From hematopoiesis to neuropoiesis: evidence of overlapping genetic programs

Out of Line or Altered States? Neural Progenitors as a Target in a Polygenic Neurodevelopmental Disorder

The genesis of a mature complement of neurons is thought to require, at least in part, precursor cell lineages in which neural progenitors have distinct identities recognized by exclusive expression of one or a few molecular markers. Nevertheless, limited progenitor types distinguished by specific markers and lineal progression through such subclasses cannot easily yield the magnitude of neuronal diversity in most regions of the nervous system. The late Verne Caviness, to whom this edition of Developmental Neuroscience is dedicated, recognized this mismatch. In his pioneering work on the histogenesis of the cerebral cortex, he acknowledged the additional flexibility required to generate multiple classes of cortical projection and interneurons. This flexibility may be accomplished by establishing cell states in which levels rather than binary expression or repression of individual genes vary across each progenitor's shared transcriptome. Such states may reflect local, stochastic signaling via soluble factors or coincidence of cell surface ligand/receptor pairs in subsets of neighboring progenitors. This probabilistic, rather than determined, signaling could modify transcription levels via multiple pathways within an apparently uniform population of progenitors. Progenitor states, therefore, rather than lineal relationships between types may underlie the generation of neuronal diversity in most regions of the nervous system. Moreover, mechanisms that influence variation required for flexible progenitor states may be targets for pathological changes in a broad range of neurodevelopmental disorders, especially those with polygenic origins.

Physical interaction between BAALC and DBN1 induces chemoresistance in leukemia

BAALC is identified as a leukemia-associated gene and is highly expressed in CD34-positive hematopoietic stem cells. High BAALC expression is associated with poor prognosis in several types of acute myeloid leukemia. We explored binding partner proteins of BAALC by means of mass spectrometry and analyzed biological properties of BAALC-expressing leukemic cells. We found that BAALC physically interacts with DBN1, which is an actin-binding protein and promotes cell adhesion and mobility by forming cell membrane spines during cell-cell interactions. Drebrin1 downregulation impeded cell adhesion to bone marrow stromal cells, resulting in improvement of sensitivity to cytarabine. Taken together, our findings suggest that BAALC-DBN1 interaction contributes to the anchoring of BAALC-expressing cells in the bone marrow, which in turn leads to resistance to cytotoxic drugs. Therefore, the BAALC-DBN1 interaction provides us with an opportunity to overcome the chemotherapy resistance in BAALC-activated leukemia via functional blockage of these genes.

Nucleolin acts as the receptor for C1QTNF4 and supports C1QTNF4-mediated innate immunity modulation

The C1q and TNF related 4 (C1QTNF4) protein is a structurally unique member of the C1QTNF family, a family of secreted proteins that have structural homology with both complement C1q and the tumor necrosis factor superfamily. C1QTNF4 has been linked to the autoimmune disease systemic lupus erythematosus through genetic studies; however, its role in immunity and inflammation remains poorly defined and a cell surface receptor of C1QTNF4 has yet to be identified. Here we report identification of nucleolin as a cell surface receptor of C1QTNF4 using mass spectrometric analysis. Additionally, we present evidence that the interaction between C1QTNF4 and nucleolin is mediated by the second C1q-like domain of C1QTNF4 and the C terminus of nucleolin. We show that monocytes and B cells are target cells of C1QTNF4 and observe extensive binding to dead cells. Imaging flow cytometry experiments in monocytes show that C1QTNF4 becomes actively internalized upon cell binding. Our results suggest that nucleolin may serve as a docking molecule for C1QTNF4 and act in a context-dependent manner through coreceptors. Taken together, these findings further our understanding of C1QTNF4's function in the healthy immune system and how dysfunction may contribute to the development of systemic lupus erythematosus.

Intramacrophage ROS Primes the Innate Immune System via JAK/STAT and Toll Activation

Tissue injury is one of the most severe environmental perturbations for a living organism. When damage occurs in adult Drosophila, there is a local response of the injured tissue and a coordinated action across different tissues to help the organism overcome the deleterious effect of an injury. We show a change in the transcriptome of hemocytes at the site of tissue injury, with pronounced activation of the Toll signaling pathway. We find that induction of the cytokine upd-3 and Toll receptor activation occur in response to injury alone, in the absence of a pathogen. Intracellular accumulation of hydrogen peroxide in hemocytes is essential for upd-3 induction and is facilitated by the diffusion of hydrogen peroxide through a channel protein Prip. Importantly, hemocyte activation and production of reactive oxygen species (ROS) at the site of a sterile injury provide protection to flies on subsequent infection, demonstrating training of the innate immune system.

The GABA receptor GABRR1 is expressed on and functional in hematopoietic stem cells and megakaryocyte progenitors

GABRR1 is a rho subunit receptor of GABA, the major inhibitory neurotransmitter in the mammalian brain. While most investigations of its function focused on the nervous system, its regulatory role in hematopoiesis has not been reported. In this study, we found GABRR1 is mainly expressed on subsets of human and mouse hematopoietic stem cells (HSCs) and megakaryocyte progenitors (MkPs). GABRR1-negative (GR-) HSCs led to higher donor-derived hematopoietic chimerism than GABRR1-positive (GR+) HSCs. GR+ but not GR- HSCs and MkPs respond to GABA in patch clamp studies. Inhibition of GABRR1 via genetic knockout or antagonists inhibited MkP differentiation and reduced platelet numbers in blood. Overexpression of GABRR1 or treatment with agonists significantly promoted MkP generation and megakaryocyte colonies. Thus, this study identifies a link between the neural and hematopoietic systems and opens up the possibility of manipulating GABA signaling for platelet-required clinical applications.

57R2A, a newly established monoclonal antibody against mouse GPR56, marks long-term repopulating hematopoietic stem cells

GPR56 molecule, a G-protein-coupled receptor, was suggested to be expressed in mouse hematopoietic stem cells (HSCs) by gene expression analyses. However, little is known about the cell surface expression of GPR56 protein in mouse HSCs due to the absence of an appropriate monoclonal antibody against GPR56 for flow cytometry analyses. In the present study, we established a novel monoclonal antibody against mouse GPR56 (57R2A) to examine the expression and distribution of GPR56 protein in HSCs. A flow cytometry analysis using 57R2A showed that GPR56 was highly expressed in the CD34^-, c-Kit⁺, Sca-1⁺, lineage-negative (Lin^-) fraction, which are highly enriched with HSCs. The competitive long-term repopulation (LTR) assay showed that LTR cells were included only within the GPR56⁺ fraction (≤15%) of bone marrow mononuclear cells (BMMNCs), but not within the remaining GPR56^- fraction (85%), suggesting that all HSCs express GPR56 protein on their surface. Furthermore, we showed that double staining of BMMNCs with only 57R2A and AMM2 (monoclonal antibody against the HSC marker MPL) enabled enrichment of all LTR cells in the double-positive fraction (0.8% of BMMNCs), within which the LTR potency was consistent with the expression of both GPR56 and MPL. In conclusion, these findings for 57R2A suggest that all HSCs in mouse BMMNCs express GPR56 protein on their surface and that GPR56 is a positive marker for HSCs.

Automatic identification of informative regions with epigenomic changes associated to hematopoiesis

Hematopoiesis is one of the best characterized biological systems but the connection between chromatin changes and lineage differentiation is not yet well understood. We have developed a bioinformatic workflow to generate a chromatin space that allows to classify 42 human healthy blood epigenomes from the BLUEPRINT, NIH ROADMAP and ENCODE consortia by their cell type. This approach let us to distinguish different cells types based on their epigenomic profiles, thus recapitulating important aspects of human hematopoiesis. The analysis of the orthogonal dimension of the chromatin space identify 32,662 chromatin determinant regions (CDRs), genomic regions with different epigenetic characteristics between the cell types. Functional analysis revealed that these regions are linked with cell identities. The inclusion of leukemia epigenomes in the healthy hematological chromatin sample space gives us insights on the healthy cell types that are more epigenetically similar to the disease samples. Further analysis of tumoral epigenetic alterations in hematopoietic CDRs points to sets of genes that are tightly regulated in leukemic transformations and commonly mutated in other tumors. Our method provides an analytical approach to study the relationship between epigenomic changes and cell lineage differentiation. Method availability: https://github.com/david-juan/ChromDet.

Engrafted Neural Progenitor Cells Express a Tissue-Restricted Reporter Gene Associated with Differentiated Retinal Photoreceptor Cells

Neural progenitor cells (NPCs) have shown ability to repair injured CNS, and might provide precursors to retinal neurons. NPCs were isolated from the brains of 14 day murine embryos of transgenic mice that express β-galactosidase (β-gal) on the arrestin promoter, which specifically directs expression to retinal photoreceptor cells. NPCs were transferred to adult, syngeneic mice via inoculation into the anterior chamber of the eye, the peritoneal cavity, or the brain. At 14 weeks postgrafting, tissues were collected and examined to determine if differentiated NPC progeny were present in retina based on histochemical detection of β-gal. Four of six anterior chamber-inoculated recipients showed Bluo-gal-stained cells in retina, indicating the presence of transferred NPCs or their progeny. Because the progenitor cells do not express β-gal, positive staining indicates differentiation leading to activation of the arrestin promoter. Two recipients inoculated by the intraperitoneal route also exhibited Bluo-gal staining in retina. The NPCs did not express β-gal if inoculated into brain, but survived and dispersed. Most recipients, regardless of inoculation route, were PCR positive for β-gal DNA in extraocular tissues, but no Bluo-gal staining was found outside of the retina. Injury to the retina promoted, but was not required, for progenitor cell engraftment. β-Gal-positive cells were concentrated in the outer layers of the retina. In summary, a reporter gene specifically expressed in differentiated retinal photoreceptor cells due to the activity of the arrestin promoter was expressed in recipient mouse retina following transfer of NPCs prepared from the β-gal transgenic mice. The presence of β-gal DNA, but not Bluo-gal staining, in spleen and other tissues revealed that the cells also migrated elsewhere and took up residence in other organs, but did not undergo differentiation that led to β-gal expression.

Loss of the interferon-γ-inducible regulatory immunity-related GTPase (IRG), Irgm1, causes activation of effector IRG proteins on lysosomes, damaging lysosomal function and predicting the dramatic susceptibility of Irgm1-deficient mice to infection

Background

The interferon-γ (IFN-γ)-inducible immunity-related GTPase (IRG), Irgm1, plays an essential role in restraining activation of the IRG pathogen resistance system. However, the loss of Irgm1 in mice also causes a dramatic but unexplained susceptibility phenotype upon infection with a variety of pathogens, including many not normally controlled by the IRG system. This phenotype is associated with lymphopenia, hemopoietic collapse, and death of the mouse.

Results

We show that the three regulatory IRG proteins (GMS sub-family), including Irgm1, each of which localizes to distinct sets of endocellular membranes, play an important role during the cellular response to IFN-γ, each protecting specific membranes from off-target activation of effector IRG proteins (GKS sub-family). In the absence of Irgm1, which is localized mainly at lysosomal and Golgi membranes, activated GKS proteins load onto lysosomes, and are associated with reduced lysosomal acidity and failure to process autophagosomes. Another GMS protein, Irgm3, is localized to endoplasmic reticulum (ER) membranes; in the Irgm3-deficient mouse, activated GKS proteins are found at the ER. The Irgm3-deficient mouse does not show the drastic phenotype of the Irgm1 mouse. In the Irgm1/Irgm3 double knock-out mouse, activated GKS proteins associate with lipid droplets, but not with lysosomes, and the Irgm1/Irgm3^−/− does not have the generalized immunodeficiency phenotype expected from its Irgm1 deficiency.

Conclusions

The membrane targeting properties of the three GMS proteins to specific endocellular membranes prevent accumulation of activated GKS protein effectors on the corresponding membranes and thus enable GKS proteins to distinguish organellar cellular membranes from the membranes of pathogen vacuoles. Our data suggest that the generalized lymphomyeloid collapse that occurs in Irgm1^−/− mice upon infection with a variety of pathogens may be due to lysosomal damage caused by off-target activation of GKS proteins on lysosomal membranes and consequent failure of autophagosomal processing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-016-0255-4) contains supplementary material, which is available to authorized users.

Control of AC133/CD133 and impact on human hematopoietic progenitor cells through nucleolin

AC133 is a prominent surface marker of CD34+ and CD34- hematopoietic stem/progenitor cell (HSPC) subsets. AC133+ HSPCs contain high progenitor cell activity and are capable of hematopoietic reconstitution. Furthermore, AC133 is used for prospective isolation of tumor-initiating cells in several hematological malignancies. Nucleolin is a multifunctional factor of growing and cancer cells, which is aberrantly active in certain hematological neoplasms, and serves as a candidate molecular target for cancer therapy. Nucleolin is involved in gene transcription and RNA metabolism and is prevalently expressed in HSPCs, as opposed to differentiated hematopoietic tissue. The present study dissects nucleolin-mediated activation of surface AC133 and its cognate gene CD133, via specific interaction of nucleolin with the tissue-dependent CD133 promoter P1, as a mechanism that crucially contributes to AC133 expression in CD34+ HSPCs. In mobilized peripheral blood (MPB)-derived HSPCs, nucleolin elevates colony-forming unit (CFU) frequencies and enriches granulocyte-macrophage CFUs. Furthermore, nucleolin amplifies long-term culture-initiating cells and also promotes long-term, cytokine-dependent maintenance of hematopoietic progenitor cells. Active β-catenin, active Akt and Bcl-2 levels in MPB-derived HSPCs are nucleolin-dependent, and effects of nucleolin on these cells partially rely on β-catenin activity. The study provides new insights into molecular network relevant to stem/progenitor cells in normal and malignant hematopoiesis.

Neuronal ceroid lipofuscinosis genes, CLN2, CLN3 and CLN5 are spatially and temporally co-expressed in a developing mouse brain

Neuronal ceroid lipofuscinosis (NCL) diseases consist of a group of genetically inherited neurodegenerative disorders that share common symptoms such as seizures, psychomotor retardation, blindness, and premature death. Although gene defects behind the NCL diseases are well characterized, very little is known how these defects affect normal development of the brain and cause the pathology of the disease. To obtain understanding of the development of the cell types that are mostly affected by defective function of CLN proteins, timing of expression of CLN2, CLN3 and CLN5 genes was investigated in developing mouse brain. The relationship between the expression pattern and the developmental stage of the brain showed that these genes are co-expressed spatially and temporally during brain development. Throughout the development strong expression of the three mRNAs was detected in germinal epithelium and in ventricle regions, hippocampus and cerebellum, all representing regions that are known to be associated with the formation of new neurons. More specifically, RT-PCR studies on developing mouse cortices revealed that the CLN genes were temporally co-expressed in the neural progenitor cells together with known stem cell markers. This suggested that CLN2, CLN3 and CLN5 genes may play an important role in early embryonal neurogenesis.

Genetic deletion of the GATA1-regulated protein α-synuclein reduces oxidative stress and nitric oxide synthase levels in mature erythrocytes

α-Synuclein is highly expressed in neural tissue and during erythropoiesis, where the key erythroid regulator GATA1 has been found to modulate its expression. While specific α-synuclein (SNCA) mutations are known to cause autosomal dominant familial Parkinson's disease, its wild-type function remains under debate. To investigate the role of α-synuclein in murine hematopoiesis and erythropoiesis, we utilized Snca knock-out mice and analyzed erythroid compartments for maturation defects, in vivo erythrocyte survival, and erythrocyte-based reactive oxygen species (ROS) and nitric oxide synthase (NOS) levels. Our findings show that while bone marrow and spleen erythropoiesis and peripheral blood erythrocyte survival in Snca(-/-) mice was comparable to controls, the levels of ROS and of NOS-2 were significantly decreased in mature erythrocytes in these animals. These results indicate a role for α-synuclein in regulating oxidative stress in erythrocytes in vivo and could open new avenues for the investigation of its function in non-neural tissue.

Metastatic cancer stem cells: from the concept to therapeutics

Metastatic cancer stem cells (MCSCs) refer to a subpopulation of cancer cells with both stem cell properties and invasion capabilities that contribute to cancer metastasis. MCSCs have capability of self-renewal, potentials of multiple differentiation and development and/or reconstruction of cancer tissues. As compared with stationary cancer stem cells, MCSCs are capable of invasion to normal tissues such as vasculatures, resistance to chemo- and/or radio-therapies, escape from immune surveillance, survival in circulation and formation of metastasis. MCSCs are derived from invasive cancer stem cells (iCSCs) due to the plasticity of cancer stem cells, which is one of the characteristics of cancer cell heterogeneity. Both stages of iCSCs and MSCSs are the potential therapeutic targets for cancer metastasis in the future strategies of personalized cancer therapy.

Lineage-specific function of Engrailed-2 in the progression of chronic myelogenous leukemia to T-cell blast crisis

In hematopoietic malignancies, oncogenic alterations interfere with cellular differentiation and lead to tumoral development. Identification of the proteins regulating differentiation is essential to understand how they are altered in malignancies. Chronic myelogenous leukemia (CML) is a biphasic disease initiated by an alteration taking place in hematopoietic stem cells. CML progresses to a blast crisis (BC) due to a secondary differentiation block in any of the hematopoietic lineages. However, the molecular mechanisms of CML evolution to T-cell BC remain unclear. Here, we have profiled the changes in DNA methylation patterns in human samples from BC-CML, in order to identify genes whose expression is epigenetically silenced during progression to T-cell lineage-specific BC. We have found that the CpG-island of the ENGRAILED-2 (EN2) gene becomes methylated in this progression. Afterwards, we demonstrate that En2 is expressed during T-cell development in mice and humans. Finally, we further show that genetic deletion of En2 in a CML transgenic mouse model induces a T-cell lineage BC that recapitulates human disease. These results identify En2 as a new regulator of T-cell differentiation whose disruption induces a malignant T-cell fate in CML progression, and validate the strategy used to identify new developmental regulators of hematopoiesis.

Comparative expression study of the endo-G protein coupled receptor (GPCR) repertoire in human glioblastoma cancer stem-like cells, U87-MG cells and non malignant cells of neural origin unveils new potential therapeutic targets

Glioblastomas (GBMs) are highly aggressive, invasive brain tumors with bad prognosis and unmet medical need. These tumors are heterogeneous being constituted by a variety of cells in different states of differentiation. Among these, cells endowed with stem properties, tumor initiating/propagating properties and particularly resistant to chemo- and radiotherapies are designed as the real culprits for tumor maintenance and relapse after treatment. These cells, termed cancer stem-like cells, have been designed as prominent targets for new and more efficient cancer therapies. G-protein coupled receptors (GPCRs), a family of membrane receptors, play a prominent role in cell signaling, cell communication and crosstalk with the microenvironment. Their role in cancer has been highlighted but remains largely unexplored. Here, we report a descriptive study of the differential expression of the endo-GPCR repertoire in human glioblastoma cancer stem-like cells (GSCs), U-87 MG cells, human astrocytes and fetal neural stem cells (f-NSCs). The endo-GPCR transcriptome has been studied using Taqman Low Density Arrays. Of the 356 GPCRs investigated, 138 were retained for comparative studies between the different cell types. At the transcriptomic level, eight GPCRs were specifically expressed/overexpressed in GSCs. Seventeen GPCRs appeared specifically expressed in cells with stem properties (GSCs and f-NSCs). Results of GPCR expression at the protein level using mass spectrometry and proteomic analysis are also presented. The comparative GPCR expression study presented here gives clues for new pathways specifically used by GSCs and unveils novel potential therapeutic targets.

Maternal embryonic leucine zipper kinase (MELK): a novel regulator in cell cycle control, embryonic development, and cancer

Maternal embryonic leucine zipper kinase (MELK) functions as a modulator of intracellular signaling and affects various cellular and biological processes, including cell cycle, cell proliferation, apoptosis, spliceosome assembly, gene expression, embryonic development, hematopoiesis, and oncogenesis. In these cellular processes, MELK functions by binding to numerous proteins. In general, the effects of multiple protein interactions with MELK are oncogenic in nature, and the overexpression of MELK in kinds of cancer provides some evidence that it may be involved in tumorigenic process. In this review, our current knowledge of MELK function and recent discoveries in MELK signaling pathway were discussed. The regulation of MELK in cancers and its potential as a therapeutic target were also described.

Pluripotent possibilities: human umbilical cord blood cell treatment after neonatal brain injury

Perinatal hypoxic-ischemic brain injury and stroke in the developing brain remain important causes of chronic neurologic morbidity. Emerging data suggest that transplantation of umbilical cord blood-derived stem cells may have therapeutic potential for neuroregeneration and improved functional outcome. The pluripotent capacity of stem cells from the human umbilical cord blood provides simultaneous targeting of multiple neuropathologic events initiated by a hypoxic-ischemic insult. Their high regenerative potential and naïve immunologic phenotype makes them a preferable choice for transplantation. A multiplicity of transplantation protocols have been studied with a variety of brain injury models; however, only a few have been conducted on immature animals. Biological recipient characteristics, such as age and sex, appear to differentially modulate responses of the animals to the transplanted cord blood stem cells. Survival, migration, and function of the transplanted cells have also been studied and reveal insights into the mechanisms of cord blood stem cell effects. Data from preclinical studies have informed current clinical safety trials of human cord blood in neonates, and further work is needed to continue progress in this field.

Bone marrow non-mesenchymal mononuclear cells induce functional differentiation of neuroblastoma cells

Less is known about the non-mesenchymal mononuclear cell fraction of human bone marrow on functional adaptation of neuroblastoma cells. Using immunocytochemistry, we showed that bone-marrow mononuclear cell (BMMC)-conditioned medium can induce tyrosine hydroxylase expression in neuroblastoma cells, which is similar to the effect of retinoic acid. Using quantitative RT-PCR, we showed that NGF, CNTF, and BDNF mRNAs were detected in unfractionated BMMC populations from all human donors at different expression levels. Our results suggest that cells of the non-mesenchymal mononuclear cell fraction can induce functional adaptation of neuroblastoma cells, probably via their secreted trophic factors.

Maintenance of the hematopoietic stem cell pool in bone marrow niches by EVI1-regulated GPR56

Acute myeloid leukemia with high ecotropic viral integration site-1 expression (EVI1(high) AML) is classified as a refractory type of leukemia with a poor prognosis. To provide new insights into the prevention and treatment of this disease, we identified the high expression of EVI1-regulated G protein-coupled receptor 56 (GPR56), and the association of high cell adhesion and antiapoptotic activities in EVI1(high) AML cells. Knockdown of GPR56 expression decreased the cellular adhesion ability through inactivation of RhoA signaling, resulting in a reduction of cellular growth rates and enhanced apoptosis. Moreover, in Gpr56(-/-) mice, the number of hematopoietic stem cells (HSCs) was significantly decreased in the bone marrow (BM) and, conversely, was increased in the spleen, liver and peripheral blood. The number of Gpr56(-/-) HSC progenitors in the G0/G1-phase was significantly reduced and was associated with impaired cellular adhesion. Finally, the loss of GPR56 function resulted in a reduction of the in vivo repopulating ability of the HSCs. In conclusion, GPR56 may represent an important GPCR for the maintenance of HSCs by acting as a co-ordinator of interactions with the BM osteosteal niche; furthermore, this receptor has the potential to become a novel molecular target in EVI1(high) leukemia.

Cytotoxic and Genotoxic effects of Arsenic and Lead on Human Adipose Derived Mesenchymal Stem Cells (AMSCs)

Arsenic and lead, known to have genotoxic and mutagenic effects, are ubiquitously distributed in the environment. The presence of arsenic in drinking water has been a serious health problem in many countries. Human exposure to these metals has also increased due to rapid industrialization and their use in formulation of many products. Liposuction material is a rich source of stem cells. In the present study cytotoxic and genotoxic effects of these metals were tested on adipose derived mesenchymal stem cells (AMSCs). Cells were exposed to 1-10 μg/ml and 10-100 μg/ml concentration of arsenic and lead, respectively, for 6, 12, 24 and 48 h. The cytotoxic effects were measured by neutral red uptake assay, while the genotoxic effects were tested by comet assay. The growth of cells decreased with increasing concentration and the duration of exposure to arsenic. Even the morphology of cells was changed; they became round at 10 μg /ml of arsenic. The cell growth was also decreased after exposure to lead, though it proved to be less toxic when cells were exposed for longer duration. The cell morphology remained unchanged. DNA damage was observed in the metal treated cells. Different parameters of comet assay were investigated for control and treated cells which indicated more DNA damage in arsenic treated cells compared to that of lead. Intact nuclei were observed in control cells. Present study clearly demonstrates that both arsenic and lead have cytotoxic and genotoxic effects on AMSCs, though arsenic compared to lead has more deleterious effects on AMSCs.

Umbilical cord blood-derived mesenchymal stem cells consist of a unique population of progenitors co-expressing mesenchymal stem cell and neuronal markers capable of instantaneous neuronal differentiation

INTRODUCTION

Umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) are self-renewing multipotent progenitors with the potential to differentiate into multiple lineages of mesoderm, in addition to generating ectodermal and endodermal lineages by crossing the germline barrier. In the present study we have investigated the ability of UCB-MSCs to generate neurons, since we were able to observe varying degrees of neuronal differentiation from a few batches of UCB-MSCs with very simple neuronal induction protocols whereas other batches required extensive exposure to combination of growth factors in a stepwise protocol. Our hypothesis was therefore that the human UCB-MSCs would contain multiple types of progenitors with varying neurogenic potential and that the ratio of the progenitors with high and low neurogenic potentials varies in different batches of UCB.

METHODS

In total we collected 45 UCB samples, nine of which generated MSCs that were further expanded and characterized using immunofluorescence, fluorescence-activated cell sorting and RT-PCR analysis. The neuronal differentiation potential of the UCB-MSCs was analyzed with exposure to combination of growth factors.

RESULTS

We could identify two different populations of progenitors within the UCB-MSCs. One population represented progenitors with innate neurogenic potential that initially express pluripotent stem cell markers such as Oct4, Nanog, Sox2, ABCG2 and neuro-ectodermal marker nestin and are capable of expanding and differentiating into neurons with exposure to simple neuronal induction conditions. The remaining population of cells, typically expressing MSC markers, requires extensive exposure to a combination of growth factors to transdifferentiate into neurons. Interesting to note was that both of these cell populations were positive for CD29 and CD105, indicating their MSC lineage, but showed prominent difference in their neurogenic potential.

CONCLUSION

Our results suggest that the expanded UCB-derived MSCs harbor a small unique population of cells that express pluripotent stem cell markers along with MSC markers and possess an inherent neurogenic potential. These pluripotent progenitors later generate cells expressing neural progenitor markers and are responsible for the instantaneous neuronal differentiation; the ratio of these pluripotent marker expressing cells in a batch determines the innate neurogenic potential.

Transcription of the human EAP1 gene is regulated by upstream components of a puberty-controlling Tumor Suppressor Gene network

Mammalian puberty is initiated by an increased pulsatile release of gonadotropin-releasing hormone (GnRH) from specialized neurons located in the hypothalamus. GnRH secretion is controlled by neuronal and glial networks, whose activity appears to be coordinated via transcriptional regulation. One of the transcription factors involved in this process is thought to be the recently described gene Enhanced at Puberty 1 (EAP1), which encodes a protein with dual transcriptional activity. In this study we used gene reporter and chromatin immunoprecipitation (ChIP) assays to examine the hypothesis that EAP1 expression is controlled by transcriptional regulators earlier postulated to serve as central nodes of a gene network involved in the neuroendocrine control of puberty. These regulators include Thyroid Transcription Factor 1 (TTF1), Yin Yang 1 (YY1), and CUX1, in addition to EAP1 itself. While TTF1 has been shown to facilitate the advent of puberty, YY1 (a zinc finger protein component of the Polycomb silencing complex) may play a repressive role. The precise role of CUX1 in this context is not known, but like EAP1, CUX1 can either activate or repress gene transcription. We observed that DNA segments of two different lengths (998 and 2744bp) derived from the 5'-flanking region of the human EAP1 gene display similar transcriptional activity. TTF1 stimulates transcription from both DNA segments with equal potency, whereas YY1, CUX1, and EAP1 itself, behave as transcriptional repressors. All four proteins are recruited in vivo to the EAP1 5'-flanking region. These observations suggest that EAP1 gene expression is under dual transcriptional regulation imposed by a trans-activator (TTF1) and two repressors (YY1 and CUX1) previously postulated to be upstream components of a puberty-controlling gene network. In addition, EAP1 itself appears to control its own expression via a negative auto-feedback loop mechanism. Further studies are needed to determine if the occupancy of the EAP1 promoter by these regulatory factors changes at the time of puberty.

Stem cells, quiescence and rectal carcinoma: an unexplored relationship and potential therapeutic target

Stem cells are responsible for maintaining differentiated cell numbers during normal physiology and at times of tissue stress. They have the unique capabilities of proliferation, self-renewal, clonogenicity and multi-potentiality. It is a widely held belief that stem-like cells, known as cancer stem cells (CSCs), maintain tumours. The majority of currently identified intestinal stem cell populations appear to be rapidly cycling. However, quiescent stem cell populations have been suggested to exist in both normal intestinal crypts and tumours. Quiescent CSCs may have particular significance in the modern management of colorectal cancer making their identification and characterisation a priority. In this review, we discuss the current evidence surrounding the identification and microenvironmental control of stem cell populations in intestinal crypts and tumours as well as exploring the evidence supporting the existence of a quiescent stem and CSC population in the gut and other tissues.

Rb and nucleolin antagonize in controlling human CD34 gene expression

Retinoblastoma protein (Rb) controls cell proliferation, differentiation, survival and gene expression and it has a central role in the signaling network that provides a cell cycle checkpoint in the G1 phase of the cell cycle. Studies in mice have shown that Rb regulates interactions between hematopoietic stem cells and their bone marrow microenvironment and it acts as a critical regulator of hematopoietic stem and progenitor cells under stress. In human hematopoiesis, the CD34 protein is expressed on a subset of progenitor cells capable of self-renewal, multilineage differentiation, and hematopoietic reconstitution, and CD34 has a role in the differentiation of hematopoietic cells. Here we find that, in CD34-positive hematopoietic cells, Rb controls the human CD34 promoter region by antagonizing the CD34 promoter factor nucleolin to provide a mechanism that links expression of endogenous CD34 to cell cycle progression. Our study suggests a direct involvement of Rb in the transcriptional program of human CD34-positive hematopoietic stem/progenitor cells, thus providing further insights into the molecular network relevant to the features of these cells.

A novel GPR56 mutation causes bilateral frontoparietal polymicrogyria

Bilateral frontoparietal polymicrogyria is an autosomal recessive inherited human brain malformation with abnormal cortical lamination. The affected cortex appears to consist of numerous small gyri, with scalloping of the cortical-white matter junction. There are associated white matter, brain stem, and cerebellar changes. Affected individuals manifest mental retardation, language impairment, motor developmental delay, and seizure disorder. GPR56 is the causative gene. Here we report a novel missense mutation of GPR56, E496K, identified in a consanguineous pedigree with bilateral frontoparietal polymicrogyria. GPR56 protein is cleaved at the G-protein-coupled receptor proteolytic site into an N- and a C-terminal fragment, named GPR56(N) and GPR56(C), respectively. E496K is located in GPR56(C). Further biochemical studies reveal that this mutation affects GPR56(C) cell surface expression similar to the effect of a previously reported mutation, R565W. These results provide further insights into how GPR56 mutation causes neurologic disease.

L-3-Phosphoserine phosphatase (PSPH) regulates cutaneous squamous cell carcinoma proliferation independent of L-serine biosynthesis

BACKGROUND

L-3-Phosphoserine phosphatase (PSPH) is a highly conserved and widely expressed member of the haloacid dehalogenase superfamily and the rate-limiting enzyme in l-serine biosynthesis. We previously found Psph expression to be uniquely upregulated in a α6β4 integrin transgenic mouse model that is predisposed to epidermal hyperproliferation and squamous cell carcinoma (SCC) formation implicating a role for Psph in epidermal homeostasis.

OBJECTIVE

We examined the status of PSPH in normal skin epidermis and skin tumors along with its sub-cellular localization in epidermal keratinocytes and its requirement for squamous cell carcinoma (SCC) proliferation.

METHODS

First, an immunohistochemical study was performed for PSPH in normal skin and skin cancer specimens and in cultured keratinocytes. Next, biochemical analyses were performed to confirm localization of PSPH and to identify candidate binding proteins. Finally, proliferation and apoptosis studies were performed in human SCC and normal keratinocytes, respectively, transduced with vectors encoding small hairpin RNAs targeting PSPH or overexpressing a phosphatase-deficient PSPH mutant.

RESULTS

PSPH is expressed throughout the proliferative layer of the epidermis and hair follicles in rodent and human skin and is highly induced in SCC. In keratinocytes, PSPH is a cytoplasmic protein that primarily localizes to endosomes and is present primarily as a homodimer. Knock down of PSPH dramatically diminished SCC cell proliferation and cyclin D1 levels in the presence of exogenous of l-serine production suggesting a non-canonical role for PSPH in epithelial carcinogenesis.

CONCLUSIONS

Psph is highly induced in proliferative normal keratinocytes and in skin tumors. PSPH appears to be critical for the proliferation of SCC cells; however, this phenomenon may not involve the phosphoserine metabolic pathway.

Neurexophilin 1 suppresses the proliferation of hematopoietic progenitor cells

Neurexin I α (NRXN1α) and Dystroglycan (DAG1) are membrane receptors which serve as mutual ligands in the neuronal system. Neurexophilins (NXPHs) bind NRXN1α. NRXN1α was expressed in primitive populations in human CB (huCB) and murine BM (muBM). DAG1 is ubiquitously expressed in hematopoietic tissue; however, osteoblasts appear to be sites of very high expression within muBM. High concentrations of NXPH were found in huCB plasma and murine lineage-positive splenocytes. We evaluated effects of these molecules on huCB and muBM hematopoietic progenitor cells (HPCs) and HSCs. At both a single and population cell level in vitro, we found that NXPH1 was a potent inhibitor of HPC proliferation acting through NRXN1α an effect down-modulated by DAG1. Injection of recombinant NXPH1 in vivo resulted in myelo- and lymphosuppression in the BM, with absolute numbers and cycling status of functional and phenotypically defined HPCs dose- and time-dependently decreased. Competitive HSC transplantations showed no change in the long-term repopulating activity of HSCs from mice exposed to recombinant NXPH1. These results demonstrate the presence and function of a regulated signaling axis in hematopoiesis centered on NRXN1α and its modulation by DAG1 and NXPH1.

Maternal embryonic leucine zipper kinase is upregulated and required in mammary tumor-initiating cells in vivo

Maternal embryonic leucine zipper kinase (MELK) is expressed in several developing tissues, in the adult germ line, and in adult neural progenitors. MELK expression is elevated in aggressive undifferentiated tumors, correlating with poor patient outcome in human breast cancer. To investigate the role of MELK in mammary tumorigenesis in vivo, we used a MELK-green fluorescent protein (GFP) reporter mouse, which allows prospective isolation of MELK-expressing cells based on GFP fluorescence. We found that in the normal mammary gland, cells expressing high levels of MELK were enriched in proliferating cells that express markers of mammary progenitors. The isolation of cells with high levels of MELK in mammary tumors from MMTV-Wnt1/MELK-GFP bitransgenic mice resulted in a significant enrichment of tumorsphere formation in culture and tumor initiation after transplantation into mammary fat pads of syngeneic mice. Furthermore, using lentiviral delivery of MELK-specific shRNA and limiting dilution cell transplantations, we showed that MELK function is required for mammary tumorigenesis in vivo. Our findings identify MELK as a potential target in breast tumor-initiating cells.

GPR56 plays varying roles in endogenous cancer progression

GPR56, a non-classical adhesion receptor, was previously reported to suppress tumor growth and metastasis in xenograft models using human melanoma cell lines. To understand whether GPR56 plays similar roles in the development of endogenous tumors, we analyzed cancer progression in Gpr56 (-/-) mice using a variety of transgenic cancer models. Our results showed that GPR56 suppressed prostate cancer progression in the TRAMP model on a mixed genetic background, similar to its roles in progression of melanoma xenografts. However, its roles in other cancer types appeared to be complex. It had marginal effects on tumor onset of mammary tumors in the MMTV-PyMT model, but had no effects on subsequent tumor progression in either the MMTV-PyMT mice or the melanoma model, Ink4a/Arf (-/-) tyr-Hras. These results indicate diverse roles of GPR56 in cancer progression and provide the first genetic evidence for the involvement of an adhesion GPCR in endogenous cancer development.

GPR56 interacts with extracellular matrix and regulates cancer progression

GPR56 is a relatively recent addition to the adhesion-GPCR family. Genetic and biochemical studies uncovered its roles in cancer and development and established its function as an adhesion receptor to mediate the interactions between cells and extracellular matrix. Despite of much progress on understanding its biological implications, the mechanism of its function remains elusive. It has not been firmly established whether GPR56 signals directly through G proteins and what its upstream stimuli and downstream effectors are to execute its various biological effects. This chapter will give an overview of the primary structures of the Gpr56 gene and its encoded protein and attempt to point out open questions in this research area, with an emphasis on its roles in cancer and signal transduction.

A glutamine-rich factor affects stem cell genesis in leech

Leech embryogenesis is a model for investigating cellular and molecular processes of development. Due to the unusually large size of embryonic stem cells (teloblasts; 50 - 300 μm) in the glossiphoniid leech, Theromyzon tessulatum, and the presence of identifiable stem cell precursors (proteloblasts), we previously isolated a group of genes up-regulated upon stem cell birth. In the current study, we show that one of these genes, designated Tpr (Theromyzon proliferation), is required for normal stem cell genesis; specifically, transient Tpr knockdown experiments conducted with antisense oligonucleotides and monitored by semi-quantitative RT-PCR, caused abnormal proteloblast proliferation leading to embryonic death, but did not overtly affect neuroectodermal or mesodermal stem cell development once these cells were born. Tpr encodes a large, glutamine-rich (~34%) domain that shares compositional similarity with strong transcriptional enhancers, many of which have been linked with trinucleotide repeat disorders (e.g., Huntingtons).

GPR56 is highly expressed in neural stem cells but downregulated during differentiation

The G-protein-coupled receptor 56 (GPR56) plays important roles in brain development and tumorigenesis. cDNA data suggest that GPR56 has potential to become a neural stem cell (NSC) or neural progenitor cell (NPC) marker. However, expression of GPR56 protein in human NSC/NPCs was not explored. Using specific antibodies and immunochemistry, we showed that GPR56 was highly expressed in nestin-positive NSC/NPCs in the ventricular/subventricular zone of human and mouse fetal brains, and in cultured neurospheres derived from both human and mouse fetal brains. Downregulation of GPR56 protein occurred earlier than that of nestin in differentiating neurosphere cultures. Loss of GPR56 protein was also evident in well-differentiated glial fibrillary acidic protein-positive astrocytes and betaIII-tubulin-positive neurons. Our data suggest that GPR56 can be used as an NSC/NPC marker within the neural cell lineage, especially in combination with nestin.

A dedicated promoter drives constitutive expression of the cell-autonomous immune resistance GTPase, Irga6 (IIGP1) in mouse liver

BACKGROUND

In general, immune effector molecules are induced by infection.

METHODOLOGY AND PRINCIPAL FINDINGS

However, strong constitutive expression of the cell-autonomous resistance GTPase, Irga6 (IIGP1), was found in mouse liver, contrasting with previous evidence that expression of this protein is exclusively dependent on induction by IFNgamma. Constitutive and IFNgamma-inducible expression of Irga6 in the liver were shown to be dependent on transcription initiated from two independent untranslated 5' exons, which splice alternatively into the long exon encoding the full-length protein sequence. Irga6 is expressed constitutively in freshly isolated hepatocytes and is competent in these cells to accumulate on the parasitophorous vacuole membrane of infecting Toxoplasma gondii tachyzoites.

CONCLUSIONS AND SIGNIFICANCE

The role of constitutive hepatocyte expression of Irga6 in resistance to parasites invading from the gut via the hepatic portal system is discussed.

Acute systemic erythropoietin therapy to reduce delayed ischemic deficits following aneurysmal subarachnoid hemorrhage: a Phase II randomized, double-blind, placebo-controlled trial

Object

Delayed ischemic deficits (DIDs), a major source of disability following aneurysmal subarachnoid hemorrhage (aSAH), are usually associated with severe cerebral vasospasm and impaired autoregulation. Systemic erythropoietin (EPO) therapy has been demonstrated to have neuroprotective properties acting via EPO receptors on cerebrovascular endothelia and ischemic neurons. In this trial, the authors explored the potential neuroprotective effects of acute EPO therapy following aSAH.

Methods

Within 72 hours of aSAH, 80 patients (age range 24–82 years) were randomized to receive intravenous EPO (30,000 U) or placebo every 48 hours for a total of 90,000 U. Primary end points were the incidence, duration, and severity of vasospasm and impaired autoregulation on transcranial Doppler ultrasonography. Secondary end points were incidence of DIDs and outcome at discharge and at 6 months.

Results

Randomization characteristics were balanced except for age, with the EPO group being older (mean age 59.6 vs 53.3 years, p = 0.034). No differences were demonstrated in the incidence of vasospasm and adverse events; however, patients receiving EPO had a decreased incidence of severe vasospasm from 27.5 to 7.5% (p = 0.037), reduced DIDs with new cerebral infarcts from 40.0 to 7.5% (p = 0.001), a shortened duration of impaired autoregulation (ipsilateral side, p < 0.001), and more favorable outcome at discharge (favorable Glasgow Outcome Scale score, p = 0.039). Among the 71 survivors, the EPO group had fewer deficits measured with National Institutes of Health Stroke Scale (median Score 2 vs 6, p = 0.008).

Conclusions

This preliminary study showed that EPO seemed to reduce delayed cerebral ischemia following aSAH via decreasing severity of vasospasm and shortening impaired autoregulation.

A novel approach to the identification and enrichment of cancer stem cells from a cultured human glioma cell line

Enrichment of cancer stem cells for studies of carcinogenesis remains a difficult issue. We hypothesized that the unique features of cancer stem cells (CSCs) may allow formation of their colonies in vitro with distinct morphology. We therefore investigated the possibility to use morphological diversity of colonies to identify and enrich CSCs from cultured malignant human glioma cells. We found that a small proportion of the cells from a human glioma cell line U251 formed tight and round-shaped colonies in culture. Most cells in such colonies were capable of self-renewal, generating tumor spheres and differentiating into lineages with markers for neurons, astrocytes and oligodendrocytes. In addition, several neural stem cell-related genes were highly expressed by tumor cells in those tight colonies. Our results thus demonstrate a novel approach to the identification and enrichment of CSCs based on unique morphology of their colonies formed in vitro.

Methods for analysis of brain tumor stem cell and neural stem cell self-renewal

Neural stem cells (NSC) self-renew and are multipotent, producing neurons and glia. Recent studies have shown that brain tumors (BT) contain cells that, like NSC, self-renew and are multipotent, producing the different types of cells found within the brain tumors. These brain tumor stem cells are a kind of cancer stem cell, competent to form tumors that mimic the parent tumor in experimental animals. Studies from our laboratory and others have demonstrated that brain tumor stem cells and NSC share similar mechanisms and pathways for proliferation. For example, we have identified that one of the AMPK/snf1 kinases, maternal embryonic leucine zipper kinase (MELK), is highly expressed in NSC and malignant brain tumors, as well as in brain tumor stem cell-enriched cell cultures. Analysis of transgenic MELK-reporter mice indicated that MELK is expressed in NSC in vivo, and our in vitro studies demonstrated that MELK is required for NSC self-renewal. We have also found that MELK is required for proliferation of putative BT stem cells. Utilizing our studies with MELK as an example, this chapter describes methods to culture NSC and BT stem cells, and to analyze the pathways, which regulate self-renewal of those cells.

Transcriptional profiling of hematopoietic stem cells by high-throughput sequencing

Microarray analysis has made it feasible to carry out extensive gene expression profiling in a single assay. Various hematopoietic stem cell (HSC) populations have been subjected to microarray analyses and their profiles of gene expression have been reported. However, this approach is not suitable to identify novel transcripts or for profiling of genes with low expression levels. To obtain a detailed gene expression profile of CD34(-)c-Kit(+)Sca-1(+)lineage marker-negative (Lin(-)) (CD34(-)KSL) HSCs, we constructed a CD34(-)KSL cDNA library, performed high-throughput sequencing, and compared the generated profile with that of another HSC fraction, side population (SP) Lin(-) (SP Lin(-)) cells. Sequencing of the 5'-termini of about 9,500 cDNAs from each HSC library identified 1,424 and 2,078 different genes from the CD34(-)KSL and SP Lin(-) libraries, respectively. To exclude ubiquitously expressed genes including housekeeping genes, digital subtraction was successfully performed against EST databases of other organs, leaving 25 HSC-specific genes including five novel genes. Among 4,450 transcripts from the CD34(-)KSL cDNA library that showed no homology to the presumable protein-coding genes, 29 were identified as strong candidates for mRNA-like non-coding RNAs by in silico analyses. Our cyclopedic approaches may contribute to understanding of novel molecular aspects of HSC function.

An identification of stem cell-resembling gene expression profiles in high-grade astrocytomas

High-grade astrocytomas are among the most intractable types of cancers and are often fatal. Previous studies have suggested that high-grade astrocytomas may adopt the self-renewal and migration properties of neural stem cells (NSCs) to proliferate and spread by expressing the stem cell-specific genes. However, despite a few common molecules being documented, the molecular basis underlying these similarities remains largely unknown. To have a better understanding of the stem cell characteristics of high-grade astrocytomas, we performed the study to identify the stem cell-resembling gene expression profile in high-grade astrocytomas. cDNA microarray analysis was used to detect the differentially expressed genes of isolated human high-grade astrocytomas versus their peritumoral tissue counterparts, and the identification of stem cell-resembling genes was approached by comparing the high-grade astrocytomas-specific gene expression profile with that of NSCs identified by our previous study and other groups. We identified more than 200 high-grade astrocytomas-specific genes in this study, and near 10% genes or gene families of them exhibited similar up or down expression patterns as in NSCs. Further analysis indicated that these genes were actively involved in cell proliferation, adhesion, migration, and metastasis. This study revealed a list of stem cell-specific genes in high-grade astrocytomas, which was likely to have critical roles in determining the "stem" characteristics of high-grade astrocytomas.

Legume lectin FRIL preserves neural progenitor cells in suspension culture in vitro

In vitro maintenance of stem cells is crucial for many clinical applications. Stem cell preservation factor FRIL (Flt3 receptor-interacting lectin) is a plant lectin extracted from Dolichos Lablab and has been found preserve hematopoietic stem cells in vitro for a month in our previous studies. To investigate whether FRIL can preserve neural progenitor cells (NPCs), it was supplemented into serum-free suspension culture media. FRIL made NPC grow slowly, induced cell adhesion, and delayed neurospheres formation. However, FRIL did not initiate NPC differentiation according to immunofluorescence and semiquantitive RT-PCR results. In conclusion, FRIL could also preserve neural progenitor cells in vitro by inhibiting both cell proliferation and differentiation.

The aryl hydrocarbon receptor has a normal function in the regulation of hematopoietic and other stem/progenitor cell populations

The aryl hydrocarbon receptor (AhR) is known mainly as the mediator for the toxicity of certain xenobiotics. However, there is also much information to indicate that this transcription factor has important biological functions. Here we review the evidence that the AhR has a significant role in the regulation of hematopoietic stem cells (HSCs). Data to support this come from studies with xenobiotic AhR ligands, phenotypic analyses of mice lacking AhR, examining the presence and regulation of the AhR within HSCs, knowledge of genes and signaling pathways regulated by the AhR, and investigations of hematopoietic disorders. Based on this information, we hypothesize that AhR expression is necessary for the proper maintenance of quiescence in HSCs, and that AhR down-regulation is essential for "escape" from quiescence and subsequent proliferation of these cells. This implicates the AhR as a negative regulator of hematopoiesis with a function of curbing excessive or unnecessary proliferation. This provides an important advantage by preventing the premature exhaustion of HSCs and sensitivity to genetic alterations, thus preserving HSC function and long-term multi-lineage generation over the lifespan of the organism. This also implicates a role of the AhR in aging processes. AhR dysregulation may result in the altered ability of HSCs to sense appropriate signals in the bone marrow microenvironment leading to hematopoietic disease. It is also reasonable to hypothesize that this protein has an important function in the regulation of other tissue stem cell populations. Suggestive evidence is consistent with a role in skin and neural stem cells.

Adipose-derived stem cells: isolation, expansion and differentiation

The emerging field of regenerative medicine will require a reliable source of stem cells in addition to biomaterial scaffolds and cytokine growth factors. Adipose tissue has proven to serve as an abundant, accessible and rich source of adult stem cells with multipotent properties suitable for tissue engineering and regenerative medical applications. There has been increased interest in adipose-derived stem cells (ASCs) for tissue engineering applications. Here, methods for the isolation, expansion and differentiation of ASCs are presented and described in detail. While this article has focused on the isolation of ASCs from human adipose tissue, the procedure can be applied to adipose tissues from other species with minimal modifications.