HSC) activity, alternatively act as ubiquitin-proteasome systems for Geminin protein to reduce the protein expression level, and sustain the HSC activity. Thus, Geminin is presumed to play an important role in determining cell fate, i.e., turning on and off cellular quiescence and proliferation/differentiation, in HSCs. We recently generated recombinant cell-penetrating Geminin (CP-Geminin), enabling rapid incorporation and withdraw of Geminin protein in cells. CP-Geminin may be useful in regulating the cell cycle and chromatin configuration. In this article, we summarize current information on the molecular functions of Geminin and the regulatory system for Geminin protein expression, and argue for the molecular role of Geminin in cell fate determination of HSCs, and future perspective of a new technology for manipulating the activities of HSCs and cancer stem cells (CSCs).

Overexpression of Bmi1 in Lymphocytes Stimulates Skeletogenesis by Improving the Osteogenic Microenvironment

To investigate whether overexpression of Bmi1 in lymphocytes can stimulate skeletogenesis by improving the osteogenic microenvironment, we examined the skeletal phenotype of EμBmi1 transgenic mice with overexpression of Bmi1 in lymphocytes. The size of the skeleton, trabecular bone volume and osteoblast number, indices of proliferation and differentiation of bone marrow mesenchymal stem cells (BM-MSCs) were increased significantly, ROS levels were reduced and antioxidative capacity was enhanced in EμBmi1 mice compared to WT mice. In PTHrP1-84 knockin (Pthrp(KI/KI)) mice, the expression levels of Bmi1 are reduced and potentially can mediate the premature osteoporosis observed. We therefore generated a Pthrp(KI/KI) mice overexpressing Bmi1 in lymphocytes and compared them with Pthrp(KI/KI) and WT littermates. Overexpression of Bmi1 in Pthrp(KI/KI) mice resulted in a longer lifespan, increased body weight and improvement in skeletal growth and parameters of osteoblastic bone formation with reduced ROS levels and DNA damage response parameters. Our results demonstrate that overexpression of Bmi1 in lymphocytes can stimulate osteogenesis in vivo and partially rescue defects in skeletal growth and osteogenesis in Pthrp(KI/KI) mice. These studies therefore indicate that overexpression of Bmi1 in lymphocytes can stimulate skeletogenesis by inhibiting oxidative stress and improving the osteogenic microenvironment.

REAC technology and hyaluron synthase 2, an interesting network to slow down stem cell senescence

Hyaluronic acid (HA) plays a fundamental role in cell polarity and hydrodynamic processes, affording significant modulation of proliferation, migration, morphogenesis and senescence, with deep implication in the ability of stem cells to execute their differentiating plans. The Radio Electric Asymmetric Conveyer (REAC) technology is aimed to optimize the ions fluxes at the molecular level in order to optimize the molecular mechanisms driving cellular asymmetry and polarization. Here, we show that treatment with 4-methylumbelliferone (4-MU), a potent repressor of type 2 HA synthase and endogenous HA synthesis, dramatically antagonized the ability of REAC to recover the gene and protein expression of Bmi1, Oct4, Sox2, and Nanog in ADhMSCs that had been made senescent by prolonged culture up to the 30^th passage. In senescent ADhMSCs, 4-MU also counteracted the REAC ability to rescue the gene expression of TERT, and the associated resumption of telomerase activity. Hence, the anti-senescence action of REAC is largely dependent upon the availability of endogenous HA synthesis. Endogenous HA and HA-binding proteins with REAC technology create an interesting network that acts on the modulation of cell polarity and intracellular environment. This suggests that REAC technology is effective on an intracellular niche level of stem cell regulation.

Concise Review: Stem Cells and Epithelial-Mesenchymal Transition in Cancer: Biological Implications and Therapeutic Targets

Cancer stem cells (CSCs) constitute a small subpopulation of cancer cells with stem-like properties that are able to self-renew, generate differentiated daughter cells, and give rise to heterogeneous tumor tissue. Tumor heterogeneity is a hallmark of cancer and underlies resistance to anticancer therapies and disease progression. The epithelial-mesenchymal transition (EMT) is a reversible phenomenon that is mediated by EMT-inducing transcription factors (EMT-TFs) and plays an important role in normal organ development, wound healing, and the invasiveness of cancer cells. Recent evidence showing that overexpression of several EMT-TFs is associated with stemness in cancer cells has suggested the existence of a link between EMT and CSCs. In this review, we focus on the roles of CSCs and EMT signaling in driving tumor heterogeneity. A better understanding of the dynamics of both CSCs and EMT-TFs in the generation of tumor heterogeneity may provide a basis for the development of new treatment options for cancer patients. Stem Cells 2016;34:1997-2007.

Adult Mammalian Neural Stem Cells and Neurogenesis: Five Decades Later

Adult somatic stem cells in various organs maintain homeostatic tissue regeneration and enhance plasticity. Since its initial discovery five decades ago, investigations of adult neurogenesis and neural stem cells have led to an established and expanding field that has significantly influenced many facets of neuroscience, developmental biology, and regenerative medicine. Here we review recent progress and focus on questions related to adult mammalian neural stem cells that also apply to other somatic stem cells. We further discuss emerging topics that are guiding the field toward better understanding adult neural stem cells and ultimately applying these principles to improve human health.

Genetics and Epigenetics in Adult Neurogenesis

The cellular basis of adult neurogenesis is neural stem cells residing in restricted areas of the adult brain. These cells self-renew and are multipotent. The maintenance of "stemness" and commitment to differentiation are tightly controlled by intricate molecular networks. Epigenetic mechanisms, including chromatin remodeling, DNA methylation, and noncoding RNAs (ncRNAs), have profound regulatory roles in mammalian gene expression. Significant advances have been made regarding the dynamic roles of epigenetic modulation and function. It has become evident that epigenetic regulators are key players in neural-stem-cell self-renewal, fate specification, and final maturation of new neurons, therefore, adult neurogenesis. Altered epigenetic regulation can result in a number of neurological and neurodevelopmental disorders. Here, we review recent discoveries that advance our knowledge in epigenetic regulation of mammalian neural stem cells and neurogenesis. Insights from studies of epigenetic gene regulation in neurogenesis may lead to new therapies for the treatment of neurodevelopmental disorders.

Polycomb Protein BMI1 Regulates Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells Downstream of GSK3

Polycomb proteins such as the B lymphoma Mo-MLV insertion region 1 homolog (BMI1) are essential chromatin factors for the self-renewal and differentiation of embryonic and adult stem cells. BMI1 also plays a critical role in osteogenesis as Bmi1-deficient mice display a skeletal phenotype caused by the exhaustion of the mesenchymal stem cell pool. In this study, we have studied the role of BMI1 in the osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hASCs). BMI1 protein, but not RNA levels, increases during in vitro osteogenic differentiation of hASCs. Overexpression of BMI1 leads to an osteogenic priming of hASCs under nondifferentiating conditions and enhanced osteogenesis upon differentiation, along with increased BMP2 and WNT11 expressions. Conversely, knockdown of BMI1 expression reduces osteogenic differentiation. Furthermore, our studies indicate that during osteogenic differentiation of hASCs, BMI1 is a downstream target of GSK3 signaling. BMI1, therefore, acts as a pro-osteogenic differentiation factor in hASCs and hence it is a promising target for active modulation of hASC-derived osteogenesis.

Hepatocellular carcinoma: thyroid hormone promotes tumorigenicity through inducing cancer stem-like cell self-renewal

Cancer stem-like cells (CSCs) play a key role in maintaining the aggressiveness of hepatocellular carcinoma (HCC), but the cell-biological regulation of CSCs is unclear. In the study, we report that thyroid hormone (TH) promotes cell self-renewal in HCC cells. TH also increases the percentage of CD90 + HCC cells and promotes drug resistance of HCC cells. By analyzing primary human HCC samples, we found that TRα transcript level is significantly elevated in primary liver cancer and portal vein metastatic tumor, compared to that of adjacent normal liver tissue. Knocking down TRα not only inhibits HCC self-renewal in vitro but also suppresses HCC tumor growth in vivo. Interestingly, treatment of TH leads to activation of NF-κB, which is required for the function of TH on inducing HCC cell self-renewal. We also found TRα and p65 cooperatively drive the expression of BMI1 by co-binding to the promoter region of BMI1 gene. In summary, our study uncovers a novel function of TH signaling in regulating the CSCs of HCC, and these findings might be useful for developing novel therapies by targeting TH function in HCC cells.

Cross-species Analyses Unravel the Complexity of H3K27me3 and H4K20me3 in the Context of Neural Stem Progenitor Cells

Neural stem progenitor cells (NSPCs) in the human subventricular zone (SVZ) potentially contribute to life-long neurogenesis, yet subtypes of glioblastoma multiforme (GBM) contain NSPC signatures that highlight the importance of cell fate regulation. Among numerous regulatory mechanisms, the post-translational methylations onto histone tails are crucial regulator of cell fate. The work presented here focuses on the role of two repressive chromatin marks tri-methylations on histone H3 lysine 27 (H3K27me3) and histone H4 lysine 20 (H4K20me3) in the adult NSPC within the SVZ. To best model healthy human NSPCs as they exist in vivo for epigenetic profiling of H3K27me3 and H4K20me3, we utilized NSPCs isolated from the adult SVZ of baboon brain (Papio anubis) with brain structure and genomic level similar to human. The putative role of H3K27me3 in normal NSPCs predominantly falls into the regulation of gene expression, cell cycle, and differentiation, whereas H4K20me3 is involved in DNA replication/repair, metabolism, and cell cycle. Using conditional knock-out mouse models to diminish Ezh2 and Suv4-20h responsible for H3K27me3 and H4K20me3, respectively, we found that both repressive marks have irrefutable function for cell cycle regulation in the NSPC population. While both EZH2/H3K27me3 and Suv4-20h/H4K20me3 have implication in cancers, our comparative genomics approach between healthy NSPCs and human GBM specimens revealed that substantial sets of genes enriched with H3K27me3 and H4K20me3 in the NSPCs are altered in the human GBM. In sum, our integrated analyses across species highlight important roles of H3K27me3 and H4K20me3 in normal and disease conditions in the context of NSPC.

The Adult Ventricular-Subventricular Zone (V-SVZ) and Olfactory Bulb (OB) Neurogenesis

A large population of neural stem/precursor cells (NSCs) persists in the ventricular-subventricular zone (V-SVZ) located in the walls of the lateral brain ventricles. V-SVZ NSCs produce large numbers of neuroblasts that migrate a long distance into the olfactory bulb (OB) where they differentiate into local circuit interneurons. Here, we review a broad range of discoveries that have emerged from studies of postnatal V-SVZ neurogenesis: the identification of NSCs as a subpopulation of astroglial cells, the neurogenic lineage, new mechanisms of neuronal migration, and molecular regulators of precursor cell proliferation and migration. It has also become evident that V-SVZ NSCs are regionally heterogeneous, with NSCs located in different regions of the ventricle wall generating distinct OB interneuron subtypes. Insights into the developmental origins and molecular mechanisms that underlie the regional specification of V-SVZ NSCs have also begun to emerge. Other recent studies have revealed new cell-intrinsic molecular mechanisms that enable lifelong neurogenesis in the V-SVZ. Finally, we discuss intriguing differences between the rodent V-SVZ and the corresponding human brain region. The rapidly expanding cellular and molecular knowledge of V-SVZ NSC biology provides key insights into postnatal neural development, the origin of brain tumors, and may inform the development regenerative therapies from cultured and endogenous human neural precursors.

From discovery to approval of an advanced therapy medicinal product-containing stem cells, in the EU

In 1997, the human corneal epithelium was reconstructed in vitro and transplanted on patients. Later, it became a routine treatment, before regulations considered advanced therapy medicinal products and drugs on the same lines. Manufacturing, before and after good manufacturing practice setting, was established in different facilities and the clinical application in several hospitals. Advanced therapy medicinal products, including stem cells, are unique products with different challenges than other drugs: some uncertainties, in addition to benefit, cannot be avoided. This review will focus on all recent developments in the stem cell-based corneal therapy.

CDKN2A-independent role of BMI1 in promoting growth and survival of Ph+ acute lymphoblastic leukemia

BMI1 is a key component of the PRC1 complex (polycomb repressive complex-1) required for maintenance of normal and cancer stem cells. Its aberrant expression is detected in chronic myeloid leukemia and Ph+ acute lymphoblastic leukemia (ALL), but no data exist on BMI1 requirement in ALL cells.

We show here that BMI1 expression is important for proliferation and survival of Ph+ ALL cells and for leukemogenesis of Ph+ cells in vivo.

Levels of BIM, interferon-α (IFNα)-regulated genes, and E2F7 were upregulated in BMI1-silenced cells, suggesting that repressing their expression is important for BMI1 biological effects. Consistent with this hypothesis, we found that: i) downregulation of BIM or E2F7 abrogated apoptosis or rescued, in part, the reduced proliferation and colony formation of BMI1 silenced BV173 cells; ii) BIM/E2F7-double silencing further enhanced colony formation and in vivo leukemogenesis of BMI1-silenced cells; iii) overexpression of BIM and E2F7 mimicked the effect of BMI1 silencing in BV173 and SUP-B15 cells and iv) treatment with IFNα suppressed proliferation and colony formation of Ph+ ALL cells.

These studies indicate that the growth-promoting effects of BMI1 in Ph+ ALL cells depend on suppression of multiple pathways and support the use of IFNα in the therapy of Ph+ ALL.

The evolutionary landscape of PRC1 core components in green lineage

The origin and evolution of plant PRC1 core components. Polycomb repressive complex1 (PRC1) plays critical roles in epigenetic silencing of homeotic genes and determination of cell fate. Animal PRC1 has been well investigated for a long time, whereas plant PRC1 was just confirmed in recent years. It is enigmatic whether PRC1 core components in plants share a common ancestor with those in animals. We evaluated the origin of plant PRC1 RING-finger proteins (RING1 and BMI1) through comparing with the homologs in some representative unikonts and using BMI1- and RING1-like proteins as reciprocal outgroup, finding both PRC1 RING-finger proteins have the earliest origin in mosses, similar to LHP1. Additionally, the gene structure, copy number, and domain organization were analyzed to deeply understand the evolutionary history of plant PRC1 complex. In conclusion, PRC1 RING-finger proteins have independent origins in plants and animals, but convergent evolution might attribute to the conservation of PRC1 complex in plants and animals. Plant LHP1 as the homolog of non-PRC1 protein HP1 was recruited to fulfill the role of Pc counterpart. Gene duplication followed by functional divergence makes a great contribution to evolutionary progress of PRC1 in green plants.

Senescence-Associated MCP-1 Secretion Is Dependent on a Decline in BMI1 in Human Mesenchymal Stromal Cells

AIMS

Cellular senescence and its secretory phenotype (senescence-associated secretory phenotype [SASP]) develop after long-term expansion of mesenchymal stromal cells (MSCs). Further investigation of this phenotype is required to improve the therapeutic efficacy of MSC-based cell therapies. In this study, we show that positive feedback between SASP and inherent senescence processes plays a crucial role in the senescence of umbilical cord blood-derived MSCs (UCB-MSCs).

RESULTS

We found that monocyte chemoattractant protein-1 (MCP-1) was secreted as a dominant component of the SASP during expansion of UCB-MSCs and reinforced senescence via its cognate receptor chemokine (c-c motif) receptor 2 (CCR2) by activating the ROS-p38-MAPK-p53/p21 signaling cascade in both an autocrine and paracrine manner. The activated p53 in turn increased MCP-1 secretion, completing a feed-forward loop that triggered the senescence program in UCB-MSCs. Accordingly, knockdown of CCR2 in UCB-MSCs significantly improved their therapeutic ability to alleviate airway inflammation in an experimental allergic asthma model. Moreover, BMI1, a polycomb protein, repressed the expression of MCP-1 by binding to its regulatory elements. The reduction in BMI1 levels during UCB-MSC senescence altered the epigenetic status of MCP-1, including the loss of H2AK119Ub, and resulted in derepression of MCP-1.

INNOVATION

Our results provide the first evidence supporting the existence of the SASP as a causative contributor to UCB-MSC senescence and reveal a so far unappreciated link between epigenetic regulation and SASP for maintaining a stable senescent phenotype.

CONCLUSION

Senescence of UCB-MSCs is orchestrated by MCP-1, which is secreted as a major component of the SASP and is epigenetically regulated by BMI1.

Lens regeneration using endogenous stem cells with gain of visual function

The repair and regeneration of tissues using endogenous stem cells represents an ultimate goal in regenerative medicine. To our knowledge, human lens regeneration has not yet been demonstrated. Currently, the only treatment for cataracts, the leading cause of blindness worldwide, is to extract the cataractous lens and implant an artificial intraocular lens. However, this procedure poses notable risks of complications. Here we isolate lens epithelial stem/progenitor cells (LECs) in mammals and show that Pax6 and Bmi1 are required for LEC renewal. We design a surgical method of cataract removal that preserves endogenous LECs and achieves functional lens regeneration in rabbits and macaques, as well as in human infants with cataracts. Our method differs conceptually from current practice, as it preserves endogenous LECs and their natural environment maximally, and regenerates lenses with visual function. Our approach demonstrates a novel treatment strategy for cataracts and provides a new paradigm for tissue regeneration using endogenous stem cells.

miR-203 inhibits cell proliferation and promotes cisplatin induced cell death in tongue squamous cancer

Oral squamous cell carcinoma (OSCC) is one of the most common types of the head and neck cancer. Chemo resistance of OSCC has been identified as a substantial therapeutic hurdle. In this study, we analyzed the role of miR-203 in the OSCC and its effects on cisplatin-induced cell death in an OSCC cell line, Tca8113. There was a significant decrease of miR-203 expression in OSCC samples, compared with the adjacent normal, non-cancerous tissue. After 3 days cisplatin treatment, the survived Tca8113 cells had a lower expression of miR-203 than that in the untreated control group. In contrast, PIK3CA showed an inverse expression in cancer and cisplatin survived Tca8113 cells. Transfection of Tca8113 cells with miR-203 mimics greatly reduced PIK3CA expression and Akt activation. Furthermore, miR-203 repressed PIK3CA expression through targeting the 3'UTR. Restoration of miR-203 not only suppressed cell proliferation, but also sensitized cells to cisplatin induced cell apoptosis. This effect was absent in cells that were simultaneously treated with PIK3CA RNAi. In summary, these findings suggest miR-203 plays an important role in cisplatin resistance in OSCC, and furthermore delivery of miR-203 analogs may serve as an adjuvant therapy for OSCC.

Downregulation of Melanoma Cell Adhesion Molecule (MCAM/CD146) Accelerates Cellular Senescence in Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells

Therapeutic applications of mesenchymal stem cells (MSCs) for treating various diseases have increased in recent years. To ensure that treatment is effective, an adequate MSC dosage should be determined before these cells are used for therapeutic purposes. To obtain a sufficient number of cells for therapeutic applications, MSCs must be expanded in long-term cell culture, which inevitably triggers cellular senescence. In this study, we investigated the surface markers of human umbilical cord blood-derived MSCs (hUCB-MSCs) associated with cellular senescence using fluorescence-activated cell sorting analysis and 242 cell surface-marker antibodies. Among these surface proteins, we selected the melanoma cell adhesion molecule (MCAM/CD146) for further study with the aim of validating observed expression differences and investigating the associated implications in hUCB-MSCs during cellular senescence. We observed that CD146 expression markedly decreased in hUCB-MSCs following prolonged in vitro expansion. Using preparative sorting, we found that hUCB-MSCs with high CD146 expression displayed high growth rates, multilineage differentiation, expression of stemness markers, and telomerase activity, as well as significantly lower expression of the senescence markers p16, p21, p53, and senescence-associated β-galactosidase, compared with that observed in hUCB-MSCs with low-level CD146 expression. In contrast, CD146 downregulation with small interfering RNAs enhanced the senescence phenotype. In addition, CD146 suppression in hUCB-MSCs caused downregulation of other cellular senescence regulators, including Bmi-1, Id1, and Twist1. Collectively, our results suggest that CD146 regulates cellular senescence; thus, it could be used as a therapeutic marker to identify senescent hUCB-MSCs.

SIGNIFICANCE

One of the fundamental requirements for mesenchymal stem cell (MSC)-based therapies is the expansion of MSCs during long-term culture because a sufficient number of functional cells is required. However, long-term growth inevitably induces cellular senescence, which potentially causes poor clinical outcomes by inducing growth arrest and the loss of stem cell properties. Thus, the identification of markers for evaluating the status of MSC senescence during long-term culture may enhance the success of MSC-based therapy. This study provides strong evidence that CD146 is a novel and useful marker for predicting senescence in human umbilical cord blood-derived MSCs (hUCB-MSCs), and CD146 can potentially be applied in quality-control assessments of hUCB-MSC-based therapy.

Dysregulation of Bmi1 promotes malignant transformation of hepatic progenitor cells

Adult hepatic progenitor cells (HPCs) are involved in a wide range of human liver diseases, including hepatocellular carcinoma (HCC). Bmi1 has been reported to have vital roles in stem cell self-renewal and carcinogenesis. We have previously demonstrated that Bmi1 is upregulated in HCC with bile duct tumor thrombi, a subtype of HCC characterized by profuse expression of hepatic stem cell markers. However, the function of Bmi1 in HPCs has not yet been well elucidated. The current study was designed to investigate the effects of Bmi1 on the biological properties of rat HPCs. To accomplish this, Bmi1 was silenced or enhanced in two HPC cell lines (WB-F344 and OC3) by, respectively, using either small interfering RNA against Bmi1 or a forced Bmi1 expression retroviral vector. The biological functions of Bmi1 in HPCs were investigated through cell proliferation assays, colony-formation assays, cell cycle analysis and invasion assays, as well as through xenograft-formation assays. In this study, genetic depletion of Bmi1 repressed cell proliferation, colony formation and invasion in both assessed HPC cell lines relative to controls. Conversely, forced expression of Bmi1 in two HPCs cell lines promoted cell proliferation, colony formation and invasion in vitro. Aldehyde dehydrogenase (ALDH) assay revealed a significant increase in the number of ALDH-positive cells following the forced expression of Bmi1 in HPCs. Most importantly, transplantation of forced Bmi1 expression HPCs into nude mice resulted in the formation of tumors with histological features of poorly differentiated HCC. Taken together, our findings indicate that forced expression of Bmi1 promotes the malignant transformation of HPCs, suggesting Bmi1 might be a potential molecular target for the treatment of HCC.

Bmi1 Regulates the Proliferation of Cochlear Supporting Cells Via the Canonical Wnt Signaling Pathway

Cochlear supporting cells (SCs), which include the cochlear progenitor cells, have been shown to be a promising resource for hair cell (HC) regeneration, but the mechanisms underlying the initiation and regulation of postnatal cochlear SC proliferation are not yet fully understood. Bmi1 is a member of the Polycomb protein family and has been reported to regulate the proliferation of stem cells and progenitor cells in multiple organs. In this study, we investigated the role of Bmi1 in regulating SC and progenitor cell proliferation in neonatal mice cochleae. We first showed that knockout of Bmi1 significantly inhibited the proliferation of SCs and Lgr5-positive progenitor cells after neomycin injury in neonatal mice in vitro, and we then showed that Bmi1 deficiency significantly reduced the sphere-forming ability of the organ of Corti and Lgr5-positive progenitor cells in neonatal mice. These results suggested that Bmi1 is required for the initiation of SC and progenitor cell proliferation in neonatal mice. Next, we found that DKK1 expression was significantly upregulated, while beta-catenin and Lgr5 expression were significantly downregulated in neonatal Bmi1^-/- mice compared to wild-type controls. The observation that Bmi1 knockout downregulates Wnt signaling provides compelling evidence that Bmi1 is required for the Wnt signaling pathway. Furthermore, the exogenous Wnt agonist BIO overcame the downregulation of SC proliferation in Bmi1^-/- mice, suggesting that Bmi1 knockout might inhibit the proliferation of SCs via downregulation of the canonical Wnt signaling pathway. Our findings demonstrate that Bmi1 plays an important role in regulating the proliferation of cochlear SCs and Lgr5-positive progenitor cells in neonatal mice through the Wnt signaling pathway, and this suggests that Bmi1 might be a new therapeutic target for HC regeneration.

Immunohistochemical markers of neural progenitor cells in the early embryonic human cerebral cortex

The development of the human central nervous system represents a delicate moment of embryogenesis. The purpose of this study was to analyze the expression of multiple immunohistochemical markers in the stem/progenitor cells in the human cerebral cortex during the early phases of development. To this end, samples from cerebral cortex were obtained from 4 human embryos of 11 weeks of gestation. Each sample was formalin-fixed, paraffin embedded and immunostained with several markers including GFAP, WT1, Nestin, Vimentin, CD117, S100B, Sox2, PAX2, PAX5, Tβ4, Neurofilament, CD44, CD133, Synaptophysin and Cyclin D1. Our study shows the ability of the different immunohistochemical markers to evidence different zones of the developing human cerebral cortex, allowing the identification of the multiple stages of differentiation of neuronal and glial precursors. Three important markers of radial glial cells are evidenced in this early gestational age: Vimentin, Nestin and WT1. Sox2 was expressed by the stem/progenitor cells of the ventricular zone, whereas the postmitotic neurons of the cortical plate were immunostained by PAX2 and NSE. Future studies are needed to test other important stem/progenitor cells markers and to better analyze differences in the immunohistochemical expression of these markers during gestation.

Lingual Epithelial Stem Cells and Organoid Culture of Them

As tongue cancer is one of the major malignant cancers in the world, understanding the mechanism of maintenance of lingual epithelial tissue, which is known to be the origin of tongue cancer, is unquestionably important. However, the actual stem cells that are responsible for the long-term maintenance of the lingual epithelium have not been identified. Moreover, a simple and convenient culture method for lingual epithelial stem cells has not yet been established. Recently, we have shown that Bmi1-positive cells, residing at the second or third layer of the epithelial cell layer at the base of the interpapillary pit (IPP), were slow-cycling and could supply keratinized epithelial cells for over one year, indicating that Bmi1-positive cells are long-term lingual epithelial stem cells. In addition, we have developed a novel lingual epithelium organoid culture system using a three-dimensional matrix and growth factors. Here, we discuss current progress in the identification of lingual stem cells and future applications of the lingual culture system for studying the regulatory mechanisms of the lingual epithelium and for regenerative medicine.

Association of BMI-1 and p16 as prognostic factors for head and neck carcinomas

CONCLUSIONS

BMI-1 is an upstream repressor of tumor suppressor p16 and their inverse expression patterns have been linked with patient survival in OPSCC. In this material only p16 remained a relevant prognostic marker in OPSCC.

OBJECTIVES

HNSCC tumors carry variable phenotypes and clinical outcomes depending on their anatomical location. In OPSCC, expression of tumor suppressor p16 is used as a surrogate marker of HPV infection and has prognostic value. There are no good prognostic biomarkers for HNSCC tumors of other anatomical locations.

AIM

To study the expression patterns of p16 and BMI-1 in not only oropharyngeal but also oral, hypopharyngeal, and laryngeal squamous cell carcinomas and to clarify their putative connections with clinical parameters, survival, and each other.

METHOD

Hospital records on 130 patients (59 OPSCC, 18 OSCC, 20 HPSCC, and 33 LSCC) diagnosed between 1997-2008 at the Helsinki University Hospital, Finland, were reviewed. BMI-1 and p16 expressions were studied by immunohistochemistry.

RESULTS

Sixty-eight per cent of OPSCC expressed p16 and expression correlated with lower age, lower T- and higher N-category, and with improved OS and DFS. BMI-1 expression was most prevalent in OPSCC and LSCC, but had no clinical correlations. No correlation between p16 and BMI-1 expression was found.

Dnajb8, a Member of the Heat Shock Protein 40 Family Has a Role in the Tumor Initiation and Resistance to Docetaxel but Is Dispensable for Stress Response

Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are defined by their abilities of tumor initiation, self-renewal and differentiation. In a previous study, we showed by gene knockdown using siRNA and gene overexpression experiments that Dnaj (Hsp40) homolog, subfamily B, member 8 (DNAJB8), a role in the maintenance, of renal cell carcinoma CSCs/CICs. In the present study, we established Dnajb8 knockout (KO) renal cell carcinoma (RCC) line cells (RenCa cells) and analyzed the cells to confirm the function of Dnajb8 in RCC CSCs/CICs. Dnajb8 KO cells showed reduced ratios of side population cells and reduced sphere forming ability. An in vivo single cell tumor initiation assay revealed that the numbers of CSCs/CICs were 3 in 4 wild-type RenCa cells and 1 in 4 Dnajb8 KO cells. Dnajb8 KO cells showed sensitivity to Docetaxel. On the other hand, Dnajb8 KO cells did not show any sensitivities to stresses including low pH, low glucose, heat shock and sensitivity to cisplatin. The results indicate that Dnajb8 has a role in tumor initiation, side population ratio and sphere formation but it is dispensable for stress responses.

Niche Regulation of Limbal Epithelial Stem Cells: Relationship between Inflammation and Regeneration

Human limbal palisades of Vogt are the ideal site for studying and practicing regenerative medicine due to their accessibility. Nonresolving inflammation in limbal stroma is common manifestation of limbal stem cell (SC) deficiency and presents as a threat to the success of transplanted limbal epithelial SCs. This pathologic process can be overcome by transplantation of cryopreserved human amniotic membrane (AM), which exerts anti-inflammatory, antiscarring and anti-angiogenic action to promote wound healing. To determine how AM might exert anti-inflammation and promote regeneration, we have purified a novel matrix, HC-HA/PTX3, responsible for the efficacy of AM efficacy. HC-HA complex is covalently formed by hyaluronan (HA) and heavy chain 1 (HC1) of inter-α-trypsin inhibitor by the catalytic action of tumor necrosis factor-stimulated gene-6 (TSG-6) and are tightly associated with pentraxin 3 (PTX3) to form HC-HA/PTX3. In vitro reconstitution of the limbal niche can be established by reunion between limbal epithelial progenitors and limbal niche cells on different substrates. In 3-dimensional Matrigel, clonal expansion indicative of SC renewal is correlated with activation of canonical Wnt signaling and suppression of canonical bone morphogenetic protein (BMP) signaling. In contrast, SC quiescence can be achieved in HC-HA/PTX3 by activation of canonical BMP signaling and non-canonical planar cell polarity (PCP) Wnt signaling, but suppression of canonical Wnt signaling. HC-HA/PTX3 is a novel matrix mitigating nonresolving inflammation and restoring SC quiescence in the niche for various applications in regenerative medicine.

Post-Translational Modifications of Histones in Vertebrate Neurogenesis

The process of neurogenesis, through which the entire nervous system of an organism is formed, has attracted immense scientific attention for decades. How can a single neural stem cell give rise to astrocytes, oligodendrocytes, and neurons? Furthermore, how is a neuron led to choose between the hundreds of different neuronal subtypes that the vertebrate CNS contains? Traditionally, niche signals and transcription factors have been on the spotlight. Recent research is increasingly demonstrating that the answer may partially lie in epigenetic regulation of gene expression. In this article, we comprehensively review the role of post-translational histone modifications in neurogenesis in both the embryonic and adult CNS.

Long Noncoding RNA-Directed Epigenetic Regulation of Gene Expression Is Associated With Anxiety-like Behavior in Mice

BACKGROUND

RNA-directed regulation of epigenetic processes has recently emerged as an important feature of mammalian differentiation and development. Perturbation of this regulatory system in the brain may contribute to the development of neuropsychiatric disorders.

METHODS

RNA sequencing was used to identify changes in the experience-dependent expression of long noncoding RNAs (lncRNAs) within the medial prefrontal cortex of adult mice. Transcripts were validated by real-time quantitative polymerase chain reaction and a candidate lncRNA, Gomafu, was selected for further investigation. The functional role of this schizophrenia-related lncRNA was explored in vivo by antisense oligonucleotide-mediated gene knockdown in the medial prefrontal cortex, followed by behavioral training and assessment of fear-related anxiety. Long noncoding RNA-directed epigenetic regulation of gene expression was investigated by chromatin and RNA immunoprecipitation assays.

RESULTS

RNA sequencing analysis revealed changes in the expression of a significant number of genes related to neural plasticity and stress, as well as the dynamic regulation of lncRNAs. In particular, we detected a significant downregulation of Gomafu lncRNA. Our results revealed that Gomafu plays a role in mediating anxiety-like behavior and suggest that this may occur through an interaction with a key member of the polycomb repressive complex 1, BMI1, which regulates the expression of the schizophrenia-related gene beta crystallin (Crybb1). We also demonstrated a novel role for Crybb1 in mediating fear-induced anxiety-like behavior.

CONCLUSIONS

Experience-dependent expression of lncRNAs plays an important role in the epigenetic regulation of adaptive behavior, and the perturbation of Gomafu may be related to anxiety and the development of neuropsychiatric disorders.