Population Of Neural Precursor Cells Research Articles

A Poly-D-lysine-Coated Coralline Matrix Promotes Hippocampal Neural Precursor Cells' Differentiation into GFAP-Positive Astrocytes.

A major goal of regenerative medicine of the central nervous system is to accelerate the regeneration of nerve tissue, where astrocytes, despite their positive and negative roles, play a critical role. Thus, scaffolds capable of producing astrocytes from neural precursor cells (NPCs) are most desirable. Our study shows that NPCs are converted into reactive astrocytes upon cultivation on coralline-derived calcium carbonate coated with poly-D-lysine (PDL-CS). As shown via nuclei staining, the adhesion of neurospheres containing hundreds of hippocampal neural cells to PDL-CS resulted in disaggregation of the cell cluster as well as the radial migration of dozens of cells away from the neurosphere core. Migrating cells per neurosphere averaged 100 on PDL-CS, significantly higher than on uncoated CS (28), PDL-coated glass (65), or uncoated glass (20). After 3 days of culture on PDL-CS, cell migration plateaued and remained stable for four more days. In addition, NPCs expressing nestin underwent continuous morphological changes from round to spiky, extending and elongating their processes, resembling activated astrocytes. The extension of the process increased continuously during the maturation of the culture and doubled after 7 days compared to day 1, whereas bifurcation increased by twofold during the first 3 days before plateauing. In addition, nestin positive cells' shape, measured through the opposite circularity level correlation, decreased approximately twofold after three days, indicating spiky transformation. Moreover, nestin-positive cells co-expressing GFAP increased by 2.2 from day 1 to 7, reaching 40% of the NPC population on day 7. In this way, PDL-CS promotes NPC differentiation into reactive astrocytes, which could accelerate the repair of neural tissue.

Metformin enhances neural precursor cells migration and functional recovery after ischemic stroke in mice

Resident neural precursor cells (NPCs) activation is a promising therapeutic strategy for brain repair. This strategy involves stimulating multiple stages of NPCs development, including proliferation, self-renewal, migration, and differentiation. Metformin, an FDA-approved diabetes drug, has been shown to promote the proliferation and differentiation of NPCs. However, it is still unclear whether metformin promotes the migration of NPCs. EVOS living cell imaging system was used for observing the migration for primary NPCs dynamically in vitro after metformin treatment. For in vivo study, a mouse model of ischemic stroke was established through middle cerebral artery occlusion (MCAO). To label the proliferating cell in subventricular zone, BrdU was injected intraperitoneally into the mice. After co-staining with BrdU and doublecortin (DCX), a marker for NPCs, the migration of Brdu and DCX double positive NPCs was detected along the rostral migratory stream (RMS) and around the infarct area using frozen brain sections. Finally, the rotarod test, corner test and beam walking were performed to evaluate the motor functions of the mice after stroke in different groups. The results showed that metformin enhanced NPCs migration in vivo and in vitro by promoting F-actin assembly and lamellipodia formation. What's more, metformin treatment also significantly reduced the infarct volume and alleviated functional dysfunction after stroke. Mechanistically, metformin promoted NPCs migration via up-regulating the CDC42 expression. Taken together, metformin represents an optimal candidate agent for neural repair that is capable of not only expanding the adult NPC population but also subsequently driving them toward the destination for neuronal differentiation.

A Comprehensive Stemness Gene Expression Analysis Signifies the Role of ABC Transporters and Molecular Chaperons in Determining the Fate of Human Neural Precursor Cells

The major aim of this study was to identify the most common stemness genes across different stem cell types and further validate them in human fetal subventricular zone-derived primary and cultured neural precursor cells (NPCs). This study involved the use of a unique method of stemness meta-analysis (SMA) for investigating comprehensive upregulation and downregulation of differentially expressed genes (DEGs) among different stem cell populations. A total of 55 mouse and human data sets targeting crucial genes identified in seven different types of stem cells population were screened and subjected to independent DEGs analysis using SMA. Identified 30 meta-gene signatures were subjected to functional enrichment analysis based on their biological processes and molecular functions. Validation of enriched meta-gene signatures was performed using RT-qPCR. Cellular localization of ABCB1 and ABCG2 was identified using immunofluorescence staining, whereas functional assessment was performed using western-blot. SMA analysis revealed that among 52 commonly expressed genes, 30 genes were either upregulated or downregulated in at least two stem cell populations. Further gene enrichment analysis showed nine genes (ABCB1, ABCG2, HSPA4, HSPA9, HSPA14, Nestin, Sox-2, Oct-4, and Notch-2) with the highest combined scores among 30 meta-gene signatures. RT-qPCR demonstrated that all the enriched gene signatures were significantly upregulated in primary NPCs and further downregulated during NPCs lineage differentiation in culture except HSPA4, HSPA9, and HSPA14 gene transcripts. The stemness meta-gene signatures were abundantly expressed in human NPCs population which categorically suggest the involvement of these genes/pathways in pluripotency maintenance and molecular switches for lineage differentiation while HSP-70 had a neuroprotective effect.

Treating cancer therapy-related cognitive impairment.

Metformin can promote the regeneration of neural precursor cell populations and improve cognitive function in a preclinical model of cranial radiation and a pilot clinical study of children after cranial radiation and chemotherapy.

Activating Resident Neural Precursor Cells in the Spinal Cord to Promote Neural Repair

Within the mammalian spinal cord there are two distinct populations of neural precursor cells: neural stem and progenitor cells (NSPCs) and oligodendrocyte progenitor cells (OPCs). NSPCs are located within the periventricular zone of the spinal cord and are relatively quiescent and non‐neurogenic under homeostatic conditions. OPCs are located throughout the grey and white matter of the spinal cord and give rise to new oligodendrocytes throughout life. Both of these populations are activated following injury, however, their response is not sufficient for functional recovery. We propose that enhancing resident precursor activation is a promising approach to improve structural and functional outcomes following SCI. The FDA‐approved drug metformin (MET) has demonstrated efficacy in promoting improved outcomes in the injured brain through pleiotropic effects including: decreased inflammation, enhanced precursor cell activation and increased neurogenesis and oligogenesis. Here, we seek to establish the influence of MET treatment on NSPC and OPC populations and explore whether MET can improve functional recovery following injury in the spinal cord. Our cellular data reveal that in uninjured animals, MET treatment significantly expands the NSPC pool in females, but not males; increases neurogenesis in males only and enhances oligogenesis across both sexes. Conversely, we observed no effect of MET treatment on the number of OPCs in uninjured mice, irrespective of sex. To test the efficacy of MET treatment following injury, we used two distinct models: (1) a dorsal column injury in the thoracic spinal cord (SCI), and (2), a model of multiple sclerosis (experimental autoimmune encephalomyelitis, EAE). In both models, MET was delivered to mice immediately following injury and for 14 days. Following SCI, mice were tested on a skilled walking test on post‐injury days (PID) 7 and 14. While all mice showed a significant deficit on PID7, by PID14, MET treated animals were not significantly impaired relative to pre‐injury performance and naive controls. In the EAE model, we evaluated the efficacy of MET treatment through both clinical scoring (based on degree of paralysis) and gait analysis. EAE resulted in significant clinical deficits 14 days following induction, which were mitigated in mice that received MET. Additionally, our gait analysis revealed improved metrics in MET treated mice. Across both injury models we observed significantly reduced inflammation. Taken together, our results support MET as a viable therapeutic strategy to expand and enhance NSPCs, improve the response of OPCs and support functional recovery following spinal cord injury.Support or Funding InformationCanadian Institute of Health ResearchMedicine by Design

Substrate-Dependent Galvanotaxis of Directly Reprogrammed Human Neural Precursor Cells.

Background: Neural precursor cells (NPCs) hold great promise for neural repair. Endogenous NPCs, found in the subventricular zone of the adult brain, proliferate and migrate toward lesion sites; however, it is not sufficient for neural repair. NPCs are electrosensitive cells that undergo directed migration in an electric field (EF). Here, we examined the EF-induced migration of a clinically relevant human NPC population. Materials & Methods: We examined the effects of different substrates and microenvironments on human NPC galvanotaxis. Results: Human NPCs increased their migration speed in the presence of an EF, and the direction of migration (anodal vs. cathodal) varied between substrates. The secretome and extracellular pH were not significant factors in EF-induced migration; however, our results are consistent with substrate stiffness playing a role in the direction of cell migration. Conclusion: These findings provide insight into the importance of the microenvironment on modulating human NPC migration and highlight substrate-dependent considerations for neurorepair.

Substrate Dependent Galvanotaxis of Directly Reprogrammed Human Neural Precursor Cells

Adult neural precursor cells show great promise for the repair of central nervous system (CNS) tissue following injury or disease. Following injury to the CNS, endogenous neural precursor cells (NPCs), found in the neurogenic subventricular zone of the adult forebrain, are activated to proliferate and migrate toward the lesion site. However, this activation is not sufficient for neurorepair. Previous work has demonstrated that murine NPCs are electrosensitive cells that undergo rapid and cathodally directed migration in an applied electric field (EF). Here, we examined the EF induced migration of a clinically relevant human NPC population. With a goal of enhancing cell-based regeneration of the CNS, we explored the role of extracellular matrix (ECM) in human NPC behavior. NPCs plated on matrigel, MaxGel, laminin, and fibronectin were found to migrate in a substrate dependent manner. Common to all substrates was an increase in migration velocity in the presence of an EF. Different, was the direction of migration on the different substrates. The EF application did not induce differentiation on any of the substrates examined, as cells continued to express the precursor markers nestin and SOX2. We determined that secreted factors from neighbouring cells and extracellular pH were not significant factors in EF induced migration, however, substrate stiffness was sufficient to alter the direction of drNPC migration. These findings provide insight into factors that modulate human NPC migration and shed light on considerations for designing cell based therapies for neurorepair.

LAR and PTPσ receptors are negative regulators of oligodendrogenesis and oligodendrocyte integrity in spinal cord injury.

Following spinal cord injury (SCI), the population of mature oligodendrocytes undergoes substantial cell death; promoting their preservation and replacement is a viable strategy for preserving axonal integrity and white matter repair in the injured spinal cord. Dramatic upregulation of matrix chondroitin sulfate proteoglycans (CSPGs) is shown to pose an obstacle to endogenous repair processes, and targeting CSPGs improves functional recovery after SCI. However, the cellular and molecular mechanisms underlying the inhibitory effects of CSPGs remain largely undefined. Modulation of CSPGs specific signaling receptors, leukocyte common antigen-related (LAR), and protein tyrosine phosphatase-sigma (PTPσ) allows us to uncover the role and mechanisms of CSPGs in regulating oligodendrocytes in SCI. Here, utilizing specific functionally blocking peptides in a clinically relevant model of contusive/compressive SCI in the rat, we demonstrate that inhibition of PTPσ and LAR receptors promotes oligodendrogenesis by endogenous precursor cells, attenuates caspase 3-mediated cell death in mature oligodendrocytes, and preserves myelin. In parallel in vitro systems, we have unraveled that CSPGs directly induce apoptosis in populations of neural precursor cells and oligodendrocyte progenitor cells and limit their ability for oligodendrocyte differentiation, maturation, and myelination. These negative effects of CSPGs are mediated through the activation of both LAR and PTPσ receptors and the downstream Rho/ROCK pathway. Thus, we have identified a novel inhibitory role for PTPσ and LAR in regulating oligodendrocyte differentiation and apoptosis in the injured adult spinal cord and a new feasible therapeutic strategy for optimizing endogenous cell replacement following SCI.

Mcl-1 and Bcl-xL are essential for survival of the developing nervous system.

During neurogenesis, proliferating neural precursor cells (NPC) exit the cell cycle and differentiate into postmitotic neurons. The proteins that regulate cell survival through the stages of differentiation, however, are still poorly understood. Here, we examined the roles of the anti-apoptotic Bcl-2 proteins, Mcl-1 and Bcl-xL, in promoting survival as cells progress through the stages of neurogenesis in the mouse embryonic central nervous system. We used Nestin-mediated, nervous system-specific conditional deletion of mcl-1, bcl-x or both to identify their distinct and overlapping roles. Individual conditional deletion of mcl-1 (MKO) and bcl-x (BKO) suggested sequential roles in promoting cell survival during developmental neurogenesis. In the MKO embryo, apoptosis begins at embryonic day 10 (E10) in the proliferating NPC population throughout the entire developing nervous system. In the BKO embryo, apoptosis begins later at E11 within the postmitotic neuron populations. In the double (mcl-1 and bcl-x) conditional knockout (DKO), cell death extended throughout both proliferating and non-proliferating cell populations resulting in embryonic lethality at E12, earlier than in either the MKO or BKO. Apoptotic cell death of the entire central nervous system in the DKO demonstrates that both genes are necessary for cell survival during developmental neurogenesis. To determine whether Mcl-1 and Bcl-xL have overlapping anti-apoptotic roles during neurogenesis, we examined the impact of gene dosage. Loss of a single bcl-x allele in the MKO embryo exasperated apoptotic cell death within the NPC population revealing a novel anti-apoptotic role for Bcl-xL in proliferating NPCs. Cells were rescued from apoptosis in both the MKO and BKO embryos by breeding with the Bax null mouse line indicating that Mcl-1 and Bcl-xL have a common pro-apoptotic target during developmental neurogenesis. Taken together, these findings demonstrate that Mcl-1 and Bcl-xL are the two essential anti-apoptotic Bcl-2 proteins required for the survival of the developing mammalian nervous system.

Systemic Inflammation Impairs Proliferation of Hippocampal Type 2 Intermediate Precursor Cells.

Neurogenesis is a plastic event modulated by external cues. Systemic inflammation decreases neurogenesis in the dentate gyrus (DG) in part through the proliferative restrain of neural precursor cells (NPCs). To evaluate if inflammation affects the cell cycle progression of particular populations of NPCs, we treated young-adult mice with a single i.p. injection of saline or 1mg/kg LPS. After 7days, we analysed proliferation of new BrdU+/DCX+ cells through immunohistochemistry. We extracted the hippocampus and performed a neurosphere assay and a flow cytometric analysis to evaluate proliferation and to identify the phase of the cell cycle in specific populations of DG-derived NPCs. We show that the number of BrdU+/DCX+ cells diminishes in the LPS-treated group and that the number of primary neurospheres derived from LPS-injected animals is significantly reduced compared to the saline-injected group. Flow cytometry revealed that inflammation does not affect the total number of Type 1 BLBP+/TBR2- cells, while the total number of Type 2 intermediate precursor cells (IPCs) (TBR2+) from the LPS-treated group was increased. Cell cycle analysis shows a decrease in the total rate of NPCs in phases S, G2 and M in the LPS-treated group. The percentage of Type 1 BLBP+/TBR2- cells in each cell cycle phase was not different between groups, while there was a fewer number of Type 2 TBR2+ cells in S/G2/M phase. These results show that inflammation alters the appropriate cell cycle progression of Type 2 IPCs, which may contribute to the decrease in the birth rate of DG neurons.

Cyclosporin A-Mediated Activation of Endogenous Neural Precursor Cells Promotes Cognitive Recovery in a Mouse Model of Stroke.

Cognitive dysfunction following stroke significantly impacts quality of life and functional independance; yet, despite the prevalence and negative impact of cognitive deficits, post-stroke interventions almost exclusively target motor impairments. As a result, current treatment options are limited in their ability to promote post-stroke cognitive recovery. Cyclosporin A (CsA) has been previously shown to improve post-stroke functional recovery of sensorimotor deficits. Interestingly, CsA is a commonly used immunosuppressant and also acts directly on endogenous neural precursor cells (NPCs) in the neurogenic regions of the brain (the periventricular region and the dentate gyrus). The immunosuppressive and NPC activation effects are mediated by calcineurin-dependent and calcineurin-independent pathways, respectively. To develop a cognitive stroke model, focal bilateral lesions were induced in the medial prefrontal cortex (mPFC) of adult mice using endothelin-1. First, we characterized this stroke model in the acute and chronic phase, using problem-solving and memory-based cognitive tests. mPFC stroke resulted in early and persistent deficits in short-term memory, problem-solving and behavioral flexibility, without affecting anxiety. Second, we investigated the effects of acute and chronic CsA treatment on NPC activation, neuroprotection, and tissue damage. Acute CsA administration post-stroke increased the size of the NPC pool. There was no effect on neurodegeneration or lesion volume. Lastly, we looked at the effects of chronic CsA treatment on cognitive recovery. Long-term CsA administration promoted NPC migration toward the lesion site and rescued cognitive deficits to control levels. This study demonstrates that CsA treatment activates the NPC population, promotes migration of NPCs to the site of injury, and leads to improved cognitive recovery following long-term treatment.

Research progress of skin-derived precursor cells

As a novel population of neural crest-origin precursor cells, skin-derived precursor cells (SKPs) can be isolated from both embryonic and adult dermis. These cells have important values for research and potential clinical application in wound healing, organ regeneration and disease treatment for advantages in the abundance of cell sources, accessibility, potential of multipotent differentiation, and absence of ethical concerns. Here we review the developmental and anatomical origins of SKPs and their potential application in regenerative medicine. SKPs originate from the embryonic neural crest, and their sources may vary in different areas of the body. SKPs are widely found in the dermis, especially in the dermal papilla (DP), which was known as a niche of SKPs. The multipotent SKPs can used for autologous transplantation and are of vital importance in tissue repair.

Antidepressant responsiveness in adulthood is permanently impaired after neonatal destruction of the neurogenic pool

The dynamic turnover of hippocampal neurons is implicated in the regulation of cognitive and affective behavior. Extending our previous demonstration that administration of dexamethasone (ND) to neonatal rats depletes the resident population of neural precursor cells (NPC) and restrains the size of the neurogenic regions, we now show that the adverse effects of ND persist into adulthood. Specifically, ND impairs repletion of the neurogenic pool and neurogenesis; ND also compromises cognitive performance, the ability to actively adapt to an acute stressor and, the efficacy of glucocorticoid (GC) negative feedback. Interestingly, although ND depletes the neurogenic pool, it does not permanently abolish the proliferative machinery of the residual NPC population; however, ND increases the susceptibility of hippocampal granule neurons to apoptosis. Although the antidepressant fluoxetine (FLX) reverses the latter phenomenon, it does not replenish the NPC pool. Treatment of ND-treated adult rats with FLX also improves GC negative feedback, albeit without rescuing the deleterious effects of ND on behavior. In summary, ND leads to protracted disruption of mental functions, some of which are resistant to antidepressant interventions. We conclude that manipulation of the NPC pool during early life may jeopardize the therapeutic potential of antidepressants in adulthood.

Deciphering cell-cell communication in the developing mammalian brain.

The diverse subtypes of neurons that comprise the mammalian cerebral cortex are produced from a single population of cortical neural precursor cells during the period of embryonic neurogenesis. While this process of neurogenesis is tightly controlled at the transcriptional and translational levels, substantial opportunity exists for extrinsic or niche control of the process of neurogenesis. In our recently published work we made use of a combination of computational and biologic approaches to characterize cell-cell communication between cortical neurons and cortical precursor cells and thereby reveal an unexpectedly complex growth factor communication network that accurately predicted new regulators of cortical neurogenesis.

Improving the therapeutic efficacy of neural progenitor cell transplantation following spinal cord injury

ABSTRACTIntroduction: There have been a wide range of preclinical studies testing cellular therapies to repair the injured spinal cord, yet they remain a challenge to translate because of inconsistencies in efficacy, limited number of patients with acute/subacute SCI and the high costs of clinical trials.Area covered: This paper focusses on the therapeutic potential of neural precursor cells (NPCs) because they can provide the cellular components capable of promoting repair and enhancing functional improvement following spinal cord injury (SCI). The authors discuss the challenges of NPC transplantation with respect to different populations of NPCs of glial and neuronal lineages, the timing of treatment relative to acute and chronic injury, and the progress in ongoing clinical trials.Expert commentary: Preclinical research will continue to elucidate mechanisms of recovery associated with NPC transplants, including increasing the partnership with related fields such as spinal atrophies and multiple sclerosis. The clinical trials landscape will grow and include both acute and chronic SCI with increased partnership and strengthened communication between biotechnology, government and academia. There will also be growing effort to develop better biomarkers, imaging and outcome measures for detailed assessment of neurological function and measures of quality of life.

Alcohol-Induced Molecular Dysregulation in Human Embryonic Stem Cell-Derived Neural Precursor Cells.

Adverse effect of alcohol on neural function has been well documented. Especially, the teratogenic effect of alcohol on neurodevelopment during embryogenesis has been demonstrated in various models, which could be a pathologic basis for fetal alcohol spectrum disorders (FASDs). While the developmental defects from alcohol abuse during gestation have been described, the specific mechanisms by which alcohol mediates these injuries have yet to be determined. Recent studies have shown that alcohol has significant effect on molecular and cellular regulatory mechanisms in embryonic stem cell (ESC) differentiation including genes involved in neural development. To test our hypothesis that alcohol induces molecular alterations during neural differentiation we have derived neural precursor cells from pluripotent human ESCs in the presence or absence of ethanol treatment. Genome-wide transcriptomic profiling identified molecular alterations induced by ethanol exposure during neural differentiation of hESCs into neural rosettes and neural precursor cell populations. The Database for Annotation, Visualization and Integrated Discovery (DAVID) functional analysis on significantly altered genes showed potential ethanol’s effect on JAK-STAT signaling pathway, neuroactive ligand-receptor interaction, Toll-like receptor (TLR) signaling pathway, cytokine-cytokine receptor interaction and regulation of autophagy. We have further quantitatively verified ethanol-induced alterations of selected candidate genes. Among verified genes we further examined the expression of P2RX3, which is associated with nociception, a peripheral pain response. We found ethanol significantly reduced the level of P2RX3 in undifferentiated hESCs, but induced the level of P2RX3 mRNA and protein in hESC-derived NPCs. Our result suggests ethanol-induced dysregulation of P2RX3 along with alterations in molecules involved in neural activity such as neuroactive ligand-receptor interaction may be a molecular event associated with alcohol-related peripheral neuropathy of an enhanced nociceptive response.

Bisphenol A Represses Dopaminergic Neuron Differentiation from Human Embryonic Stem Cells through Downregulating the Expression of Insulin-like Growth Factor 1.

Bisphenol A (BPA) is a ubiquitous compound emerging as a possible toxicant during embryonic development. Human embryonic stem cell (hESC) promises a valuable model for evaluating the effects of environmental chemicals on human prenatal development. In our study, 1μM BPA were applied to hESC-derived embryoid bodies (hEBs) and effects of BPA on neural cell differentiation were investigated. The expression level of insulin-like growth factor 1 (IGF-1) and marker genes for ectoderm, neuron progenitor cells, and dopaminergic (DA) neurons were all repressed upon BPA exposure. The population of hESC-derived neural precursor cells (NPCs) and DA neurons were decreased. Furthermore, yield of DA neuron-secreted tyrosine hydroxylase (TH) and dopamine were also reduced. When recombinant IGF-1 supplied, BPA-caused repressions were partially or completely relieved. Our further methylation microarray analysis indicated that there was a higher methylation level on the promoter of SRY-related HMG-box 5 (SOX5), a possible enhancer of IGF-1. Consistently, next quantitative polymerase chain reaction (qPCR) results confirmed that SOX5 expression was downregulated. Our investigation suggests that BPA represses DA neuron differentiation mainly through downregulating IGF-1 expression, which may attribute to the altered methylation level on the promoter of IGF-1 upstream genes. Our findings first elaborate the mechanism of IGF-1-mediated BPA effects on neuronal differentiation, which is helpful to illuminate the unique mechanism of BPA toxicity on prenatal neurodevelopment.

Neural precursor cells in the ischemic brain - integration, cellular crosstalk, and consequences for stroke recovery.

After an ischemic stroke, neural precursor cells (NPCs) proliferate within major germinal niches of the brain. Endogenous NPCs subsequently migrate toward the ischemic lesion where they promote tissue remodeling and neural repair. Unfortunately, this restorative process is generally insufficient and thus unable to support a full recovery of lost neurological functions. Supported by solid experimental and preclinical data, the transplantation of exogenous NPCs has emerged as a potential tool for stroke treatment. Transplanted NPCs are thought to act mainly via trophic and immune modulatory effects, thereby complementing the restorative responses initially executed by the endogenous NPC population. Recent studies have attempted to elucidate how the therapeutic properties of transplanted NPCs vary depending on the route of transplantation. Systemic NPC delivery leads to potent immune modulatory actions, which prevent secondary neuronal degeneration, reduces glial scar formation, diminishes oxidative stress and stabilizes blood–brain barrier integrity. On the contrary, local stem cell delivery allows for the accumulation of large numbers of transplanted NPCs in the brain, thus achieving high levels of locally available tissue trophic factors, which may better induce a strong endogenous NPC proliferative response. Herein we describe the diverse capabilities of exogenous (systemically vs. locally transplanted) NPCs in enhancing the endogenous neurogenic response after stroke, and how the route of transplantation may affect migration, survival, bystander effects and integration of the cellular graft. It is the authors’ claim that understanding these aspects will be of pivotal importance in discerning how transplanted NPCs exert their therapeutic effects in stroke.

Tcf3 represses Wnt-β-catenin signaling and maintains neural stem cell population during neocortical development.

During mouse neocortical development, the Wnt–β-catenin signaling pathway plays essential roles in various phenomena including neuronal differentiation and proliferation of neural precursor cells (NPCs). Production of the appropriate number of neurons without depletion of the NPC population requires precise regulation of the balance between differentiation and maintenance of NPCs. However, the mechanism that suppresses Wnt signaling to prevent premature neuronal differentiation of NPCs is poorly understood. We now show that the HMG box transcription factor Tcf3 (also known as Tcf7l1) contributes to this mechanism. Tcf3 is highly expressed in undifferentiated NPCs in the mouse neocortex, and its expression is reduced in intermediate neuronal progenitors (INPs) committed to the neuronal fate. We found Tcf3 to be a repressor of Wnt signaling in neocortical NPCs in a reporter gene assay. Tcf3 bound to the promoter of the proneural bHLH gene Neurogenin1 (Neurog1) and repressed its expression. Consistent with this, Tcf3 repressed neuronal differentiation and increased the self-renewal activity of NPCs. We also found that Wnt signal stimulation reduces the level of Tcf3, and increases those of Tcf1 (also known as Tcf7) and Lef1, positive mediators of Wnt signaling, in NPCs. Together, these results suggest that Tcf3 antagonizes Wnt signaling in NPCs, thereby maintaining their undifferentiated state in the neocortex and that Wnt signaling promotes the transition from Tcf3-mediated repression to Tcf1/Lef1-mediated enhancement of Wnt signaling, constituting a positive feedback loop that facilitates neuronal differentiation.

Comparison of the molecular profiles of human embryonic and induced pluripotent stem cells of isogenic origin

Many studies have compared the genetic and epigenetic profiles of human induced pluripotent stem cells (hiPSCs) to human embryonic stem cells (hESCs) and yet the picture remains unclear. To address this, we derived a population of neural precursor cells (NPCs) from the H1 (WA01) hESC line and generated isogenic iPSC lines by reprogramming. The gene expression and methylation profile of three lines were compared to the parental line and intermediate NPC population. We found no gene probe with expression that differed significantly between hESC and iPSC samples under undifferentiated or differentiated conditions. Analysis of the global methylation pattern also showed no significant difference between the two PSC populations. Both undifferentiated populations were distinctly different from the intermediate NPC population in both gene expression and methylation profiles. One point to note is that H1 is a male line and so extrapolation to female lines should be cautioned. However, these data confirm our previous findings that there are no significant differences between hESCs and hiPSCs at the gene expression or methylation level.