Sox2 transcription network acts as a molecular switch to regulate properties of neural stem cells

Dissecting SOX2 expression and function reveals an association with multiple signaling pathways during embryonic development and in cancer progression

SRY (Sex Determining Region) box 2 (SOX2) is an essential transcription factor that plays crucial roles in activating genes involved in pre- and post-embryonic development, adult tissue homeostasis, and lineage specifications. SOX2 maintains the self-renewal property of stem cells and is involved in the generation of induced pluripotency stem cells. SOX2 protein contains a particular high-mobility group domain that enables SOX2 to achieve the capacity to participate in a broad variety of functions. The information about the involvement of SOX2 with gene regulatory elements, signaling networks, and microRNA is gradually emerging, and the higher expression of SOX2 is functionally relevant to various cancer types. SOX2 facilitates the oncogenic phenotype via cellular proliferation and enhancement of invasive tumor properties. Evidence are accumulating in favor of three dimensional (higher order) folding of chromatin and epigenetic control of the SOX2 gene by chromatin modifications, which implies that the expression level of SOX2 can be modulated by epigenetic regulatory mechanisms, specifically, via DNA methylation and histone H3 modification. In view of this, and to focus further insights into the roles SOX2 plays in physiological functions, involvement of SOX2 during development, precisely, the advances of our knowledge in pre- and post-embryonic development, and interactions of SOX2 in this scenario with various signaling pathways in tumor development and cancer progression, its potential as a therapeutic target against many cancers are summarized and discussed in this article.

Deubiquitinase PSMD7 facilitates pancreatic cancer progression through activating Nocth1 pathway via modifying SOX2 degradation

BACKGROUND

Ubiquitination is a critical post-translational modification which can be reversed with an enzyme family known as deubiquitinating enzymes (DUBs). It has been reported that dysregulation of deubiquitination leads to carcinogenesis. As a member of the DUBs family, proteasome 26 S subunit non-ATPase 7 (PSMD7) serves as an underlying tumour-promoting factor in multiple cancers. However, the clinical significance and biological functions of PSMD7 in pancreatic cancer (PC) remain unclear.

RESULTS

In this study, we first reported frequent overexpression of PSMD7 in PC tissues, and high levels of PSMD7 were markedly linked to shorter survival and a malignant phenotype in PC patients. An array of in vitro and in vivo gain/loss-of-function tests revealed that PSMD7 facilitates the progression of PC cells. Additionally, we found that PSMD7 promotes PC cell progression by activating the Notch homolog 1 (Notch1) signalling. Interestingly, in PC cells, the inhibitory effect of PSMD7 knockdown on cellular processes was comparable to that observed upon Notch1 knockdown. Mechanistically, PSMD7 deubiquitinated and stabilised sex determining region Y (SRY)-box 2 (SOX2), a key mediator of Notch1 signalling. The stabilisation of SOX2, mediated by PSMD7, dramatically increased SOX2 protein levels, subsequently activating the Notch1 pathway. Finally, restoration of SOX2 expression abrogated the PSMD7-silenced antitumour effect.

CONCLUSIONS

Taken together, our work identifies and validates PSMD7 as a promoter of PC progression through augmentation of the Notch1 signalling pathway mediated by SOX2. This finding suggests that PSMD7 holds promise as a potential therapeutic target for the management of this refractory disease.

Neural stem cells characterization in the vagal complex of adult ovine brain: A combined neurosphere assay/RTqPCR approach

Neural stem cells are the effectors of adult neurogenesis, which occurs in discrete restricted areas of adult mammalian brain. In ovine species, like in rodents, in vivo incorporation of labeled DNA precursor led to characterize neurogenic proliferation in the subventricular zone and progeny migration and differentiation into the olfactory bulb. The present study addresses directly the existence of neural stem cells in the neurogenic niche of the vagal centre (area postrema) by in vitro neurosphere assay and RT-qPCR of specific markers on ex-vivo adult tissue explants, comparatively with the canonical neurogenic niche: the subventricular zone (SVZ) of the forebrain. Explants defined from the neuroanatomical patterns of in vivo BrdU incorporation yielded expandable and self-renewing spheres from both SVZ and AP. Within SVZ though, the density of sphere-forming cells was higher in ventral SVZ (SVZ-V) than in its latero-dorsal (SVZ-D) and lateral (SVZ-L) regions, which differs from the distributions of neural stem cells in mouse and swine brains. Consistently, RT-qPCR of the biomarker of neural stem cells, Sox2, yields highest expression in SVZ-V ahead of SVZ-D, SVZ-L and AP. These results are discussed with regard to previously published dynamics of adult ovine neurogenesis in vivo, and in light of corresponding features in other mammalian species. This confirms existence of neurogenetic plasticity in the vagal complex of adult mammals.

In Vitro Embryogenesis and Gastrulation Using Stem Cells in Mice and Humans

During early mammalian embryonic development, fertilized one-cell embryos develop into pre-implantation blastocysts and subsequently establish three germ layers through gastrulation during post-implantation development. In recent years, stem cells have emerged as a powerful tool to study embryogenesis and gastrulation without the need for eggs, allowing for the generation of embryo-like structures known as synthetic embryos or embryoids. These in vitro models closely resemble early embryos in terms of morphology and gene expression and provide a faithful recapitulation of early pre- and post-implantation embryonic development. Synthetic embryos can be generated through a combinatorial culture of three blastocyst-derived stem cell types, such as embryonic stem cells, trophoblast stem cells, and extraembryonic endoderm cells, or totipotent-like stem cells alone. This review provides an overview of the progress and various approaches in studying in vitro embryogenesis and gastrulation in mice and humans using stem cells. Furthermore, recent findings and breakthroughs in synthetic embryos and gastruloids are outlined. Despite ethical considerations, synthetic embryo models hold promise for understanding mammalian (including humans) embryonic development and have potential implications for regenerative medicine and developmental research.

Proteomics and disease network associations evaluation of environmentally relevant Bisphenol A concentrations in a human 3D neural stem cell model

Bisphenol A (BPA) exposure is associated with a plethora of neurodevelopmental abnormalities and brain disorders. Previous studies have demonstrated BPA-induced perturbations to critical neural stem cell (NSC) characteristics, such as proliferation and differentiation, although the underlying molecular mechanisms remain under debate. The present study evaluated the effects of a repeated-dose exposure of environmentally relevant BPA concentrations during the in vitro 3D neural induction of human induced pluripotent stem cells (hiPSCs), emulating a chronic exposure scenario. Firstly, we demonstrated that our model is suitable for NSC differentiation during the early stages of embryonic brain development. Our morphological image analysis showed that BPA exposure at 0.01, 0.1 and 1 µM decreased the average spheroid size by day 21 (D21) of the neural induction, while no effect on cell viability was detected. No alteration to the rate of the neural induction was observed based on the expression of key neural lineage and neuroectodermal transcripts. Quantitative proteomics at D21 revealed several differentially abundant proteins across all BPA-treated groups with important functions in NSC proliferation and maintenance (e.g., FABP7, GPC4, GAP43, Wnt-8B, TPPP3). Additionally, a network analysis demonstrated alterations to the glycolytic pathway, potentially implicating BPA-induced changes to glycolytic signalling in NSC proliferation impairments, as well as the pathophysiology of brain disorders including intellectual disability, autism spectrum disorders, and amyotrophic lateral sclerosis (ALS). This study enhances the current understanding of BPA-related NSC aberrations based mostly on acute, often high dose exposures of rodent in vivo and in vitro models and human GWAS data in a novel human 3D cell-based model with real-life scenario relevant prolonged and low-level exposures, offering further mechanistic insights into the ramifications of BPA exposure on the developing human brain and consequently, later life neurological disorders.

Neural Progenitor Cells and the Hypothalamus

Neural progenitor cells (NPCs) are multipotent neural stem cells (NSCs) capable of self-renewing and differentiating into neurons, astrocytes and oligodendrocytes. In the postnatal/adult brain, NPCs are primarily located in the subventricular zone (SVZ) of the lateral ventricles (LVs) and subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). There is evidence that NPCs are also present in the postnatal/adult hypothalamus, a highly conserved brain region involved in the regulation of core homeostatic processes, such as feeding, metabolism, reproduction, neuroendocrine integration and autonomic output. In the rodent postnatal/adult hypothalamus, NPCs mainly comprise different subtypes of tanycytes lining the wall of the 3^rd ventricle. In the postnatal/adult human hypothalamus, the neurogenic niche is constituted by tanycytes at the floor of the 3^rd ventricle, ependymal cells and ribbon cells (showing a gap-and-ribbon organization similar to that in the SVZ), as well as suprachiasmatic cells. We speculate that in the postnatal/adult human hypothalamus, neurogenesis occurs in a highly complex, exquisitely sophisticated neurogenic niche consisting of at least four subniches; this structure has a key role in the regulation of extrahypothalamic neurogenesis, and hypothalamic and extrahypothalamic neural circuits, partly through the release of neurotransmitters, neuropeptides, extracellular vesicles (EVs) and non-coding RNAs (ncRNAs).

Characterization of Schistosome Sox Genes and Identification of a Flatworm Class of Sox Regulators

Schistosome helminths infect over 200 million people across 78 countries and are responsible for nearly 300,000 deaths annually. However, our understanding of basic genetic pathways crucial for schistosome development is limited. The sex determining region Y-box 2 (Sox2) protein is a Sox B type transcriptional activator that is expressed prior to blastulation in mammals and is necessary for embryogenesis. Sox expression is associated with pluripotency and stem cells, neuronal differentiation, gut development, and cancer. Schistosomes express a Sox-like gene expressed in the schistosomula after infecting a mammalian host when schistosomes have about 900 cells. Here, we characterized and named this Sox-like gene SmSOXS1. SmSoxS1 protein is a developmentally regulated activator that localizes to the anterior and posterior ends of the schistosomula and binds to Sox-specific DNA elements. In addition to SmSoxS1, we have also identified an additional six Sox genes in schistosomes, two Sox B, one SoxC, and three Sox genes that may establish a flatworm-specific class of Sox genes with planarians. These data identify novel Sox genes in schistosomes to expand the potential functional roles for Sox2 and may provide interesting insights into early multicellular development of flatworms.

A Bone Morphogenetic Protein Signaling Inhibitor, LDN193189, Converts Ischemia-Induced Multipotent Stem Cells into Neural Stem/Progenitor Cell-Like Cells

Stem cell therapy is used to restore neurological function in stroke patients. We have previously reported that ischemia-induced multipotent stem cells (iSCs), which are likely derived from brain pericytes, develop in poststroke human and mouse brains. Although we have demonstrated that iSCs can differentiate into neural lineage cells, the factors responsible for inducing this differentiation remain unclear. In this study, we found that LDN193189, a bone morphogenetic protein (BMP) inhibitor, caused irreversible changes in the shape of iSCs. In addition, compared with iSCs incubated without LDN193189, the iSCs incubated with LDN193189 (LDN-iSCs) showed upregulated expression of neural lineage-related genes and proteins, including those expressed in neural stem/progenitor cells (NSPCs), and downregulated expression of mesenchymal and pericytic-related genes and proteins. Moreover, microarray analysis revealed that LDN-iSCs and NSPCs had similar gene expression profiles. Furthermore, LDN-iSCs differentiated into electrophysiologically functional neurons. These results indicate that LDN193189 induces NSPC-like cells from iSCs, suggesting that bioactive molecules regulating BMP signaling are potential targets for promoting neurogenesis from iSCs in the pathological brain, such as during ischemic stroke. We believe that our findings will bring us one step closer to the clinical application of iSCs.

High-Contrast Stimulation Potentiates the Neurotrophic Properties of Müller Cells and Suppresses Their Pro-Inflammatory Phenotype

High-contrast visual stimulation promotes retinal regeneration and visual function, but the underlying mechanism is not fully understood. Here, we hypothesized that Müller cells (MCs), which express neurotrophins such as brain-derived neurotrophic factor (BDNF), could be key players in this retinal plasticity process. This hypothesis was tested by conducting in vivo and in vitro high-contrast stimulation of adult mice and MCs. Following stimulation, we examined the expression of BDNF and its inducible factor, VGF, in the retina and MCs. We also investigated the alterations in the expression of VGF, nuclear factor kappa B (NF-κB) and pro-inflammatory mediators in MCs, as well as their capacity to proliferate and develop a neurogenic or reactive gliosis phenotype after high-contrast stimulation and treatment with BDNF. Our results showed that high-contrast stimulation upregulated BDNF levels in MCs in vivo and in vitro. The additional BDNF treatment significantly augmented VGF production in MCs and their neuroprotective features, as evidenced by increased MC proliferation, neurodifferentiation, and decreased expression of the pro-inflammatory factors and the reactive gliosis marker GFAP. These results demonstrate that high-contrast stimulation activates the neurotrophic and neuroprotective properties of MCs, suggesting their possible direct involvement in retinal neuronal survival and improved functional outcomes in response to visual stimulation.

DNA repair proteins cooperate with SOX2 in regulating the transition of human embryonic stem cells to neural progenitor cells

SOX2, a well-established pluripotency factor supporting the self-renewal of pluripotent stem cells (PSCs), is also a crucial factor for maintaining the properties and functionalities of neural progenitor cells (NPCs). It regulates the transcription of target genes by forming complexes with its partner factors, but systematic comparison of SOX2 binding partners in human PSCs versus NPCs is lacking. Here, by deciphering and comparing the SOX2-protein interactomes in human embryonic stem cells (hESCs) versus the NPCs derived from them, we identified 23 proteins with high reproducibility that are most differentially associated with SOX2, of which 9 are DNA repair proteins (PARP1, PARP2, PRKDC, XRCC1, XRCC5, XRCC6, RPA1, LIG3, DDB1). Genetic knocking-down or pharmacological inhibiting two of the DNA repair proteins (PARP1 and PRKDC) significantly up-regulated certain NPC or ectodermal biomarkers that are transcriptionally-suppressed by the SOX2/DNA repair protein complexes. These findings point to a crucial role of DNA repair proteins in pluripotent state transition and neural induction.

Tissue-Restricted Stem Cells as Starting Cell Source for Efficient Generation of Pluripotent Stem Cells: An Overview

Induced pluripotent stem cells (iPSCs) have vast biomedical potential concerning disease modeling, drug screening and discovery, cell therapy, tissue engineering, and understanding organismal development. In the year 2006, a groundbreaking study reported the generation of iPSCs from mouse embryonic fibroblasts by viral transduction of four transcription factors, namely, Oct4, Sox2, Klf4, and c-Myc. Subsequently, human iPSCs were generated by reprogramming fibroblasts as a starting cell source using two reprogramming factor cocktails [(i) OCT4, SOX2, KLF4, and c-MYC, and (ii) OCT4, SOX2, NANOG, and LIN28]. The wide range of applications of these human iPSCs in research, therapeutics, and personalized medicine has driven the scientific community to optimize and understand this reprogramming process to achieve quality iPSCs with higher efficiency and faster kinetics. One of the essential criteria to address this is by identifying an ideal cell source in which pluripotency can be induced efficiently to give rise to high-quality iPSCs. Therefore, various cell types have been studied for their ability to generate iPSCs efficiently. Cell sources that can be easily reverted to a pluripotent state are tissue-restricted stem cells present in the fetus and adult tissues. Tissue-restricted stem cells can be isolated from fetal, cord blood, bone marrow, and other adult tissues or can be obtained by differentiation of embryonic stem cells or trans-differentiation of other tissue-restricted stem cells. Since these cells are undifferentiated cells with self-renewal potential, they are much easier to reprogram due to the inherent characteristic of having an endogenous expression of few pluripotency-inducing factors. This review presents an overview of promising tissue-restricted stem cells that can be isolated from different sources, namely, neural stem cells, hematopoietic stem cells, mesenchymal stem cells, limbal epithelial stem cells, and spermatogonial stem cells, and their reprogramming efficacy. This insight will pave the way for developing safe and efficient reprogramming strategies and generating patient-specific iPSCs from tissue-restricted stem cells derived from various fetal and adult tissues.

Neural stem cell therapy for brain disease

Brain diseases, including brain tumors, neurodegenerative disorders, cerebrovascular diseases, and traumatic brain injuries, are among the major disorders influencing human health, currently with no effective therapy. Due to the low regeneration capacity of neurons, insufficient secretion of neurotrophic factors, and the aggravation of ischemia and hypoxia after nerve injury, irreversible loss of functional neurons and nerve tissue damage occurs. This damage is difficult to repair and regenerate the central nervous system after injury. Neural stem cells (NSCs) are pluripotent stem cells that only exist in the central nervous system. They have good self-renewal potential and ability to differentiate into neurons, astrocytes, and oligodendrocytes and improve the cellular microenvironment. NSC transplantation approaches have been made for various neurodegenerative disorders based on their regenerative potential. This review summarizes and discusses the characteristics of NSCs, and the advantages and effects of NSCs in the treatment of brain diseases and limitations of NSC transplantation that need to be addressed for the treatment of brain diseases in the future.

Melatonin and Melatonergic Influence on Neuronal Transcription Factors: Implications for the Development of Novel Therapies for Neurodegenerative Disorders

Melatonin is a multifunctional signalling molecule that is secreted by the mammalian pineal gland, and also found in a number of organisms including plants and bacteria. Research has continued to uncover an ever-increasing number of processes in which melatonin is known to play crucial roles in mammals. Amongst these functions is its contribution to cell multiplication, differentiation and survival in the brain. Experimental studies show that melatonin can achieve these functions by influencing transcription factors which control neuronal and glial gene expression. Since neuronal survival and differentiation are processes that are important determinants of the pathogenesis, course and outcome of neurodegenerative disorders; the known and potential influences of melatonin on neuronal and glial transcription factors are worthy of constant examination. In this review, relevant scientific literature on the role of melatonin in preventing or altering the course and outcome of neurodegenerative disorders, by focusing on melatonin's influence on transcription factors is examined. A number of transcription factors whose functions can be influenced by melatonin in neurodegenerative disease models have also been highlighted. Finally, the therapeutic implications of melatonin's influences have also been discussed and the potential limitations to its applications have been highlighted.

An atlas of dynamic chromatin landscapes in mouse fetal development

The Encyclopedia of DNA Elements (ENCODE) project has established a genomic resource for mammalian development, profiling a diverse panel of mouse tissues at 8 developmental stages from 10.5 days after conception until birth, including transcriptomes, methylomes and chromatin states. Here we systematically examined the state and accessibility of chromatin in the developing mouse fetus. In total we performed 1,128 chromatin immunoprecipitation with sequencing (ChIP-seq) assays for histone modifications and 132 assay for transposase-accessible chromatin using sequencing (ATAC-seq) assays for chromatin accessibility across 72 distinct tissue-stages. We used integrative analysis to develop a unified set of chromatin state annotations, infer the identities of dynamic enhancers and key transcriptional regulators, and characterize the relationship between chromatin state and accessibility during developmental gene regulation. We also leveraged these data to link enhancers to putative target genes and demonstrate tissue-specific enrichments of sequence variants associated with disease in humans. The mouse ENCODE data sets provide a compendium of resources for biomedical researchers and achieve, to our knowledge, the most comprehensive view of chromatin dynamics during mammalian fetal development to date.

Spheroids Spontaneously Generated In Vitro from Sheep Ovarian Cortical Cells Contain Integrating Cells That Exhibit Hallmarks of Neural Stem/Progenitor Cells

Cell spheroids are inducible or spontaneously generated cell aggregates produced in vitro that can provide a valuable model for developmental biology, stem cell biology, and cancer therapy research. This investigation aimed to define the cellular identity of spheroids spontaneously generated in vitro from sheep ovarian cortical cells cultured under specific serum-free conditions. Spheroids were characterized during 21 days of culture by morphometric evaluation, detection of alkaline phosphatase (AP) activity, gene expression analyses of stemness transcription factors and several lineage markers, immunolocalization analyses, as well as assessment of self-renewal and differentiation potential. Cell aggregation, evidenced from day 3 of culture onward, resulted in efficient generation of 65-75 spheroids for every 500,000 cells seeded. The spheroids reached maximum diameter (187 ± 15.9 μm) during the second week of culture and exhibited AP activity. Sox2, Oct4, and Nanog were expressed throughout the culture period, with upregulation of Sox2. Neural lineage specification genes (eg, nestin, vimentin, Pax6, and p75NTR) were expressed from day 10 onward at levels above that of Oct4, Nanog and those for endoderm [alpha-fetoprotein (AFP)], and mesoderm (brachyury) specification. Neural stem cell (NSC)/neural progenitor cell (NPC) markers, nestin, Pax6, p75NTR, and vimentin, were extensively localized in cells on day 10, 15 (44.75% ± 5.84%; 93.54% ± 1.35%; 78.90% ± 4.80%; 73.82% ± 3.40%, respectively), and 21 (49.98% ± 5.30%; 91.84% ± 1.9%; 76.74% ± 11.0%; 95.80% ± 3.60%, respectively). Spheroid cell self-renewal was evidenced by cell proliferation and the generation of new spheroids during two consecutive expansion periods. Culture of spheroid cells under differentiation conditions gave rise to cells showing immunolocalization of the neuron-specific antigen NeuN and the astroglial antigen GFAP (glial fibrillary acidic protein). Our results indicate that spheroids spontaneously generated in this culture system were comprised of cells with molecular characteristics of NSC/NPC that can self-renew and differentiate into neurons and glia, supporting the identity of spheroids as neurospheres.

The Role of Long Noncoding RNAs in Central Nervous System and Neurodegenerative Diseases

Long noncoding RNAs (lncRNAs) refer to a group of noncoding RNAs (ncRNAs) that has a transcript of more than 200 nucleotides in length in eukaryotic cells. The lncRNAs regulate gene expression at epigenetic, transcriptional, and post-transcriptional levels by multiple action modes. In this review, we describe the diverse roles reported for lncRNAs, and discuss how they could mechanistically be involved in the development of central nervous system (CNS) and neurodegenerative diseases. Further studies on the function of lncRNAs and their mechanism will help deepen our understanding of the development, function, and diseases of the CNS, and provide new ideas for the design and development of some therapeutic drugs.

Study of pallial neurogenesis in shark embryos and the evolutionary origin of the subventricular zone

The dorsal part of the developing telencephalon is one of the brain areas that has suffered most drastic changes throughout vertebrate evolution. Its evolutionary increase in complexity was thought to be partly achieved by the appearance of a new neurogenic niche in the embryonic subventricular zone (SVZ). Here, a new kind of amplifying progenitors (basal progenitors) expressing Tbr2, undergo a second round of divisions, which is believed to have contributed to the expansion of the neocortex. Accordingly, the existence of a pallial SVZ has been classically considered exclusive of mammals. However, the lack of studies in ancient vertebrates precludes any clear conclusion about the evolutionary origin of the SVZ and the neurogenic mechanisms that rule pallial development. In this work, we explore pallial neurogenesis in a basal vertebrate, the shark Scyliorhinus canicula, through the study of the expression patterns of several neurogenic markers. We found that apical progenitors and radial migration are present in sharks, and therefore, their presence must be highly conserved throughout evolution. Surprisingly, we detected a subventricular band of ScTbr2-expressing cells, some of which also expressed mitotic markers, indicating that the existence of basal progenitors should be considered an ancestral condition rather than a novelty of mammals or amniotes. Finally, we report that the transcriptional program for the specification of glutamatergic pallial cells (Pax6, Tbr2, NeuroD, Tbr1) is also present in sharks. However, the segregation of these markers into different cell types is not clear yet, which may be linked to the lack of layering in anamniotes.

Sox2 is required for olfactory pit formation and olfactory neurogenesis through BMP restriction and Hes5 upregulation

The transcription factor Sox2 is necessary to maintain pluripotency of embryonic stem cells, and to regulate neural development. Neurogenesis in the vertebrate olfactory epithelium persists from embryonic stages through adulthood. The role Sox2 plays for the development of the olfactory epithelium and neurogenesis within has, however, not been determined. Here, by analysing Sox2 conditional knockout mouse embryos and chick embryos deprived of Sox2 in the olfactory epithelium using CRISPR-Cas9, we show that Sox2 activity is crucial for the induction of the neural progenitor gene Hes5 and for subsequent differentiation of the neuronal lineage. Our results also suggest that Sox2 activity promotes the neurogenic domain in the nasal epithelium by restricting Bmp4 expression. The Sox2-deficient olfactory epithelium displays diminished cell cycle progression and proliferation, a dramatic increase in apoptosis and finally olfactory pit atrophy. Moreover, chromatin immunoprecipitation data show that Sox2 directly binds to the Hes5 promoter in both the PNS and CNS. Taken together, our results indicate that Sox2 is essential to establish, maintain and expand the neuronal progenitor pool by suppressing Bmp4 and upregulating Hes5 expression.

Summary: Analysis of Sox2 mutant mouse and Sox2 CRISPR-targeted chick embryos reveals that Sox2 controls the establishment of sensory progenitors in the olfactory epithelium by suppressing Bmp4 and upregulating Hes5 expression.

Migratory potential of transplanted glial progenitors as critical factor for successful translation of glia replacement therapy: The gap between mice and men

Neurological disorders are a major threat to public health. Stem cell-based regenerative medicine is now a promising experimental paradigm for its treatment, as shown in pre-clinical animal studies. Initial attempts have been on the replacement of neuronal cells only, but glial progenitors (GPs) are now becoming strong alternative cellular therapeutic candidates to replace oligodendrocytes and astrocytes as knowledge accumulates about their important emerging role in various disease processes. There are many examples of successful therapeutic outcomes for transplanted GPs in small animal models, but clinical translation has proved to be challenging due to the 1,000-fold larger volume of the human brain compared to mice. Human GPs transplanted into the mouse brain migrate extensively and can induce global cell replacement, but a similar extent of migration in the human brain would only allow for local rather than global cell replacement. We review here the mechanisms that govern cell migration, which could potentially be exploited to enhance the migratory properties of GPs through cell engineering pre-transplantation. We furthermore discuss the (dis)advantages of the various cell delivery routes that are available, with particular emphasis on intra-arterial injection as the most suitable route for achieving global cell distribution in the larger brain. Now that therapeutic success has proven to be feasible in small animal models, future efforts will need to be directed to enhance global cell delivery and migration to make bench-to-bedside translation a reality.

Integrative analysis of methylome and transcriptome in human blood identifies extensive sex- and immune cell-specific differentially methylated regions

The relationship between DNA methylation and gene expression is complex and elusive. To further elucidate these relations, we performed an integrative analysis of the methylome and transcriptome of 4 circulating immune cell subsets (B cells, monocytes, CD4(+), and CD8(+) T cells) from healthy females. Additionally, in light of the known sex bias in the prevalence of several immune-mediated diseases, the female datasets were compared with similar public available male data sets. Immune cell-specific differentially methylated regions (DMRs) were found to be highly similar between sexes, with an average correlation coefficient of 0.82; however, numerous sex-specific DMRs, shared by the cell subsets, were identified, mainly on autosomal chromosomes. This provides a list of highly interesting candidate genes to be studied in disorders with sexual dimorphism, such as autoimmune diseases. Immune cell-specific DMRs were mainly located in the gene body and intergenic region, distant from CpG islands but overlapping with enhancer elements, indicating that distal regulatory elements are important in immune cell specificity. In contrast, sex-specific DMRs were overrepresented in CpG islands, suggesting that the epigenetic regulatory mechanisms of sex and immune cell specificity may differ. Both positive and, more frequently, negative correlations between subset-specific expression and methylation were observed, and cell-specific DMRs of both interactions were associated with similar biological pathways, while sex-specific DMRs were linked to networks of early development or estrogen receptor and immune-related molecules. Our findings of immune cell- and sex-specific methylome and transcriptome profiles provide novel insight on their complex regulatory interactions and may particularly contribute to research of immune-mediated diseases.

A new role of hindbrain boundaries as pools of neural stem/progenitor cells regulated by Sox2

Background

Compartment boundaries are an essential developmental mechanism throughout evolution, designated to act as organizing centers and to regulate and localize differently fated cells. The hindbrain serves as a fascinating example for this phenomenon as its early development is devoted to the formation of repetitive rhombomeres and their well-defined boundaries in all vertebrates. Yet, the actual role of hindbrain boundaries remains unresolved, especially in amniotes.

Results

Here, we report that hindbrain boundaries in the chick embryo consist of a subset of cells expressing the key neural stem cell (NSC) gene Sox2. These cells co-express other neural progenitor markers such as Transitin (the avian Nestin), GFAP, Pax6 and chondroitin sulfate proteoglycan. The majority of the Sox2⁺ cells that reside within the boundary core are slow-dividing, whereas nearer to and within rhombomeres Sox2⁺ cells are largely proliferating. In vivo analyses and cell tracing experiments revealed the contribution of boundary Sox2⁺ cells to neurons in a ventricular-to-mantle manner within the boundaries, as well as their lateral contribution to proliferating Sox2⁺ cells in rhombomeres. The generation of boundary-derived neurospheres from hindbrain cultures confirmed the typical NSC behavior of boundary cells as a multipotent and self-renewing Sox2⁺ cell population. Inhibition of Sox2 in boundaries led to enhanced and aberrant neural differentiation together with inhibition in cell-proliferation, whereas Sox2 mis-expression attenuated neurogenesis, confirming its significant function in hindbrain neuronal organization.

Conclusions

Data obtained in this study deciphers a novel role of hindbrain boundaries as repetitive pools of neural stem/progenitor cells, which provide proliferating progenitors and differentiating neurons in a Sox2-dependent regulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-016-0277-y) contains supplementary material, which is available to authorized users.

nNOS Translocates into the Nucleus and Interacts with Sox2 to Protect Neurons Against Early Excitotoxicity via Promotion of Shh Transcription

Cerebral ischemic stroke is a major public health problem leading to high mortality rates and disability in adults. The NMDA receptor (NMDAR)/neuronal nitric oxide synthase (nNOS)/NO-dependent excitotoxicity has been recognized to play an important role in cerebral ischemic stroke pathogenesis. Accumulating evidence suggests that the biological function of nNOS is associated with its ability to couple proteins and its subcellular localization. Previously, we and others determined that nNOS could translocate into the nucleus in cultured astrocytes, but the underlying mechanisms and biological significance remained unclear. In the present study, we identified a specific interaction between nNOS and Sox2 (SRY (sex determining region Y)-box 2), a member of the Sox family of transcription factors, both in vivo and in vitro. Our studies showed that nNOS is transported into the nucleus and interacted with Sox2 to form a nNOS-Sox2 complex in neurons at the early stage following glutamate stimulation. Mechanistically, via activating the transcription of Shh (Sonic hedgehog), the downstream target of Sox2, this nNOS-Sox2 complex exerted a neuroprotective function against glutamate-induced excitotoxicity. Utilizing the MCAO focal ischemia model on rats, we further verified that the 'nNOS-Sox2-Shh' axis was involved in the ischemic neuronal injury. Taken together, our studies revealed that the 'nNOS-Sox2-Shh' axis functions as a novel feedback compensatory mechanism to protect neurons against the early excitotoxicity and ischemic injury.

Induced neural stem/precursor cells for fundamental studies and potential application in neurodegenerative diseases

Recent research has shown that defined sets of exogenous factors are sufficient to convert rodent and human somatic cells directly into induced neural stem cells or neural precursor cells (iNSCs/iNPCs). The process of transdifferentiation bypasses the step of a pluripotent state and reduces the risk of tumorigenesis and genetic instability while retaining the self-renewing capacity. This iNSC/iNPC technology has fueled much excitement in regenerative medicine, as these cells can be differentiated into target cells for re placement therapy for neurodegenerative diseases. Patients' somatic cell-derived iNSCs/iNPCs have also been proposed to serve as disease models with potential value in both fundamental studies and clinical applications. This review focuses on the mechanisms, techniques, and app lications of iNSCs/iNPCs from a series of related studies, as well as further efforts in designing novel strategies using iNSC/iNPC technology and its potential applications in neurodegenerative diseases.

Horizontal Basal Cell-Specific Deletion of Pax6 Impedes Recovery of the Olfactory Neuroepithelium Following Severe Injury

In the mammalian olfactory epithelium (OE), olfactory receptor neurons (ORNs) are continuously regenerated throughout the animal's lifetime. Horizontal basal cells (HBCs) in the OE express the epithelial marker keratin 5 (K5) and the stem cell marker Pax6 and are considered relatively quiescent tissue stem cells in the OE. Pax6 is a key regulator of several developmental processes in the central nervous system and in sensory organs. Although Pax6 is expressed in the OE, its precise role remains unknown, particularly with respect to stem cell-like HBCs. To investigate the function of Pax6 in the developmental and regenerative processes in the OE, we generated conditional Pax6-knockout mice carrying a loxP-floxed Pax6 gene. Homozygous Pax6-floxed mice were crossed with K5-Cre transgenic mice to generate HBC-specific Pax6-knockout (Pax6-cKO) mice. We confirmed that the deletion of Pax6 expression in HBCs was sufficiently achieved in zone 1 of the OE in Pax6-cKO mice 3 days after methimazole-induced severe damage. In this condition, regeneration of the OE was dramatically impaired; both OE thickness and the number of ORNs were significantly decreased in the regenerated OE of Pax6-cKO mice. These results suggest that Pax6 expression is essential for HBCs to differentiate into neuronal cells during the regeneration process following severe injury.