POU transcription factors control expression of CNS stem cell-specific genes

A Sox2 enhancer cluster regulates region-specific neural fates from mouse embryonic stem cells

Sex-determining region Y box 2 (Sox2) is a critical transcription factor for embryogenesis and neural stem and progenitor cell (NSPC) maintenance. While distal enhancers control Sox2 in embryonic stem cells (ESCs), enhancers closer to the gene are implicated in Sox2 transcriptional regulation in neural development. We hypothesize that a downstream enhancer cluster, termed Sox2 regulatory regions 2-18 (SRR2-18), regulates Sox2 transcription in neural stem cells and we investigate this in NSPCs derived from mouse ESCs. Using functional genomics and CRISPR-Cas9-mediated deletion analyses, we investigate the role of SRR2-18 in Sox2 regulation during neural differentiation. Transcriptome analyses demonstrate that the loss of even 1 copy of SRR2-18 disrupts the region-specific identity of NSPCs, reducing the expression of genes associated with more anterior regions of the embryonic nervous system. Homozygous deletion of this Sox2 neural enhancer cluster causes reduced SOX2 protein, less frequent interaction with transcriptional machinery, and leads to perturbed chromatin accessibility genome-wide further affecting the expression of neurodevelopmental and anterior-posterior regionalization genes. Furthermore, homozygous NSPC deletants exhibit self-renewal defects and impaired differentiation into cell types found in the brain. Altogether, our data define a cis-regulatory enhancer cluster controlling Sox2 transcription in NSPCs and highlight the sensitivity of neural differentiation processes to decreased Sox2 transcription, which causes differentiation into posterior neural fates, specifically the caudal neural tube. This study highlights the importance of precise Sox2 regulation by SRR2-18 in neural differentiation.

POU3F4 up-regulates Gli1 expression and promotes neuronal differentiation and synaptic development of hippocampal neural stem cells

BACKGROUND

Neural stem cells (NSCs) are considered to be the most promising cell type for cell replacement therapy in neurodegenerative diseases. However, their low neuronal differentiation ratio impedes their application in such conditions. Elucidating the molecular mechanism of NSC differentiation may provide the necessary experimental basis for expanding their application. Previous studies have indicated that POU3F4 can induce neuronal differentiation of NSCs, this study aims to underly the possible exact mechanism of POU3F4 on the NSC differentiation and development.

METHODS

NSCs were isolated and cultured from the hippocampus of neonatal mice. The frozen hippocampal sections were prepared for immunohistochemical staining. Synaptic development was assessed using electron microscopy. High-throughput sequencing was employed to analyze the gene expression profile following the overexpression of Brn4. Gene expression levels were determined through Western blotting and qRT-PCR. Cell cycle and differentiation were evaluated using flow cytometry and immunofluorescent staining.

RESULTS

It was found that POU3F4 promoted the neuronal differentiation of hippocampal NSCs and synapse development, and inhibited NSC proliferation. POU3F4-deficient mice exhibited impairments in learning and memory. RNA sequencing and ChIP assays confirmed that Gli1 was downstream of POU3F4. Loss and gain function experiments indicated that Gli1 mediated POU3F4 promoting neuronal differentiation and synapse development. Forced expression of Gli1 in hippocampus improved learning and memory function of animal models.

CONCLUSIONS

The results suggest that POU3F4 and Gli1 promote neuronal differentiation and synaptic development of NSCs, and that Gli1 partially mediates the effects of POU3F4.

FABP7: a glial integrator of sleep, circadian rhythms, plasticity, and metabolic function

Sleep and circadian rhythms are observed broadly throughout animal phyla and influence neural plasticity and cognitive function. However, the few phylogenetically conserved cellular and molecular pathways that are implicated in these processes are largely focused on neuronal cells. Research on these topics has traditionally segregated sleep homeostatic behavior from circadian rest-activity rhythms. Here we posit an alternative perspective, whereby mechanisms underlying the integration of sleep and circadian rhythms that affect behavioral state, plasticity, and cognition reside within glial cells. The brain-type fatty acid binding protein, FABP7, is part of a larger family of lipid chaperone proteins that regulate the subcellular trafficking of fatty acids for a wide range of cellular functions, including gene expression, growth, survival, inflammation, and metabolism. FABP7 is enriched in glial cells of the central nervous system and has been shown to be a clock-controlled gene implicated in sleep/wake regulation and cognitive processing. FABP7 is known to affect gene transcription, cellular outgrowth, and its subcellular localization in the fine perisynaptic astrocytic processes (PAPs) varies based on time-of-day. Future studies determining the effects of FABP7 on behavioral state- and circadian-dependent plasticity and cognitive processes, in addition to functional consequences on cellular and molecular mechanisms related to neural-glial interactions, lipid storage, and blood brain barrier integrity will be important for our knowledge of basic sleep function. Given the comorbidity of sleep disturbance with neurological disorders, these studies will also be important for our understanding of the etiology and pathophysiology of how these diseases affect or are affected by sleep.

A critical period of translational control during brain development at codon resolution

Translation modulates the timing and amplification of gene expression after transcription. Brain development requires uniquely complex gene expression patterns, but large-scale measurements of translation directly in the prenatal brain are lacking. We measure the reactants, synthesis and products of mRNA translation spanning mouse neocortex neurogenesis, and discover a transient window of dynamic regulation at mid-gestation. Timed translation upregulation of chromatin-binding proteins like Satb2, which is essential for neuronal subtype differentiation, restricts protein expression in neuronal lineages despite broad transcriptional priming in progenitors. In contrast, translation downregulation of ribosomal proteins sharply decreases ribosome biogenesis, coinciding with a major shift in protein synthesis dynamics at mid-gestation. Changing activity of eIF4EBP1, a direct inhibitor of ribosome biogenesis, is concurrent with ribosome downregulation and affects neurogenesis of the Satb2 lineage. Thus, the molecular logic of brain development includes the refinement of transcriptional programs by translation. Modeling of the developmental neocortex translatome is provided as an open-source searchable resource at https://shiny.mdc-berlin.de/cortexomics .

Global Transcriptional Analyses of the Wnt-Induced Development of Neural Stem Cells from Human Pluripotent Stem Cells

The differentiation of human pluripotent stem cells (hPSCs) to neural stem cells (NSCs) is the key initial event in neurogenesis and is thought to be dependent on the family of Wnt growth factors, their receptors and signaling proteins. The delineation of the transcriptional pathways that mediate Wnt-induced hPSCs to NSCs differentiation is vital for understanding the global genomic mechanisms of the development of NSCs and, potentially, the creation of new protocols in regenerative medicine. To understand the genomic mechanism of Wnt signaling during NSCs development, we treated hPSCs with Wnt activator (CHIR-99021) and leukemia inhibitory factor (LIF) in a chemically defined medium (N2B27) to induce NSCs, referred to as CLNSCs. The CLNSCs were subcultured for more than 40 passages in vitro; were positive for AP staining; expressed neural progenitor markers such as NESTIN, PAX6, SOX2, and SOX1; and were able to differentiate into three neural lineage cells: neurons, astrocytes, and oligodendrocytes in vitro. Our transcriptome analyses revealed that the Wnt and Hedgehog signaling pathways regulate hPSCs cell fate decisions for neural lineages and maintain the self-renewal of CLNSCs. One interesting network could be the deregulation of the Wnt/β-catenin signaling pathway in CLNSCs via the downregulation of c-MYC, which may promote exit from pluripotency and neural differentiation. The Wnt-induced spinal markers HOXA1-4, HOXA7, HOXB1-4, and HOXC4 were increased, however, the brain markers FOXG1 and OTX2, were absent in the CLNSCs, indicating that CLNSCs have partial spinal cord properties. Finally, a CLNSC simple culture condition, when applied to hPSCs, supports the generation of NSCs, and provides a new and efficient cell model with which to untangle the mechanisms during neurogenesis.

Hierarchical reactivation of transcription during mitosis-to-G1 transition by Brn2 and Ascl1 in neural stem cells

During mitosis, chromatin condensation is accompanied by a global arrest of transcription. Recent studies suggest transcriptional reactivation upon mitotic exit occurs in temporally coordinated waves, but the underlying regulatory principles have yet to be elucidated. In particular, the contribution of sequence-specific transcription factors (TFs) remains poorly understood. Here we report that Brn2, an important regulator of neural stem cell identity, associates with condensed chromatin throughout cell division, as assessed by live-cell imaging of proliferating neural stem cells. In contrast, the neuronal fate determinant Ascl1 dissociates from mitotic chromosomes. ChIP-seq analysis reveals that Brn2 mitotic chromosome binding does not result in sequence-specific interactions prior to mitotic exit, relying mostly on electrostatic forces. Nevertheless, surveying active transcription using single-molecule RNA-FISH against immature transcripts reveals differential reactivation kinetics for key targets of Brn2 and Ascl1, with transcription onset detected in early (anaphase) versus late (early G1) phases, respectively. Moreover, by using a mitotic-specific dominant-negative approach, we show that competing with Brn2 binding during mitotic exit reduces the transcription of its target gene Nestin Our study shows an important role for differential binding of TFs to mitotic chromosomes, governed by their electrostatic properties, in defining the temporal order of transcriptional reactivation during mitosis-to-G1 transition.

Sox17 Controls Emergence and Remodeling of Nestin-Expressing Coronary Vessels

RATIONALE

The molecular mechanisms underlying the formation of coronary arteries during development and during cardiac neovascularization after injury are poorly understood. However, a detailed description of the relevant signaling pathways and functional TFs (transcription factors) regulating these processes is still incomplete.

OBJECTIVE

The goal of this study is to identify novel cardiac transcriptional mechanisms of coronary angiogenesis and vessel remodeling by defining the molecular signatures of coronary vascular endothelial cells during these complex processes.

METHODS AND RESULTS

We demonstrate that Nes-gfp and Nes-CreERT2 transgenic mouse lines are novel tools for studying the emergence of coronary endothelium and targeting sprouting coronary vessels (but not ventricular endocardium) during development. Furthermore, we identify Sox17 as a critical TF upregulated during the sprouting and remodeling of coronary vessels, visualized by a specific neural enhancer from the Nestin gene that is strongly induced in developing arterioles. Functionally, genetic-inducible endothelial deletion of Sox17 causes deficient cardiac remodeling of coronary vessels, resulting in improper coronary artery formation.

CONCLUSIONS

We demonstrated that Sox17 TF regulates the transcriptional activation of Nestin's enhancer in developing coronary vessels while its genetic deletion leads to inadequate coronary artery formation. These findings identify Sox17 as a critical regulator for the remodeling of coronary vessels in the developing heart.

Brn4 promotes the differentiation of radial glial cells into neurons by inhibiting CtBP2

Neural stem cells (NSCs) are pluripotent cells that are capable of differentiating into neurons and considered as the most promising cell source for cell replacement therapy. However, the difficulty in inducing neuronal differentiation and maturation from NSCs is a major challenge for their clinical application. Clarifying the molecular mechanisms underlying the neuronal differentiation of NSCs can provide a basis for expanding their uses. Brain 4 (Brn4) is a member of the POU domain family of transcription factors and can induce the neuronal differentiation of NSCs, but its precise function in NSCs is unclear. To address this question, in this study we isolated and expanded radial glial cells (RGCs), a type of NSC, from the cerebral cortex of 14-day embryonic rats and used lentivirus carrying the human Brn4 gene to overexpress Brn4 in these cells. This induced the differentiation of RGCs into neurons and inhibited the expression of C-terminal binding protein 2 (CtBP2), a transcriptional co-repressor. CtBP2 overexpression in RGCs suppressed their differentiation into neurons, whereas CtBP2 knockdown had the opposite effect. These results indicated that Brn4 promoted the neuronal differentiation of NSCs via inhibition of CtBP2 and is a potential tool for generating neurons in cell replacement therapy of neurodegenerative diseases and brain injury.

Genomic analysis of transcriptional networks directing progression of cell states during MGE development

Background

Homeodomain (HD) transcription factor (TF) NKX2–1 critical for the regional specification of the medial ganglionic eminence (MGE) as well as promoting the GABAergic and cholinergic neuron fates via the induction of TFs such as LHX6 and LHX8. NKX2–1 defines MGE regional identity in large part through transcriptional repression, while specification and maturation of GABAergic and cholinergic fates is mediated in part by transcriptional activation via TFs such as LHX6 and LHX8. Here we analyze the signaling and TF pathways, downstream of NKX2–1, required for GABAergic and cholinergic neuron fate maturation.

Methods

Differential ChIP-seq analysis was used to identify regulatory elements (REs) where chromatin state was sensitive to change in the Nkx2–1cKO MGE at embryonic day (E) 13.5. TF motifs in the REs were identified using RSAT. CRISPR-mediated genome editing was used to generate enhancer knockouts. Differential gene expression in these knockouts was analyzed through RT-qPCR and in situ hybridization. Functional analysis of motifs within hs623 was analyzed via site directed mutagenesis and reporter assays in primary MGE cultures.

Results

We identified 4782 activating REs (aREs) and 6391 repressing REs (rREs) in the Nkx2–1 conditional knockout (Nkx2–1cKO) MGE. aREs are associated with basic-Helix-Loop-Helix (bHLH) TFs. Deletion of hs623, an intragenic Tcf12 aRE, caused a reduction of Tcf12 expression in the sub-ventricular zone (SVZ) and mantle zone (MZ) of the MGE. Mutation of LHX, SOX and octamers, within hs623, caused a reduction of hs623 activity in MGE primary cultures.

Conclusions

Tcf12 expression in the SVZ of the MGE is mediated through aRE hs623. The activity of hs623 is dependent on LHX6, SOX and octamers. Thus, maintaining the expression of Tcf12 in the SVZ involves on TF pathways parallel and genetically downstream of NKX2–1.

Electronic supplementary material

The online version of this article (10.1186/s13064-018-0119-4) contains supplementary material, which is available to authorized users.

Pax6-dependent regulation of the rat Fabp7 promoter activity

Fabp7 gene encodes a brain-specific fatty acid-binding protein that is widely used as a marker for neural stem cells. Here, we report that the activity of rat Fabp7 promoter was regulated directly by a transcription factor, Pax6. Deletion analyses identified an essential region (-837 to -64 from transcription start site) in the rat Fabp7 promoter. This region controls promoter activity in rat embryos and in the mouse cultured cell line MEB5. Over-expressing wild-type Pax6 or a dominant-negative Pax6 mutant enhanced and suppressed, respectively, the promoter activity. Pax6 can bind the region directly, although the region contains no clear binding motif for Pax6. The rat Fabp7 promoter also contains conserved binding sites for Pbx/POU (-384 to -377) and CBF1 (-270 to -262). However, specific deletion of the sites showed no significant reduction in the promoter activity, although a gel mobility shift assay confirmed that CBF1 binds the conserved sequence. Taken together, these results suggest that the rat Fabp7 promoter is mainly regulated by Pax6. The Pax6-dependent regulation of the rat Fabp7 expression might have an evolutionary aspect between rat and mouse; the former may need to efficiently use fatty acids to make the brain bigger than the latter.

Nestin-expressing progenitor cells: function, identity and therapeutic implications

The neuroepithelial stem cell protein, or Nestin, is a cytoskeletal intermediate filament initially characterized in neural stem cells. However, current extensive evidence obtained in in vivo models and humans shows presence of Nestin+ cells with progenitor and/or regulatory functions in a number of additional tissues, remarkably bone marrow. This review presents the current knowledge on the role of Nestin in essential stem cell functions, including self-renewal/proliferation, differentiation and migration, in the context of the cytoskeleton. We further discuss the available in vivo models for the study of Nestin+ cells and their progeny, their function and elusive nature in nervous system and bone marrow, and their potential mechanistic role and promising therapeutic value in preclinical models of disease. Future improved in vivo models and detection methods will allow to determine the true essence of Nestin+ cells and confirm their potential application as therapeutic target in a range of diseases.

Transgenic mouse models for studying adult neurogenesis

The mammalian hippocampus shows a remarkable capacity for continued neurogenesis throughout life. Newborn neurons, generated by the radial neural stem cells (NSCs), are important for learning and memory as well as mood control. During aging, the number and responses of NSCs to neurogenic stimuli diminish, leading to decreased neurogenesis and age-associated cognitive decline and psychiatric disorders. Thus, adult hippocampal neurogenesis has garnered significant interest because targeting it could be a novel potential therapeutic strategy for these disorders. However, if we are to use neurogenesis to halt or reverse hippocampal-related pathology, we need to understand better the core molecular machinery that governs NSC and their progeny. In this review, we summarize a wide variety of mouse models used in adult neurogenesis field, present their advantages and disadvantages based on specificity and efficiency of labeling of different cell types, and review their contribution to our understanding of the biology and the heterogeneity of different cell types found in adult neurogenic niches.

Nestin-Based Reporter Transgenic Mouse Lines

Nestin expression marks stem and progenitor cells of the neural lineage. Transgenic mouse lines, originally generated to identify neural stem cells, can also help to identify, track, and isolate stem and progenitor cells in a range of tissues of the ectodermal, endodermal, and mesodermal origin. Here, we describe the generation of transgenic mouse lines expressing fluorescent proteins (FP) under the control of critical regulatory elements of the nestin gene and their use for identifying and analyzing adult stem and progenitor cells in various tissues.

IGF-1 promotes Brn-4 expression and neuronal differentiation of neural stem cells via the PI3K/Akt pathway

Our previous studies indicated that transcription factor Brn-4 is upregulated in the surgically denervated hippocampus in vivo, promoting neuronal differentiation of hippocampal neural stem cells (NSCs) in vitro. The molecules mediating Brn-4 upregulation in the denervated hippocampus remain unknown. In this study we examined the levels of insulin-like growth factor-1 (IGF-1) in hippocampus following denervation. Surgical denervation led to a significant increase in IGF-1 expression in vivo. We also report that IGF-1 treatment on NSCs in vitro led to a marked acceleration of Brn-4 expression and cell differentiation down neuronal pathways. The promotion effects were blocked by PI3K-specific inhibitor (LY294002), but not MAPK inhibitor (PD98059); levels of phospho-Akt were increased by IGF-1 treatment. In addition, inhibition of IGF-1 receptor (AG1024) and mTOR (rapamycin) both attenuated the increased expression of Brn-4 induced by IGF-1. Together, the results demonstrated that upregulation of IGF-1 induced by hippocampal denervation injury leads to activation of the PI3K/Akt signaling pathway, which in turn gives rise to upregulation of the Brn-4 and subsequent stem cell differentiation down neuronal pathways.

Nestin involvement in tissue injury and cancer--a potential tumor marker?

BACKGROUND

In eukaryotic cells, the cytoskeleton contains three major filamentous components: actin microfilaments, microtubules and intermediate filaments. Nestin represents one of the class VI intermediate filament proteins. Clinical and molecular analyses have revealed substantial information regarding the presence of Nestin in cells with progenitor or stem cell properties. During tissue injury Nestin is expressed in cells with progenitor cell-like properties. These cells may serve as a tissue reserve and, as such, may contribute to tissue repair. Based on currently available data, Nestin also appears to be implicated in two oncogenic processes. First, Nestin has been found to be expressed in cancer stem-like cells and poorly differentiated cancer cells and, as such, Nestin is thought to contribute to the aggressive behavior of these cells. Second, Nestin has been found to be involved in tumor angiogenesis through an interaction of cancer cells and blood vessel endothelial cells and, as such, Nestin is thought to facilitate tumor growth.

CONCLUSIONS

We conclude that Nestin may serve as a promising tumor marker and as a potential therapeutic target amenable to tumor suppression and angiogenesis inhibition.

Lineage-specific purification of neural stem/progenitor cells from differentiated mouse induced pluripotent stem cells

Since induced pluripotent stem (iPS) cells have differentiation potential into all three germ layer-derived tissues, efficient purification of target cells is required in many fields of iPS research. One useful strategy is isolation of desired cells from differentiated iPS cells by lineage-specific expression of a drug-resistance gene, followed by drug selection. With this strategy, we purified neural stem/progenitor cells (NSCs), a good candidate source for regenerative therapy, from differentiated mouse iPS cells. We constructed a bicistronic expression vector simultaneously expressing blasticidin S resistance gene and DsRed under the control of tandem enhancer of a 257-base pair region of nestin second intron, an NSC-specific enhancer. This construct was efficiently inserted into the iPS genome by piggyBac transposon-mediated gene transfer, and the established subclone was differentiated into NSCs in the presence or absence of blasticidin S. Consequently, incubation with blasticidin S led to purification of NSCs from differentiated iPS cells. Our results suggest that a lineage-specific drug selection strategy is useful for purification of NSCs from differentiated iPS cells and that this strategy can be applied for the purification of other cell types.

Characterization of enhancers active in the mouse embryonic cerebral cortex suggests Sox/Pou cis-regulatory logics and heterogeneity of cortical progenitors

We aimed to identify cis-regulatory elements that control gene expression in progenitors of the cerebral cortex. A list of 975 putative enhancers were retrieved from a ChIP-Seq experiment performed in NS5 mouse stem cells with antibodies to Sox2, Brn2/Pou3f2, or Brn1/Pou3f3. Through a selection pipeline including gene ontology and expression pattern, we reduced the number of candidate enhancer sequences to 20. Ex vivo electroporation of green fluorescent pProtein (GFP) reporter constructs in the telencephalon of mouse embryos showed that 35% of the 20 selected candidate sequences displayed enhancer activity in the developing cortex at E13.5. In silico transcription factor binding site (TFBS) searches and mutagenesis experiments showed that enhancer activity is related to the presence of Sox/Pou TFBS pairs in the sequence. Comparative genomic analyses showed that enhancer activity is not related to the evolutionary conservation of the sequence. Finally, the combination of in utero electroporation of GFP reporter constructs with immunostaining for Tbr2 (basal progenitor marker) and phospho-histoneH3 (mitotic activity marker) demonstrated that each enhancer is specifically active in precise subpopulations of progenitors in the cortical germinal zone, highlighting the heterogeneity of these progenitors in terms of cis-regulation.

Fibroblast growth factor-2 up-regulates the expression of nestin through the Ras-Raf-ERK-Sp1 signaling axis in C6 glioma cells

Nestin is a 240-kDa intermediate filament protein expressed mainly in neural and myogenic stem cells. Although a substantial number of studies have focused on the expression of nestin during development of the central nervous system, little is known about the factors that induce and regulate its expression. Fibroblast growth factor-2 (FGF-2) is an effective mitogen and stimulates the proliferation and differentiation of a subset of nestin-expressing cells, including neural progenitor cells, glial precursor cells, and smooth muscle cells. To assess whether FGF-2 is a potent factor that induces the expression of nestin, C6 glioma cells were used. The results showed that nestin expression was up-regulated by FGF-2 via de novo RNA and protein synthesis. Our RT-PCR results showed that C6 glioma cells express FGFR1/3, and FGFRs is required for FGF-2-induced nestin expression. Further signaling analysis also revealed that FGF-2-induced nestin expression is mediated through FGFR-MAPK-ERK signaling axis and the transcriptional factor Sp1. These findings provide new insight into the regulation of nestin in glial system and enable the further studies on the function of nestin in glial cells.

A radial glia gene marker, fatty acid binding protein 7 (FABP7), is involved in proliferation and invasion of glioblastoma cells

Glioblastoma multiforme (GBM) is among the most deadly cancers. A number of studies suggest that a fraction of tumor cells with stem cell features (Glioma Stem-like Cells, GSC) might be responsible for GBM recurrence and aggressiveness. GSC similarly to normal neural stem cells, can form neurospheres (NS) in vitro, and seem to mirror the genetic features of the original tumor better than glioma cells growing adherently in the presence of serum. Using cDNA microarray analysis we identified a number of relevant genes for glioma biology that are differentially expressed in adherent cells and neurospheres derived from the same tumor. Fatty acid-binding protein 7 (FABP7) was identified as one of the most highly expressed genes in NS compared to their adherent counterpart. We found that down-regulation of FABP7 expression in NS by small interfering RNAs significantly reduced cell proliferation and migration. We also evaluated the potential involvement of FABP7 in response to radiotherapy, as this treatment may cause increased tumor infiltration. Migration of irradiated NS was associated to increased expression of FABP7. In agreement with this, in vivo reduced tumorigenicity of GBM cells with down-regulated expression of FABP7 was associated to decreased expression of the migration marker doublecortin. Notably, we observed that PPAR antagonists affect FABP7 expression and decrease the migration capability of NS after irradiation. As a whole, the data emphasize the role of FABP7 expression in GBM migration and provide translational hints on the timing of treatment with anti-FABP7 agents like PPAR antagonists during GBM evolution.

The effects of Fabp7 and Fabp5 on postnatal hippocampal neurogenesis in the mouse

New neurons are continually produced after birth from neural stem/progenitor cells (NSCs/NPCs) in the hippocampal dentate gyrus (DG). Recent studies have reported that fatty acid binding protein 7 (Fabp7/brain lipid binding protein (BLBP)) is required for the maintenance of embryonic NSCs/NPCs and have identified an association between the Fabp7 gene and behavioral paradigms that correlate with hippocampal functions. However, the specific roles of Fabps in postnatal neurogenesis remain unknown. Herein, we demonstrate the effects of Fabp7, and another Fabp, Fabp5, on postnatal neurogenesis. Fabp7 and Fabp5 were detected in the subgranular zone (SGZ) of the DG, and Fabp7+ cells were less differentiated than Fabp5+ cells. We analyzed the differentiation state of NSCs/NPCs in the SGZ of 4-week-old (4w) Fabp7 knockout (7KO), Fabp5 KO (5KO), and Fabp7/Fabp5 double KO (7/5KO) mice and found that the number of NSCs/NPCs was dramatically reduced compared with wild-type mice. Although the uptake of BrdU 1 day after injection was decreased in all KO mice, the survival of BrdU+ cells 1 month after injection was increased in the 7/5KO mice compared to other three genotypes. We also observed an enhancement of neuronal differentiation in all Fabp KO mice. In addition, the proliferation and survival of NSCs/NPCs differed along the anterior-posterior axis (A-P axis). A greater number of newborn cells in the posterior region became extinct, but this tendency was not apparent in the Fabps KO mice. These data suggest that Fabp7 and Fabp5 have differential roles for proliferation and survival of the NSCs/NPCs during postnatal DG neurogenesis.

Single-cell mRNA profiling identifies progenitor subclasses in neurospheres

Neurospheres are widely used to propagate and investigate neural stem cells (NSCs) and neural progenitors (NPs). However, the exact cell types present within neurospheres are still unknown. To identify cell types, we used single-cell mRNA profiling of 48 genes in 187 neurosphere cells. Using a clustering algorithm, we identified 3 discrete cell populations within neurospheres. One cell population [cluster unsorted (US) 1] expresses high Bmi1 and Hes5 and low Myc and Klf12. Cluster US2 shows intermediate expression of most of the genes analyzed. Cluster US3 expresses low Bmi1 and Hes5 and high Myc and Klf12. The mRNA profiles of these 3 cell populations correlate with a developmental timeline of early, intermediate, and late NPs, as seen in vivo from the mouse brain. We enriched the cell population for neurosphere-forming cells (NFCs) using morphological criteria of forward scatter (FSC) and side scatter (SSC). FSC/SSC(high) cells generated 2.29-fold more neurospheres than FSC/SSC(low) cells at clonal density. FSC/SSC(high) cells were enriched for NSCs and Lewis-X(+ve) cells, possessed higher phosphacan levels, and were of a larger cell size. Clustering of both FSC/SSC(high) and FSC/SSC(low) cells identified an NFC cluster. Significantly, the mRNA profile of the NFC cluster drew close resemblance to that of early NPs. Taken together, data suggest that the neurosphere culture system can be used to model central nervous system development, and that early NPs are the cell population that gives rise to neurospheres. In future work, it may be possible to further dissect the NFCs and reveal the molecular signature for NSCs.

Investigation of neural stem cell-specific regulatory promoter elements

The present study aimed to investigate neural stem cell (NSC)-specific regulatory promoter elements. PCR was employed to amplify the full sequence (4,000 bp) and core sequence (400 bp) of the promoter and intron-2 of the mouse nestin gene. pcDNA3.1 was used as a template to construct 6 different recombinant plasmids. CMV, CMV + intron-2, the full sequence of the nestin gene promoter, the full sequence of the nestin gene promoter + intron-2, the core sequence of the nestin gene promoter and the core sequence of the nestin gene promoter + intron-2 were independently used as promoters to regulate EGFP expression. The 6 recombinant plasmids were independently used to transfect nestin-positive and nestin-negative cells, and the expression of EGFP was observed under a fluorescence microscope. At the same time, flow cytometry was carried out to measure the proportion of cells positive for EGFP. The results showed that the full sequence and core sequence of the nestin gene promoter non-specifically regulated EGFP expression in cells and exhibit potent regulatory potency. The full sequence or core sequence of the nestin gene promoter which was fused with intron-2 can only regulate the EGFP expression in nestin-positive cells. CMV + intron-2 have non-specific regulation of EGFP alone. Thus, we conclude that the full sequence of the nestin gene promoter which is fused with intron-2 can specifically regulate the expression of exogenous genes in nestin-positive cells.

The co-transduction of Nurr1 and Brn4 genes induces the differentiation of neural stem cells into dopaminergic neurons

Fetal brain tissue can be used in cell replacement therapy for PD (Parkinson's disease), but there is a poor donor supply of this tissue. NSCs (neural stem cells) may overcome this problem as they can be isolated and expanded in vitro. However, the usage of NSCs is limited because the differentiation of NSCs into specific dopaminergic neurons has proven difficult. In the present study, we investigated the effect of Nurr1 (nuclear receptor related factor 1), a transcription factor specific for the development and maintenance of the midbrain dopaminergic neurons on inducing the differentiation of NSCs into TH (tyrosine hydroxylase) immunoreactive dopaminergic neurons. Nonetheless, these cells exhibited an immature neuronal morphology with small cell bodies and short neurite processes, and they seldom expressed DAT (dopamine transporter), a late marker of mature dopaminergic neurons. However, forced co-expression of Nurr1 with Brn4, a member of the POU domain family of transcription factors, caused immature Nurr1-induced dopaminergic neurons to differentiate into morphologically and phenotypically more mature neurons. Thus the enriched generation of mature dopaminergic neurons by forced expression of Nurr1 with Brn4 may be of future importance in NSC-based cell replacement therapy for PD.

Regulation of the FABP7 gene by PAX6 in malignant glioma cells

Brain fatty acid-binding protein (FABP7) and PAX6 are both expressed in radial glial cells and have been implicated in neurogenesis and glial cell differentiation. FABP7 and PAX6 have also been postulated to play a role in malignant glioma cell growth and invasion. Here, we address the role of PAX6 in regulating FABP7 gene expression in malignant glioma cells. We report that PAX6 and FABP7 RNA are generally co-expressed in malignant glioma cell lines, tumors and tumor neurospheres. Using the CAT reporter gene assay, we show that FABP7 promoter activity is upregulated by PAX6. Sequential deletion analysis of the FABP7 promoter, combined with gel shift and supershift assays demonstrate the presence of a PAX6 responsive region located upstream of the FABP7 gene, at -862 to -1033 bp. Inclusion of sequences between -1.2 and -1.8 kb reduced CAT activity, suggesting the presence of a repressor element within this region. While PAX6 overexpression did not induce endogenous FABP7 expression in FABP7-negative cells, knock-down of PAX6 in PAX6-positive malignant glioma cells resulted in reduced FABP7 levels. These data provide the first evidence of direct transactivation of the FABP7 proximal promoter by PAX6 and suggest a synergistic mechanism for PAX6 and other co-factor(s) in regulating FABP7 expression in malignant glioma.

Emx2 is a dose-dependent negative regulator of Sox2 telencephalic enhancers

The transcription factor Sox2 is essential for neural stem cells (NSC) maintenance in the hippocampus and in vitro. The transcription factor Emx2 is also critical for hippocampal development and NSC self-renewal. Searching for ‘modifier’ genes affecting the Sox2 deficiency phenotype in mouse, we observed that loss of one Emx2 allele substantially increased the telencephalic β-geo (LacZ) expression of a transgene driven by the 5′ or 3′ Sox2 enhancer. Reciprocally, Emx2 overexpression in NSC cultures inhibited the activity of the same transgene. In vivo, loss of one Emx2 allele increased Sox2 levels in the medial telencephalic wall, including the hippocampal primordium. In hypomorphic Sox2 mutants, retaining a single ‘weak’ Sox2 allele, Emx2 deficiency substantially rescued hippocampal radial glia stem cells and neurogenesis, indicating that Emx2 functionally interacts with Sox2 at the stem cell level. Electrophoresis mobility shift assays and transfection indicated that Emx2 represses the activities of both Sox2 enhancers. Emx2 bound to overlapping Emx2/POU-binding sites, preventing binding of the POU transcriptional activator Brn2. Additionally, Emx2 directly interacted with Brn2 without binding to DNA. These data imply that Emx2 may perform part of its functions by negatively modulating Sox2 in specific brain areas, thus controlling important aspects of NSC function in development.

SRY-box-containing gene 2 regulation of nuclear receptor tailless (Tlx) transcription in adult neural stem cells

Adult neurogenesis is maintained by self-renewable neural stem cells (NSCs). Their activity is regulated by multiple signaling pathways and key transcription factors. However, it has been unclear whether these factors interplay with each other at the molecular level. Here we show that SRY-box-containing gene 2 (Sox2) and nuclear receptor tailless (TLX) form a molecular network in adult NSCs. We observed that both Sox2 and TLX proteins bind to the upstream region of Tlx gene. Sox2 positively regulates Tlx expression, whereas the binding of TLX to its own promoter suppresses its transcriptional activity in luciferase reporter assays. Such TLX-mediated suppression can be antagonized by overexpressing wild-type Sox2 but not a mutant lacking the transcriptional activation domain. Furthermore, through regions involved in DNA-binding activity, Sox2 and TLX physically interact to form a complex on DNAs that contain a consensus binding site for TLX. Finally, depletion of Sox2 revealed the potential negative feedback loop of TLX expression that is antagonized by Sox2 in adult NSCs. These data suggest that Sox2 plays an important role in Tlx transcription in cultured adult NSCs.

Experience dictates stem cell fate in the adult hippocampus

Adult hippocampal neurogenesis has been implicated in cognitive and emotional processes, as well as in response to antidepressant treatment. However, little is known about how the adult stem cell lineage contributes to hippocampal structure and function and how this process is modulated by the animal's experience. Here we perform an indelible lineage analysis and report that neural stem cells can produce expanding and persisting populations of not only neurons, but also stem cells in the adult hippocampus. Furthermore, the ratio of stem cells to neurons depends on experiences of the animal or the location of the stem cell. Surprisingly, social isolation facilitated accumulation of stem cells, but not neurons. These results show that neural stem cells accumulate in the adult hippocampus and that the stem cell-lineage relationship is under control of anatomic and experiential niches. Our findings suggest that, in the hippocampus, fate specification may act as a form of cellular plasticity for adapting to environmental changes.

Identification of a novel intronic enhancer responsible for the transcriptional regulation of musashi1 in neural stem/progenitor cells

Background

The specific genetic regulation of neural primordial cell determination is of great interest in stem cell biology. The Musashi1 (Msi1) protein, which belongs to an evolutionarily conserved family of RNA-binding proteins, is a marker for neural stem/progenitor cells (NS/PCs) in the embryonic and post-natal central nervous system (CNS). Msi1 regulates the translation of its downstream targets, including m-Numb and p21 mRNAs. In vitro experiments using knockout mice have shown that Msi1 and its isoform Musashi2 (Msi2) keep NS/PCs in an undifferentiated and proliferative state. Msi1 is expressed not only in NS/PCs, but also in other somatic stem cells and in tumours. Based on previous findings, Msi1 is likely to be a key regulator for maintaining the characteristics of self-renewing stem cells. However, the mechanisms regulating Msi1 expression are not yet clear.

Results

To identify the DNA region affecting Msi1 transcription, we inserted the fusion gene ffLuc, comprised of the fluorescent Venus protein and firefly Luciferase, at the translation initiation site of the mouse Msi1 gene locus contained in a 184-kb bacterial artificial chromosome (BAC). Fluorescence and Luciferase activity, reflecting the Msi1 transcriptional activity, were observed in a stable BAC-carrying embryonic stem cell line when it was induced toward neural lineage differentiation by retinoic acid treatment. When neuronal differentiation was induced in embryoid body (EB)-derived neurosphere cells, reporter signals were detected in Msi1-positive NSCs and GFAP-positive astrocytes, but not in MAP2-positive neurons. By introducing deletions into the BAC reporter gene and conducting further reporter experiments using a minimized enhancer region, we identified a region, "D5E2," that is responsible for Msi1 transcription in NS/PCs.

Conclusions

A regulatory element for Msi1 transcription in NS/PCs is located in the sixth intron of the Msi1 gene. The 595-bp D5E2 intronic enhancer can transactivate Msi1 gene expression with cell-type specificity markedly similar to the endogenous Msi1 expression patterns.

Effects of Brn-4 on the neuronal differentiation of neural stem cells derived from rat midbrain

NSCs (neural stem cells) provide a powerful research tool for the design and discovery of new approaches to cell replacement therapy during brain repair. However, the usefulness of this tool has been particularly obstructed by limited neuronal differentiation of NSCs. Brn-4, a member of the POU domain family of transcription factors, has been previously implicated in the development of neurons by expression analysis. Here, we directly investigated the effects of Brn-4 on the neuronal differentiation and development of NSCs derived from the E13 rat midbrain. We found that Brn-4 knockdown in NSCs resulted in a significant decrease of MAP-2-positive neurons with immature morphology. Overexpression of Brn-4 in NSCs markedly increased the production and maturation of newborn neurons. These results suggest that Brn-4 has a critical role in the neuronal differentiation of mesencephalic NSCs and the maturation of newborn neurons. Brn-4 may be utilized to manipulate NSCs for gene and cell therapy of several neurological diseases.

Identification of the Tctex-1 regulatory element that directs expression to neural stem/progenitor cells in developing and adult brain

Previous studies showed that Tctex-1 immunoreactivity is selectively enriched in the germinal zones of adult brain. In this report we identify a regulatory region of the Tctex-1 gene that is capable of directing transgenic expression of green fluorescent protein (GFP) reporter that recapitulates the spatial and temporal expression pattern of endogenous Tctex-1. This construct specifically targeted expression to the nestin(+)/Pax6(+)/GLAST(+) radial glial cells and Tbr2(+) intermediate progenitors when the reporter construct was delivered to developing mouse neocortex via in utero electroporation. Characterization of mice transgenically expressing GFP under the same regulatory element showed that the GFP expression is faithful to endogenous Tctex-1 at the subgranular zone (SGZ) of dentate gyrus, ventricular/subventricular zone of lateral ventricles, and ependymal layer of 3rd ventricle of adult brains. Immunolocalization and bromodeoxyuridine incorporation studies of adult SGZ in four independent mouse lines showed that Tctex-1:GFP reporter selectively marks nestin(+)/GFAP(+)/Sox2(+) neural stem-like cells in two mouse lines (4 and 13). In two other mouse lines (17 and 18), Tctex-1:GFP is selectively expressed in Type-2 and Type-3 transient amplifying progenitors and a small subset of young neuronal progeny. The P/E-Tctex-1 reporter mouse studies independently confirmed the specific enrichment of Tctex-1 at adult SGZ stem/progenitor cells. Furthermore, these studies supported the notion that an analogous transcriptional program may be used to regulate neurogenesis in embryonic cerebral cortex and adult hippocampus. Finally, the genomic sequences and the reporter mouse lines described here provide useful experimental tools to advance adult neural stem cell research.

Transcription factor Sox11b is involved in spinal cord regeneration in adult zebrafish

Adult zebrafish have the ability to recover from spinal cord injury and exhibit re-growth of descending axons from the brainstem to the spinal cord. We performed gene expression analysis using microarray to find damage-induced genes after spinal cord injury, and found that Sox11b mRNA is up-regulated at 11 days after injury. However, the functional relevance of Sox11b for regeneration is not known. Here, we report that the up-regulation of Sox11b mRNA after spinal cord injury is mainly localized in ependymal cells lining the central canal and in newly differentiating neuronal precursors or immature neurons. Using an in vivo morpholino-based gene knockout approach, we demonstrate that Sox11b is essential for locomotor recovery after spinal cord injury. In the injured spinal cord, expression of the neural stem cell associated gene Nestin, and the proneural gene Ascl1a (Mash1a), which are involved in the self-renewal and cell fate specification of endogenous neural stem cells, respectively, is regulated by Sox11b. Our data indicate that Sox11b promotes neuronal determination of endogenous stem cells and regenerative neurogenesis following spinal cord injury in the adult zebrafish. Enhancing Sox11b expression to promote proliferation and neurogenic determination of endogenous neural stem cells after injury may be a promising strategy in restorative therapy after spinal cord injury in mammals.

Expression of the stem cell marker nestin in peripheral blood of patients with melanoma

BACKGROUND

There is continued interest in markers indicative of circulating melanoma cells. Nestin is a neuroepithelial intermediate filament protein that was found to be expressed in melanoma and in various cancer stem cells.

OBJECTIVES

We investigated expression of nestin in peripheral blood of patients with melanoma.

METHODS

We analysed nestin expression by flow cytometry and by quantitative reverse transcription-polymerase chain reaction both in tissues (n = 23) and in blood samples (n = 102) from patients with American Joint Committee on Cancer stage III-IV melanoma. Forty-six negative controls were also added.

RESULTS

Flow cytometry did not reveal nestin-expressing cells in peripheral blood of healthy volunteers. In patients with melanoma, however, nestin protein was expressed in a proportion of melanoma cells enriched from peripheral blood by immunomagnetic sorting. In melanoma tissue samples a significant correlation was found between mRNAs coding for nestin and tyrosinase (P = 0.001) and melan-A (P = 0.002), whereas in blood a significant correlation was observed only for tyrosinase (P = 0.015), but not for melan-A (P = 0.53). Nestin expression was higher in stage IV patients compared with stage III/IV with no evidence of disease, in patients with high tumour burden, and was positively correlated to expression of tyrosinase and melan-A.

CONCLUSIONS

Nestin was found to be an additional marker of interest for circulating melanoma cells. Prospective studies should investigate its potential added informative value in comparison with markers already in use for melanoma cell detection.

The role of Brn-4 in the regulation of neural stem cell differentiation into neurons

Brn-4, a member of the homeobox family of transcription factors, has previously been implicated in the regeneration and repair of denervated striatum. We investigated the effects of Brn-4 on the differentiation and development of neural stem cells (NSCs) from E16 rat hippocampus. Immunocytochemistry revealed that extracts of deafferented hippocampus promoted neuronal differentiation to a greater extent than extracts from normal hippocampus. Deafferented extracts also promoted maturation of newborn neurons as reflected in changes in cell areas and perimeters, and enhanced Brn-4 expression in MAP-2 positive neurons. Suppression or overexpression of Brn-4 in NSCs markedly decreased or increased neuronal differentiation and maturation of newborn neurons, respectively. These results suggest that Brn-4 expression is required both for neuronal differentiation of NSCs and maturation of newborn neurons, and that there may be some regulatory factors in deafferented hippocampus that can regulate Brn-4 expression in neuronal progenitors. Brn-4 is therefore a potential research target for the development of new therapeutics to promote brain repair.

Human cytomegalovirus infection causes premature and abnormal differentiation of human neural progenitor cells

Congenital human cytomegalovirus (HCMV) infection is a leading cause of birth defects, largely manifested as central nervous system (CNS) disorders. The principal site of manifestations in the mouse model is the fetal brain's neural progenitor cell (NPC)-rich subventricular zone. Our previous human NPC studies found these cells to be fully permissive for HCMV and a useful in vitro model system. In continuing work, we observed that under culture conditions favoring maintenance of multipotency, infection caused NPCs to quickly and abnormally differentiate. This phenotypic change required active viral transcription. Whole-genome expression analysis found rapid downregulation of genes that maintain multipotency and establish NPCs' neural identity. Quantitative PCR, Western blot, and immunofluorescence assays confirmed that the mRNA and protein levels of four hallmark NPC proteins (nestin, doublecortin, sex-determining homeobox 2, and glial fibrillary acidic protein) were decreased by HCMV infection. The decreases required active viral replication and were due, at least in part, to proteasomal degradation. Our results suggest that HCMV infection causes in utero CNS defects by inducing both premature and abnormal differentiation of NPCs.

Role of SoxB1 transcription factors in development

SoxB1 factors, which include Sox1, 2, and 3, share more than 90% amino acid identity in their DNA binding HMG box and participate in diverse developmental events. They are known to exert cell-type-specific functions in concert with other transcription factors on Sox factor-dependent regulatory enhancers. Due to the high degree of sequence similarity both within and outside the HMG box, SoxB1 members show almost identical biological activities. As a result, they exhibit strong functional redundancy in regions where SoxB1 members are coexpressed, such as neural stem/progenitor cells in the developing central nervous system.

Coordinate regulation of gene expression in the C. elegans excretory cell by the POU domain protein CEH-6

Excretory renal organs are critical in animals for osmoregulation and the elimination of waste. Renal organs across a range of species exhibit cellular and molecular similarities. For example, class III POU-homeodomain transcription factors are expressed in the renal organs of many invertebrates and vertebrates. However, the functional role for these factors is not well characterized. To better understand the role of class III POU-homeodomain proteins in animal excretory systems, we have characterized a set of genes expressed in the Caenorhabditis elegans excretory cell, and determined their regulation by the POU-III transcription factor CEH-6. Our molecular and biochemical studies show that CEH-6 regulates a subset of genes expressed in the excretory cell. Additionally, we find that the CEH-6-dependent genes share two molecular features: they contain at least one octamer regulatory element and they encode for transport and channel proteins. This work suggests that a role for POU-III factors in renal organs is to coordinate the expression of a set of functionally related genes.

Inhibition of Eyes Absent Homolog 4 expression induces malignant peripheral nerve sheath tumor necrosis

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas without effective therapeutics. Bioinformatics was used to identify potential therapeutic targets. Paired Box (PAX), Eyes Absent (EYA), Dachsund (DACH), and Sine Oculis (SIX) genes, which form a regulatory interactive network in drosophila, were found to be dysregulated in human MPNST cell lines and solid tumors. We identified a decrease in DACH1 expression, and increases in expression of PAX6, EYA1, EYA2, EYA4, and SIX1- 4. Consistent with the observation that half of MPNSTs develop in neurofibromatosis type 1 patients, subsequent to NF1 mutation, we found that exogenous expression of the NF1-GAP related domain (GRD) normalized DACH1 expression. EYA4 mRNA was elevated more than 100-fold as estimated by quantitative real time PCR in most MPSNT cell lines. In vitro, suppression of EYA4 expression using shRNA reduced cell adhesion and migration and caused cellular necrosis without affecting cell proliferation or apoptotic cell death. MPNST cells expressing sh-EYA4 either failed to form tumors in nude mice or formed very small tumors, with extensive necrosis but similar levels of proliferation and apoptosis as control cells. Our findings identify a role for EYA4 and possibly interacting SIX and DACH proteins in MPNSTs and suggest the EYA4 pathway as a rational therapeutic target.

Transcription factors and neural stem cell self-renewal, growth and differentiation

The central nervous system (CNS) is a large network of interconnecting and intercommunicating cells that form functional circuits. Disease and injury of the CNS are prominent features of the healthcare landscape. There is an urgent unmet need to generate therapeutic solutions for CNS disease/injury. To increase our understanding of the CNS we need to generate cellular models that are experimentally tractable. Neural stem cells (NSCs), cells that generate the CNS during embryonic development, have been identified and propagated in vitro. To develop NSCs as a cellular model for the CNS we need to understand more about their genetics and cell biology. In particular, we need to define the mechanisms of self-renewal, proliferation and differentiation--i.e. NSC behavior. The analysis of pluripotency of embryonic stem cells through mapping regulatory networks of transcription factors has proven to be a powerful approach to understanding embryonic development. Here, we discuss the role of transcription factors in NSC behavior.

Epigenetic hierarchy governing Nestin expression

Nestin is an intermediate filament protein expressed specifically in neural stem cells and progenitor cells of the central nervous system. DNA demethylation and histone modifications are two types of epigenetic modifications working in a coordinate or synergistic manner to regulate the expression of various genes. This study investigated and elucidated the epigenetic regulation of Nestin gene expression during embryonic differentiation along the neural cell lineage. Nestin exhibits differential DNA methylation and histone acetylation patterns in Nestin-expressing and nonexpressing cells. In P19 embryonic carcinoma cells, activation of Nestin expression is mediated by both trichostatin A and 5-aza-2'-deoxycytidine treatment, concomitant with histone acetylation, but not with DNA demethylation. Nestin transcription is also mediated by treatment with retinoic acid, again in the absence of DNA demethylation. Thus, histone acetylation is sufficient to mediate the activation of Nestin transcription. This study proposed that the regulation of Nestin gene expression can be used as a model to study the epigenetic regulation of gene expression mediated by histone acetylation, but not by DNA demethylation.

Nuclear factor I regulates brain fatty acid-binding protein and glial fibrillary acidic protein gene expression in malignant glioma cell lines

Glial fibrillary acidic protein (GFAP), an intermediate filament protein normally found in astrocytes, and the radial glial marker brain fatty acid-binding protein (B-FABP; also known as FABP7) are co-expressed in malignant glioma cell lines and tumors. Nuclear factor I (NFI) recognition sites have been identified in the B-FABP and GFAP promoters, and transcription of both genes is believed to be regulated by NFI. Here, we study the role of the different members of the NFI family in regulating endogenous and ectopic B-FABP and GFAP gene transcription in human malignant glioma cells. We show by gel shifts that all four members of the NFI family (NFIA, NFIB, NFIC, and NFIX) bind to B-FABP and GFAP NFI consensus sites. Over-expression of NFIs, in conjunction with mutation analysis of NFI consensus sites using a reporter gene assay, supports a role for all four NFIs in the regulation of the GFAP and B-FABP genes. Knock-down of single or combined NFIs reveals promoter-dependent and promoter-context-dependent interaction patterns and suggests cross talk between the different members of the NFI family. Our data indicate that the NFI family of transcription factors plays a key role in the regulation of both the B-FABP and GFAP genes in malignant glioma cells.

Different transcription factors regulate nestin gene expression during P19 cell neural differentiation and central nervous system development

Nestin is a molecular marker for neural progenitor cells. Rat and human nestin genes possess a central nervous system-specific enhancer within their second introns. However, the transcription factors that bind to the nestin enhancer have not been fully elucidated. Here, we show that the second intron of the mouse nestin gene is sufficient to drive reporter gene expression in the developing nervous system. The core sequence of this central nervous system-specific enhancer localizes to the 3' 320-bp region. The cis-elements for Sox and POU family transcription factors and the hormone-responsive element are essential for nestin expression during embryonic carcinoma P19 cell neural differentiation and in the developing chick neural tube. Interestingly, different transcription factors bind to the nestin enhancer at different stages of P19 cell neural differentiation and central nervous system development. Sox2 and SF1 may mediate basal nestin expression in undifferentiated P19EC cells, whereas Sox2, Brn1, and Brn2 bind to the enhancer in P19 neural progenitor cells. Similarly, in vivo, Oct1 binds to the nestin enhancer in embryonic day 8.5 (E8.5) mouse embryos, and Oct1, Brn1, and Brn2 bind to this enhancer in E10.5 and E12.5 mouse embryos. Our studies therefore suggest a temporal coordination of transcription factors in determining nestin gene expression.

Thrombin induces nestin expression via the transactivation of EGFR signalings in rat vascular smooth muscle cells

Regulation of nestin gene expression is largely unknown despite that it is widely used as a progenitor cell marker. In this study, we showed that nestin expression is regulated by the thrombin-mediated EGFR transactivation in serum-deprived primary cultures of rat vascular smooth muscle cells (VSMCs). This resulted from the direct binding of thrombin to PAR-1 rather than indirectly affecting through the binding to thrombomodulin, as demonstrated by thrombomodulin RNAi. In this process, the PAR-1-induced c-Src plays a critical role through two routes; one was the direct intracellular phosphorylation of EGFR and the other was the extracellular activation of the MMP-2-mediated shedding of HB-EGF. The transactivated EGFR then led to the downstream Ras-Raf-ERK signaling axis, but not the p38 or JNK pathways. In addition, the EMSA experiment showed that the transcriptional factor Sp1 is critical for the thrombin-induced nestin expression in rat VSMCs. Furthermore, RNAi of nestin attenuated the thrombin-induced cell proliferation, indicating that thrombin-induced nestin expression and cell proliferation share the same EGFR transactivation mechanism. This study also suggested that nestin may play an important role in cell proliferation induced by the thrombin-mediated EGFR transactivation.

SOX9 and SOX10 but not BRN2 are required for nestin expression in human melanoma cells

Nestin is an intermediate filament protein and a marker of neuroectodermal stem cells indicating multipotentiality and regenerative capability. In melanoma tissues, nestin re-expression was correlated with tumor progression. Activation of the nestin neural enhancer was shown to be dependent on the binding of class III POU transcription factors, with brain-2 (BRN2) suggested to play a key role. We found both nestin and BRN2 mRNA in almost all of 13 analyzed melanoma cell lines of different progression stages, but expression levels did not correlate. Nestin protein was detected in 11 of 13 and BRN2 protein in 7 of 13 melanoma cell lines independent of progression stage. Downregulation of BRN2 by small-interfering RNA did not alter nestin expression in melanoma cells. However, POU proteins, such as BRN2, commonly cooperate with transcription factors of the Sry-box (SOX) family by binding to a nearby DNA site necessary for their action. SOX9 and SOX10 have been shown to be expressed in melanocyte precursors, with SOX10 downregulated upon differentiation. We now demonstrate SOX9 and SOX10 protein expression in melanoma tissues and cell lines. Downregulation of SOX9 and of SOX10 markedly decreased nestin levels in melanoma cells in a cooperative manner. Thus, SOX9 and SOX10 but not BRN2 seem to be required for nestin expression in human melanoma.

First intron of nestin gene regulates its expression during C2C12 myoblast differentiation

Nestin is an intermediate filament protein expressed in neural progenitor cells and in developing skeletal muscle. Nestin has been widely used as a neural progenitor cell marker. It is well established that the specific expression of the nestin gene in neural progenitor cells is conferred by the neural-specific enhancer located in the second intron of the nestin gene. However, the transcriptional mechanism of nestin expression in developing muscle is still unclear. In this study, we identified a muscle cell-specific enhancer in the first intron of mouse nestin gene in mouse myoblast C2C12 cells. We localized the core enhancer activity to the 291-661 region of the first intron, and showed that the two E-boxes in the core enhancer region were important for enhancer activity in differentiating C2C12 cells. We also showed that MyoD protein was involved in the regulation of nestin expression in the myogenic differentiation of C2C12 cells.

Concise review: Pax6 transcription factor contributes to both embryonic and adult neurogenesis as a multifunctional regulator

Pax6 is a highly conserved transcription factor among vertebrates and is important in various developmental processes in the central nervous system (CNS), including patterning of the neural tube, migration of neurons, and formation of neural circuits. In this review, we focus on the role of Pax6 in embryonic and postnatal neurogenesis, namely, production of new neurons from neural stem/progenitor cells, because Pax6 is intensely expressed in these cells from the initial stage of CNS development and in neurogenic niches (the subgranular zone of the hippocampal dentate gyrus and the subventricular zone of the lateral ventricle) throughout life. Pax6 is a multifunctional player regulating proliferation and differentiation through the control of expression of different downstream molecules in a highly context-dependent manner.