Microarray analysis of neural stem cell differentiation in the striatum of the fetal rat

Matrin-3 is essential for fibroblast growth factor 2-dependent maintenance of neural stem cells

To investigate the mechanisms underlying the maintenance of neural stem cells, we performed two-dimensional fluorescence-difference gel electrophoresis (2D-DIGE) targeting the nuclear phosphorylated proteins. Nuclear phosphorylated protein Matrin-3 was identified in neural stem cells (NSCs) after stimulation using fibroblast growth factor 2 (FGF2). Matrin-3 was expressed in the mouse embryonic subventricular and ventricular zones. Small interfering RNA (siRNA)-mediated knockdown of Matrin-3 caused neuronal differentiation of NSCs in vitro, and altered the cerebral layer structure of foetal brain in vivo. Transfection of Matrin-3 plasmids in which the serine 208 residue was point-mutated to alanine (Ser208Ala mutant Matrin3) and inhibition of Ataxia telangiectasia mutated kinase (ATM kinase), which phosphorylates Matrin-3 Ser208 residue, caused neuronal differentiation and decreased the proliferation of neurosphere-forming stem cells. Thus, our proteomic approach revealed that Matrin-3 phosphorylation was essential for FGF2-dependent maintenance of NSCs in vitro and in vivo.

Monosialoganglioside 1 may alleviate neurotoxicity induced by propofol combined with remifentanil in neural stem cells

Monosialoganglioside 1 (GM1) is the main ganglioside subtype and has neuroprotective properties in the central nervous system. In this study, we aimed to determine whether GM1 alleviates neurotoxicity induced by moderate and high concentrations of propofol combined with remifentanil in the immature central nervous system. Hippocampal neural stem cells were isolated from newborn Sprague-Dawley rats and treated with remifentanil (5, 10, 20 ng/mL) and propofol (1.0, 2.5, 5.0 μg/mL), and/or GM1 (12.5, 25, 50 μg/mL). GM1 reversed combined propofol and remifentanil-induced decreases in the percentage of 5-bromodeoxyuridine(+) cells and also reversed the increase in apoptotic cell percentage during neural stem cell proliferation and differentiation. However, GM1 with combined propofol and remifentanil did not affect β-tubulin(+) or glial fibrillary acidic protein(+) cell percentage during neural stem cell differentiation. In conclusion, we show that GM1 alleviates the damaging effects of propofol combined with remifentanil at moderate and high exposure concentrations in neural stem cells in vitro, and exerts protective effects on the immature central nervous system.

Propofol and remifentanil at moderate and high concentrations affect proliferation and differentiation of neural stem/progenitor cells

Propofol and remifentanil alter intracellular Ca²⁺ concentration ([Ca²⁺]_i) in neural stem/progenitor cells by activating γ-aminobutyric acid type A receptors and by reducing testosterone levels. However, whether this process affects neural stem/progenitor cell proliferation and differentiation remains unknown. In the present study, we applied propofol and remifentanil, alone or in combination, at low, moderate or high concentrations (1, 2–2.5 and 4–5 times the clinically effective blood drug concentration), to neural stem/progenitor cells from the hippocampi of newborn rat pups. Low concentrations of propofol, remifentanil or both had no noticeable effect on cell proliferation or differentiation; however, moderate and high concentrations of propofol and/or remifentanil markedly suppressed neural stem/progenitor cell proliferation and differentiation, and induced a decrease in [Ca²⁺]_i during the initial stage of neural stem/progenitor cell differentiation. We therefore propose that propofol and remifentanil interfere with the proliferation and differentiation of neural stem/progenitor cells by altering [Ca²⁺]_i. Our findings suggest that propofol and/or remifentanil should be used with caution in pediatric anesthesia.

A quantitative study of exocytosis of titanium dioxide nanoparticles from neural stem cells

Nanoparticles (NPs) have been widely studied and applied in biomedicine and other fields. It is important to know the basic process of interaction between NPs and cells in terms of cellular endocytosis and exocytosis. However, little attention has been paid to the cellular exocytosis of NPs. Herein, using a multi-step cellular subculture method, we ascertain quantitatively the endocytosis and exocytosis of widely used TiO2 NPs using the neural stem cells (NSC) as a cellular model and ICP-AES as an analytic measure. Irrespective of the type and dose of TiO2 NPs, approximately 30% of the total TiO2 NPs entered NSCs after 48 h incubation. In the first 24 h after removing TiO2NPs, from the culture medium, about 35.0%, 34.6% and 41.7% of NP1 (50 nm), NP2 (30 nm) and NTs (nanotubes, 100 nm × 4-6 nm) were released (exocytosed) from cells, respectively. The release decreased over time, and became negligible at 72 h. Exocytosis did not happen during cell division. In addition, our results suggested that both endocytosis and exocytosis of TiO2NPs were energy-dependent processes, and NPs uptake by cells was influenced by serum proteins. Furthermore, we achieved primary dynamic confocal imaging of the exocytosis, allowing tracking of TiO2 NPs from NSCs. These findings may benefit studies on nanotoxicology and nanomedicine of TiO2 NPs.

A systems biology approach to identify the signalling network regulated by Rho-GDI-γ during neural stem cell differentiation

Understanding the molecular mechanism that underlies the differentiation of neural stem cells (NSCs) is vital to develop regenerative medicines for neurological disorders. In our previous work, Rho-GDI-γ was found to be able to prompt neuronal differentiation when it was down regulated. However, it is unclear how Rho-GDI-γ regulates this differentiation process. Therefore, a novel systems biology approach is presented here to identify putative signalling pathways regulated by Rho-GDI-γ during NSC differentiation, and these pathways can provide insights into the NSC differentiation mechanisms. In particular, our proposed approach combines the predictive power of computational biology and molecular experiments. With different biological experiments, the genes in the computationally identified signalling network were validated to be indeed regulated by Rho-GDI-γ during the differentiation of NSCs. In particular, one randomly selected pathway involving Vcp, Mapk8, Ywhae and Ywhah was experimentally verified to be regulated by Rho-GDI-γ. These promising results demonstrate the effectiveness of our proposed systems biology approach, indicating the potential predictive power of integrating computational and experimental approaches.

Changes in expression and secretion patterns of fibroblast growth factor 8 and Sonic Hedgehog signaling pathway molecules during murine neural stem/progenitor cell differentiation in vitro

In the present study, we investigated the dynamic expression of fibroblast growth factor 8 and Sonic Hedgehog signaling pathway related factors in the process of in vitro hippocampal neural stem/progenitor cell differentiation from embryonic Sprague-Dawley rats or embryonic Kunming species mice, using fluorescent quantitative reverse transcription-PCR and western blot analyses. Results demonstrated that the dynamic expression of fibroblast growth factor 8 was similar to fibroblast growth factor receptor 1 expression but not to other fibroblast growth factor receptors. Enzyme-linked immunosorbent assay demonstrated that fibroblast growth factor 8 and Sonic Hedgehog signaling pathway protein factors were secreted by neural cells into the intercellular niche. Our experimental findings indicate that fibroblast growth factor 8 and Sonic Hedgehog expression may be related to the differentiation of neural stem/progenitor cells.

Distribution and localization of fibroblast growth factor-8 in rat brain and nerve cells during neural stem/progenitor cell differentiation

The present study explored the distribution and localization of fibroblast growth factor-8 and its potential receptor, fibroblast growth factor receptor-3, in adult rat brain in vivo and in nerve cells during differentiation of neural stem/progenitor cells in vitro. Immunohistochemistry was used to examine the distribution of fibroblast growth factor-8 in adult rat brain in vivo. Localization of fibroblast growth factor-8 and fibroblast growth factor receptor-3 in cells during neural stem/progenitor cell differentiation in vitro was detected by immunofluorescence. Flow cytometry and immunofluorescence were used to evaluate the effect of an anti-fibroblast growth factor-8 antibody on neural stem/progenitor cell differentiation and expansion in vitro. Results from this study confirmed that fibroblast growth factor-8 was mainly distributed in adult midbrain, namely the substantia nigra, compact part, dorsal tier, substantia nigra and reticular part, but was not detected in the forebrain comprising the caudate putamen and striatum. Unusual results were obtained in retrosplenial locations of adult rat brain. We found that fibroblast growth factor-8 and fibroblast growth factor receptor-3 were distributed on the cell membrane and in the cytoplasm of nerve cells using immunohistochemistry and immunofluorescence analyses. We considered that the distribution of fibroblast growth factor-8 and fibroblast growth factor receptor-3 in neural cells corresponded to the characteristics of fibroblast growth factor-8, a secretory factor. Addition of an anti-fibroblast growth factor-8 antibody to cultures significantly affected the rate of expansion and differentiation of neural stem/progenitor cells. In contrast, addition of recombinant fibroblast growth factor-8 to differentiation medium promoted neural stem/progenitor cell differentiation and increased the final yields of dopaminergic neurons and total neurons. Our study may help delineate the important roles of fibroblast growth factor-8 in brain activities and neural stem/progenitor cell differentiation.

Silencing of Rho-GDIgamma by RNAi promotes the differentiation of neural stem cells

RNA interference (RNAi) technology is one of the main means in the study of stem cell differentiation. This study describes Rho-GDIgamma function during the differentiation of neural stem cells by using RNAi. Rho-GDIgamma belongs to the Rho-GDI protein family, which is expressed at high level throughout the brain. Although it exists in neuronal population, its physiological function is poorly understood. By using RNAi technology to downregulate expression of Rho-GDIgamma, we found distinct morphological changes in neural stem cell line C17.2. More important, RT-PCR confirmed that RNAi-mediated downregulation of Rho-GDIgamma decreased expression of Rho-GDIgamma-regulated genes RhoA and slightly increased expression of Rac1. Further, immunochemical staining indicated that downregulation of Rho-GDIgamma increased the tendency of C17.2 cells to differentiate. These data strongly suggest that Rho-GDIgamma plays a key role in the differentiation of neural stem cells.

A protein interaction network for the analysis of the neuronal differentiation of neural stem cells in response to titanium dioxide nanoparticles

The effects of titanium dioxide (TiO(2)) nanoparticles (NPs) on the differentiation of neural stem cells are reported. Our findings indicate that TiO(2) NPs lead to a differentiational tendency towards neurons from neural stem cells, suggesting TiO(2) NPs might be a beneficial inducer for neuronal differentiation. To insight into the possible molecular mechanism of the neuronal differentiation, we conducted a protein-protein interaction network (PIN) analysis. To this end, a global mapping of target proteins induced by TiO(2) NPs was first made by a 2-dimensional electrophoresis analysis. Results showed that 9 proteins were significantly changed and then they were subjected to the mass spectrometric assay. All 9 identified proteins are involved in signal, molecular chaperones, cytoskeleton, and nucleoprotein. Further, based on our experimental data and DIP, IntAct-EBI, GRID database, a protein-protein interaction network was constructed, which provides highly integrated information exhibiting the protein-protein interaction. By analysis of the gene expression, the signal pathway involving Cx43 phosphorylation, which is negatively regulated by the protein kinase C epsilon (PKCepsilon), is demonstrated. It is inferred that PKCepsilon plays a pivotal negative role in the neuronal differentiation of stem neural cells in response to the TiO(2) NPs exposure.

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.

Downregulation of Rho-GDI gamma promotes differentiation of neural stem cells

Rho-GDIgamma belongs to the Rho-GDI protein family, which was observed to have high level expression in the entire brain. Although it exists in neuronal population, its physiological function is poorly understood. This study shows that Rho-GDIgamma is a key factor in the G13 signaling pathway based on an analysis of global gene expression. By using RNAi technology to downregulate expression of Rho-GDIgamma we found distinct morphological changes in neural stem cell line C17.2. More important, RT-PCR confirmed that RNAi-mediated downregulation of Rho-GDIgamma decreased expression of Rho-GDIgamma-regulated genes RhoA, Cdc42, Limk2, and N-WASP and slightly increased expression of Rac1. Further, immunochemical staining indicated that downregulation of Rho-GDIgamma increased the tendency of C17.2 cells to differentiate. These data strongly suggest that Rho-GDIgamma plays a key role in the differentiation of neural stem cells.

Blocking BE301622 gene expression by RNAi initiates differentiation of neural stem cells in rat

Neural stem cells (NSCs) are capable of differentiating into neurons, astrocytes and oligodendrocytes. However, the molecular mechanisms regulating NSCs differentiation are not well understood. Our previous research by microarray analysis certified that a lot of genes are differentially expressed in the course of NSC differentiation. In this study we report the function of one of these genes, BE301622, by RNAi techniques. To silence the BE301622 gene, a long, double-stranded RNA (dsRNA) was synthesized by using a kit (Ambion T7 MegaScript) and transformed into NSCs. Expression of mRNA was tested through RT-PCR. The result showed the expression of BE301622 gene was specificially suppressed. This finding effectively validated that BE301622 is involved in the differentiation of NSCs.

Identification and functional analysis of candidate genes regulating mesenchymal stem cell self-renewal and multipotency

Adult human mesenchymal stem cells (hMSCs) possess multilineage differentiation potential, and differentiated hMSCs have recently been shown to have the ability to transdifferentiate into other lineages. However, the molecular signature of hMSCs is not well-known, and the mechanisms regulating their self-renewal, differentiation, and transdifferentiation are not completely understood. In this study, we demonstrate that fully differentiated hMSCs could dedifferentiate, a likely critical step for transdifferentiation. By comparing the global gene expression profiles of undifferentiated, differentiated, and dedifferentiation cells in three mesenchymal lineages (osteogenesis, chondrogenesis, and adipogenesis), we identified a number of "stemness" and "differentiation" genes that might be essential to maintain adult stem cell multipotency as well as to drive lineage-specific commitment. These genes include those that encode cell surface molecules, as well as components of signaling pathways. These genes may be valuable for developing methods to isolate, enrich, and purify homogeneous population of hMSCs and/or maintain and propagate hMSCs as well as guide or regulate their differentiation for gene and cell-based therapy. Using small interfering RNA gene inactivation, we demonstrate that five genes (actin filament-associated protein, frizzled 7, dickkopf 3, protein tyrosine phosphatase receptor F, and RAB3B) promote cell survival without altering cell proliferation, as well as exhibiting different effects on the commitment of hMSCs into multiple mesenchymal lineages.

Gene expression profiling and analysis of signaling pathways involved in priming and differentiation of human neural stem cells

Human neural stem cells have the ability to differentiate into all three major cell types in the CNS including neurons, astrocytes and oligodendrocytes. The multipotency of human neural stem cells shed a light on the possibility of using stem cells as a therapeutic tool for various neurological disorders including neurodegenerative diseases and neurotrauma that involve a loss of functional neurons. We have discovered previously a priming procedure to direct primarily cultured human neural stem cells to differentiate into almost pure neurons when grafted into adult CNS. However, the molecular mechanism underlying this phenomenon is still unknown. To unravel transcriptional changes of human neural stem cells upon priming, cDNA microarray was used to study temporal changes in human neural stem cell gene expression profile during priming and differentiation. As a result, transcriptional levels of 520 annotated genes were detected changed in at least at two time points during the priming process. In addition, transcription levels of more than 3000 hypothetical protein encoding genes and EST genes were modulated during the priming and differentiation processes of human neural stem cells. We further analyzed the named genes and grouped them into 14 functional categories. Of particular interest, key cell signal transduction pathways, including the G-protein-mediated signaling pathways (heterotrimeric and small monomeric GTPase pathways), the Wnt signaling pathway and the TGF-beta pathway, are modulated by the neural stem cell priming, suggesting important roles of these key signaling pathways in priming and differentiation of human neural stem cells.

In vivo transcriptional profile analysis reveals RNA splicing and chromatin remodeling as prominent processes for adult neurogenesis

Neural stem cells and neurogenesis persist in the adult mammalian brain subventricular zone (SVZ). Cells born in the rodent SVZ migrate to the olfactory bulb (Ob) where they differentiate into interneurons. To determine the gene expression and functional profile of SVZ neurogenesis, we performed three complementary sets of transcriptional analysis experiments using Affymetrix GeneChips: (1) comparison of adult mouse SVZ and Ob gene expression profiles with those of the striatum, cerebral cortex, and hippocampus; (2) profiling of SVZ stem cells and ependyma isolated by fluorescent-activated cell sorting (FACS); and (3) analysis of gene expression changes during in vivo SVZ regeneration after anti-mitotic treatment. Gene Ontology (GO) analysis of data from these three separate approaches showed that in adult SVZ neurogenesis, RNA splicing and chromatin remodeling are biological processes as statistically significant as cell proliferation, transcription, and neurogenesis. In non-neurogenic brain regions, RNA splicing and chromatin remodeling were not prominent processes. Fourteen mRNA splicing factors including Sf3b1, Sfrs2, Lsm4, and Khdrbs1/Sam68 were detected along with 9 chromatin remodeling genes including Mll, Bmi1, Smarcad1, Baf53a, and Hat1. We validated the transcriptional profile data with Northern blot analysis and in situ hybridization. The data greatly expand the catalogue of cell cycle components, transcription factors, and migration genes for adult SVZ neurogenesis and reveal RNA splicing and chromatin remodeling as prominent biological processes for these germinal cells.

Down-regulation of specific gene expression by double-strand RNA induces neural stem cell differentiation in vitro

In the postgenomic era the elucidation of the physiological function of genes has become the rate-limiting step in the quest to understand the development and function of living organisms. Double-stranded RNA (dsRNA) interferes with gene expression in various species, a phenomenon known as RNA interference (RNAi). We show here that RNAi is also effective in modifying gene expression in neural stem cell differentiation. The progenitor cells were obtained from E14 mouse embryonic forebrain and maintained using N-2 medium containing basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and B27.A gene (NM017084.1) was previously discovered and validated to express obviously differently between differentiated and undifferentiated neural stem cells in our laboratory. Here we report a long double-stranded RNA to knock out or knock down this gene. The results demonstrated that following RNAi inhibition of expression of the NM017084.1 gene, the differentiation of neural stem cells is accelerated. Thus the NM017084.1 gene may play a pivotal role in the process of differentiation of neural stem cells.

Gene expression changes in the course of neural progenitor cell differentiation

The molecular changes underlying neural progenitor differentiation are essentially unknown. We applied cDNA microarrays with 13,627 clones to measure dynamic gene expression changes during the in vitro differentiation of neural progenitor cells that were isolated from the subventricular zone of postnatal day 7 mice and grown in vitro as neurospheres. In two experimental series in which we withdrew epidermal growth factor and added the neurotrophins Neurotrophin-4 or BDNF, four time points were investigated: undifferentiated cells grown as neurospheres, and cells 24, 48, and 96 hr after differentiation. Expression changes of selected genes were confirmed by semiquantitative RT-PCR. Ten different groups of gene expression dynamics obtained by cluster analysis are described. To correlate selected gene expression changes to the localization of respective proteins, we performed immunostainings of cultured neurospheres and of brain sections from adult mice. Our results provide new insights into the genetic program of neural progenitor differentiation and give strong hints to as yet unknown cellular communications within the adult subventricular zone stem cell niche.

Comprehensive transcriptome analysis of differentiation of embryonic stem cells into midbrain and hindbrain neurons

Neurogenesis is one of the most complex events in embryonic development. However, little information is available regarding the molecular events that occur during neurogenesis. To identify regulatory genes and underlying mechanisms involved in the differentiation of embryonic stem (ES) cells to neurons, gene expression profiling was performed using cDNA microarrays. In mouse ES cells, we compared the gene expression of each differentiated cell stage using a five-stage lineage selection method. Of 10,368 genes, 1633 (16%) known regulatory genes were differentially expressed at least 2-fold or greater at one or more stages. At stage 3, during which ES cells differentiate into neural stem cells, modulation of nearly 1000 genes was observed. Most of transcription factors (Otx2, Ebf-3, Ptx3, Sox4, 13, 18, engrailed, Irx2, Pax8, and Lim3), signaling molecules (Wnt, TGF, and Shh family members), and extracellular matrix/adhesion molecules (collagens, MAPs, and NCAM) were up-regulated. However, some genes which may play important roles in maintaining the pluripotency of ES cells (Kruppel-like factor 2, 4, 5, 9, myeloblast oncogene like2, ZFP 57, and Esg-1) were down-regulated. The many genes identified with this approach that are modulated during neurogenesis will facilitate studies of the mechanisms underlying ES cell differentiation, neural induction, and neurogenesis.