Dynamic changes in Wnt signaling are required for neuronal differentiation of mouse embryonic stem cells

Zeb2 DNA-Binding Sites in Neuroprogenitor Cells Reveal Autoregulation and Affirm Neurodevelopmental Defects, Including in Mowat-Wilson Syndrome

Functional perturbation and action mechanism studies have shown that the transcription factor Zeb2 controls cell fate decisions, differentiation, and/or maturation in multiple cell lineages in embryos and after birth. In cultured embryonic stem cells (ESCs), Zeb2’s mRNA/protein upregulation is necessary for the exit from primed pluripotency and for entering general and neural differentiation. We edited mouse ESCs to produce Flag-V5 epitope-tagged Zeb2 protein from one endogenous allele. Using chromatin immunoprecipitation coupled with sequencing (ChIP-seq), we mapped 2432 DNA-binding sites for this tagged Zeb2 in ESC-derived neuroprogenitor cells (NPCs). A new, major binding site maps promoter-proximal to Zeb2 itself. The homozygous deletion of this site demonstrates that autoregulation of Zeb2 is necessary to elicit the appropriate Zeb2-dependent effects in ESC-to-NPC differentiation. We have also cross-referenced all the mapped Zeb2 binding sites with previously obtained transcriptome data from Zeb2 perturbations in ESC-derived NPCs, GABAergic interneurons from the ventral forebrain of mouse embryos, and stem/progenitor cells from the post-natal ventricular-subventricular zone (V-SVZ) in mouse forebrain, respectively. Despite the different characteristics of each of these neurogenic systems, we found interesting target gene overlaps. In addition, our study also contributes to explaining developmental disorders, including Mowat-Wilson syndrome caused by ZEB2 deficiency, and also other monogenic syndromes.

A Wnt/β-catenin signaling pathway is involved in early dopaminergic differentiation of trabecular meshwork-derived mesenchymal stem cells

Permanent degeneration and loss of dopaminergic (DA) neurons in substantia nigra is the main cause of Parkinson's disease. Considering the therapeutic application of stem cells in neurodegeneration, we sought to examine the neurogenic differentiation potential of the newly introduced neural crest originated mesenchymal stem cells (MSCs), namely, trabecular meshwork-derived mesenchymal stem cells (TM-MSCs) compared to two other sources of MSCs, adipose tissue-derived stem cells (ADSCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs). The three types of cells were therefore cultured in the presence and absence of a neural induction medium followed by the analysis of their differentiation potentials. Our results showed that TM-MSCs exhibited enhanced neural morphologies as well as higher expressions of MAP2 as the general neuron marker and Nurr-1 as an early DA marker compared to the adipose tissue-derived mesenchymal stem cells (AD-MSCs) and bone marrow-derived stem cells (BMSCs). Also, analysis of Nurr-1 immunostaining showed more intense Nurr-1 stained nuclei in the neurally induced TM-MSCs compared to those in the AD-MSCs, BMSCs, and noninduced control TM-MSCs. To examine if Wnt/beta-catenin pathway drives TM-MSCs towards a DA fate, we treated them with the Wnt agonist (CHIR, 3 μM) and the Wnt antagonist (IWP-2, 3 μM). Our results showed that the expressions of Nurr-1 and MAP2, as well as the Wnt/beta-catenin target genes, c-Myc and Cyclin D1, were significantly increased in the CHIR-treated TM-MSCs, but significantly reduced in those treated with IWP-2. Altogether, we declare first a higher neural potency of TM-MSCs compared to the more commonly used MSCs, BMSCs and ADSCs, and second that Wnt/beta-catenin activation directs the neurally induced TM-MSCs towards a DA fate.

miR-222-3p is involved in neural tube closure by directly targeting Ddit4 in RA induced NTDs mouse model

Previously our results showed miR-222-3p was significantly downregulated in retinoic acid-induced neural tube defect (NTD) mouse model through transcriptome. Down-regulation of miR-222-3p may be a causative biomarker in NTDs. In this study, RNA was extracted from mouse embryos at E8.5, E9.5 and E10.5, and the expression level of miR-222-3p was measured by quantitative real-time PCR analysis. The preliminary mechanism of miR-222-3p in NTDs involved in cell proliferation, apoptosis and migration was investigated in mouse HT-22 cell line. The expression of miR-222-3p was significantly decreased at E8.5, E9.5 and E10.5 developed in mouse embryos which were consistent with our transcriptome sequencing. Suppression of miR-222-3p in HT-22 cells resulted in the inhibition of cell proliferation and migration, cell cycle and apoptosis. Moreover, DNA damage transcript 4 (Ddit4) was identified as a direct and functional target of miR-222-3p. miR-222-3p is negatively regulated by Ddit4. The mutation of binding site of Ddit4 3'UTR abrogated the responsiveness of luciferase reporters to miR-222-3p and showed that Ddit4 expression partially attenuated the function of miR-222-3p. We preliminatively confirmed that low expression of miR-222-3p has reduced the expression of β-catenin, TCF4 and other related genes in the Wnt/β-catenin signaling pathway.Collectively, these results demonstrated that miR-222-3p regulates the Wnt/β-catenin signaling pathway through Ddit4 inhibition in HT-22 cells, resulted in cell proliferation and apoptosis imbalance, and thus led to neural tube defects.

Nuclear localisation of West Nile virus NS5 protein modulates host gene expression

The involvement of the nucleus during flavivirus infection has been observed in only a small number of cases and can be limited to primarily two viral proteins; the structural protein C and the RNA polymerase NS5. Previously we observed that by blocking nuclear transport, WNV strain Kunjin (WNV_KUN) replication is severely affected and through mutation of the identified NLS in WNV_KUN NS5 protein. In this study, we interrogated the potential nuclear functions of WNV_KUN NS5 has on the host transcriptome, by means of RNA sequencing (RNAseq). In a direct comparison between wild type and mutant NS5, it can also be determined that the nuclear translocation of NS5 results in a significant down-regulation of host genes involved in the innate immune response. When compared to published RNAseq data from WNV infection, many of these genes were overlapping indicting the role of NS5 induced transcription during infection.

Inter-individual variation in genes governing human hippocampal progenitor differentiation in vitro is associated with hippocampal volume in adulthood

Hippocampal volumes are smaller in psychiatric disorder patients and lower levels of hippocampal neurogenesis are the hypothesized cause. Understanding which molecular processes regulate hippocampal progenitor differentiation might aid in the identification of novel drug targets that can promote larger hippocampal volumes. Here we use a unique human cell line to assay genome-wide expression changes when hippocampal progenitor cells differentiate. RNA was extracted from proliferating cells versus differentiated neural cells and applied to Illumina Human HT-12 v4 Expression BeadChips. Linear regressions were used to determine the effect of differentiation on probe expression and we assessed enrichment for gene ontology (GO) terms. Genetic pathway analysis (MAGMA) was used to evaluate the relationship between hippocampal progenitor cell differentiation and adult hippocampal volume, using results from the imaging genomics consortium, ENIGMA. Downregulated transcripts were enriched for mitotic processes and upregulated transcripts were enriched for cell differentiation. Upregulated (differentiation) transcripts specifically, were also predictive of adult hippocampal volume; with Early growth response protein 2 identified as a hub transcription factor within the top GO term, and a potential drug target. Our results suggest that genes governing differentiation, rather than mitosis, have an impact on adult hippocampal volume and that these genes represent important drug targets.

Involvement of Wnt pathway in ethanol-induced inhibition of mouse embryonic stem cell differentiation

Ethanol has been reported to have toxicity on embryonic stem cells (ESCs). The present study aims to address the teratogenic effects of ethanol on the growth and cardiac differentiation of ESCs. Mouse embryonic stem D3 cells were employed. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays were used to determine cytotoxicity. Quantitative real time polymerase chain reaction (qRT-PCR) and Western blotting were used to analyze the expressions of cardiac differentiation-related and Wnt signaling factors. The beating profile of cardiomyocytes was recorded to assess cardiac differentiation. Ethanol induced growth inhibition in both undifferentiated and differentiated ESCs after 5 days of exposure. Ethanol inhibited the loss of pluripotent gene expressions including Nanog, Sox2 and Oct4. The expressions of cardiac markers, Nkx2.5, Mef2c, Tbx5, dHand, αMHC, Cx43 and troponin C1, were suppressed by ethanol treatment. Furthermore, ethanol delayed cardiac differentiation of ESCs till 11 days of differentiation. The expressions of Wnt-related regulators, β-catenin and its target cyclin D1, were downregulated by ethanol. Wnt pathway agonist wnt3a could greatly rescue ethanol-induced inhibition of cardiac differentiation and Wnt-pathway-related protein expressions. These finding suggested that ethanol suppresses mouse ESC differentiation largely by inhibiting Wnt signaling pathway.

Neurotrophic Factor-α1: A Key Wnt-β-Catenin Dependent Anti-Proliferation Factor and ERK-Sox9 Activated Inducer of Embryonic Neural Stem Cell Differentiation to Astrocytes in Neurodevelopment

Embryonic neurodevelopment involves inhibition of proliferation of multipotent neural stem cells (NSCs) followed by differentiation into neurons, astrocytes and oligodendrocytes to form the brain. We have identified a new neurotrophic factor, NF-α1, which inhibits proliferation and promotes differentiation of NSC/progenitors derived from E13.5 mouse cortex. Inhibition of proliferation of these cells was mediated through negatively regulating the Wnt pathway and decreasing β-catenin. NF-α1 induced differentiation of NSCs to astrocytes by enhancing Glial Fibrillary Acidic Protein (GFAP) expression through activating the ERK1/2-Sox9 signaling pathway. Cultured E13.5 cortical stem cells from NF-α1-knockout mice showed decreased astrocyte numbers compared to wild-type mice, which was rescued by treatment with NF-α1. In vivo, immunocytochemistry of brain sections and Western blot analysis of neocortex of mice showed a gradual increase of NF-α1 expression from E14.5 to P1 and a surge of GFAP expression at P1, the time of increase in astrogenesis. Importantly, NF-α1-Knockout mice showed ∼49% fewer GFAP positive astrocytes in the neocortex compared to WT mice at P1. Thus, NF-α1 is critical for regulating antiproliferation and cell fate determination, through differentiating embryonic stem cells to GFAP-positive astrocytes for normal neurodevelopment. Stem Cells 2017;35:557-571.

miR-410 controls adult SVZ neurogenesis by targeting neurogenic genes

Over-expression of the early neural inducer, Noggin, in nestin positive subventricular zone (SVZ), neural stem cells (NSC) promotes proliferation and neuronal differentiation of neural progenitors and inhibits the expression of a CNS-enriched microRNA-410 (miR-410) (Morell et al., 2015). When expressed in neurospheres derived from the adult SVZ, miR-410 inhibits neuronal and oligodendrocyte differentiation, and promotes astrocyte differentiation. miR-410 also reverses the increase in neuronal differentiation and decreased astroglial differentiation caused by Noggin over-expression. Conversely, inhibition of miR-410 activity promotes neuronal and decreases astroglial differentiation of NSC. Using computer prediction algorithms and luciferase reporter assays we identified multiple neurogenic genes including Elavl4 as downstream targets of miR-410 via the canonical miRNA-3'UTR interaction. Over-expression of Elavl4 transcripts without the endogenous 3'UTR rescued the decrease in neuronal differentiation caused by miR-410 overexpression. Interestingly, we also observed that miR-410 affected neurite morphology; over-expression of miR-410 resulted in the formation of short, unbranched neurites. We conclude that miR-410 expression provides a new link between BMP signaling and the crucial lineage choice of adult neural stem cells via its ability to bind and control the expression of neurogenic gene transcripts.

Inhibition of glycogen synthase kinase-3 (GSK3) promotes the neural differentiation of full-term amniotic fluid-derived stem cells towards neural progenitor cells

The amniotic fluid has a heterogeneous population of cells. Some human amniotic fluid-derived stem (hAFS) cells have been shown to harbor the potential to differentiate into neural cells. However, the neural differentiation efficiency of hAFS cells remains low. In this study, we isolated CD117-positive hAFS cells from amniotic fluid and then examined the pluripotency of these cells through the formation of embryoid bodies (EBs). Additionally, we induced the neural differentiation of these cells using neuroectodermal medium. This study revealed that the GSK3-beta inhibitor SB216763 was able to stimulate the proliferation of CD117-positive hAFS cells without influencing their undifferentiated state. Moreover, SB216763 can efficiently promote the neural differentiation of CD117-positive hAFS cells towards neural progenitor cells in the presence of DMEM/F12 and N2 supplement. These findings provide an easy and low-cost method to maintain the proliferation of hAFS cells, as well as induce an efficacious generation of neural progenitor cells from hAFS cells. Such induction of the neural commitment of hAFS cells may provide an option for the treatment of neurodegenerative diseases by hAFS cells-based therapies.

Canonical and noncanonical Wnt signaling in neural stem/progenitor cells

The first mammalian Wnt to be discovered, Wnt-1, was found to be essential for the development of a large part of the mouse brain over 25 years ago. We have since learned that Wnt family secreted glycolipoproteins, of which there are nineteen, which activate a diverse network of signals that are particularly important during embryonic development and tissue regeneration. Wnt signals in the developing and adult brain can drive neural stem cell self-renewal, expansion, asymmetric cell division, maturation and differentiation. The molecular events taking place after a Wnt binds to its cell-surface receptors are complex and, at times, controversial. A deeper understanding of these events is anticipated to lead to improvements in the treatment of neurodegenerative diseases and stem cell-based replacement therapies. Here, we review the roles played by Wnts in neural stem cells in the developing mouse brain, at neurogenic sites of the adult mouse and in neural stem cell culture models.

Wnt/β-catenin and FGF signalling direct the specification and maintenance of a neuromesodermal axial progenitor in ensembles of mouse embryonic stem cells

The development of the central nervous system is known to result from two sequential events. First, an inductive event of the mesoderm on the overlying ectoderm that generates a neural plate that, after rolling into a neural tube, acts as the main source of neural progenitors. Second, the axial regionalization of the neural plate that will result in the specification of neurons with different anteroposterior identities. Although this description of the process applies with ease to amphibians and fish, it is more difficult to confirm in amniote embryos. Here, a specialized population of cells emerges at the end of gastrulation that, under the influence of Wnt and FGF signalling, expands and generates the spinal cord and the paraxial mesoderm. This population is known as the long-term neuromesodermal precursor (NMp). Here, we show that controlled increases of Wnt/β-catenin and FGF signalling during adherent culture differentiation of mouse embryonic stem cells (mESCs) generates a population with many of the properties of the NMp. A single-cell analysis of gene expression within this population reveals signatures that are characteristic of stem cell populations. Furthermore, when this activation is triggered in three-dimensional aggregates of mESCs, the population self-organizes macroscopically and undergoes growth and axial elongation that mimics some of the features of the embryonic spinal cord and paraxial mesoderm. We use both adherent and three-dimensional cultures of mESCs to probe the establishment and maintenance of NMps and their differentiation.

An interplay between extracellular signalling and the dynamics of the exit from pluripotency drives cell fate decisions in mouse ES cells

Embryonic Stem cells derived from the epiblast tissue of the mammalian blastocyst retain the capability to differentiate into any adult cell type and are able to self-renew indefinitely under appropriate culture conditions. Despite the large amount of knowledge that we have accumulated to date about the regulation and control of self-renewal, efficient directed differentiation into specific tissues remains elusive. In this work, we have analysed in a systematic manner the interaction between the dynamics of loss of pluripotency and Activin/Nodal, BMP4 and Wnt signalling in fate assignment during the early stages of differentiation of mouse ES cells in culture. During the initial period of differentiation, cells exit from pluripotency and enter an Epi-like state. Following this transient stage, and under the influence of Activin/Nodal and BMP signalling, cells face a fate choice between differentiating into neuroectoderm and contributing to Primitive Streak fates. We find that Wnt signalling does not suppress neural development as previously thought and that it aids both fates in a context dependent manner. Our results suggest that as cells exit pluripotency they are endowed with a primary neuroectodermal fate and that the potency to become endomesodermal rises with time. We suggest that this situation translates into a “race for fates” in which the neuroectodermal fate has an advantage.

The responses of neural stem cells to the level of GSK-3 depend on the tissue of origin

Neural stem cells (NSCs) can be obtained from a variety of sources, but not all NSCs exhibit the same characteristics. We have examined how the level of glycogen synthase kinase-3 activity regulates NSCs obtained from different sources: the mouse embryonic striatum, embryonic hippocampus, and mouse ES cells. Growth of striatal NSCs is enhanced by mild inhibition of GSK-3 but not by strong inhibition that is accompanied by Wnt/TCF transcriptional activation. In contrast, the growth of hippocampal NSCs is enhanced by both mild inhibition of GSK-3 as well as stronger inhibition. Active Wnt/TCF signaling, which occurs normally in the embryonic hippocampus, is required for growth of neural stem and progenitor cells. In the embryonic striatal germinal zone, however, TCF signaling is normally absent and its activation inhibits growth of NSCs from this region. Using a genetic model for progressive loss of GSK-3, we find that primitive ES cell-derived NSCs resemble striatal NSCs. That is, partial loss of GSK-3 alleles leads to an increase in NSCs while complete ablation of GSK-3, and activation of TCF-signaling, leads to their decline. Furthermore, expression of dominant negative TCF-4 in the GSK-3-null background was effective in blocking expression of Wnt-response genes and was also able to rescue neuronal gene expression. These results reveal that GSK-3 regulates NSCs by divergent pathways depending on the tissue of origin. The responses of these neural precursor cells may be contingent on baseline Wnt/TCF signaling occurring in a particular tissue.

Transcriptional characterization of Wnt pathway during sequential hepatic differentiation of human embryonic stem cells and adipose tissue-derived stem cells

Human embryonic stem cells (hESs) and adipose-derived stem cells (hADSCs) are able to differentiate into hepatocytes. However, a role of Wnt signaling in hepatic differentiation of stem cells is unclear. This study characterized the transcriptional expression pattern of Wnt signaling genes during the sequential hepatocytes differentiation of hES and hADSC. The sequential hepatocytes differentiation of hES and hADSC was induced by three steps including induction, differentiation and maturation steps with the treatment of cytokines. Hepatocytes differentiation was more efficient in hES than hADSC in terms of the expression of hepatocyte-specific genes and the cellular uptake of ICG. The expression of WNT2B, WNT5A, and WISP1 increased at late hepatic differentiation of hES, but the expression of DKK1 and CCND1 decreased during early hepatic differentiation of hES. During hepatic differentiation of hADSC, the expression of WNT2B and WISP1 decreased, but the expression of WNT5B and DKK1 increased at late hepatic differentiation. These results showed that Wnt signaling appears to be activated in hepatic differentiation of hES, but repressed in hepatic differentiation of hADSC in a time-dependent manner, which suggests the differential regulation of Wnt signaling for hepatic differentiation of hES and hADSC.

Geminin promotes an epithelial-to-mesenchymal transition in an embryonic stem cell model of gastrulation

Geminin is a nuclear protein that performs the related functions of modulating cell cycle progression by binding Cdt1, and controlling differentiation by binding transcription factors. Since embryonic stem cells (ESC) and the epiblast share a similar gene expression profile and an attenuated cell cycle, ESC form an accessible and tractable model system to study lineage choice at gastrulation. We derived several ESC lines in which Geminin can be inducibly expressed, and employed short hairpin RNAs targeting Geminin. As in the embryo, a lack of Geminin protein resulted in DNA damage and cell death. In monolayer culture, in defined medium, Geminin supported neural differentiation; however, in three-dimensional culture, overexpression of Geminin promoted mesendodermal differentiation and epithelial-to-mesenchymal transition. In vitro, ESC overexpressing Geminin rapidly recolonized a wound, downregulated E-cadherin expression, and activated Wnt signaling. We suggest that Geminin may promote differentiation via binding Groucho/TLE proteins and upregulating canonical Wnt signaling.

Novel β-catenin target genes identified in thalamic neurons encode modulators of neuronal excitability

Background

LEF1/TCF transcription factors and their activator β-catenin are effectors of the canonical Wnt pathway. Although Wnt/β-catenin signaling has been implicated in neurodegenerative and psychiatric disorders, its possible role in the adult brain remains enigmatic. To address this issue, we sought to identify the genetic program activated by β-catenin in neurons. We recently showed that β-catenin accumulates specifically in thalamic neurons where it activates Cacna1g gene expression. In the present study, we combined bioinformatics and experimental approaches to find new β-catenin targets in the adult thalamus.

Results

We first selected the genes with at least two conserved LEF/TCF motifs within the regulatory elements. The resulting list of 428 putative LEF1/TCF targets was significantly enriched in known Wnt targets, validating our approach. Functional annotation of the presumed targets also revealed a group of 41 genes, heretofore not associated with Wnt pathway activity, that encode proteins involved in neuronal signal transmission. Using custom polymerase chain reaction arrays, we profiled the expression of these genes in the rat forebrain. We found that nine of the analyzed genes were highly expressed in the thalamus compared with the cortex and hippocampus. Removal of nuclear β-catenin from thalamic neurons in vitro by introducing its negative regulator Axin2 reduced the expression of six of the nine genes. Immunoprecipitation of chromatin from the brain tissues confirmed the interaction between β-catenin and some of the predicted LEF1/TCF motifs. The results of these experiments validated four genes as authentic and direct targets of β-catenin: Gabra3 for the receptor of GABA neurotransmitter, Calb2 for the Ca²⁺-binding protein calretinin, and the Cacna1g and Kcna6 genes for voltage-gated ion channels. Two other genes from the latter cluster, Cacna2d2 and Kcnh8, appeared to be regulated by β-catenin, although the binding of β-catenin to the regulatory sequences of these genes could not be confirmed.

Conclusions

In the thalamus, β-catenin regulates the expression of a novel group of genes that encode proteins involved in neuronal excitation. This implies that the transcriptional activity of β-catenin is necessary for the proper excitability of thalamic neurons, may influence activity in the thalamocortical circuit, and may contribute to thalamic pathologies.

Human cytomegalovirus infection dysregulates the canonical Wnt/β-catenin signaling pathway

Human Cytomegalovirus (HCMV) is a ubiquitous herpesvirus that currently infects a large percentage of the world population. Although usually asymptomatic in healthy individuals, HCMV infection during pregnancy may cause spontaneous abortions, premature delivery, or permanent neurological disabilities in infants infected in utero. During infection, the virus exerts control over a multitude of host signaling pathways. Wnt/β-catenin signaling, an essential pathway involved in cell cycle control, differentiation, embryonic development, placentation and metastasis, is frequently dysregulated by viruses. How HCMV infection affects this critical pathway is not currently known. In this study, we demonstrate that HCMV dysregulates Wnt/β-catenin signaling in dermal fibroblasts and human placental extravillous trophoblasts. Infection inhibits Wnt-induced transcriptional activity of β-catenin and expression of β-catenin target genes in these cells. HCMV infection leads to β-catenin protein accumulation in a discrete juxtanuclear region. Levels of β-catenin in membrane-associated and cytosolic pools, as well as nuclear β-catenin, are reduced after infection; while transcription of the β-catenin gene is unchanged, suggesting enhanced degradation. Given the critical role of Wnt/β-catenin signaling in cellular processes, these findings represent a novel and important mechanism whereby HCMV disrupts normal cellular function.

A large percentage of the world population is infected with HCMV. As a leading viral cause of birth defects in the developed world, HCMV represents a significant public health burden. For the first time, we report that HCMV infection dysregulates the canonical Wnt/β-catenin signaling pathway which is essential in regulating a diverse range of biological functions. We demonstrate that HCMV infection leads to sequestration and degradation of β-catenin protein, the effector transcription factor in the pathway, thus preventing its downstream signaling activities. Since this pathway is essential in regulating mammalian development and homeostasis, the finding that HCMV impairs this pathway becomes globally important for understanding viral pathogenesis, particularly that related to HCMV disease.

Investigating tonic Wnt signaling throughout the adult CNS and in the hippocampal neurogenic niche of BatGal and ins-TopGal mice

Wnt/β-catenin signaling has a well-established role in the development of the central nervous system (CNS), and recent evidence is extending this role to include the regulation of adult hippocampal function, including neurogenesis within the dentate gyrus. While the neuroanatomical expression pattern of many canonical Wnt signaling components have been investigated, the sites of signal integration and functional downstream β-catenin activation remain comparatively less characterized in the adult CNS. Using two independent transgenic β-catenin-activated LacZ reporter mouse lines (BatGal and ins-TopGal), we demonstrate that Wnt/β-catenin signaling is active in discrete regions of the adult mouse CNS. Intriguingly, BatGal mice exhibit a broad pattern of reporter expression in the CNS, while expression in ins-TopGal mice is more restricted. Further investigation of these two lines reveals temporal differences in β-catenin-activated reporter expression during neurogenesis within the adult hippocampus. Ins-TopGal mice display peaks of Wnt/β-catenin-activated reporter expression during early and later stages of neurogenesis suggesting Wnt/β-catenin signaling plays an important role during both progenitor cell amplification as well as neuronal maturation, integration, and/or maintenance; however, results from BatGal mice are not as convincing. Thus our data using ins-TopGal mice are consistent with the idea that Wnt signaling plays diverse roles during adult hippocampal neurogenesis and support the idea that multiple transgenic reporter lines must be rigorously compared during scientific investigations.

Gene expression profile of adult human olfactory bulb and embryonic neural stem cell suggests distinct signaling pathways and epigenetic control

Global gene expression profiling was performed using RNA from human embryonic neural stem cells (hENSC), and adult human olfactory bulb-derived neural stem cells (OBNSCs), to define a gene expression pattern and signaling pathways that are specific for each cell lineage. We have demonstrated large differences in the gene expression profile of human embryonic NSC, and adult human OBNSCs, but less variability between parallel cultures. Transcripts of genes involved in neural tube development and patterning (ALDH1A2, FOXA2), progenitor marker genes (LMX1a, ALDH1A1, SOX10), proliferation of neural progenitors (WNT1 and WNT3a), neuroplastin (NPTN), POU3F1 (OCT6), neuroligin (NLGN4X), MEIS2, and NPAS1 were up-regulated in both cell populations. By Gene Ontology, 325 out of 3875 investigated gene sets were scientifically different. 41 out of the 307 investigated Cellular Component (CC) categories, 45 out of the 620 investigated Molecular Function (MF) categories, and 239 out of the 2948 investigated Biological Process (BP) categories were significant. KEGG Pathway Class Comparison had revealed that 75 out of 171 investigated gene sets passed the 0.005 significance threshold. Levels of gene expression were explored in three signaling pathways, Notch, Wnt, and mTOR that are known to be involved in NS cell fates determination. The transcriptional signature also deciphers the role of genes involved in epigenetic modifications. SWI/SNF DNA chromatin remodeling complex family, including SMARCC1 and SMARCE1, were found specifically up-regulated in our OBNSC but not in hENSC. Differences in gene expression profile of transcripts controlling epigenetic modifications, and signaling pathways might indicate differences in the therapeutic potential of our examined two cell populations in relation to in cell survival, proliferation, migration, and differentiation following engraftments in different CNS insults.