Sox1 marks an activated neural stem/progenitor cell in the hippocampus

Klf10 Regulates the Emergence of Glial Phenotypes During Hypothalamic Development

Glial cells play a pivotal role in the Central Nervous System (CNS), constituting most brain cells. Gliogenesis, crucial in CNS development, occurs after neurogenesis. In the hypothalamus, glial progenitors first generate oligodendrocytes and later astrocytes. However, the precise molecular mechanisms governing the emergence of glial lineages in the developing hypothalamus remain incompletely understood. This study reveals the pivotal role of the transcription factor KLF10 in regulating the emergence of both astrocyte and oligodendrocyte lineages during embryonic hypothalamic development. Through transcriptomic and bioinformatic analyses, we identified novel KLF10 putative target genes, which play important roles in the differentiation of neurons, astrocytes, and oligodendrocytes. Notably, in the absence of KLF10, there is an increase in the oligodendrocyte population, while the astrocyte population decreases in the embryonic hypothalamus. Strikingly, this decline in the number of astrocytes persists into adulthood, indicating that the absence of KLF10 leads to an extended period of oligodendrocyte emergence while delaying the appearance of astrocytes. Our findings also unveil a novel signaling pathway for Klf10 gene expression regulation. We demonstrate that Klf10 is a target of CREB and that its expression is upregulated via the BDNF-p38-CREB pathway. Thus, we postulate that KLF10 is an integral part of the hypothalamic developmental program that ensures the correct timing for glial phenotypes' generation. Importantly, we propose that the Klf10-/- mouse model represents a valuable tool for investigating the impact of reduced astrocyte and microglia populations in the homeostasis of the adult hypothalamus.

Astrocytes in Primary Familial Brain Calcification (PFBC): Emphasis on the Importance of Induced Pluripotent Stem Cell-Derived Human Astrocyte Models

Primary familial brain calcification (PFBC) is a rare, progressive central nervous system (CNS) disorder without a cure, and the current treatment methodologies primarily aim to relieve neurological and psychiatric symptoms of the patients. The disease is characterized by abnormal bilateral calcifications in the brain, however, our mechanistic understanding of the biology of the disease is still limited. Determining the roles of the specific cell types and molecular mechanisms involved in the pathophysiological processes of the disease is of great importance for the development of novel and effective treatment methodologies. There is a growing interest in the involvement of astrocytes in PFBC, as recent studies have suggested that astrocytes play a central role in the disease and that functional defects in these cells are critical for the development and progression of the disease. This review aims to discuss recent findings on the roles of astrocytes in PFBC pathophysiology, with a focus on known expression and roles of PFBC genes in astrocytes. Additionally, we discuss the importance of human astrocytes for PFBC disease modeling, and astrocytes as a potential therapeutic target in PFBC. Utilization of species-specific and physiologically relevant PFBC model systems can open new avenues for basic research, drug development, and regenerative medicine.

The Generation of Genetically Engineered Human Induced Pluripotent Stem Cells Overexpressing IFN-β for Future Experimental and Clinically Oriented Studies

Induced pluripotent stem cells (iPSCs) can be generated from various adult cells, genetically modified and differentiated into diverse cell populations. Type I interferons (IFN-Is) have multiple immunotherapeutic applications; however, their systemic administration can lead to severe adverse outcomes. One way of overcoming the limitation is to introduce cells able to enter the site of pathology and to produce IFN-Is locally. As a first step towards the generation of such cells, here, we aimed to generate human iPSCs overexpressing interferon-beta (IFNB, IFNB-iPSCs). IFNB-iPSCs were obtained by CRISPR/Cas9 editing of the previously generated iPSC line K7-4Lf. IFNB-iPSCs overexpressed IFNB RNA and produced a functionally active IFN-β. The cells displayed typical iPSC morphology and expressed pluripotency markers. Following spontaneous differentiation, IFNB-iPSCs formed embryoid bodies and upregulated endoderm, mesoderm, and some ectoderm markers. However, an upregulation of key neuroectoderm markers, PAX6 and LHX2, was compromised. A negative effect of IFN-β on iPSC neuroectoderm differentiation was confirmed in parental iPSCs differentiated in the presence of a recombinant IFN-β. The study describes new IFN-β-producing iPSC lines suitable for the generation of various types of IFN-β-producing cells for future experimental and clinical applications, and it unravels an inhibitory effect of IFN-β on stem cell neuroectoderm differentiation.

MARK2 variants cause autism spectrum disorder via the downregulation of WNT/β-catenin signaling pathway

Microtubule affinity-regulating kinase 2 (MARK2) contributes to establishing neuronal polarity and developing dendritic spines. Although large-scale sequencing studies have associated MARK2 variants with autism spectrum disorder (ASD), the clinical features and variant spectrum in affected individuals with MARK2 variants, early developmental phenotypes in mutant human neurons, and the pathogenic mechanism underlying effects on neuronal development have remained unclear. Here, we report 31 individuals with MARK2 variants and presenting with ASD, other neurodevelopmental disorders, and distinctive facial features. Loss-of-function (LoF) variants predominate (81%) in affected individuals, while computational analysis and in vitro expression assay of missense variants supported the effect of MARK2 loss. Using proband-derived and CRISPR-engineered isogenic induced pluripotent stem cells (iPSCs), we show that MARK2 loss leads to early neuronal developmental and functional deficits, including anomalous polarity and dis-organization in neural rosettes, as well as imbalanced proliferation and differentiation in neural progenitor cells (NPCs). Mark2+/- mice showed abnormal cortical formation and partition and ASD-like behavior. Through the use of RNA sequencing (RNA-seq) and lithium treatment, we link MARK2 loss to downregulation of the WNT/β-catenin signaling pathway and identify lithium as a potential drug for treating MARK2-associated ASD.

A Perspective on the Characterization of Early Neural Progenitor Cell-Derived Extracellular Vesicles for Targeted Delivery to Neuroblastoma Cells

As an element of the cellular signaling systems, extracellular vesicles (EVs) exhibit many desirable traits for usage as targeted delivery vehicles. When administered, EVs cause little to no toxic or immune response, stay in circulation for longer periods compared to synthetic carriers, preferentially accumulate in tissues that are the same or similar to their cell-of-origin and can pass through the blood-brain barrier. Combined, these traits make neural EVs a particularly promising tool for delivering drugs to the brain. This study aims to combine tissue and EVs engineering to prepare neural differentiated cells derived EVs that exhibit neural properties, to develop an effective, tissue-homing drug and gene delivery platform for the brain. Early neural differentiated cell-derived EVs were produced with neural characteristics from neural differentiated human neonatal dermal fibroblasts. The EVs carried key neural proteins such as Nestin, Sox2 and Doublecortin. The cellular uptake of early neural differentiated cell-derived EVs was higher compared to non-neural EVs during in vitro uptake assays on neuroblastoma cells. Moreover, eND-EVs were significantly decreased the viability of neuroblastoma cells. In conclusion, this study revealed that early neural differentiated cell-derived EVs have potential as a promising drug carrier for the treatment of various neural disorders.

Hindbrain boundaries as niches of neural progenitor and stem cells regulated by the extracellular matrix proteoglycan chondroitin sulphate

The interplay between neural progenitors and stem cells (NPSCs), and their extracellular matrix (ECM) is a crucial regulatory mechanism that determines their behavior. Nonetheless, how the ECM dictates the state of NPSCs remains elusive. The hindbrain is valuable to examine this relationship, as cells in the ventricular surface of hindbrain boundaries (HBs), which arise between any two neighboring rhombomeres, express the NPSC marker Sox2, while being surrounded with the membrane-bound ECM molecule chondroitin sulphate proteoglycan (CSPG), in chick and mouse embryos. CSPG expression was used to isolate HB Sox2+ cells for RNA-sequencing, revealing their distinguished molecular properties as typical NPSCs, which express known and newly identified genes relating to stem cells, cancer, the matrisome and cell cycle. In contrast, the CSPG- non-HB cells, displayed clear neural-differentiation transcriptome. To address whether CSPG is significant for hindbrain development, its expression was manipulated in vivo and in vitro. CSPG manipulations shifted the stem versus differentiation state of HB cells, evident by their behavior and altered gene expression. These results provide further understanding of the uniqueness of hindbrain boundaries as repetitive pools of NPSCs in-between the rapidly growing rhombomeres, which rely on their microenvironment to maintain their undifferentiated state during development.

Effects of Rhazya Stricta plant organic extracts on human induced pluripotent stem cells derived neural stem cells

Rhazya Stricta (R. stricta) has been employed as a natural remedy for several diseases for centuries. Numerous studies revealed that R. stricta extracts contain alkaloids, tannins, and flavonoids that possess antimicrobial, anticancer, antihypertensive, and antioxidant activities. In this study, we examined the effects of organic extracts from different parts of R. stricta plant on human pluripotent stem cells (hiPSCs)-derived neural stem cells (NSCs) for medical purposes. NSCs were incubated with different concentrations of organic extracts from the leaves, stem, and fruits, and we assessed the growth and viability of the cells by using MTS assay and the chemical composition of the potential plant extract by using gas chromatography-mass spectrometry (GC/MS). Our results revealed that the methanolic extract from the stem increased NSCs growth significantly, particularly at a concentration of 25 μg/ml. GC/MS analysis was utilized to identify the potential compounds of the methanolic extract. In conclusion, our results demonstrated for the first time that methanolic stem extract of R. stricta contains compounds that can positively impact NSCs growth. These compounds can be further investigated to determine the potential bioactive compounds that can be used for research and medical purposes.

Derivation and characteristics of induced pluripotent stem cells from a patient with acute myelitis

The emergence and development of induced pluripotent stem cells (iPSCs) provides an approach to understand the regulatory mechanisms of cell pluripotency and demonstrates the great potential of iPSCs in disease modeling. Acute myelitis defines a group of inflammatory diseases that cause acute nerve damage in the spinal cord; however, its pathophysiology remains to be elusive. In this study, we derived skin fibroblasts from a patient with acute myelitis (P-HAF) and then reprogrammed P-HAF cells to iPSCs using eight exogenous factors (namely, OCT4, SOX2, c-MYC, KLF4, NANOG, LIN28, RARG, and LRH1). We performed transcriptomic analysis of the P-HAF and compared the biological characteristics of the iPSCs derived from the patient (P-iPSCs) with those derived from normal individuals in terms of pluripotency, transcriptomic characteristics, and differentiation ability toward the ectoderm. Compared to the control iPSCs, the P-iPSCs displayed similar features of pluripotency and comparable capability of ectoderm differentiation in the specified culture. However, when tested in the common medium, the P-iPSCs showed attenuated potential for ectoderm differentiation. The transcriptomic analysis revealed that pathways enriched in P-iPSCs included those involved in Wnt signaling. To this end, we treated iPSCs and P-iPSCs with the Wnt signaling pathway inhibitor IWR1 during the differentiation process and found that the expression of the ectoderm marker Sox1 was increased significantly in P-iPSCs. This study provides a novel approach to investigating the pathogenesis of acute myelitis.

The Role of SOX Transcription Factors in Ageing and Age-Related Diseases

The quest for eternal youth and immortality is as old as humankind. Ageing is an inevitable physiological process accompanied by many functional declines that are driving factors for age-related diseases. Stem cell exhaustion is one of the major hallmarks of ageing. The SOX transcription factors play well-known roles in self-renewal and differentiation of both embryonic and adult stem cells. As a consequence of ageing, the repertoire of adult stem cells present in various organs steadily declines, and their dysfunction/death could lead to reduced regenerative potential and development of age-related diseases. Thus, restoring the function of aged stem cells, inducing their regenerative potential, and slowing down the ageing process are critical for improving the health span and, consequently, the lifespan of humans. Reprograming factors, including SOX family members, emerge as crucial players in rejuvenation. This review focuses on the roles of SOX transcription factors in stem cell exhaustion and age-related diseases, including neurodegenerative diseases, visual deterioration, chronic obstructive pulmonary disease, osteoporosis, and age-related cancers. A better understanding of the molecular mechanisms of ageing and the roles of SOX transcription factors in this process could open new avenues for developing novel strategies that will delay ageing and prevent age-related diseases.

ZFP462 safeguards neural lineage specification by targeting G9A/GLP-mediated heterochromatin to silence enhancers

ZNF462 haploinsufficiency is linked to Weiss-Kruszka syndrome, a genetic disorder characterized by neurodevelopmental defects, including autism. Though conserved in vertebrates and essential for embryonic development, the molecular functions of ZNF462 remain unclear. We identified its murine homologue ZFP462 in a screen for mediators of epigenetic gene silencing. Here we show that ZFP462 safeguards neural lineage specification of mouse embryonic stem cells (ESCs) by targeting the H3K9-specific histone methyltransferase complex G9A/GLP to silence meso-endodermal genes. ZFP462 binds to transposable elements that are potential enhancers harbouring pluripotency and meso-endoderm transcription factor binding sites. Recruiting G9A/GLP, ZFP462 seeds heterochromatin, restricting transcription factor binding. Loss of ZFP462 in ESCs results in increased chromatin accessibility at target sites and ectopic expression of meso-endodermal genes. Taken together, ZFP462 confers lineage and locus specificity to the broadly expressed epigenetic regulator G9A/GLP. Our results suggest that aberrant activation of lineage non-specific genes in the neuronal lineage underlies ZNF462-associated neurodevelopmental pathology.

Genetic control of the pluripotency epigenome determines differentiation bias in mouse embryonic stem cells

Genetically diverse pluripotent stem cells display varied, heritable responses to differentiation cues. Here, we harnessed these disparities through derivation of mouse embryonic stem cells from the BXD genetic reference panel, along with C57BL/6J (B6) and DBA/2J (D2) parental strains, to identify loci regulating cell state transitions. Upon transition to formative pluripotency, B6 stem cells quickly dissolved naïve networks adopting gene expression modules indicative of neuroectoderm lineages, whereas D2 retained aspects of naïve pluripotency. Spontaneous formation of embryoid bodies identified divergent differentiation where B6 showed a propensity toward neuroectoderm and D2 toward definitive endoderm. Genetic mapping identified major trans-acting loci co-regulating chromatin accessibility and gene expression in both naïve and formative pluripotency. These loci distally modulated occupancy of pluripotency factors at hundreds of regulatory elements. One trans-acting locus on Chr 12 primarily impacted chromatin accessibility in embryonic stem cells, while in epiblast-like cells, the same locus subsequently influenced expression of genes enriched for neurogenesis, suggesting early chromatin priming. These results demonstrate genetically determined biases in lineage commitment and identify major regulators of the pluripotency epigenome.

Experimental and Clinical Biomarkers for Progressive Evaluation of Neuropathology and Therapeutic Interventions for Acute and Chronic Neurological Disorders

This article describes commonly used experimental and clinical biomarkers of neuronal injury and neurodegeneration for the evaluation of neuropathology and monitoring of therapeutic interventions. Biomarkers are vital for diagnostics of brain disease and therapeutic monitoring. A biomarker can be objectively measured and evaluated as a proxy indicator for the pathophysiological process or response to therapeutic interventions. There are complex hurdles in understanding the molecular pathophysiology of neurological disorders and the ability to diagnose them at initial stages. Novel biomarkers for neurological diseases may surpass these issues, especially for early identification of disease risk. Validated biomarkers can measure the severity and progression of both acute neuronal injury and chronic neurological diseases such as epilepsy, migraine, Alzheimer's disease, Parkinson's disease, Huntington's disease, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, and other brain diseases. Biomarkers are deployed to study progression and response to treatment, including noninvasive imaging tools for both acute and chronic brain conditions. Neuronal biomarkers are classified into four core subtypes: blood-based, immunohistochemical-based, neuroimaging-based, and electrophysiological biomarkers. Neuronal conditions have progressive stages, such as acute injury, inflammation, neurodegeneration, and neurogenesis, which can serve as indices of pathological status. Biomarkers are critical for the targeted identification of specific molecules, cells, tissues, or proteins that dramatically alter throughout the progression of brain conditions. There has been tremendous progress with biomarkers in acute conditions and chronic diseases affecting the central nervous system.

Transcriptomic study of anastasis for reversal of ethanol-induced apoptosis in mouse primary liver cells

Anastasis is a cell recovery mechanism that rescues dying cells from the brink of death. Reversal of apoptosis is the first example of anastasis. Here, we describe a comprehensive dataset containing time-course mRNA expression profiles for reversal of ethanol-induced apoptosis in mouse primary liver cells in νitro. This transcriptome dataset includes the conditions of the untreated cells, cells undergoing apoptosis triggered by incubating with cell death inducer of 4.5% ethanol for 5 hours, and apoptosis reversal of ethanol-induced cells at the early (3rd hour), middle (6th hour), and late (24th, 48th hour) stages after being washed with and incubated in fresh cell culture medium. By comparing this dataset with the transcriptomic profiles of other anastasis models generated with different combinations of cell types and cell death inducers, investigators can identify the key regulators governing reversal of apoptosis and other reversible cell death processes. Therefore, reusing or reanalysing this dataset will facilitate the future studies on the physiological, pathological, and therapeutic implications of anastasis.

Absence of Connexin 43 Results in Smaller Retinas and Arrested, Depolarized Retinal Progenitor Cells in Human Retinal Organoids

The development of the vertebrate retina relies on complex regulatory mechanisms to achieve its characteristic layered morphology containing multiple neuronal cell types. While connexin 43 (CX43) is not expressed by mature retinal neurons, mutations in its gene GJA1 are associated with microphthalmia and low vision in patients. To delineate how lack of CX43 affects retinal development, GJA1 was disrupted in human induced pluripotent stem cells (hiPSCs) (GJA1-/-) using CRISPR/Cas9 editing, and these were subsequently differentiated into retinal organoids. GJA1-/- hiPSCs do not display defects in self-renewal and pluripotency, but the resulting organoids are smaller with a thinner neural retina and decreased abundance of many retinal cell types. CX43-deficient organoids express lower levels of the neural marker PAX6 and the retinal progenitor cell (RPC) markers PAX6, SIX3, and SIX6. Conversely, expression of the early neuroectoderm markers SOX1 and SOX2 remains high in GJA1-/- organoids throughout their development. The lack of CX43 results in an increased population of CHX10-positive RPCs that are smaller, disorganized, do not become polarized, and possess a limited ability to commit to retinal fate specification. Our data indicate that lack of CX43 causes a developmental arrest in RPCs that subsequently leads to pan-retinal defects and stunted ocular growth.

Singular Adult Neural Stem Cells Do Not Exist

Adult neural stem cells (aNSCs) are the source for the continuous production of new neurons throughout life. This so-called adult neurogenesis has been extensively studied; the intermediate cellular stages are well documented. Recent discoveries have raised new controversies in the field, such as the notion that progenitor cells hold similar self-renewal potential as stem cells, or whether different types of aNSCs exist. Here, we discuss evidence for heterogeneity of aNSCs, including short-term and long-term self-renewing aNSCs, regional and temporal differences in aNSC function, and single cell transcriptomics. Reviewing various genetic mouse models used for targeting aNSCs and lineage tracing, we consider potential lineage relationships between Ascl1-, Gli1-, and Nestin-targeted aNSCs. We present a multidimensional model of adult neurogenesis that incorporates recent findings and conclude that stemness is a phenotype, a state of properties that can change with time, rather than a cell property, which is static and immutable. We argue that singular aNSCs do not exist.

Transcriptional regulation of neural stem cell expansion in the adult hippocampus

Experience governs neurogenesis from radial-glial neural stem cells (RGLs) in the adult hippocampus to support memory. Transcription factors (TFs) in RGLs integrate physiological signals to dictate self-renewal division mode. Whereas asymmetric RGL divisions drive neurogenesis during favorable conditions, symmetric divisions prevent premature neurogenesis while amplifying RGLs to anticipate future neurogenic demands. The identities of TFs regulating RGL symmetric self-renewal, unlike those that regulate RGL asymmetric self-renewal, are not known. Here, we show in mice that the TF Kruppel-like factor 9 (Klf9) is elevated in quiescent RGLs and inducible, deletion of Klf9 promotes RGL activation state. Clonal analysis and longitudinal intravital two-photon imaging directly demonstrate that Klf9 functions as a brake on RGL symmetric self-renewal. In vivo translational profiling of RGLs lacking Klf9 generated a molecular blueprint for RGL symmetric self-renewal that was characterized by upregulation of genetic programs underlying Notch and mitogen signaling, cell cycle, fatty acid oxidation, and lipogenesis. Together, these observations identify Klf9 as a transcriptional regulator of neural stem cell expansion in the adult hippocampus.

Higher Transduction Efficiency of AAV5 to Neural Stem Cells and Immature Neurons in Gerbil Dentate Gyrus Compared to AAV2 and rh10

The safety and high efficiency of adeno-associated virus (AAV) vectors has facilitated their wide scale use to deliver therapeutic genes for experimental and clinical purposes in diseases affecting the central nervous system (CNS). AAV1, 2, 5, 8, 9, and rh10 are the most commonly used serotypes for CNS applications. Most AAVs are known to transduce genes predominantly into neurons. However, the precise tropism of AAVs in the dentate gyrus (DG), the region where persistent neurogenesis occurs in the adult brain, is not fully understood. We stereotaxically injected 1.5 × 10¹⁰ viral genomes of AAV2, 5, or rh10 carrying green fluorescent protein (GFP) into the right side of gerbil hippocampus, and performed immunofluorescent analysis using differentiation stage-specific markers one week after injection. We found that AAV5 showed a significantly larger number of double positive cells for GFP and Sox2 in the DG, compared to the AAV2 and rh10 groups. On the other hand, AAVrh10 presented a substantially larger number of double positive cells for GFP and NeuN in the DG, compared to AAV2 and AAV5. Our findings indicated that AAV5 showed high transduction efficiency to neural stem cells and precursor cells, while AAVrh10 showed much higher efficiency to mature neurons in the DG.

SOX Transcription Factors as Important Regulators of Neuronal and Glial Differentiation During Nervous System Development and Adult Neurogenesis

The SOX proteins belong to the superfamily of transcription factors (TFs) that display properties of both classical TFs and architectural components of chromatin. Since the cloning of the Sox/SOX genes, remarkable progress has been made in illuminating their roles as key players in the regulation of multiple developmental and physiological processes. SOX TFs govern diverse cellular processes during development, such as maintaining the pluripotency of stem cells, cell proliferation, cell fate decisions/germ layer formation as well as terminal cell differentiation into tissues and organs. However, their roles are not limited to development since SOX proteins influence survival, regeneration, cell death and control homeostasis in adult tissues. This review summarized current knowledge of the roles of SOX proteins in control of central nervous system development. Some SOX TFs suspend neural progenitors in proliferative, stem-like state and prevent their differentiation. SOX proteins function as pioneer factors that occupy silenced target genes and keep them in a poised state for activation at subsequent stages of differentiation. At appropriate stage of development, SOX members that maintain stemness are down-regulated in cells that are competent to differentiate, while other SOX members take over their functions and govern the process of differentiation. Distinct SOX members determine down-stream processes of neuronal and glial differentiation. Thus, sequentially acting SOX TFs orchestrate neural lineage development defining neuronal and glial phenotypes. In line with their crucial roles in the nervous system development, deregulation of specific SOX proteins activities is associated with neurodevelopmental disorders (NDDs). The overview of the current knowledge about the link between SOX gene variants and NDDs is presented. We outline the roles of SOX TFs in adult neurogenesis and brain homeostasis and discuss whether impaired adult neurogenesis, detected in neurodegenerative diseases, could be associated with deregulation of SOX proteins activities. We present the current data regarding the interaction between SOX proteins and signaling pathways and microRNAs that play roles in nervous system development. Finally, future research directions that will improve the knowledge about distinct and various roles of SOX TFs in health and diseases are presented and discussed.

SOX1 Is a Backup Gene for Brain Neurons and Glioma Stem Cell Protection and Proliferation

Failed neuroprotection leads to the initiation of several diseases. SOX1 plays many roles in embryogenesis, oncogenesis, and male sex determination, and can promote glioma stem cell proliferation, invasion, and migration due to its high expression in glioblastoma cells. The functional versatility of the SOX1 gene in malignancy, epilepsy, and Parkinson's disease, as well as its adverse effects on dopaminergic neurons, makes it an interesting research focus. Hence, we collate the most important discoveries relating to the neuroprotective effects of SOX1 in brain cancer and propose hypothesis worthy of SOX1's role in the survival of senescent neuronal cells, its roles in fibroblast cell proliferation, and cell fat for neuroprotection, and the discharge of electrical impulses for homeostasis. Increase in electrical impulses transmitted by senescent cells affects the synthesis of neurotransmitters, which will modify the brain cell metabolism and microenvironment.

Neural Stem Cells and Methods for Their Generation From Induced Pluripotent Stem Cells in vitro

Neural stem cells (NSCs) provide promising approaches for investigating embryonic neurogenesis, modeling of the pathogenesis of diseases of the central nervous system, and for designing drug-screening systems. Such cells also have an application in regenerative medicine. The most convenient and acceptable source of NSCs is pluripotent stem cells (embryonic stem cells or induced pluripotent stem cells). However, there are many different protocols for the induction and differentiation of NSCs, and these result in a wide range of neural cell types. This review is intended to summarize the knowledge accumulated, to date, by workers in this field. It should be particularly useful for researchers who are beginning investigations in this area of cell biology.

The core spliceosomal factor U2AF1 controls cell-fate determination via the modulation of transcriptional networks

Alternative splicing (AS) plays a central role during cell-fate determination. However, how the core spliceosomal factors (CSFs) are involved in this process is poorly understood. Here, we report the down-regulation of the U2AF1 CSF during stem cell differentiation. To investigate its function in stemness and differentiation, we downregulated U2AF1 in human induced pluripotent stem cells (hiPSCs), using an inducible-shRNA system, to the level found in differentiated ectodermal, mesodermal and endodermal cells. RNA sequencing and computational analysis reveal that U2AF1 down-regulation modulates the expression of development-regulating genes and regulates transcriptional networks involved in cell-fate determination. Furthermore, U2AF1 down-regulation induces a switch in the AS of transcription factors (TFs) required to establish specific cell lineages, and favours the splicing of a differentiated cell-specific isoform of DNMT3B. Our results showed that the differential expression of the core spliceosomal factor U2AF1, between stem cells and the precursors of the three germ layers regulates a cell-type-specific alternative splicing programme and a transcriptional network involved in cell-fate determination via the modulation of gene expression and alternative splicing of transcription regulators.

Controlling properties of human neural progenitor cells using 2D and 3D conductive polymer scaffolds

Human induced pluripotent stem cell-derived neural progenitor cells (hNPCs) are a promising cell source for stem cell transplantation to treat neurological diseases such as stroke and peripheral nerve injuries. However, there have been limited studies investigating how the dimensionality of the physical and electrical microenvironment affects hNPC function. In this study, we report the fabrication of two- and three-dimensional (2D and 3D respectively) constructs composed of a conductive polymer to compare the effect of electrical stimulation of hydrogel-immobilized hNPCs. The physical dimension (2D vs 3D) of stimulating platforms alone changed the hNPCs gene expression related to cell proliferation and metabolic pathways. The addition of electrical stimulation was critical in upregulating gene expression of neurotrophic factors that are important in regulating cell survival, synaptic remodeling, and nerve regeneration. This study demonstrates that the applied electrical field controls hNPC properties depending on the physical nature of stimulating platforms and cellular metabolic states. The ability to control hNPC functions can be beneficial in understanding mechanistic changes related to electrical modulation and devising novel treatment methods for neurological diseases.

Anticancer Properties of Curcumin and Interactions With the Circadian Timing System

The phytochemical curcumin is a major component of turmeric. It has recognized activity against cancer cells and affects several intracellular signaling pathways. Many molecules targeted by curcumin also regulate the circadian timing system that has effects on carcinogenesis, tumor growth, and metastasis. Although the circadian clock within cells may be suppressed in tumors, cancer cells are subjected to daily hormonal and neural activity that should be considered when timing optimal curcumin treatments. Rapid curcumin degradation in blood and tissues provides a challenge to maintaining sustained levels suitable for inducing cancer cell death, increasing the need to identify when during the circadian cycle rhythmically expressed molecular targets are present. Curcumin is well tolerated by individuals ingesting it for possible cancer prevention or in combination with conventional cancer therapies, and it shows low toxicity toward noncancerous cells at low dosages. In contrast, curcumin is particularly effective against cancer stem cells, which are treatment-resistant, aggressive, and tumor-initiating. Although curcumin has poor bioavailability, more stable curcumin analogs retain the anti-inflammatory, antioxidant, antimitotic, and pro-apoptotic benefits of curcumin. Anticancer properties are also present in congeners of curcumin in turmeric and after curcumin reduction by intestinal microbes. Various commercial curcuminoid products are highly popular dietary supplements, but caution is warranted. Although antioxidant properties of curcumin may prevent carcinogenesis, studies suggest curcumin interferes with certain chemotherapeutic agents. This review delves into the complex network of curcuminoid effects to identify potential anticancer strategies that may work in concert with daily physiological cycles controlled by the circadian timing system.

Neuron-Astroglia Cell Fate Decision in the Adult Mouse Hippocampal Neurogenic Niche Is Cell-Intrinsically Controlled by COUP-TFI In Vivo

In the dentate gyrus (DG) of the mouse hippocampus, neurogenesis and astrogliogenesis persist throughout life. Adult-born neurons and astrocytes originate from multipotent neural stem cells (NSCs) whose activity is tightly regulated within the neurogenic niche. However, the cell-intrinsic mechanisms controlling neuron-glia NSC fate choice are largely unknown. Here, we show COUP-TFI/NR2F1 expression in DG NSCs and its downregulation upon neuroinflammation. By using in vivo inducible knockout lines, a retroviral-based loss-of-function approach and genetic fate mapping, we demonstrate that COUP-TFI inactivation in adult NSCs and/or mitotic progenitors reduces neurogenesis and increases astrocyte production without depleting the NSC pool. Moreover, forced COUP-TFI expression in adult NSCs/progenitors decreases DG astrogliogenesis and rescues the neuro-astrogliogenic imbalance under neuroinflammation. Thus, COUP-TFI is necessary and sufficient to promote neurogenesis by suppressing astrogliogenesis. Our data propose COUP-TFI as a central regulator of the neuron-astroglia cell fate decision and a key modulator during neuroinflammation in the adult hippocampus.

An optimized method for neuronal differentiation of embryonic stem cells in vitro

BACKGROUND

Neural differentiation from embryonic stem cells (ESCs) is an excellent model for elucidating the key mechanisms involved in neurogenesis, and also provides an unlimited source of progenitors for cell-based nerve regeneration. However, the existing protocols such as small molecule substances, 3D matrix, co-culture technique and transgenic method, are complicated and difficult to operate, thus are limited by laboratory conditions. Looking for an easy-to-operate protocol with easily gained material and high induction efficiency has always been a hot issue in neuroscience research.

NEW METHODS

This paper established an optimized method for embryonic neurogenesis using a strategy of "combinatorial screening". In our study, the whole process of embryonic neurogenesis was divided into two phases, and the differentiation efficiency of seven experimental protocols in phase I and three protocols in phase II were systematically evaluated in A2lox and 129 ESCs.

RESULTS

In phase I differentiation, "2-day embryoid bodies formation + 6-day retinoic acid induction" (Phase I-protocol 3) could effectively induce the differentiation of ESCs into neural precursor cells (NPCs). Furthermore, in phase II, N2B27 medium II (Phase II-protocol 3) could better support the subsequent differentiation from NPCs into neurons.

COMPARISON WITH EXISTING METHOD(S)

Such a combinational method (phase I-protocol 3 and phase II-protocol 3) can realize embryonic neurogenesis with high efficiency, easy implementation and low-cost, and is suitable for promotion in most laboratories.

CONCLUSIONS

Through "combinatorial screening" strategy, we established an optimized method for embryonic neurogenesis in vitro, which is expected to be a powerful tool for neuroscience research.

Targeted removal of epigenetic barriers during transcriptional reprogramming

Master transcription factors have the ability to direct and reverse cellular identities, and consequently their genes must be subject to particular transcriptional control. However, it is unclear which molecular processes are responsible for impeding their activation and safeguarding cellular identities. Here we show that the targeting of dCas9-VP64 to the promoter of the master transcription factor Sox1 results in strong transcript and protein up-regulation in neural progenitor cells (NPCs). This gene activation restores lost neuronal differentiation potential, which substantiates the role of Sox1 as a master transcription factor. However, despite efficient transactivator binding, major proportions of progenitor cells are unresponsive to the transactivating stimulus. By combining the transactivation domain with epigenome editing we find that among a series of euchromatic processes, the removal of DNA methylation (by dCas9-Tet1) has the highest potential to increase the proportion of cells activating foreign master transcription factors and thus breaking down cell identity barriers.

Induction of typical and atypical neurogenesis in the adult substantia nigra after mouse embryonic stem cells transplantation

Neurogenesis in the substantia nigra (SN) has been a controversial issue. Here we report that neurogenesis can be induced in the adult rodent SN by transplantation of embryoid body cells (EBCs) derived from mouse embryonic stem cells. The detection of Sox2⁺ dividing (BrdU⁺) putative host neural precursor cells (NPCs) between 1 and 6 days post-transplantation (dpt) supported the neurogenic capacity of the adult SN. In agreement with the awakening of NPCs by EBCs, only host cells from implant-bearing SN were able to generate neurosphere-like aggregates in the presence of Egf and Fgf2. Later, at 15 dpt, a significant number of SN Dcx⁺ neuroblasts were detected. However, a continuous BrdU administration after transplantation showed that only a fraction (about 20-30%) of those host Dcx⁺ progeny derived from dividing cells and few BrdU⁺ cells, some of them NeuN⁺, survived up to 30 dpt. Unexpectedly, 25-30% of Dcx⁺ or Psa-Ncam⁺ cells at 15 dpt displayed astrocytic markers such as Gfap and S100b. Using a genetic lineage tracing strategy, we demonstrated that a large proportion of host Dcx⁺ and/or Tubb3⁺ neuroblasts originated from Gfap⁺ cells. Remarkably, new blood vessels formed in association with the neurogenic process that, when precluded, caused a reduction in neuroblast production. Accordingly, two proteins secreted by EBCs, Fgf2 and Vegf, were able to promote the emergence of Dcx⁺/Psa-Ncam⁺, Tubb3⁺ and NeuN⁺/BrdU⁺ cells in vivo in the absence of EBCs. We propose that the adult SN is a mostly silent neurogenic niche with the ability to generate new neurons by typical and atypical mechanisms.

Differentiation of Human Induced Pluripotent Stem Cells (iPSCs) into an Effective Model of Forebrain Neural Progenitor Cells and Mature Neurons

Induced Pluripotent Stem Cells (iPSCs) are pluripotent stem cells that can be generated from somatic cells, and provide a way to model the development of neural tissues in vitro. One particularly interesting application of iPSCs is the development of neurons analogous to those found in the human forebrain. Forebrain neurons play a central role in cognition and sensory processing, and deficits in forebrain neuronal activity contributes to a host of conditions, including epilepsy, Alzheimer's disease, and schizophrenia. Here, we present our protocol for differentiating iPSCs into forebrain neural progenitor cells (NPCs) and neurons, whereby neural rosettes are generated from stem cells without dissociation and NPCs purified from rosettes based on their adhesion, resulting in a more rapid generation of pure NPC cultures. Neural progenitor cells can be maintained as long-term cultures, or differentiated into forebrain neurons. This protocol provides a simplified and fast methodology of generating forebrain NPCs and neurons, and enables researchers to generate effective in vitro models to study forebrain disease and neurodevelopment. This protocol can also be easily adapted to generate other neural lineages.

Long-Term Labeling of Hippocampal Neural Stem Cells by a Lentiviral Vector

Using a lentivirus-mediated labeling method, we investigated whether the adult hippocampus retains long-lasting, self-renewing neural stem cells (NSCs). We first showed that a single injection of a lentiviral vector expressing a green fluorescent protein (LV PGK-GFP) into the subgranular zone (SGZ) of the adult hippocampus enabled an efficient, robust, and long-term marking of self-renewing NSCs and their progeny. Interestingly, a subset of labeled cells showed the ability to proliferate multiple times and give rise to Sox2⁺ cells, clearly suggesting the ability of NSCs to self-renew for an extensive period of time (up to 6 months). In addition, using GFP⁺ cells isolated from the SGZ of mice that received a LV PGK-GFP injection 3 months earlier, we demonstrated that some GFP⁺ cells displayed the essential properties of NSCs, such as self-renewal and multipotency. Furthermore, we investigated the plasticity of NSCs in a perforant path transection, which has been shown to induce astrocyte formation in the molecular layer of the hippocampus. Our lentivirus (LV)-mediated labeling study revealed that hippocampal NSCs are not responsible for the burst of astrocyte formation, suggesting that signals released from the injured perforant path did not influence NSC fate determination. Therefore, our studies showed that a gene delivery system using LVs is a unique method to be used for understanding the complex nature of NSCs and may have translational impact in gene therapy by efficiently targeting NSCs.

EGFR Cooperates with EGFRvIII to Recruit Macrophages in Glioblastoma

: Amplification of the EGFR gene and its truncation mutant EGFRvIII are hallmarks of glioblastoma. Although coexpression of EGFR and EGFRvIII confers a growth advantage, how EGFR and EGFRvIII influence the tumor microenvironment remains incompletely understood. Here, we show that EGFR and EGFRvIII cooperate to induce macrophage infiltration via upregulation of the chemokine CCL2. EGFRvIII was significantly enriched in glioblastoma patient samples with high CCL2, and knockout of CCL2 in tumors coexpressing EGFR and EGFRvIII led to decreased infiltration of macrophages. KRAS was a critical signaling intermediate for EGFR- and EGFRvIII-induced expression of CCL2. Our results illustrate how EGFR and EGFRvIII direct the microenvironment in glioblastoma. SIGNIFICANCE: Full-length EGFR and truncated EGFRvIII work through KRAS to upregulate the chemokine CCL2 and drive macrophage infiltration in glioblastoma.

Congenital Zika Virus Infection in Immunocompetent Mice Causes Postnatal Growth Impediment and Neurobehavioral Deficits

A small percentage of babies born to Zika virus (ZIKV)-infected mothers manifest severe defects at birth, including microcephaly. Among those who appeared healthy at birth, there are increasing reports of postnatal growth or developmental defects. However, the impact of congenital ZIKV infection in postnatal development is poorly understood. Here, we report that a mild congenital ZIKV-infection in pups born to immunocompetent pregnant mice did not display apparent defects at birth, but manifested postnatal growth impediments and neurobehavioral deficits, which include reduced locomotor and cognitive deficits that persisted into adulthood. We found that the brains of these pups were smaller, had a thinner cortical layer 1, displayed increased astrogliosis, decreased expression of microcephaly- and neuron development- related genes, and increased pathology as compared to mock-infected controls. In summary, our results showed that even a mild congenital ZIKV infection in immunocompetent mice could lead to postnatal deficits, providing definitive experimental evidence for a necessity to closely monitor postnatal growth and development of presumably healthy human infants, whose mothers were exposed to ZIKV infection during pregnancy.

Stem cell colony interspacing effect on differentiation to neural cells

Efforts to enhance the efficiency of neural differentiation of stem cells are primarily focused on exogenous modulation of physical niche parameters such as surface topography and extracellular matrix proteins, or addition of certain growth factors or small molecules to culture media. We report a novel neurogenic niche to enhance the neural differentiation of embryonic stem cells (ESCs) without any external intervention by micropatterning ESCs into spatially organized colonies of controlled size and interspacing. Using an aqueous two-phase system cell microprinting technology, we generated pairs of uniformly sized isolated ESC colonies at defined interspacing distances over a layer of differentiation-inducing stromal cells. Our comprehensive analysis of temporal expression of neural genes and proteins of cells in colony pairs showed that interspacing two colonies at approximately 0.66 times the colony diameter (0.66D) significantly enhanced neural differentiation of ESCs. Cells in these colonies displayed higher expression of neural genes and proteins and formed thick neurite bundles between the two colonies. A computational model of spatial distribution of soluble factors of cells in interspaced colony pairs showed that the enhanced neural differentiation is due to the presence of stable concentration gradients of soluble signalling factors between the two colonies. Our results indicate that culturing ESCs in colony pairs with defined interspacing is a promising approach to efficiently derive neural cells. Additionally, this approach provides a platform for quantitative studies of molecular mechanisms that regulate neurogenesis of stem cells.

A Meta-Analysis Characterizing Stem-Like Gene Expression in the Suprachiasmatic Nucleus and Its Circadian Clock

Cells expressing proteins characteristic of stem cells and progenitor cells are present in the suprachiasmatic nucleus (SCN) of the adult mammalian hypothalamus. Any relationship between this distinctive feature and the master circadian clock of the SCN is unclear. Considering the lack of obvious neurogenesis in the adult SCN relative to the hippocampus and other structures that provide neurons and glia, it is possible that the SCN has partially differentiated cells that can provide neural circuit plasticity rather than ongoing neurogenesis. To test this possibility, available databases and publications were explored to identify highly expressed genes in the mouse SCN that also have known or suspected roles in cell differentiation, maintenance of stem-like states, or cell-cell interactions found in adult and embryonic stem cells and cancer stem cells. The SCN was found to have numerous genes associated with stem cell maintenance and increased motility from which we selected 25 of the most relevant genes. Over ninety percent of these stem-like genes were expressed at higher levels in the SCN than in other brain areas. Further analysis of this gene set could provide a greater understanding of how adjustments in cell contacts alter period and phase relationships of circadian rhythms. Circadian timing and its role in cancer, sleep, and metabolic disorders are likely influenced by genes selected in this study.

Statistical analysis of multi-dimensional, temporal gene expression of stem cells to elucidate colony size-dependent neural differentiation

High throughput gene expression analysis using qPCR is commonly used to identify molecular markers of complex cellular processes. However, statistical analysis of multi-dimensional, temporal gene expression data is complicated by limited biological replicates and large number of measurements. Moreover, many available statistical tools for analysis of time series data assume that the data sequence is static and does not evolve over time. With this assumption, the parameters used to model the time series are fixed and thus, can be estimated by pooling data together. However, in many cases, dynamic processes of biological systems involve abrupt changes at unknown time points, making the assumption of stationary time series break down. We addressed this problem using a combination of statistical methods including hierarchical clustering, change point detection, and multiple testing. We applied this multi-step method to multi-dimensional, temporal gene expression data that resulted from our study of colony size-dependent neural cell differentiation of stem cells. The gene expression data were time series as the observations were recorded sequentially over time. Hierarchical clustering segregated the genes into three distinct clusters based on their temporal expression profiles; change point detection identified specific time points at which the entire dataset was divided into several homogenous subsets to allow a separate analysis of each subset; and multiple testing procedure identified the differentially expressed genes in each cluster within each subset of data. We established that our multi-step approach pinpoints specific sets of genes that underlie colony size-mediated neural differentiation of stem cells and demonstrated its advantages over conventional parametric and non-parametric tests that do not take into account temporal dynamics of the data. Importantly, our proposed approach is broadly applicable to any multivariate data sets of limited sample size from high throughput and high content screening such as in drug and biomarker discovery studies.

Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults

New neurons continue to be generated in the subgranular zone of the dentate gyrus of the adult mammalian hippocampus. This process has been linked to learning and memory, stress and exercise, and is thought to be altered in neurological disease. In humans, some studies have suggested that hundreds of new neurons are added to the adult dentate gyrus every day, whereas other studies find many fewer putative new neurons. Despite these discrepancies, it is generally believed that the adult human hippocampus continues to generate new neurons. Here we show that a defined population of progenitor cells does not coalesce in the subgranular zone during human fetal or postnatal development. We also find that the number of proliferating progenitors and young neurons in the dentate gyrus declines sharply during the first year of life and only a few isolated young neurons are observed by 7 and 13 years of age. In adult patients with epilepsy and healthy adults (18-77 years; n = 17 post-mortem samples from controls; n = 12 surgical resection samples from patients with epilepsy), young neurons were not detected in the dentate gyrus. In the monkey (Macaca mulatta) hippocampus, proliferation of neurons in the subgranular zone was found in early postnatal life, but this diminished during juvenile development as neurogenesis decreased. We conclude that recruitment of young neurons to the primate hippocampus decreases rapidly during the first years of life, and that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans. The early decline in hippocampal neurogenesis raises questions about how the function of the dentate gyrus differs between humans and other species in which adult hippocampal neurogenesis is preserved.

Effect of Vitamin D in HN9.10e Embryonic Hippocampal Cells and in Hippocampus from MPTP-Induced Parkinson's Disease Mouse Model

It has long been proven that neurogenesis continues in the adult brains of mammals in the dentatus gyrus of the hippocampus due to the presence of neural stem cells. Although a large number of studies have been carried out to highlight the localization of vitamin D receptor in hippocampus, the expression of vitamin D receptor in neurogenic dentatus gyrus of hippocampus in Parkinson's disease (PD) and the molecular mechanisms triggered by vitamin D underlying the production of differentiated neurons from embryonic cells remain unknown. Thus, we performed a preclinical in vivo study by inducing PD in mice with MPTP and showed a reduction of glial fibrillary acidic protein (GFAP) and vitamin D receptor in the dentatus gyrus of hippocampus. Then, we performed an in vitro study by inducing embryonic hippocampal cell differentiation with vitamin D. Interestingly, vitamin D stimulates the expression of its receptor. Vitamin D receptor is a transcription factor that probably is responsible for the upregulation of microtubule associated protein 2 and neurofilament heavy polypeptide genes. The latter increases heavy neurofilament protein expression, essential for neurofilament growth. Notably N-cadherin, implicated in activity for dendritic outgrowth, is upregulated by vitamin D.

The Effect of Traditional Chinese Medicine on Neural Stem Cell Proliferation and Differentiation

Neural stem cells (NSCs) are special types of cells with the potential for self-renewal and multi-directional differentiation. NSCs are regulated by multiple pathways and pathway related transcription factors during the process of proliferation and differentiation. Numerous studies have shown that the compound medicinal preparations, single herbs, and herb extracts in traditional Chinese medicine (TCM) have specific roles in regulating the proliferation and differentiation of NSCs. In this study, we investigate the markers of NSCs in various stages of differentiation, the related pathways regulating the proliferation and differentiation, and the corresponding transcription factors in the pathways. We also review the influence of TCM on NSC proliferation and differentiation, to facilitate the development of TCM in neural regeneration and neurodegenerative diseases.

Comparison of 2D and 3D neural induction methods for the generation of neural progenitor cells from human induced pluripotent stem cells

Neural progenitor cells (NPCs) from human induced pluripotent stem cells (hiPSCs) are frequently induced using 3D culture methodologies however, it is unknown whether spheroid-based (3D) neural induction is actually superior to monolayer (2D) neural induction. Our aim was to compare the efficiency of 2D induction with 3D induction method in their ability to generate NPCs, and subsequently neurons and astrocytes. Neural differentiation was analysed at the protein level qualitatively by immunocytochemistry and quantitatively by flow cytometry for NPC (SOX1, PAX6, NESTIN), neuronal (MAP2, TUBB3), cortical layer (TBR1, CUX1) and glial markers (SOX9, GFAP, AQP4). Electron microscopy demonstrated that both methods resulted in morphologically similar neural rosettes. However, quantification of NPCs derived from 3D neural induction exhibited an increase in the number of PAX6/NESTIN double positive cells and the derived neurons exhibited longer neurites. In contrast, 2D neural induction resulted in more SOX1 positive cells. While 2D monolayer induction resulted in slightly less mature neurons, at an early stage of differentiation, the patch clamp analysis failed to reveal any significant differences between the electrophysiological properties between the two induction methods. In conclusion, 3D neural induction increases the yield of PAX6⁺/NESTIN⁺ cells and gives rise to neurons with longer neurites, which might be an advantage for the production of forebrain cortical neurons, highlighting the potential of 3D neural induction, independent of iPSCs' genetic background.

Induced haploinsufficiency of Kit receptor tyrosine kinase impairs brain development

Kit receptor tyrosine kinase is highly expressed in the developing mammalian brain, yet little is known about its contribution to neural cell development and function. Here we introduced a brain-specific conditional Kit loss-of-function mutation in mice and observed severe hypoplasia of the central nervous system. This was accompanied by an increase in apoptotic cell death in the early embryonic brain and the gradual loss of the self-renewal capacity of neuronal stem/precursor cells. A single copy of the brain-specific conditional Kit loss-of-function allele resulted in the observed phenotype, including impaired in vitro differentiation of neural cells from Kit-haploinsufficient embryonic stem (ES) cells. Our findings demonstrate that Kit signaling is required for the early development of neural cells. This potentially novel Kit-haploinsufficient lethal phenotype may represent an embryonic lethal phenomenon previously unobserved because of its dominantly acting nature.

Gene regulation in adult neural stem cells. Current challenges and possible applications

Adult neural stem and progenitor cells (NSPCs) offer a unique opportunity for neural regeneration and niche modification in physiopathological conditions, harnessing the capability to modify from neuronal circuits to glial scar. Findings exposing the vast plasticity and potential of NSPCs have accumulated over the past years and we currently know that adult NSPCs can naturally give rise not only to neurons but also to astrocytes and reactive astrocytes, and eventually to oligodendrocytes through genetic manipulation. We can consider NSPCs as endogenous flexible tools to fight against neurodegenerative and neurological disorders and aging. In addition, NSPCs can be considered as active agents contributing to chronic brain alterations and as relevant cell populations to be preserved, so that their main function, neurogenesis, is not lost in damage or disease. Altogether we believe that learning to manipulate NSPC is essential to prevent, ameliorate or restore some of the cognitive deficits associated with brain disease and injury, and therefore should be considered as target for future therapeutic strategies. The first step to accomplish this goal is to target them specifically, by unveiling and understanding their unique markers and signaling pathways.

Direct reprogramming with SOX factors: masters of cell fate

Over the last decade significant advances have been made toward reprogramming the fate of somatic cells, typically by overexpression of cell lineage-determinant transcription factors. As key regulators of cell fate, the SOX family of transcription factors has emerged as potent drivers of direct somatic cell reprogramming into multiple lineages, in some cases as the sole overexpressed factor. The vast capacity of SOX factors, especially those of the SOXB1, E and F subclasses, to reprogram cell fate is enlightening our understanding of organismal development, cancer and disease, and offers tremendous potential for regenerative medicine and cell-based therapies. Understanding the molecular mechanisms through which SOX factors reprogram cell fate is essential to optimize the development of novel somatic cell transdifferentiation strategies.

Oncogenic activity of SOX1 in glioblastoma

Glioblastoma remains the most common and deadliest type of brain tumor and contains a population of self-renewing, highly tumorigenic glioma stem cells (GSCs), which contributes to tumor initiation and treatment resistance. Developmental programs participating in tissue development and homeostasis re-emerge in GSCs, supporting the development and progression of glioblastoma. SOX1 plays an important role in neural development and neural progenitor pool maintenance. Its impact on glioblastoma remains largely unknown. In this study, we have found that high levels of SOX1 observed in a subset of patients correlate with lower overall survival. At the cellular level, SOX1 expression is elevated in patient-derived GSCs and it is also higher in oncosphere culture compared to differentiation conditions in conventional glioblastoma cell lines. Moreover, genetic inhibition of SOX1 in patient-derived GSCs and conventional cell lines decreases self-renewal and proliferative capacity in vitro and tumor initiation and growth in vivo. Contrarily, SOX1 over-expression moderately promotes self-renewal and proliferation in GSCs. These functions seem to be independent of its activity as Wnt/β-catenin signaling regulator. In summary, these results identify a functional role for SOX1 in regulating glioma cell heterogeneity and plasticity, and suggest SOX1 as a potential target in the GSC population in glioblastoma.

Molecular Analysis of Stromal Cells-Induced Neural Differentiation of Mouse Embryonic Stem Cells

Deriving specific neural cells from embryonic stem cells (ESCs) is a promising approach for cell replacement therapies of neurodegenerative diseases. When co-cultured with certain stromal cells, mouse ESCs (mESCs) differentiate efficiently to neural cells. In this study, a comprehensive gene and protein expression analysis of differentiating mESCs is performed over a two-week culture period to track temporal progression of cells from a pluripotent state to specific terminally-differentiated neural cells such as neurons, astrocytes, and oligodendrocytes. Expression levels of 26 genes consisting of marker genes for pluripotency, neural progenitors, and specific neuronal, astroglial, and oligodendrocytic cells are tracked using real time q-PCR. The time-course gene expression analysis of differentiating mESCs is combined with the hierarchal clustering and functional principal component analysis (FPCA) to elucidate the evolution of specific neural cells from mESCs at a molecular level. These statistical analyses identify three major gene clusters representing distinct phases of transition of stem cells from a pluripotent state to a terminally-differentiated neuronal or glial state. Temporal protein expression studies using immunohistochemistry demonstrate the generation of neural stem/progenitor cells and specific neural lineages and show a close agreement with the gene expression profiles of selected markers. Importantly, parallel gene and protein expression analysis elucidates long-term stability of certain proteins compared to those with a quick turnover. Describing the molecular regulation of neural cells commitment of mESCs due to stromal signaling will help identify major promoters of differentiation into specific cell types for use in cell replacement therapy applications.

A mosaic world: puzzles revealed by adult neural stem cell heterogeneity

Neural stem cells (NSCs) reside in specialized niches in the adult mammalian brain. The ventricular-subventricular zone (V-SVZ), adjacent to the lateral ventricles, gives rise to olfactory bulb (OB) neurons, and some astrocytes and oligodendrocytes throughout life. In vitro assays have been widely used to retrospectively identify NSCs. However, cells that behave as stem cells in vitro do not reflect the identity, diversity, and behavior of NSCs in vivo. Novel tools including fluorescence activated cell sorting, lineage-tracing, and clonal analysis have uncovered multiple layers of adult V-SVZ NSC heterogeneity, including proliferation state and regional identity. In light of these findings, we reexamine the concept of adult NSCs, considering heterogeneity as a key parameter for analyzing their dynamics in vivo. V-SVZ NSCs form a mosaic of quiescent (qNSCs) and activated cells (aNSCs) that reside in regionally distinct microdomains, reflecting their regional embryonic origins, and give rise to specific subtypes of OB interneurons. Prospective purification and transcriptome analysis of qNSCs and aNSCs has illuminated their molecular and functional properties. qNSCs are slowly dividing, have slow kinetics of neurogenesis in vivo, can be recruited to regenerate the V-SVZ, and only rarely give rise to in vitro colonies. aNSCs are highly proliferative, undergo rapid clonal expansion of the neurogenic lineage in vivo, and readily form in vitro colonies. Key open questions remain about stem cell dynamics in vivo and the lineage relationship between qNSCs and aNSCs under homeostasis and regeneration, as well as context-dependent plasticity of regionally distinct adult NSCs under different external stimuli. WIREs Dev Biol 2016, 5:640-658. doi: 10.1002/wdev.248 For further resources related to this article, please visit the WIREs website.

Three Dimensional Human Neuro-Spheroid Model of Alzheimer's Disease Based on Differentiated Induced Pluripotent Stem Cells

The testing of candidate drugs to slow progression of Alzheimer’s disease (AD) requires clinical trials that are lengthy and expensive. Efforts to model the biochemical milieu of the AD brain may be greatly facilitated by combining two cutting edge technologies to generate three-dimensional (3D) human neuro-spheroid from induced pluripotent stem cells (iPSC) derived from AD subjects. We created iPSC from blood cells of five AD patients and differentiated them into 3D human neuronal culture. We characterized neuronal markers of our 3D neurons by immunocytochemical staining to validate the differentiation status. To block the generation of pathologic amyloid β peptides (Aβ), the 3D-differentiated AD neurons were treated with inhibitors targeting β-secretase (BACE1) and γ-secretases. As predicted, both BACE1 and γ-secretase inhibitors dramatically decreased Aβ generation in iPSC-derived neural cells derived from all five AD patients, under standard two-dimensional (2D) differentiation conditions. However, BACE1 and γ-secretase inhibitors showed less potency in decreasing Aβ levels in neural cells differentiated under 3D culture conditions. Interestingly, in a single subject AD1, we found that BACE1 inhibitor treatment was not able to significantly reduce Aβ42 levels. To investigate underlying molecular mechanisms, we performed proteomic analysis of 3D AD human neuronal cultures including AD1. Proteomic analysis revealed specific reduction of several proteins that might contribute to a poor inhibition of BACE1 in subject AD1. To our knowledge, this is the first iPSC-differentiated 3D neuro-spheroid model derived from AD patients’ blood. Our results demonstrate that our 3D human neuro-spheroid model can be a physiologically relevant and valid model for testing efficacy of AD drug.

Transgenic mouse models for studying adult neurogenesis

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