Neural Stem Cell Function Research Articles

Phosphatase and actin regulator 4 is associated with intermediate filaments in adult neural stem cells and their progenitor astrocytes.

Phosphatase and actin regulator 4 (Phactr4) is a newly discovered protein that inhibits protein phosphatase 1 and shows actin-binding activity. We previously found that Phactr4 is expressed in the neurogenic niche in adult mice, although its precise subcellular localization and possible function in neural stem cells (NSCs) is not yet understood. Here, we show that Phactr4 formed punctiform clusters in the cytosol of subventricular zone-derived adult NSCs and their progeny in vitro. These Phactr4 signals were not associated with F-actin fibers but were closely associated with intermediate filaments such as nestin and glial fibrillary acidic protein (GFAP) fibers. Direct binding of Phactr4 with nestin and GFAP filaments was demonstrated using Duolink protein interaction analyses and immunoprecipitation assays. Interestingly, when nestin fibers were de-polymerized during the mitosis or by the phosphatase inhibitor, Phactr4 appeared to be dissociated from nestin, suggesting that their protein interaction is regulated by the protein phosphorylation. These results suggest that Phactr4 forms functional associations with intermediate filament networks in adult NSCs.

Galanin promotes neuronal differentiation from neural progenitor cells in vitro and contributes to the generation of new olfactory neurons in the adult mouse brain

Galanin is a pleiotropic neuropeptide widely expressed in the nervous system. It plays a role in many diverse physiological functions – including nociception, cognition and metabolism regulation – and acts as neurotrophic/neuroprotective factor for several neuronal populations. In this article we sought to determine the role of galanin on neural stem cell function and its contribution to the plasticity of the nervous system. Here we show that galanin and its receptors are expressed in neural progenitor cells (NPCs) isolated from the developing striatum. Stimulation with galanin results in upregulation of Bcl-Xl, Bcl-2, Mash-1 and Olig-2 that are part of well known pro-survival/pro-neuronal signalling pathways. Accordingly, treatment with galanin increases the number of neurons upon differentiation from these progenitors. We then show that these effects are recapitulated in NPCs isolated from the adult subventricular zone (SVZ), where galanin increases the total number of neurons and the number of newly-generated neurons upon differentiation in vitro. The significance of these findings is highlighted in the adult brain where loss of galanin leads to a marked decrease in the rate of adult SVZ neurogenesis and a reduction in the number of newly generated cells in the olfactory bulb. Interestingly, Gal-KO mice display normal performances in simple tasks of olfactory detection and discrimination, which points to the existence of a certain degree of redundancy in SVZ neurogenesis. Our findings establish the role of galanin as a modulator of neural stem cell function and support the importance of galanin for brain plasticity and repair.

Neurogenesis and vascularization of the damaged brain using a lactate-releasing biomimetic scaffold

Regenerative medicine strategies to promote recovery following traumatic brain injuries are currently focused on the use of biomaterials as delivery systems for cells or bioactive molecules. This study shows that cell-free biomimetic scaffolds consisting of radially aligned electrospun poly-l/dl lactic acid (PLA70/30) nanofibers release l-lactate and reproduce the 3D organization and supportive function of radial glia embryonic neural stem cells. The topology of PLA nanofibers supports neuronal migration while l-lactate released during PLA degradation acts as an alternative fuel for neurons and is required for progenitor maintenance. Radial scaffolds implanted into cavities made in the postnatal mouse brain fostered complete implant vascularization, sustained neurogenesis, and allowed the long-term survival and integration of the newly generated neurons. Our results suggest that the endogenous central nervous system is capable of regeneration through the in vivo dedifferentiation induced by biophysical and metabolic cues, with no need for exogenous cells, growth factors, or genetic manipulation.

Palmitic acid affects proliferation and differentiation of neural stem cells in vitro

High-lipid diet composed of saturated fatty acids (SFAs) has significant detrimental effects on brain homeostasis, and deleterious effects of SFAs on various cells have been well documented. However, the effects of SFAs on neural stem Cells (NSCs) function have not been fully explored. The aim of this study was to determine whether palmitic acid (PA) affected the proliferation and differentiation of murine-derived NSCs. The results showed that PA dose dependently suppressed viability of NSCs and was cytotoxic at high concentrations. The toxic levels of PA inhibited the proliferation of NSCs as shown by reduced bromodeoxyuridine labeling of NSCs, which is correlated with reactive oxygen species generation. Pretreatment of the cells with the antioxidant N-acetyl-L-cysteine inhibitor significantly attenuated the effects of PA on the proliferation of NSCs. Furthermore, nontoxic levels of PA promoted astrocytogenesis in the differentiated NSCs, associated with Stat3 activation and altered expression of serial of basic helix-loop-helix transcription factor genes. Altogether, our data have demonstrated that PA has a significant impact on proliferation and differentiation of NSCs in vitro and may be useful for elucidating the role of SFAs in regulating NSCs fate in physiological and pathological settings.

Ketamine Inhibits Proliferation of Neural Stem Cell from Neonatal Rat Hippocampus in Vitro

Background/Aims: Ketamine is a widely used anesthetic in obstetric and pediatric anesthesia. In the developing brain, the widespread neuron apoptosis triggered by ketamine has been demonstrated. However, little is known about its effect on neural stem cells (NSCs) function. This study aimed to investigate the effect of ketamine on proliferation of NSCs from neonatal rat hippocampus. Methods: Neural stem cells were isolated from the hippocampus of Sprague-Dawley rats on postnatal day 3. In dose-response experiments, cultured neural stem cells (NSCs) were exposed to different concentrations of ketamine (0-1000 µM) for 24 hrs. The proliferative activity of NSCs was evaluated by 5-Bromo-2′-deoxyuridine (BrdU) incorporation assay. Apoptosis of neural stem cells were assessed using caspase-3 by western blot. The intracellular Ca²⁺ concentration ([Ca²⁺]i) in NSCs was analyzed by flow cytometry. The activation of protein kinase C-α (PKCα) and the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) were measured by western blot analysis. Results: Clinical relevant concentration of ketamine (10, 20 and 50 µM) did not markedly alter the proliferation of NSCs from neonatal rat hippocampus in vitro. However, ketamine (200, 500, 800 and 1000μM) significantly inhibited the proliferation of NSCs and did not affect the expression of caspase-3. Meanwhile, ketamine (200, 500, 800 and 1000μM) also markedly decreased [Ca²⁺]i as well as suppressed PKCα activation and ERK1/2 phosphorylation in NSCs. A combination of subthreshold concentrations of ketamine (100 μM) and Ca²⁺ channel blocker verapamil (2.5 μM), PKCα inhibitor chelerythrine (2.5 μM) or ERK1/2 kinase inhibitor PD98059 (5 μM) significantly produced suprathreshold effects on PKCα activation, ERK1/2 phosphorylation and NSC proliferation. Conclusion: Ketamine inhibited proliferation of NSCs from neonatal rat hippocampus in vitro. Suppressing Ca²⁺-PKCα-ERK1/2 signaling pathway may be involved in this inhibitory effect of ketamine on NSCs proliferation.

Surfaceome Profiling Reveals Regulators of Neural Stem Cell Function

The composition of cell-surface proteins changes during lineage specification, altering cellular responses to their milieu. The changes that characterize maturation of early neural stem cells (NSCs) remain poorly understood. Here we use mass spectrometry-based cell surface capture technology to profile the cell surface of early NSCs and demonstrate functional requirements for several enriched molecules. Primitive NSCs arise from embryonic stem cells upon removal of Transforming growth factor-β signaling, while definitive NSCs arise from primitive NSCs upon Lif removal and FGF addition. In vivo aggregation assays revealed that N-cadherin upregulation is sufficient for the initial exclusion of definitive NSCs from pluripotent ectoderm, while c-kit signaling limits progeny of primitive NSCs. Furthermore, we implicate EphA4 in primitive NSC survival signaling and Erbb2 as being required for NSC proliferation. This work elucidates several key mediators of NSC function whose relevance is confirmed on forebrain-derived populations and identifies a host of other candidates that may regulate NSCs.

Changes in the frequencies of human hematopoietic stem and progenitor cells with age and site

This study enumerated CD45(hi)/CD34(+) and CD45(hi)/CD133(+) human hematopoietic stem cells (HSCs) and progenitor granulocyte-macrophage colony forming cells (GM-CFCs) in blood and trochanteric and femoral bone marrow in 233 individuals. Stem cell frequencies were determined with multiparameter flow cytometry and using an internal control to determine the intrinsic variance of the assays. Progenitor cell frequency was determined using a standard colony assay technique. The frequency of outliers from undetermined methodological causes was highest for blood, but less than 5% for all values. The frequency of CD45(hi)/CD133(+) cells correlated highly with the frequency of CD45(hi)/CD34(+) cells in trochanteric and femoral bone marrow. The frequency of these HSC populations in trochanteric and femoral bone marrow rose significantly with age. In contrast, there was no significant trend of either of these cell populations with age in the blood. Trochanteric marrow progenitor GM-CFCs showed no significant trends with age, but femoral marrow GM-CFCs trended downward with age, potentially because of the reported conversion of red marrow at this site to fat with age. Hematopoietic stem and progenitor cells exhibited changes in frequencies with age that differed between blood and bone marrow. We previously reported that side population (SP) multipotential HSC, which includes the precursors of CD45(hi)/CD133(+) and CD45(hi)/CD34(+), decline with age. Potentially the increases in stem cell frequencies in the intermediate compartment between SP and GM progenitor cells observed in this study represent a compensatory increase for the loss of more potent members of the HSC hierarchy.

Light‐controlled astrocytes promote human mesenchymal stem cells toward neuronal differentiation and improve the neurological deficit in stroke rats

Astrocytes are key components of the central nervous system (CNS) and release factors to support neural stem cell proliferation, differentiation, and migration. Adenosine 5'-triphosphate (ATP) is one of the key factors released upon activation of astrocytes that regulates the neural stem cell's function. However, it is not clear whether ATP derived from the depolarized astrocytes plays a vital role in promoting the neuronal differentiation of mesenchymal stem cells (MSCs) in vitro and in vivo. Herein, for the first time, we co-cultured MSCs with light-stimulated-channelrhodopsin-2 (ChR2)-astrocytes, and observed that the neuronal differentiation of MSCs was enhanced by expressing more neuronal markers, Tuj1 and NeuN. The ChR2-astrocyte-conditioned medium also stimulated MSCs differentiating into neuronal lineage cells by expressing more Tuj1 and Pax6, which was blocked by the P2X receptor antagonist, TNP-ATP. Then we found that light-depolarization of astrocytes significantly increased ATP accumulation in their bathing medium without impairing the cell membrane. We further found that ATP up-regulated the Tuj1, Pax6, FZD8 and β-catenin mRNA levels of MSCs, which could be reversed by application of TNP-ATP. Together these in vitro data provided convergent evidence that ATP from light-depolarized-astrocytes activated the wnt/β-catenin signaling of MSCs through binding to the P2X receptors, and promoted the neuronal differentiation of MSCs. Finally but importantly, our study also demonstrated in stroke rats that light-controlled astrocytes stimulated endogenous ATP release into the ischemic area to influence the transplanted MSCs, resulting in promoting the MSCs towards neuronal differentiation and improvements of neurological deficit.

Derivation of neural stem cells from an animal model of psychiatric disease

Several psychiatric and neurological diseases are associated with altered hippocampal neurogenesis, suggesting differing neural stem cell (NSC) function may play a critical role in these diseases. To investigate the role of resident NSCs in a murine model of psychiatric disease, we sought to isolate and characterize NSCs from alpha-calcium-/calmodulin-dependent protein kinase II heterozygous knockout (CaMK2α-hKO) mice, a model of schizophrenia/bipolar disorder. These mice display altered neurogenesis, impaired neuronal development and are part of a larger family possessing phenotypic and behavioral correlates of schizophrenia/bipolar disorder and a shared pathology referred to as the immature dentate gyrus (iDG). The extent to which NSCs contribute to iDG pathophysiology remains unclear. To address this, we established heterogeneous cultures of NSCs isolated from the hippocampal neuropoietic niche. When induced to differentiate, CaMK2α-hKO-derived NSCs recapitulate organotypic hippocampal neurogenesis, but generate larger numbers of immature neurons than wild-type (WT) littermates. Furthermore, mutant neurons fail to assume mature phenotypes (including morphology and MAP2/calbindin expression) at the same rate observed in WT counterparts. The increased production of immature neurons which fail to mature indicates that this reductionist model retains key animal- and iDG-specific maturational deficits observed in animal models and human patients. This is doubly significant, as these stem cells lack several developmental inputs present in vivo. Interestingly, NSCs were isolated from animals prior to the emergence of overt iDG pathophysiology, suggesting mutant NSCs may possess lasting intrinsic alterations and that altered NSC function may contribute to iDG pathophysiology in adult animals.

Titration of GLI3 Repressor Activity by Sonic Hedgehog Signaling Is Critical for Maintaining Multiple Adult Neural Stem Cell and Astrocyte Functions

Sonic hedgehog (SHH), a key regulator of embryonic neurogenesis, signals directly to neural stem cells (NSCs) in the subventricular zone (SVZ) and to astrocytes in the adult mouse forebrain. The specific mechanism by which the GLI2 and GLI3 transcriptional activators (GLI2(A) and GLI3(A)) and repressors (GLI2(R) and GLI3(R)) carry out SHH signaling has not been addressed. We found that the majority of slow-cycling NSCs express Gli2 and Gli3, whereas Gli1 is restricted ventrally and all three genes are downregulated when NSCs transition into proliferating progenitors. Surprisingly, whereas conditional ablation of Smo in postnatal glial fibrillary acidic protein-expressing cells results in cell-autonomous loss of NSCs and a progressive reduction in SVZ proliferation, without an increase in glial cell production, removal of Gli2 or Gli3 does not alter adult SVZ neurogenesis. Significantly, removing Gli3 in Smo conditional mutants largely rescues neurogenesis and, conversely, expression of a constitutive GLI3(R) in the absence of normal Gli2 and Gli3 abrogates neurogenesis. Thus unattenuated GLI3(R) is a primary inhibitor of adult SVZ NSC function. Ablation of Gli2 and Gli3 revealed a minor role for GLI2(R) and little requirement for GLI(A) function in stimulating SVZ neurogenesis. Moreover, we found that similar rules of GLI activity apply to SHH signaling in regulating SVZ-derived olfactory bulb interneurons and maintaining cortical astrocyte function. Namely, fewer superficial olfactory bulb interneurons are generated in the absence of Gli2 and Gli3, whereas astrocyte partial gliosis results from an increase in GLI3(R). Thus precise titration of GLI(R) levels by SHH is critical to multiple functions of adult NSCs and astrocytes.

CHD7 and retinoic acid signaling cooperate to regulate neural stem cell and inner ear development in mouse models of CHARGE syndrome

CHARGE syndrome is a multiple congenital anomaly disorder that leads to life-threatening birth defects, such as choanal atresia and cardiac malformations as well as multiple sensory impairments, that affect hearing, vision, olfaction and balance. CHARGE is caused by heterozygous mutations in CHD7, which encodes an ATP-dependent chromatin remodeling enzyme. Identification of the mechanisms underlying neurological and sensory defects in CHARGE is a first step toward developing treatments for CHARGE individuals. Here, we used mouse models of Chd7 deficiency to explore the function of CHD7 in the development of the subventricular zone (SVZ) neural stem cell niche and inner ear, structures that are important for olfactory bulb neurogenesis and hearing and balance, respectively. We found that loss of Chd7 results in cell-autonomous proliferative, neurogenic and self-renewal defects in the perinatal and mature mouse SVZ stem cell niche. Modulation of retinoic acid (RA) signaling prevented in vivo inner ear and in vitro neural stem cell defects caused by Chd7 deficiency. Our findings demonstrate critical, cooperative roles for RA and CHD7 in SVZ neural stem cell function and inner ear development, suggesting that altered RA signaling may be an effective method for treating Chd7 deficiency.

Nanotopographical Manipulation of Focal Adhesion Formation for Enhanced Differentiation of Human Neural Stem Cells

Manipulating neural stem cell (NSC) fate is of great importance for improving the therapeutic efficacy of NSCs to treat neurodegenerative disorders. Biophysical cues, in addition to biochemical factors, regulate NSC phenotype and function. In this study, we assessed the extent to which surface nanotopography of culture substrates modulates human NSC (hNSC) differentiation. Fibronectin-coated polymer substrates with diverse nanoscale shapes (groove and pillar) and dimensions (ranging from 300 to 1500 nm groove width and pillar gap) were used to investigate the effects of topographical cues on hNSC morphology, alignment, focal adhesion, and differentiation. The majority of nanopatterned substrates induced substantial changes in cellular morphology and alignment along the patterned shapes, leading to alterations in focal adhesion and F-actin reorganization. Certain types of nanopatterned substrates, in particular the ones with small nanostructures (e.g., 300-300 nm groove ridges and 300-300 nm pillar diameter gaps), were found to effectively enhance focal adhesion complex development. Consequently, these substrates enhanced hNSC differentiation toward neurons and astrocytes. Nanotopographical-induced formation of focal adhesions in hNSCs activates integrin-mediated mechanotransduction and intracellular signaling pathways such as MEK-ERK, which may ultimately promote gene expression related to NSC differentiation. This strategy of manipulating matrix surface topography could be applied to develop culture substrates and tissue engineered scaffolds that improve the efficacy of NSC therapeutics.

S28 * ALCOHOL ABUSE COMORBIDITY ESBRA, APSAAR & JMSAS JOINT SYMPOSIUM

S28 * ALCOHOL ABUSE COMORBIDITY ESBRA, APSAAR & JMSAS JOINT SYMPOSIUM

Dynamic Activity of miR-125b and miR-93 during Murine Neural Stem Cell Differentiation In Vitro and in the Subventricular Zone Neurogenic Niche

Several microRNAs (miRNAs) that are either specifically enriched or highly expressed in neurons and glia have been described, but the identification of miRNAs modulating neural stem cell (NSC) biology remains elusive. In this study, we exploited high throughput miRNA expression profiling to identify candidate miRNAs enriched in NSC/early progenitors derived from the murine subventricular zone (SVZ). Then, we used lentiviral miRNA sensor vectors (LV.miRT) to monitor the activity of shortlisted miRNAs with cellular and temporal resolution during NSC differentiation, taking advantage of in vitro and in vivo models that recapitulate physiological neurogenesis and gliogenesis and using known neuronal- and glial-specific miRNAs as reference. The LV.miRT platform allowed us monitoring endogenous miRNA activity in low represented cell populations within a bulk culture or within the complexity of CNS tissue, with high sensitivity and specificity. In this way we validated and extended previous results on the neuronal-specific miR-124 and the astroglial-specific miR-23a. Importantly, we describe for the first time a cell type- and differentiation stage-specific modulation of miR-93 and miR-125b in SVZ-derived NSC cultures and in the SVZ neurogenic niche in vivo, suggesting key roles of these miRNAs in regulating NSC function.

Site‐Specific Differentiation of Neural Stem Cell Regulated by Micropatterned Multicomponent Interfaces

Stem cell microenvironments are enriched by signals from a variety of components, which cooperate spatially and temporally to regulate cellular function. In vitro recapitulating such complexity in a well-controlled manner is elusive. Here, a platform for patterning multiple bio-active proteins on a single substrate is developed and optimized, and is used it to study the cooperative involvement of cell-matrix interaction and cell-cell signaling in regulating neural stem cell (NSC) function. An affinity-capturing-based multi-step microcontact printing is used to pattern, extracellular matrix proteins, and cell-cell signaling ligands, as intersecting lines on a nonadhesive background. Such design provides spatial segregation of signals from different extrinsic components, while allowing cell traffic between them during their proliferation and differentiation processes. Rat embryonic neural stem cells are cultured and characterized on the multicomponent substrates patterned with different combinations of fibronectin, N-cadherin, and Jagged1 proteins and allow to proliferate and differentiate over long term. It is found that local presentation of Notch signaling ligand (Jagged1) or cell adhesion molecule (N-cadherin) effectively modulate the balance between cell-cell and cell-matrix interaction, and significantly change the overall spatial remodeling of NSC differentiation. This platform provides an unambiguous approach to study the spatial and temporal cooperative involvement of different extrinsic components in regulating stem cell behavior. It is also readily expandable for inclusion of extra components and applicable to use with other types of cells, which provide a powerful tool for basic study of cell-material interaction or advanced tissue-interface engineering.

A Novel Fluorescent Reporter CDy1 Enriches for Neural Stem Cells Derived from the Murine Brain

Neurogenesis occurs continuously in two brain regions of adult mammals, underpinned by a pool of resident neural stem cells (NSCs) that can differentiate into all neural cell types. To advance our understanding of NSC function and to develop therapeutic and diagnostic approaches, it is important to accurately identify and enrich for NSCs. There are no definitive markers for the identification and enrichment of NSCs present in the mouse brain. Recently, a fluorescent rosamine dye, CDy1, has been identified as a label for pluripotency in cultured human embryonic and induced pluripotent stem cells. As similar cellular characteristics may enable the uptake and retention of CDy1 by other stem cell populations, we hypothesized that this dye may also enrich for primary NSCs from the mouse brain. Because the subventricular zone (SVZ) and the hippocampus represent brain regions that are highly enriched for NSCs in adult mammals, we sampled cells from these areas to test this hypothesis. These experiments revealed that CDy1 staining indeed allows for enrichment and selection of all neurosphere-forming cells from both the SVZ and the hippocampus. We next examined the effectiveness of CDy1 to select for NSCs derived from the SVZ of aged animals, where the total pool of NSCs present is significantly lower than in young animals. We found that CDy1 effectively labels the NSCs in adult and aged animals as assessed by the neurosphere assay and reflects the numbers of NSCs present in aged animals. CDy1, therefore, appears to be a novel marker for enrichment of NSCs in primary brain tissue preparations.

Lineage tracing with Axin2 reveals distinct developmental and adult populations of Wnt/β-catenin–responsive neural stem cells

Since the discovery of neural stem cells in the mammalian brain, there has been significant interest in understanding their contribution to tissue homeostasis at both the cellular and molecular level. Wnt/β-catenin signaling is crucial for development of the central nervous system and has been implicated in stem cell maintenance in multiple tissues. Based on this, we hypothesized that the Wnt pathway likely controls neural stem cell maintenance and differentiation along the entire developmental continuum. To test this, we performed lineage tracing experiments using the recently developed tamoxifen-inducible Cre at Axin2 mouse strain to follow the developmental fate of Wnt/β-catenin-responsive cells in both the embryonic and postnatal mouse brain. From as early as embryonic day 8.5 onwards, Axin2(+) cells can give rise to spatially and functionally restricted populations of adult neural stem cells in the subventricular zone. Similarly, progeny from Axin2(+) cells labeled from E12.5 contribute to both the subventricular zone and the dentate gyrus of the hippocampus. Labeling in the postnatal brain, in turn, demonstrates the persistence of long-lived, Wnt/β-catenin-responsive stem cells in both of these sites. These results demonstrate the continued importance of Wnt/β-catenin signaling for neural stem and progenitor cell formation and function throughout developmental time.

Effects of atelocollagen on neural stem cell function and its migrating capacity into brain in psychiatric disease model

Stem cell therapy is well proposed as a potential method for the improvement of neurodegenerative damage in the brain. Among several different procedures to reach the cells into the injured lesion, the intravenous (IV) injection has benefit as a minimally invasive approach. However, for the brain disease, prompt development of the effective treatment way of cellular biodistribution of stem cells into the brain after IV injection is needed. Atelocollagen has been used as an adjunctive material in a gene, drug and cell delivery system because of its extremely low antigenicity and bioabsorbability to protect these transplants from intrabody environment. However, there is little work about the direct effect of atelocollagen on stem cells, we examined the functional change of survival, proliferation, migration and differentiation of cultured neural stem cells (NSCs) induced by atelocollagen in vitro. By 72-h treatment 0.01-0.05% atelocollagen showed no significant effects on survival, proliferation and migration of NSCs, while 0.03-0.05% atelocollagen induced significant reduction of neuronal differentiation and increase of astrocytic differentiation. Furthermore, IV treated NSCs complexed with atelocollagen (0.02%) could effectively migrate into the brain rather than NSC treated alone using chronic alcohol binge model rat. These experiments suggested that high dose of atelocollagen exerts direct influence on NSC function but under 0.03% of atelocollagen induces beneficial effect on regenerative approach of IV administration of NSCs for CNS disease.

FIP200 is required for maintenance and differentiation of postnatal neural stem cells

Despite recent studies showing depletion of hematopoietic stem cells (HSCs) pool accompanied by increased intracellular ROS upon autophagy inhibition, it remains unknown whether autophagy is essential in the maintenance of other stem cells. Moreover, it is unclear whether and how the aberrant ROS increase causes depletion of stem cells. Here, we report that ablation of FIP200, an essential gene for autophagy induction in mammalian cells, results in a progressive loss of neural stem cells (NSCs) pool and impairment in neuronal differentiation specifically in the postnatal brain, but not the embryonic brain, in mice. The defect in maintaining the postnatal NSC pool was caused by p53-dependent apoptotic responses and cell cycle arrest. However, the impaired neuronal differentiation was rescued by anti-oxidant NAC treatment, but not by p53 inactivation. These data reveal a role of FIP200-mediated autophagy in the maintenance and functions of NSCs through regulation of oxidative state.

Loss of Dickkopf-1 Restores Neurogenesis in Old Age and Counteracts Cognitive Decline

Memory impairment has been associated with age-related decline in adult hippocampal neurogenesis. Although Notch, bone morphogenetic protein, and Wnt signaling pathways are known to regulate multiple aspects of adult neural stem cell function, the molecular basis of declining neurogenesis in the aging hippocampus remains unknown. Here, we show that expression of the Wnt antagonist Dickkopf-1 (Dkk1) increases with age and that its loss enhances neurogenesis in the hippocampus. Neural progenitors with inducible loss of Dkk1 increase their Wnt activity, which leads to enhanced self-renewal and increased generation of immature neurons. This Wnt-expanded progeny subsequently matures into glutamatergic granule neurons with increased dendritic complexity. As a result, mice deficient in Dkk1 exhibit enhanced spatial working memory and memory consolidation and also show improvements in affective behavior. Taken together, our findings show that upregulating Wnt signaling by reducingDkk1 expression can counteract age-related decrease in neurogenesis and its associated cognitive decline.