Proliferation Of Neural Cells Research Articles

Global Programmed Switch in Neural Daughter Cell Proliferation Mode Triggered by a Temporal Gene Cascade

During central nervous system (CNS) development, progenitors typically divide asymmetrically, renewing themselves while budding off daughter cells with more limited proliferative potential. Variation in daughter cell proliferation has a profound impact on CNS development and evolution, but the underlying mechanisms remain poorly understood. We find that Drosophila embryonic neural progenitors (neuroblasts) undergo a programmed daughter proliferation mode switch, from generating daughters that divide once (type I) to generating neurons directly (type 0). This typeI>0 switch is triggered by activation of Dacapo (mammalian p21(CIP1)/p27(KIP1)/p57(Kip2)) expression in neuroblasts. In the thoracic region, Dacapo expression is activated by the temporal cascade (castor) and the Hox gene Antennapedia. In addition, castor, Antennapedia, and the late temporal gene grainyhead act combinatorially to control the precise timing of neuroblast cell-cycle exit by repressing Cyclin E and E2f. This reveals a logical principle underlying progenitor and daughter cell proliferation control in the Drosophila CNS.

Expression of hippocampal toll-like receptors 4 and proliferation of neural progenitor cells in mouse model of traumatic brain injury

Objective To investigate the expression of hippocampal toll-like receptors 4 (TLR4) and the proliferation of neural progenitor cells (NPCs) in mouse model of traumatic brain injury (TBI).Methods Adult male Balb/c mice were randomly divided into the sham groups and the 1st,3rd,7th,14th,21st days post-traumatic groups.The TBI mouse model was induced by Mamarou weight-drop device.NPCs were labeled with thymidine analog 5-Bromo-2-deoxyUridine (BrdU).The expression and distribution of BrdU and TLR4 in hippocampus were observed by inmmunofluorescence.The expression of TLR4 in protein level was detected by Western-blot.Results It was observed that TLR4 expressed on the NPCs in hippocampus by double-labeling inmmunofluorescence,and the expression of TLR4 protein in hippocampus raised at the 1st day,got to the peak around the 3rd day,then decreased over the 7th day,14th day,and 21st day to a lower value but still higher than the sham group(P ＜ 0.05).NPCs increased at the 1st post-traumatic day,reached the peak at the 3rd day,followed by a gradual reduction from the 3rd day to the 21st day when maintained a higher number than that of the sham group (P ＜ 0.05).Conclusions TLR4 expressed on the NPCs in hippocampus,and the expression of hippocampal TLR4 varied in a similar temporal pattern with the proliferation of NPCs after injury.It suggested that hippocampal TLR4 might play a potential role in the endogenous neurogenesis after TBI. Key words: Craniocerebral trauma; Toll-like receptors 4; Neural progenitor cells

Highly conductive stretchable and biocompatible electrode-hydrogel hybrids for advanced tissue engineering.

Hydrogel-based, molecular permeable electronic devices are considered to be promising for electrical stimulation and recording of living tissues, either in vivo or in vitro. This study reports the fabrication of the first hydrogel-based devices that remain highly electrically conductive under substantial stretch and bending. Using a simple technique involving a combination of chemical polymerization and electropolymerization of poly (3,4-ethylenedioxythiophene) (PEDOT), a tight bonding of a conductive composite of PEDOT and polyurethane (PU) to an elastic double-network hydrogel is achieved to make fully organic PEDOT/PU-hydrogel hybrids. Their response to repeated bending, mechanical stretching, hydration-dessication cycles, storage in aqueous condition for up to 6 months, and autoclaving is assessed, demonstrating excellent stability, without any mechanical or electrical damage. The hybrids exhibit a high electrical conductivity of up to 120 S cm(-1) at 100% elongation. The adhesion, proliferation, and differentiation of neural and muscle cells cultured on these hybrids are demonstrated, as well as the fabrication of 3D hybrids, advancing the field of tissue engineering with integrated electronics.

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.

Neural crest cell‐specific inactivation of Nipbl or Mau2 during mouse development results in a late onset of craniofacial defects

Nipbl (Scc2) and Mau2 (Scc4) encode evolutionary conserved proteins that play a vital role for loading the cohesin complex onto chromosomes, thereby ensuring accurate chromosome segregation during cell division. While mutations in human NIPBL are known to cause the developmental disorder Cornelia de Lange syndrome, the functions of Nipbl and Mau2 in mammalian development are poorly defined. Here we generated conditional alleles for both genes in mice and show that neural crest cell-specific inactivation of Nipbl or Mau2 strongly affects craniofacial development. Surprisingly, the early phase of neural crest cell proliferation and migration is only moderately affected in these mutants. Moreover, we found that Mau2 single homozygous mutants exhibited a more severe craniofacial phenotype when compared to that of Nipbl;Mau2 double homozygous mutants. This raises the possibility that the Mau2/Nipbl protein interaction is not only required for cohesin loading, but may also be required to restrict the level of Nipbl involved in regulating gene expression. Together, the data suggest that proliferating neural crest cells tolerate a substantial reduction of cohesin loading proteins and we propose that the successive decrease of cohesin loading proteins in neural crest cells may alter developmental gene regulation in a highly dynamic manner.

NPAS3 variants in schizophrenia: a neuroimaging study

BackgroundThis research is a one-site neuroimaging component of a two-site genetic study involving patients with schizophrenia at early and later stages of illness. Studies support a role for the neuronal Per-Arnt-Sim 3 (NPAS3) gene in processes that are essential for normal brain development. Specific NPAS3 variants have been observed at an increased frequency in schizophrenia. In humans, NPAS3 protein was detected in the hippocampus from the first trimester of gestation. In addition, NPAS3 protein levels were reduced in the dorsolateral prefrontal cortex of some patients with schizophrenia. Npas3 knockout mice display behavioural, neuroanatomical and structural changes with associated severe reductions in neural precursor cell proliferation in the hippocampal dentate gyrus. This study will evaluate the hypothesis that the severe reductions in neural precursor cell proliferation in the dentate gyrus will be present to some degree in patients carrying schizophrenia-associated NPAS3 variants and less so in other patients.Methods/DesignPatients enrolled in the larger genetic study (n = 150) will be invited to participate in this neuroimaging arm. The genetic data will be used to ensure a sample size of 45 participants in each genetic subgroup of patients (with and without NPAS3 variants). In addition, we will recruit 60 healthy controls for acquisition of normative data. The following neuroimaging measures will be acquired from the medial temporal region: a) an index of the microcellular environment; b) a macro-structural volumetric measure of the hippocampus; and c) concentration levels of N-acetylaspartate, a marker of neuronal health.DiscussionThis study will help to establish the contribution of the NPAS3 gene and its variants to brain tissue abnormalities in schizophrenia. Given the genetic and phenotypic heterogeneity of the disorder and the large variation in outcomes, the identification of biological subgroups may in future support tailoring of treatment approaches in order to optimize recovery.

Social isolation disrupts hippocampal neurogenesis in young non-human primates.

Social relationships are crucial for the development and maintenance of normal behavior in non-human primates. Animals that are raised in isolation develop abnormal patterns of behavior that persist even when they are later reunited with their parents. In rodents, social isolation is a stressful event and is associated with a decrease in hippocampal neurogenesis but considerably less is known about the effects of social isolation in non-human primates during the transition from adolescence to adulthood. To investigate how social isolation affects young marmosets, these were isolated from other members of the colony for 1 or 3 weeks and evaluated for alterations in their behavior and hippocampal cell proliferation. We found that anxiety-related behaviors like scent-marking and locomotor activity increased after social isolation when compared to baseline levels. In agreement, grooming—an indicative of attenuation of tension—was reduced among isolated marmosets. These results were consistent with increased cortisol levels after 1 and 3 weeks of isolation. After social isolation (1 or 3 weeks), reduced proliferation of neural cells in the subgranular zone of dentate granule cell layer was identified and a smaller proportion of BrdU-positive cells underwent neuronal fate (doublecortin labeling). Our data is consistent with the notion that social deprivation during the transition from adolescence to adulthood leads to stress and produces anxiety-like behaviors that in turn might affect neurogenesis and contribute to the deleterious consequences of prolonged stressful conditions.

Vinyl chloride monomer (VCM) induces high occurrence of neural tube defects in embryonic mouse brain during neurulation.

The aim of this study was to explore the direct embryonic teratogenicity of vinyl chloride monomer (VCM), especially the toxic effects on the early development of the nervous system and its underlying mechanisms. Pregnant mice at embryonic day 6.5 (E6.5) were injected with different doses of VCM (200, 400 and 600 mg/kg) and embryos were harvested at E10.5. Our results showed that doses higher than 400 mg/kg of VCM increased the incidence of malformed embryos, especially the neural tube defects (NTDs). In addition, high-dose of VCM decreased mitotic figure counts in the neuroepithelium and enhanced the percentage of cells in G0/G1 phase, while they were reduced in S phase. The more VCM was injected into mice, the fewer positive PCNA cells were seen and the more positive TUNEL cells were observed in the neuroepithelium. Moreover, significant increases in the levels of caspase-3 protein were observed in NTD embryos. Our results demonstrate that during early pregnancy, exposure to doses higher than 400 mg/kg of VCM increases the incidence of malformations and particularly the rate of NTDs. High-dose of VCM inhibits the proliferation of neural cells and induces cell apoptosis, leading to an imbalance in the ratio of proliferation and apoptosis. Meanwhile, the apoptosis of neuroepithelial cells might be accelerated by the activation of the caspase-3 pathway, and it might be a reason for NTDs.

Electroacupuncture promotes neural cell proliferation in vivo through activation of the ERK1/2 signaling pathway

The aim of this study was to investigate the effect of electroacupuncture (EA) on cell proliferation and its molecular mechanisms. Sixty rats were randomly divided into 5 groups: sham operation control (SC), ischemia control (IC), EA, EA and DMSO injection (ED), EA and U0126 injection (EU). All the groups, with the exception of SC, underwent middle cerebral artery occlusion (MCAO), and DMSO or U0126 was injected into the rat in the ED or EU group 30 min prior to MCAO. Cell proliferation was evaluated by proliferating cell nuclear antigen (PCNA) immunostaining. The changes of cell cycle proteins (cyclin D1, CDK4, cyclin E, CDK2, p21 and p27) and the ERK1/2 pathway activation were examined by RT-PCR and western blot analysis. The results showed that the positive cell numbers of PCNA immunostaining in the EA and ED groups were more than those in the IC group (P<0.05). The mRNA and protein levels of p21 or p27 were obviously increased, however, the mRNA and protein levels of cyclin D1, CDK4, cyclin E and CDK2 were reduced in the IC and EU groups. The findings suggested that EA activates the ERK1/2 signaling pathway to protect brain injury during cerebral ischemia. However, this positive effect of EA can be blocked by U0126.

Multiple mechanisms mediate the taurine-induced proliferation of neural stem/progenitor cells from the subventricular zone of the adult mouse

Taurine was previously reported to increase the proliferation of neural precursor cells (NPCs) from subventricular zone of the mouse brain. The results of a study that aimed to understand the mechanisms of this effect are presented here. Because taurine was not found in NPC nuclei, direct interactions with nuclear elements seem unlikely. A gene expression profile analysis indicated that genes that are regulated by taurine have roles in i) proliferation, including the Shh and Wnt pathways; ii) cellular adhesion; iii) cell survival; and iv) mitochondrial functioning. Cell cycle analysis of propidium iodide and CFSE-labeled cells using flow cytometry revealed an increase in the number of cells in the S-phase and a decrease in those in the G0/G1 phase in taurine-treated cultures. No changes in the length of the cell cycle were observed. Quantification of the viable, apoptotic, and necrotic cells in cultures using flow cytometry and calcein-AM, annexin-V, and propidium iodide staining showed reductions in the number of apoptotic and necrotic cells (18% to 11% and 13% to 10%, respectively) and increases in the number of viable cells (61% to 69%) in the taurine-treated cultures. Examination of the relative mitochondrial potential values by flow cytometry and rhodamine123 or JC-1 staining showed a 44% increase in the number of cells with higher mitochondrial potential and a 38% increase in the mitochondrial membrane potential in taurine cultures compared with those of controls. Taken together, the results suggest that taurine provides more favorable conditions for cell proliferation by improving mitochondrial functioning.

Study advancement of glial cell line-derived neurotrophic factor in the enteric nervous system

Glial cell line-derived neurotrophic factor(GDNF) is a kind of protein factor which can regulate the enteric nervous system in survival, differentiation, colonization and injury repair.It has been confirmed in the disorders of the enteric nervous system, such as hirschsprung and anorectal malformations, but the specific mechanism in regulation of this factor is still unknown.Studies have found that GDNF/GFRa1/RET and GDNF/GFRa1 / NCAM pathway may be involved in the growth and maturation of the enteric nervous system, the disorders of those pathways above may lead to diseases by affecting the differentiation, proliferation and migration of intestinal neural stem cells, causing dysfunctions in the anatomical structure and function of the intestinal neurons. Key words: Glial cell line-derived neurotrophic factor; Enteric nervous system; Signal pathway

One Mouse, Two Cultures: Isolation and Culture of Adult Neural Stem Cells from the Two Neurogenic Zones of Individual Mice

The neurosphere assay and the adherent monolayer culture system are valuable tools to determine the potential (proliferation or differentiation) of adult neural stem cells in vitro. These assays can be used to compare the precursor potential of cells isolated from genetically different or differentially treated animals to determine the effects of exogenous factors on neural precursor cell proliferation and differentiation and to generate neural precursor cell lines that can be assayed over continuous passages. The neurosphere assay is traditionally used for the post-hoc identification of stem cells, primarily due to the lack of definitive markers with which they can be isolated from primary tissue and has the major advantage of giving a quick estimate of precursor cell numbers in brain tissue derived from individual animals. Adherent monolayer cultures, in contrast, are not traditionally used to compare proliferation between individual animals, as each culture is generally initiated from the combined tissue of between 5-8 animals. However, they have the major advantage that, unlike neurospheres, they consist of a mostly homogeneous population of precursor cells and are useful for following the differentiation process in single cells. Here, we describe, in detail, the generation of neurosphere cultures and, for the first time, adherent cultures from individual animals. This has many important implications including paired analysis of proliferation and/or differentiation potential in both the subventricular zone (SVZ) and dentate gyrus (DG) of treated or genetically different mouse lines, as well as a significant reduction in animal usage.

One Mouse, Two Cultures: Isolation and Culture of Adult Neural Stem Cells from the Two Neurogenic Zones of Individual Mice

The neurosphere assay and the adherent monolayer culture system are valuable tools to determine the potential (proliferation or differentiation) of adult neural stem cells in vitro. These assays can be used to compare the precursor potential of cells isolated from genetically different or differentially treated animals to determine the effects of exogenous factors on neural precursor cell proliferation and differentiation and to generate neural precursor cell lines that can be assayed over continuous passages. The neurosphere assay is traditionally used for the post-hoc identification of stem cells, primarily due to the lack of definitive markers with which they can be isolated from primary tissue and has the major advantage of giving a quick estimate of precursor cell numbers in brain tissue derived from individual animals. Adherent monolayer cultures, in contrast, are not traditionally used to compare proliferation between individual animals, as each culture is generally initiated from the combined tissue of between 5-8 animals. However, they have the major advantage that, unlike neurospheres, they consist of a mostly homogeneous population of precursor cells and are useful for following the differentiation process in single cells. Here, we describe, in detail, the generation of neurosphere cultures and, for the first time, adherent cultures from individual animals. This has many important implications including paired analysis of proliferation and/or differentiation potential in both the subventricular zone (SVZ) and dentate gyrus (DG) of treated or genetically different mouse lines, as well as a significant reduction in animal usage.

Detection of primary cilia in human glioblastoma

Glioblastoma (GBM) is the most common malignant adult brain tumor and carries a poor prognosis due to primary and acquired resistance. While many cellular features of GBM have been documented, it is unclear if cells within these tumors extend a primary cilium, an organelle whose associated signaling pathways may regulate proliferation, migration, and survival of neural precursor and tumor cells. Using immunohistochemical and electron microscopy (EM) techniques, we screened human GBM tumor biopsies and primary cell lines for cilia. Immunocytochemical staining of five primary GBM cell lines revealed that between 8 and 25 % of the cells in each line possessed gamma tubulin-positive basal bodies from which extended acetylated, alpha-tubulin-positive axonemes. EM analyses confirmed the presence of cilia at the cell surface and revealed that their axonemes contained organized networks of microtubules, a structural feature consistent with our detection of IFT88 and Arl13b, two trafficked cilia proteins, along the lengths of the axonemes. Notably, cilia were detected in each of 23 tumor biopsies (22 primary and 1 recurrent) examined. These cilia were distributed across the tumor landscape including regions proximal to the vasculature and within necrotic areas. Moreover, ciliated cells within these tumors co-stained with Ki67, a marker for actively dividing cells, and ZEB1, a transcription factor that is upregulated in GBM and linked to tumor initiation, invasion, and chemoresistance. Collectively, our data show that subpopulations of cells within human GBM tumors are ciliated. In view of mounting evidence supporting roles of primary cilia in tumor initiation and propagation, it is likely that further study of the effects of cilia on GBM tumor cell function will improve our understanding of GBM pathogenesis and may provide new directions for GBM treatment strategies.

Abstract 191: Optical Inhibition of Striatum Neuron Promotes Recovery After Ischemic Stroke

Introduction: Neurons of peri-infarct region in the cortex have effects on neurogenesis and remodeling after ischemic stroke. However the role of penumbral striatum neuron in neurogenesis and remodeling after ischemic stroke is unknown. In this study, we use optogenetic tools to specifically regulate the activity of striatum neuron and investigate its roles in neurogenesis and remodeling after ischemic stroke. Methods: Lentivirus carrying NpHR and YFP fusion protein under CaMKII promoter was injected into striatum of experimental mice. 7 days after injection, ferrule with fiber or optrode was implanted at the same position and MCAO surgery was performed 14 days after the injection. 4 days after MCAO, mice were stimulated with constant 594 nm laser for two 15-min sessions each day for 4 days. Electrophysiology test was used to confirm the validity of NpHR in vivo. Neurobehavioral tests were carried out at 3, 7 and 35 days after MCAO. Results: When stimulated with 594nm laser, the firing rate of striatum neuron was reduced in NpHR transduced mouse after MCAO. Immunohistochemistry showed that the number of BrdU and DCX double positive cells was significantly increased in the SVZ area. Nestin positive cells were increased both in SVZ and peri-infarct area. Western blotting showed that Netrin-1 expression was significantly up-regulated. BrdU and NeuN double positive cells was increased and brain atrophy volume was reduced in laser-stimulated mice compared with control mice (p&lt;0.05). Neurobehavioral test showed that inhibition of striatum neuron promotes motor function after MCAO compared to the control (p&lt;0.05). Conclusion: Laser induced activation of NpHR reduces the firing rate of penumbral striatum neuron using optogenetics tools. Inhibition of striatum neuron promotes proliferation and migration of neural progenietor cells and neurobehavioral function recovery. This effect is related to Netrin-1 secretion.

Abstract A29: Advanced nano-proteomics based on ultrasensitive CE toquantitate protein expression/phosphorylation levels: Discovery of novel proteins involved in chemoresistance/invasion of lung cancer cells.

Abstract Our laboratory has shown that resistance to chemotherapeutic agent cisplatin (chemoresistance) in non-small cell lung cancer (NSCLC) cells involves exaggerated phosphorylation of transcription factor CREB and high-level expression of pro-survival/anti-apoptotic proteins c-IAP1, livin, Mcl-1 and survivin, resulting from hyperactivation of a novel serine/threonine kinase, protein kinase G-Iα (PKG-Iα) (Wong et al. 2012). PKG-Iα also promotes cell proliferation/DNA synthesis and migration/invasion in both NSCLC and ovarian cancer cells (Fiscus et al., 2012; Wong et al. 2012). Because of low expression levels, these proteins are difficult to accurately quantify by conventional Western blotting. To solve this problem, we are developing new applications for NanoPro 100 and NanoPro 1000 (ProteinSimple), state-of-the-art instruments based on advanced “nano-proteomics” ultilizing ultrasensitive capillary electrophoresis (CE)-based technologies (Fiscus and Johlfs, 2012; Fiscus et al., 2012). The NanoPro 100/NanoPro 1000 are capable of accurately quantifying protein expression/phosphorylation levels with sensitivities &amp;gt;100-times and &amp;gt;500-times, respectively, that of conventional Western blots, thus allowing, for the first time, accurate measurements of lower-abundance proteins (e.g. PKG-Iα, survivin and other pro-survival proteins). Extremely small samples of &amp;lt;100 cells are needed. Because of exceptional sensitivity and superior separation of proteins of similar molecular weight (e.g. isoforms/splice variants), compared with Western blots, NanoPro 100/1000 are used in our laboratory to discover novel signaling proteins and their isoforms/splice variants involved in chemoresistance and migration/invasion of lung cancer and mesothelioma cells. We found that some lung cancer/mesothelioma cells express two splice variants of PKG-I, i.e. PKG-Iα and PKG-Iβ (difficult to detect by Western blot). This new technology shows a novel “signaling interdependence” between c-Src tyrosine kinase and PKG-Iα in lung cancer and mesothelioma cells, similar to c-Src/PKG-Iα interdependence that promotes cell proliferation and chemoresistance in ovarian cancer cells (Fiscus et al. 2012). This advanced “nano-proteomics” helps in discovery of many more novel proteins and phosphorylations, which can be used for developing new anti-cancer therapies (based on accurate molecular targeting) for treating lung cancer and mesothelioma. Wong JC, Bathina M and RR Fiscus (2012) Cyclic GMP/protein kinase G type-Iα (PKG-Iα signaling pathway promotes CREB phosphorylation and maintains higher c-IAP1, livin, survivin and Mcl-1 expression and the inhibition of PKG-Iα kinase activity synergizes with cisplatin in non-small cell lung cancer cells. J Cell Biochem. 113: 3587-3598. Fiscus RR, Leung EL, Wong JC and MG Johlfs (2012) Nitric Oxide/Protein Kinase G-IαPromotes c-Src Activation, Proliferation and Chemoresistance in Ovarian Cancer. In: Farghaly, S. (ed). Ovarian Cancer - Basic Science Perspective. Intech Open Access Publisher. pp 315-334. Fiscus RR and MG Johlfs (2012) Protein Kinase G (PKG): Involvement in Promoting Neural Cell Survival, Proliferation, Synaptogenesis and Synaptic Plasticity and the Use of New Ultrasensitive Capillary-Electrophoresis-based Methodologies for Measuring PKG Expression and Molecular Actions. In: Mukai H (ed). Protein Kinase Technologies, in NEUROMETHODS series, Springer. pp 319-348. Citation Format: Ronald R. Fiscus, Mary G. Johlfs, Janica C. Wong, Renee Coffman, Harry Rosenberg. Advanced nano-proteomics based on ultrasensitive CE toquantitate protein expression/phosphorylation levels: Discovery of novel proteins involved in chemoresistance/invasion of lung cancer cells. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr A29.

Antagonistic Interplay between Necdin and Bmi1 Controls Proliferation of Neural Precursor Cells in the Embryonic Mouse Neocortex

Neural precursor cells (NPCs) in the neocortex exhibit a high proliferation capacity during early embryonic development and give rise to cortical projection neurons after maturation. Necdin, a mammal-specific MAGE (melanoma antigen) family protein that possesses anti-mitotic and pro-survival activities, is expressed abundantly in postmitotic neurons and moderately in tissue-specific stem cells or progenitors. Necdin interacts with E2F transcription factors and suppresses E2F1-dependent transcriptional activation of the cyclin-dependent kinase Cdk1 gene. Here we show that necdin serves as a suppressor of NPC proliferation in the embryonic neocortex. Necdin is moderately expressed in the ventricular zone of mouse embryonic neocortex, in which proliferative cell populations are significantly increased in necdin-null mice. In the neocortex of necdin-null embryos, expression of Cdk1 and Sox2, a stem cell marker, is significantly increased, whereas expression of p16, a cyclin-dependent kinase inhibitor, is markedly diminished. Cdk1 and p16 expression levels are also significantly increased and decreased, respectively, in primary NPCs prepared from necdin-null embryos. Intriguingly, necdin interacts directly with Bmi1, a Polycomb group protein that suppresses p16 expression and promotes NPC proliferation. In HEK293A cells transfected with luciferase reporter constructs, necdin relieves Bmi1-dependent repression of p16 promoter activity, whereas Bmi1 counteracts necdin-mediated repression of E2F1-dependent Cdk1 promoter activity. In lentivirus-infected primary NPCs, necdin overexpression increases p16 expression, suppresses Cdk1 expression, and inhibits NPC proliferation, whereas Bmi1 overexpression suppresses p16 expression, increases Cdk1 expression, and promotes NPC proliferation. Our data suggest that embryonic NPC proliferation in the neocortex is regulated by the antagonistic interplay between necdin and Bmi1.

Functional electrical stimulation-facilitated proliferation and regeneration of neural precursor cells in the brains of rats with cerebral infarction.

Previous studies have shown that proliferation of endogenous neural precursor cells cannot alone compensate for the damage to neurons and axons. From the perspective of neural plasticity, we observed the effects of functional electrical stimulation treatment on endogenous neural precursor cell proliferation and expression of basic fibroblast growth factor and epidermal growth factor in the rat brain on the infarct side. Functional electrical stimulation was performed in rat models of acute middle cerebral artery occlusion. Simultaneously, we set up a placebo stimulation group and a sham-operated group. Immunohistochemical staining showed that, at 7 and 14 days, compared with the placebo group, the numbers of nestin (a neural precursor cell marker)-positive cells in the subgranular zone and subventricular zone were increased in the functional electrical stimulation treatment group. Western blot assays and reverse-transcription PCR showed that total protein levels and gene expression of epidermal growth factor and basic fibroblast growth factor were also upregulated on the infarct side. Prehensile traction test results showed that, at 14 days, prehension function of rats in the functional electrical stimulation group was significantly better than in the placebo group. These results suggest that functional electrical stimulation can promote endogenous neural precursor cell proliferation in the brains of acute cerebral infarction rats, enhance expression of basic fibroblast growth factor and epidermal growth factor, and improve the motor function of rats.

Polygenic scores from the MiR137 pathway explain variability in cognitive performance in patients with schizophrenia and controls.

Introduction Genome-wide association studies have identified rs1622579, a common variant located within an intronic region of MiR137, as a risk variant for schizophrenia. MiR137 has a hypothesized role in neural cell proliferation, migration and maturation. Cognitively, this variant is associated with deficits in verbal episodic memory, and altered fronto-amygdala connectivity. As MiR137 interacts with several other genome wide associated variants (e.g. ZNF804A, TCF4, CACNA1C, CSMD1 and WBP1L), we tested whether these cognitive effects were associated with polygenic risk in a set of identified downstream targets of MiR137. Methodology Polygene scores were calculated by (1) selecting all identified downstream genetic targets of MiR137 (Hill et al., 2014); (2) selecting risk SNPs within each of these genes based on risk estimates from the Psychiatric Genomics Consortium (Ripke et al., 2011), and (3) ascribing a polygenic risk score to each participant based on the total number of risk alleles they carried. To define risk, we used 3 arbitrary p-value thresholds (p < 10-5, p < 0.05, and p < 0.5) from the PGC1 case-control analysis. To estimate these polygene effects on cognitive deficits associated with SZ (IQ, episodic and working memory, attention control, and theory of mind) linear regression analyses was performed, with age and gender entered as variables of no interest. We carried out three separate analyses: all cases and controls (n=586), patients with a broad diagnosis of psychosis including non-schizophrenia psychosis (n=489) and patients with schizophrenia and schizoaffective disorder (n=379). Results MiR137 polygenic risk scores were significantly higher in the broad and narrow diagnosis groups compared to the controls (F(2,1081) =5.52, p<0.01). Poorer performance on measures of IQ, memory, and attention were each found to be associated with higher MiR137 polygene scores thresholded at p=0.05, including paired associated learning (p<0.001); faces, letter-number sequencing (LNS) sustained attention to reaction time (SART) (p<0.01); full-scale IQ, logical memory (LM) and spatial working memory (SWM) (p<0.05). The amount of variance explained on the measures varied between 1% and 2.6% Discussion These data support a modest but significant influence of this MiR137 'pathway' on cognition, across multiple measures of cognition. These widespread cognitive effects are consistent with MiR137’s previously described role in brain development. Greater variance was explained when all cases and controls were included, rather than considering narrow, broad, and controls separately. Extending on previous findings, MiR137's effects on cognition were significantly more apparent when considered in combination with the other risk variants with which it interacts rather than when the rs1622579 risk variant was considered in isolation.

Neural differentiation from pluripotent stem cells: The role of natural and synthetic extracellular matrix.

Neural cells differentiated from pluripotent stem cells (PSCs), including both embryonic stem cells and induced pluripotent stem cells, provide a powerful tool for drug screening, disease modeling and regenerative medicine. High-purity oligodendrocyte progenitor cells (OPCs) and neural progenitor cells (NPCs) have been derived from PSCs recently due to the advancements in understanding the developmental signaling pathways. Extracellular matrices (ECM) have been shown to play important roles in regulating the survival, proliferation, and differentiation of neural cells. To improve the function and maturation of the derived neural cells from PSCs, understanding the effects of ECM over the course of neural differentiation of PSCs is critical. During neural differentiation of PSCs, the cells are sensitive to the properties of natural or synthetic ECMs, including biochemical composition, biomechanical properties, and structural/topographical features. This review summarizes recent advances in neural differentiation of human PSCs into OPCs and NPCs, focusing on the role of ECM in modulating the composition and function of the differentiated cells. Especially, the importance of using three-dimensional ECM scaffolds to simulate the in vivo microenvironment for neural differentiation of PSCs is highlighted. Future perspectives including the immediate applications of PSC-derived neural cells in drug screening and disease modeling are also discussed.