Glial Precursor Cells Research Articles

TARGET ONCOGENIC RECEPTORS IN TUMOURS, FROM ITS INITIAL CLINICAL BREAKTHROUGHS TO CURRENT CLINICAL STANDARD THERAPY

Epidermal growth factor (EGF) is a polypeptide hormone originally isolated from mouse submaxillary gland, which is a potent mitogen for a wide variety of culture cells of both epithelial and mesenchymal origin, and its important role in the proliferation, differentiation, and survival of neural and glial precursor cells. The physiological effects of EGF are mediated by an EGF receptor with tyrosine-specific protein kinase activity. The traditionally accepted view is that normal epidermal growth factor receptor (EGFR) is no tumorigenic, whereas mutated EGFR such as an oncogenic receptor EGFRvIII is oncogenic. In recent, it has been implicated that EGF could be beneficial for burn, wound healing, diabetic foot ulcer, and show an attractive perspective. In addition, cosmetic containing EGF would be effective in improving the plasticity of skin, helps in anti-aging and whitening, and controls the amount of erythema and sebum in the skin. In our team we have successfully prepared a series of 350 bottles of Shampoo liquid and 26 bottles of recombinant human EGF (rhEGF) spray, and 4 bottles of EGF-Silvadence ointment. The initial results indicated that prepared rhEGF is safe and available in clinical use. On the other hand, progress on the interaction of EGF with its altered oncogenic receptor signaling through its downstream molecules such Ras/Raf/MAPK (see figure in the full text, George Zhu,1991) and/or PI3k/akt pathway in the development of some cancers such as A431 human epidermoid carcinoma cells, brain glioblastoma, breast, pancreas and lung cancers. In addition to a series of gefitinib, erlotinib, osimertinib and the CIMA vax-EGF vaccine, an antioncogenic receptor antibody based fusion protein [for example Cetuximab-based IL-10 fusion protein, CmAb-(IL10)2] provide a potential strategy to improve cancer immunotherapy. Peer Review History: Received 1 December 2023; Revised 26 January 2024; Accepted 2 March; Available online 15 March 2024 Academic Editor: Dr. Tamer Elhabibi, Suez Canal University, Egypt, tamer_hassan@pharm.suez.edu.eg Average Peer review marks at initial stage: 6.0/10 Average Peer review marks at publication stage: 8.0/10 Reviewers: Dr. Bilge Ahsen KARA, Ankara Gazi Mustafa Kemal Hospital, Turkey, ahsndkyc@gmail.com Dr. Asia Selman Abdullah, University of Basrah, Iraq, asia_abdullah65@yahoo.com

Stem Cell Scaffolds for the Treatment of Spinal Cord Injury-A Review.

Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.

Abstract 15: Investigating the spectrum of brain tumors associated with Adgrb3 and Tp53 loss in a mouse model of Li-Fraumeni syndrome

Abstract Adhesion G protein-coupled receptor 3 (ADGRB3), also known as brain specific angiogenesis inhibitor (BAI3) is a member of the ADGRB1-3 subfamily of adhesion transmembrane proteins, which are highly expressed in the brain specifically in cerebellum and hippocampal neurons. ADGRB3 has been shown to play diverse roles under physiological and pathological conditions which include dendritic morphogenesis, synaptic plasticity, synaptogenesis, and myogenesis. Loss of ADGRB3 expression and point mutations in the gene have been observed in sporadic tumors, including brain tumors, but the significance of this observation has not been investigated. Moreover, no mouse models to understand the role of ADGRB3 in brain tumor susceptibility and pathobiology have been developed thus far. Li-Fraumeni syndrome (LFS) is a rare inherited autosomal dominant disorder caused by a germline mutation in one TP53 allele, predisposing patients to the development of a variety of tumors from a pediatric age, including gliomas and medulloblastoma. The secondary molecular alterations that predispose LFS patients to brain tumors are currently unknown. Interestingly, a LFS patient was reported to carry a translocation in ADGRB3 and HGMLL genes. To investigate the molecular mechanisms underlying brain tumor formation in LFS patients and the role of p53 and ADGRB3 in the process, we have generated a LFS mouse model. The mice harbor a germline p53 deleted allele and a second floxed allele. Loss of the second allele is induced in the brain by crossing with mice harboring a Nestin promoter driven Cre recombinase, since Nestin is expressed along the craniospinal axis and in glial precursor cells. We observed that the majority of nestin-Cre p53m/f mice all died between 8 and 10 months of age while nestin-Cre p53m/+ mice did not. About 20% of the mice developed hind leg paralysis and harbored large gliomas, which likely caused their demise. The remainder mice lacked brain tumors, but had other malignancies (sarcomas, etc.) as observed in patients. Remarkably, the addition of Adgrb3 deletion to the genotype led to a dramatic increase (from 20% to 60%??) in the number of brain tumors, including medulloblastoma formation, which are also reported in LFS patients. The Adgrb3-/- p53+/- Nestin-Cre mouse model constitutes a useful tool to understand the tumorigenic landscape caused by the loss of Adgrb3. We are now performing genomic analyses on the excised tumors and derived neurosphere cultures to further study the transformation process and the molecular changes induced by Adgrb3 loss. Citation Format: Alex B. Torrelli-Diljohn, Svetlana Komarova, Vipul Sheth, Benjamin Lin, Paran Goel, Ryan Miller, Robert Welner, Erwin G. Van Meir. Investigating the spectrum of brain tumors associated with Adgrb3 and Tp53 loss in a mouse model of Li-Fraumeni syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 15.

Astroglial differentiation of fibronectin‑positive human "glia-like" cells.

Fibronectin (Fn) is a glycoprotein of extracellular matrix produced by a variety of mesenchymal and neoplastic cell types. In adult brain tissue, Fn is restricted to blood vessels. However, adult human brain cultures are almost entirely comprised of flat or spindle‑shaped Fn-positive cells usually referred to as "glia-like" cells. Since Fn is primarily present in fibroblasts, these cultures may be considered to be of non-glial origin. Cells gained by long-term culturing of adult human brain tissue derived from brain biopsies obtained from 12 patients with non-malignant diagnoses were examined by immunofluorescence methods. Primary cultures contained GFAP-/Vim+/Fn+ "glia-like" cells (95-98 %) and GFAP+/Vim+/Fn- astrocytes (0.1 %) which disappeared by passage number 3. The formation of cell processes and enlargement of cell bodies was observed in 9 of 12 cultures with decreased cell growth during passages 12 to 17. It is remarkable that during this period, all "glia-like" cells became GFAP+/Vim+/Fn+. Herein, we confirm our previously published hypothesis about the origin of adult human "glia-like" cells, which we consider to be precursor cells scattered through the brain cortex and subcortical white matter. Cultures were comprised entirely of GFAP-/Fn+ "glia-like" cells and showed morphological and immunochemical astroglial differentiation with spontaneously decelerated growth during prolonged passaging. We propose that the adult human brain tissue contains a "dormant population" of undefined glial precursor cells. Under culture, these cells show to have a high proliferative capacity and different stages of cell dedifferentiation (Fig. 2, Ref. 21).

HGG-30. H3.3 G34R/V mutations disrupt H3.3 mitotic phosphorylation leading to high-grade glioma formation through the induction of chromosomal instability

Pediatric high-grade gliomas (pHGG) are among the most lethal of all human cancers. Histone H3.3 G34R/V mutations are an early event in these tumors and show reduced H3.3 K36 trimethylation; implicating epigenetic dysregulation in tumorigenesis. Here we present evidence that H3.3 G34R/V mutations promote tumor formation via the induction of chromosomal instability (CIN). Pericentromeric H3.3 is phosphorylated at S31 by Chk1 during mitosis. We observed that the H3.3 G34R mutation reduced Chk1 phosphorylation of H3.3 S31 by >90% in vitro. Furthermore, H3.3 G34 mutant cells have reduced pericentromeric H3.3 S31 phosphorylation in mitosis compared to WT H3.3 cell lines. H3.3 G34 mutant pHGG cells also have significantly elevated rates of CIN as compared to H3.3 WT cells. Overexpression of H3.3 G34R, G34V or non-phosphorylatable S31A in H3.3 WT, diploid cells caused a significant increase in CIN, but H3.3 K36M overexpression had no effect on chromosome segregation. These studies demonstrate that H3.3 G34R/V mutations are sufficient to induce CIN in normal, diploid cells. To determine if this process contributes to tumorigenesis, we used RCAS Nestin-TVA mice to overexpress H3.3 WT, G34R, or S31A – P2A-linked to PDGFB in glial precursor cells of newborn mice. Over 100 days, S31A and G34R mice had drastically reduced survival (averaging 77, 81, and 100 days for S31A, G34R, and WT). Furthermore, most G34R and S31A mice developed HGG, while H3.3 WT mice remained tumor-free. Our work implicates CIN as a driver of H3.3 G34 mutant pHGG formation.

Toll-like receptors 2 and 4 differentially regulate the self-renewal and differentiation of spinal cord neural precursor cells

BackgroundToll-like receptors (TLRs) represent critical effectors in the host defense response against various pathogens; however, their known function during development has also highlighted a potential role in cell fate determination and neural differentiation. While glial cells and neural precursor cells (NPCs) of the spinal cord express both TLR2 and TLR4, their influence on self-renewal and cell differentiation remains incompletely described.MethodsTLR2, TLR4 knock-out and the wild type mice were employed for spinal cord tissue analysis and NPCs isolation at early post-natal stage. Sox2, FoxJ1 and Ki67 expression among others served to identify the undifferentiated and proliferative NPCs; GFAP, Olig2 and β-III-tubulin markers served to identify astrocytes, oligodendrocytes and neurons respectively after NPC spontaneous differentiation. Multiple comparisons were analyzed using one-way ANOVA, with appropriate corrections such as Tukey's post hoc tests used for comparisons.ResultsWe discovered that the deletion of TLR2 or TLR4 significantly reduced the number of Sox2-expressing NPCs in the neonatal mouse spinal cord. While TLR2-knockout NPCs displayed enhanced self-renewal, increased proliferation and apoptosis, and delayed neural differentiation, the absence of TLR4 promoted the neural differentiation of NPCs without affecting proliferation, producing long projecting neurons. TLR4 knock-out NPCs showed significantly higher expression of Neurogenin1, that would be involved in the activation of this neurogenic program by a ligand and microenvironment-independent mechanism. Interestingly, the absence of both TLR2 and TLR4, which induces also a significant reduction in the expression of TLR1, in NPCs impeded oligodendrocyte precursor cell maturation to a similar degree.ConclusionsOur data suggest that Toll-like receptors are needed to maintain Sox2 positive neural progenitors in the spinal cord, however possess distinct regulatory roles in mouse neonatal spinal cord NPCs—while TLR2 and TLR4 play a similar role in oligodendrocytic differentiation, they differentially influence neural differentiation.

Effect of Passage Number on Human Induced Pluripotent Stem Cell Derived Neurons Culture Contaminants with Non-Neuronal Cell Types

Background: The study of live human neurons has been hindered due to the complexity and potential irreversible damage to the patient during biopsy. However, reprogramming of adult human somatic cells into induced pluripotent stem cells (iPSCs) has proved to be a novel method in the study of the pathophysiology of disease and therapeutic targets of the human nervous system. There are several approaches, and the optimum time (i.e., passage number) to generate highly pure cultures is being studied. Therefore, our laboratory has investigated the effect of passage number on culture contaminants with non-neuronal cell types. 
 
 Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood from three cell lines and reprogrammed into iPSCs. Each cell line consisted of three samples that were analyzed after low (5-10), middle (20-26), and high (30-38) number of passages. Cells were maintained in an induction medium for eight days. On day nine, cells were dissociated and replated in a maintenance medium. On day 33, total RNA was extracted from cells. Normalized values for non-neuronal cell marker genes were compared using paired Student’s t-tests and two-way ANOVA, with the cell line and passage number as independent variables. P-values less than 0.05 were considered significant. 
 
 Results: Our results showed that lower passage number was associated with decreased astrocyte and chondrocyte marker expression. High passage number was associated with decreased oligodendrocyte and glial precursor marker expression. Of the fibroblast markers evaluated, there were similar trends of expression between all three groups. There was no significant difference in microglial cell marker gene expression between all three groups. 
 
 Conclusion and Potential Impact: Low gene expression suggests a purer culture. According to these results, as passage number increases, there is more contaminants with oligodendrocytes and glial precursor cells. Conversely, with low passage numbers, there are more contaminants with astrocytes and chondrocytes. Future studies will identify the impact of these non-neuronal contaminants and implications on research.

Phenotypical changes of satellite glial cells in a murine model of GM1 -gangliosidosis.

Satellite glial cells (SGCs) of dorsal root ganglia (DRG) react in response to various injuries in the nervous system. This study investigates reactive changes within SGCs in a murine model for GM1‐gangliosidosis (GM1). DRG of homozygous β‐galactosidase‐knockout mice and homozygous C57BL/6 wild‐type mice were investigated performing immunostaining on formalin‐fixed, paraffin‐embedded tissue. A marked upregulation of glial fibrillary acidic protein (GFAP), the progenitor marker nestin and Ki67 within SGCs of diseased mice, starting after 4 months at the earliest GFAP, along with intracytoplasmic accumulation of ganglioside within neurons and deterioration of clinical signs was identified. Interestingly, nestin‐positive SGCs were detected after 8 months only. No changes regarding inwardly rectifying potassium channel 4.1, 2, 3‐cyclic nucleotide 3‐phosphodiesterase, Sox2, doublecortin, periaxin and caspase3 were observed in SGCs. Iba1 was only detected in close vicinity of SGCs indicating infiltrating or tissue‐resident macrophages. These results indicate that SGCs of DRG show phenotypical changes during the course of GM1, characterized by GFAP upregulation, proliferation and expression of a neural progenitor marker at a late time point. This points towards an important role of SGCs during neurodegenerative disorders and supports that SGCs represent a multipotent glial precursor cell line with high plasticity and functionality.

CBIO-11. HISTONE H3.3 G34R/V MUTATIONS STIMULATE PEDIATRIC HIGH-GRADE GLIOMA FORMATION THROUGH THE INDUCTION OF CHROMOSOMAL INSTABILITY

Abstract H3.3 G34R/V mutations are drivers of high-grade pediatric glioma (pHGG). H3.3 G34R/V mutations are linked to altered H3.3 K36 trimethylation (H3K36me3); implicating epigenetic gene regulation as a possible contributor to pHGG formation. Here we show that H3.3 G34R/V also induces chromosomal instability (CIN); a hallmark of pHGG. If CIN promotes pHGG formation is unknown. We observed that H3.3 G34 mutant pHGG cells have reduced mitotic H3.3 S31 phosphorylation compare to WT H3.3 cell lines. And, H3.3 G34R reduced Chk1 phosphorylation at S31 by >90% in an in vitro kinase assay. Chk1 regulates chromosome segregation through phosphorylation of pericentromeric H3.3 S31 during early mitosis. Overexpression of H3.3 G34R or non-phosphorylatable S31A in H3.3 WT, diploid cells caused a significant increase in CIN. Likewise, H3.3 G34 mutant pHGG cells have significantly elevated rates of CIN as compare to H3.3 WT pHGG cells. During normal cell division, phospho-S31 is lost in anaphase. However, following chromosome missegregation, phospho-S31 spreads and stimulates p53-induced cell cycle arrest. Here we show that WT p53 cells expressing mutant G34 fail to arrest following chromosome mis-segregation. These studies demonstrate that H3.3 G34R/V mutations are sufficient to transform normal, diploid cells into proliferating CIN cells. To determine if this process contributes to tumorigenesis, we used RCAS Nestin-TVA mice to overexpress H3.3 WT, G34R, or S31A – P2A-linked to PDGFB expression in glial precursor cells of newborn mice. Over 100 days, S31A and G34R mice had drastically reduced survival (averaging 77, 81, and 100 days for S31A, G34R, and WT). Furthermore, most G34R and S31A mice developed HGG, while H3.3 WT mice remained tumor-free. Our work implicates CIN as a driver of H3.3 G34 mutant pHGG formation. Our ongoing studies utilize K36M and double mutants to further define the contributions of S31 phosphorylation (CIN) and H3K36me3 (epigenetic gene regulation) to tumorigenesis.

HGG-06. EARLY GABAERGIC NEURONAL LINEAGE DEFINES DEPENDENCIES IN HISTONE H3 G34R/V GLIOMA

High-grade gliomas harboring H3 G34R/V mutations exclusively occur in the cerebral hemispheres of adolescents and young adults, suggesting a distinct neurodevelopmental origin. Combining multimodal bulk and single-cell genomics with unbiased genome-scale CRISPR/Cas9 approaches, we here describe a GABAergic interneuron progenitor lineage as the most likely context from which these H3 G34R/V mutations drive gliomagenesis, conferring unique and tumor-selective gene targets essential for glioma cell survival, as validated genetically and pharmacologically. Phenotypically, we demonstrate that while H3 G34R/V glioma cells harbor the neurotransmitter GABA, they are developmentally stalled, and do not induce the neuronal hyperexcitability described in other glioma subtypes. These findings offer a striking counter-example to the prevailing view of glioma origins in glial precursor cells, resulting in distinct cellular, microenvironmental, and therapeutic consequences.

HGG-31. HISTONE H3.3 G34R/V MUTATIONS STIMULATE PEDIATRIC HIGH-GRADE GLIOMA FORMATION THROUGH THE INDUCTION OF CHROMOSOMAL INSTABILITY

The histone H3.3 G34R/V mutations are known drivers of high-grade pediatric glioma (pHGG). However, the mechanism(s) for H3.3 G34R/V induced tumor formation are unclear. Chk1 phosphorylates H3.3 S31 at the pericentromere during early mitosis, suggesting a novel mitotic function. We observed that H3.3 G34 mutant pHGG cells have reduced mitotic H3.3 S31 phosphorylation compare to WT H3.3 cell lines. The H3.3 G34R mutation reduced Chk1 phosphorylation at S31 by >90% in an in vitro kinase assay. Overexpression of either H3.3 G34R or non-phosphorylatable S31A in H3.3 WT, diploid cells led to a significant increase in chromosome mis-segregations. Likewise, H3.3 G34 mutant pHGG cells have significantly elevated rates of mis-segregation as compare to H3.3 WT pHGG cells. During normal cell division, phospho-S31 is lost in late anaphase. However, when chromosome missegregation occurs, phospho-S31 spreads and stimulates p53 accumulation in G1 – thus suppressing aneuploid cell proliferation. Here we show that cells expressing mutant G34 fail to arrest following mis-segregation, despite having WT p53. These studies demonstrate that the H3.3 G34R/V mutations are sufficient to transform normal, diploid cells into proliferative, chromosomally instable cells. To determine if this process contributes to tumorigenesis, we used the RCAS/TVA mouse model to overexpress H3.3 WT, G34R, or S31A in the glial precursor cells of mice pups. Over 100 days, S31A and G34R mice had drastically reduced survival (averaging 77, 81, and 100 days for S31A, G34R, and WT mice). Furthermore, most G34R and S31A mice developed HGG, while H3.3 WT mice remained tumor-free and did not develop high-grade tumors. Our work strongly indicates that a major factor in H3.3 G34R pHGG formation is the induction of chromosomal instability – which occurs directly through the suppression of H3.3 S31 phosphorylation.

Progressions on the Coexistence of Neuronal and Glial Precursor Cells in the Cerebral Ventricular Zone.

Heterogeneity is defined as the quality or state of being diverse in character or content. This article summarizes the natural progression from my studies, reported in the first issue of the Journal of Neuroscience, that identified molecular heterogeneity in precursor cells of the developing primate cerebral cortex to the current state in which differences defined at the molecular, cellular, circuit, and systems levels are building data encyclopedias. The emphasis on heterogeneity has impacted many contributors in the field of developmental neuroscience, who have led a quest to determine the extent to which there is diversity, when it appears developmentally, and what heritable and nonheritable factors mediate nervous system assembly and function. Since the appearance of the article on progenitor cell heterogeneity in the inaugural issue of the Journal of Neuroscience, there have been continuous advances in technologies and data analytics that are contributing to a much better understanding of the origins of neurobiological and behavioral heterogeneity.

Genetic Architectures and Cell-of-Origin in Glioblastoma.

An aggressive primary brain cancer, glioblastoma (GBM) is the most common cancer of the central nervous system in adults. However, an inability to identify its cell-of-origin has been a fundamental issue hindering further understanding of the nature and pathogenesis of GBM, as well as the development of novel therapeutic targets. Researchers have hypothesized that GBM arises from an accumulation of somatic mutations in neural stem cells (NSCs) and glial precursor cells that confer selective growth advantages, resulting in uncontrolled proliferation. In this review, we outline genomic perspectives on IDH-wildtype and IDH-mutant GBMs pathogenesis and the cell-of-origin harboring GBM driver mutations proposed by various GBM animal models. Additionally, we discuss the distinct neurodevelopmental programs observed in either IDH-wildtype or IDH-mutant GBMs. Further research into the cellular origin and lineage hierarchy of GBM will help with understanding the evolution of GBMs and with developing effective targets for treating GBM cancer cells.

Age-related loss of axonal regeneration is reflected by the level of local translation

Regeneration capacity is reduced as CNS axons mature. Using laser-mediated axotomy, proteomics and puromycin-based tagging of newly-synthesized proteins in a human embryonic stem cell-derived neuron culture system that allows isolation of axons from cell bodies, we show here that efficient regeneration in younger axons (d45 in culture) is associated with local axonal protein synthesis (local translation). Enhanced regeneration, promoted by co-culture with human glial precursor cells, is associated with increased axonal synthesis of proteins, including those constituting the translation machinery itself. Reduced regeneration, as occurs with the maturation of these axons by d65 in culture, correlates with reduced levels of axonal proteins involved in translation and an inability to respond by increased translation of regeneration promoting axonal mRNAs released from stress granules. Together, our results provide evidence that, as in development and in the PNS, local translation contributes to CNS axon regeneration.

The Strange Case of Jekyll and Hyde: Parallels Between Neural Stem Cells and Glioblastoma-Initiating Cells.

During embryonic development, radial glial precursor cells give rise to neural lineages, and a small proportion persist in the adult mammalian brain to contribute to long-term neuroplasticity. Neural stem cells (NSCs) reside in two neurogenic niches of the adult brain, the hippocampus and the subventricular zone (SVZ). NSCs in the SVZ are endowed with the defining stem cell properties of self-renewal and multipotent differentiation, which are maintained by intrinsic cellular programs, and extrinsic cellular and niche-specific interactions. In glioblastoma, the most aggressive primary malignant brain cancer, a subpopulation of cells termed glioblastoma stem cells (GSCs) exhibit similar stem-like properties. While there is an extensive overlap between NSCs and GSCs in function, distinct genetic profiles, transcriptional programs, and external environmental cues influence their divergent behavior. This review highlights the similarities and differences between GSCs and SVZ NSCs in terms of their gene expression, regulatory molecular pathways, niche organization, metabolic programs, and current therapies designed to exploit these differences.

Glial restricted precursor cells in central nervous system disorders: Current applications and future perspectives.

The crosstalk between glial cells and neurons represents an exceptional feature for maintaining the normal function of the central nervous system (CNS). Increasing evidence has revealed the importance of glial progenitor cells in adult neurogenesis, reestablishment of cellular pools, neuroregeneration, and axonal (re)myelination. Several types of glial progenitors have been described, as well as their potentialities for recovering the CNS from certain traumas or pathologies. Among these precursors, glial-restricted precursor cells (GRPs) are considered the earliest glial progenitors and exhibit tripotency for both Type I/II astrocytes and oligodendrocytes. GRPs have been derived from embryos and embryonic stem cells in animal models and have maintained their capacity for self-renewal. Despite the relatively limited knowledge regarding the isolation, characterization, and function of these progenitors, GRPs are promising candidates for transplantation therapy and reestablishment/repair of CNS functions in neurodegenerative and neuropsychiatric disorders, as well as in traumatic injuries. Herein, we review the definition, isolation, characterization and potentialities of GRPs as cell-based therapies in different neurological conditions. We briefly discuss the implications of using GRPs in CNS regenerative medicine and their possible application in a clinical setting. MAIN POINTS: GRPs are progenitors present in the CNS with differentiation potential restricted to the glial lineage. These cells have been employed in the treatment of a myriad of neurodegenerative and traumatic pathologies, accompanied by promising results, herein reviewed.

Identification of Qk as a Glial Precursor Cell Marker that Governs the Fate Specification of Neural Stem Cells to a Glial Cell Lineage.

SummaryDuring brain development, neural stem cells (NSCs) initially produce neurons and change their fate to generate glias. While the regulation of neurogenesis is well characterized, specific markers for glial precursor cells (GPCs) and the master regulators for gliogenesis remain unidentified. Accumulating evidence suggests that RNA-binding proteins (RBPs) have significant roles in neuronal development and function, as they comprehensively regulate the expression of target genes in a cell-type-specific manner. We systematically investigated the expression profiles of 1,436 murine RBPs in the developing mouse brain and identified quaking (Qk) as a marker of the putative GPC population. Functional analysis of the NSC-specific Qk-null mutant mouse revealed the key role of Qk in astrocyte and oligodendrocyte generation and differentiation from NSCs. Mechanistically, Qk upregulates gliogenic genes via quaking response elements in their 3′ untranslated regions. These results provide crucial directions for identifying GPCs and deciphering the regulatory mechanisms of gliogenesis from NSCs.

Profile of MIF in Developing Hippocampus: Association With Cell Proliferation and Neurite Outgrowth.

Proinflammatory cytokine macrophage migration inhibitory factor (MIF) is a multifunctional cytokine and has been found involved in many neurological diseases such as Alzheimer disease (AD), epilepsy, and multiple sclerosis. Previous studies have shown that MIF is expressed in neocortex, hippocampus, hypothalamus, cerebellum, and spinal cord in adult mice. It is expressed by astrocytes and activates microglias in neuroinflammation. Further studies have shown that MIF is detected in moss fibers of dentate granule cells and in apical dendrites of pyramidal neurons in adult hippocampus. Only NeuroD-positive immature granule neurons but not NeuN-positive mature neurons express MIF. These findings led us eager to know the exact role of MIF in the development of hippocampus. Therefore, we systematically checked the spatial and temporal expression pattern of MIF and characterized MIF-positive cells in hippocampus from mice aged from postnatal day 0 (P0) to 3 months. Our results showed that the lowest level of MIF protein occurred at P7 and mif mRNA increased from P0, reached a peak at P7, and stably expressed until P30 before declining dramatically at 3 months. MIF was localized in fibers of GFAP- and BLBP-positive radial glial precursor cells in dentate gyrus (DG). DCX-expressing newly generated neurons were MIF-negative. Inhibition of MIF by MIF antagonist S, R-3-(4-hydroxyphenyl)-4, 5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) reduced BrdU-positive cells. Interestingly, MIF was expressed by NeuN-positive GABAergic interneurons including parvalbumin-and Reelin-expressing cells in the DG. Neither NeuN-positive granule cells nor NeuN-positive pyramidal neurons expressed MIF. In transgenic mice, POMC-EGFP–positive immature dentate granule cells and Thy1-EGFP–positive mature granule cells were MIF-negative. Treatment of neuronal cultures with ISO-1 inhibited neurite outgrowth. Therefore, we conclude that MIF might be important for feature maintenance of neural stem cells and neurite outgrowth during hippocampal development.

Long Noncoding RNA Expression Profiling During the Neuronal Differentiation of Glial Precursor Cells from Rat Dorsal Root Ganglia

Long noncoding RNAs (lncRNAs) play important roles in the process of cell fate determination. However, their function and expression profiles have not yet been systematically investigated during the transdifferentiation of glial precursor cells derived from dorsal root ganglia (DRG) in the peripheral nervous system. Our results demonstrated significant differences in gene architecture and expression among the three transcript types (lncRNA, mRNA, and TUCP). Distinct differences in transcript length, exon number, and ORF length were identified between lncRNAs and mRNAs after comparative analysis of their structure and sequence conservation. We found that the upregulated lncRNAs outnumbered the downregulated lncRNAs in glial precursor cells cultured with proBDNF antiserum compared with the levels in glial precursor cells cultured without proBDNF antiserum. By a series of GO and KEGG analyses, we found that the effects of some lncRNAs on their target genes in cis were related to nerve growth factor-induced cell cycle, cell phenotype change, and neuronal differentiation. The qRT-PCR verification results of lncRNAs ENSRNOT00000091991, ENSRNOT00000087717, and LNC000429 were mostly consistent with the sequencing results. The candidate lncRNAs may be associated with the neuronal transdifferentiation of glial precursor cells. Our study provides the first evidence for a remarkably diverse pattern of lncRNA expression during neuronal differentiation of glial precursor cells from rat DRG and also provides a resource for lncRNA studies in the field of cell differentiation.

IPL Sublamination in Chicken Retinal Spheroids Is Initiated via Müller Cells and Cholinergic Differentiation, and Is Disrupted by NMDA Signaling.

Reaggregates from E6 embryonic chicken retina exhibit areas corresponding to an inner plexiform layer (IPL), which presents an ideal in vitro model to test conditions and constraints of cholinergic and glutamatergic network formation, providing a basis for retinal tissue engineering. Here, we show that ipl formation is regulated by cholinergic starburst amacrine cells (SACs), a glial scaffold and by L-glutamate. Rosetted spheroids were cultured in absence or presence of 0.2 to 0.4 mM L-glutamate and analyzed by immuno- and enzyme histochemistry, proliferation, and apoptosis assays. After 2 days in vitro (div), ipl formation was announced by acetylcholinesterase+ (AChE) and choline acetyltransferase+ (ChAT) cells. Individual vimentin+ or transitin+ Müller glial cell precursors (MCPs) in ipl centers coexpressed ChAT. Comparable to in vivo, pairwise arranged ChAT+ SACs formed two laminar subbands. Projections of calretinin+ amacrine cells (ACs) into ipl associated with MCP processes. In L-glutamate-, or NMDA-treated spheroids ipls were disrupted, including loss of SACs and MCs; coincubation with NMDA receptor inhibitor MK-801 prevented these effects. Also, many Pax6+ cells, comprising most ACs, were lost, while rho4D2+ rod photoreceptors were increased. Cell proliferation was slightly increased, while apoptosis remained unaffected. This demonstrated: (1) a far-advanced differentiation of an IPL in retinal spheroids, as never described before; (2) ipl sublamination was initiated by cholinergic precursor cells, which-functioning as "ipl founder cells"-(3) gave rise to neurons and glial cells; (4) these SACs and MCPs together organized ipl formation; and (5) this process was counteracted by NMDA-dependent glutamate actions.