Musashi1: an evolutionally conserved marker for CNS progenitor cells including neural stem cells

Dissecting RNA selectivity mediated by tandem RNA-binding domains

RNA-protein interactions are pivotal to proper gene regulation. Many RNA-binding proteins possess multiple RNA-binding domains; however, how these domains interplay to select and regulate RNA targets remains poorly understood. Here, we investigate three multidomain proteins, Musashi-1, Musashi-2, and unkempt, which share a high degree of RNA specificity, a common feature across RNA-binding proteins. We used massively parallel in vitro assays with unprecedented depth with random or naturally derived RNA sequences and find that individual domains within a protein can have differing affinities, specificities, and motif spacing preferences. We conducted large scale competition assays between these proteins and determined how individual protein specificities and affinities influence competitive binding. Integration of binding and regulation in cells with in vitro specificities showed that target selection involves a combination of the protein intrinsic specificities described here, but cellular context is critical to drive these proteins to motifs in specific transcript regions. Finally, evolutionarily conserved RNA regions displayed evidence of binding multiple RBPs in cultured cells, and these RNA regions represent the highest affinity targets. This work emphasizes the importance of in vitro and in cultured cells studies to fully profile RNA-binding proteins and highlights the complex modes of RNA-protein interactions and the contributing factors in target selection.

Comparative Analysis of Localization and Composition of Adult Neurogenic Niches in the Chondrichthyans Raja asterias and Torpedo ocellata

Adult neurogenesis in cartilaginous fish remains a relatively unexplored area, particularly in terms of comparative analysis. This process, defined as the ability of specialized stem cells to generate new functional neurons, has gained prominence due to its relevance in neurodegenerative disease research and regenerative medicine. However, there is an ongoing discussion about when and where it first appeared. Evidence of adult neurogenesis in both teleosts and mammals highlights significant differences, such as the number of newly formed cells and the brain regions involved. Investigating additional cartilaginous fish species, which occupy a basal position in vertebrate phylogeny, could provide valuable insights into the ancient origins of this trait and potentially new general knowledge about the adult neurogenesis process. In this study, we combined immunohistochemistry and in situ hybridization to examine neurogenic activity in three brain regions-the telencephalon, mesencephalon, and cerebellum-of two batoid species: Raja asterias and Torpedo ocellata. Immunohistochemical methods were used to identify neurogenic cells by employing markers for cell proliferation (PCNA), mitosis (pH3), glial cells (S100B), and stem cells (Msi1). Additionally, in situ hybridization was performed to detect neural stem cell mRNA for Notch1, Notch3, and Sox2 in the telencephalon and mesencephalon of Raja asterias.

Pathogenic oligomeric Tau alters neuronal RNA processes through the formation of nuclear heteromeric amyloids with RNA-binding protein Musashi1

Alzheimer's disease (AD) is marked by cytoplasmic proteinopathies, primarily involving misfolded Tau protein. Pathogenic Tau species, such as soluble oligomers and fibrils, disrupt RNA metabolism, though the mechanisms are unclear. Recent research indicates that RNA has a crucial role in Tau aggregation. Our study builds on this by noting significant co-deposition of RNA-Binding Proteins (RBPs) with Tau in AD and Frontotemporal dementia (FTLD) brains. Using molecular and cellular techniques, we investigate the interaction between RNA dynamics and Tau aggregation, focusing on the localization and aggregation of Tau and RBPs, particularly Musashi (MSI), within neuronal nuclei. Through cyto-fluorometric, biochemical, and cellular assays, we reveal the importance of Tau/RBP interplay in primary cortical neurons expressing wild-type and mutant Tau. Pathogenic Tau oligomers alter MSI protein localization and function, causing cytoplasmic and nuclear aggregation. Mass spectrometry of the MSI1 nuclear interactome in Tau models shows disrupted RNA metabolism pathways, including ribosomal biogenesis, RNA splicing, and protein folding. Moreover, RNA immunoprecipitation assay revealed a remarkable impact of mutant P301L Tau on MSI1 ability to bind RNA targets. These findings highlight potential targets for early neurodegenerative therapeutic interventions.

The function and mechanism of circRNAs in 5-fluorouracil resistance in tumors: Biological mechanisms and future potential

5-Fluorouracil (5-FU) is a well-known chemotherapy drug extensively used in the treatment of breast cancer. It works by inhibiting cancer cell proliferation and inducing cell death through direct incorporation into DNA and RNA via thymidylate synthase (TS). Circular RNAs (circRNAs), a novel family of endogenous non-coding RNAs (ncRNAs) with limited protein-coding potential, contribute to 5-FU resistance. Their identification and targeting are crucial for enhancing chemosensitivity. CircRNAs can regulate tumor formation and invasion by adhering to microRNAs (miRNAs) and interacting with RNA-binding proteins, regulating transcription and translation. MiRNAs can influence enzymes responsible for 5-FU metabolism in cancer cells, affecting their sensitivity or resistance to the drug. In the context of 5-FU resistance, circRNAs can target miRNAs and regulate biological processes such as cell proliferation, cell death, glucose metabolism, hypoxia, epithelial-to-mesenchymal transition (EMT), and drug efflux. This review focuses on the function of circRNAs in 5-FU resistance, discussing the underlying molecular pathways and biological mechanisms. It also presents recent circRNA/miRNA-targeted cancer therapeutic strategies for future clinical application.

RNA-binding MSI proteins and their related cancers: A medicinal chemistry perspective

Musashi1 and Musashi2 are RNA-binding proteins originally found in drosophila, in which they play a crucial developmental role. These proteins are pivotal in the maintenance and differentiation of stem cells in other organisms. Research has confirmed that the Musashi proteins are highly involved in cell signal-transduction pathways such as Notch and TGF-β. These signaling pathways are related to the induction and development of cancers, such as breast cancer, leukemia, hepatoma and liver cancer. In this review we focus on how Musashi proteins interact with molecules in different signaling pathways in various cancers and how they affect the physiological functions of these pathways. We further illustrate the status quo of Musashi proteins-targeted therapies and predict the target RNA regions that Musashi proteins interact with, in the hope of exploring the prospect of the design of Musashi protein-targeted medicines.

Establishing Brain Tumor Stem Cell Culture from Patient Brain Tumors and Imaging Analysis of Patient-Derived Xenografts

Brain tumor stem cells (BTSCs) have been isolated from different types of brain tumors including glioblastoma. Although BTSCs share common characteristics with neural stem cells (NSCs), such as capacity to self-renew and undergo long-term proliferation, they have tumor-propagating capabilities. A small population of BTSC can give rise to secondary tumor when transplanted into severe immunodeficient (SCID) mice. The histological and cytological features, as well as genetic heterogeneity of the xenografted tumors in mice, closely resemble those of primary tumors in patients. Patient-derived xenografts (PDX), therefore, provide a clinically relevant model to study brain tumors. Here, we describe our protocol for establishing BTSC cultures following surgical excision of human brain tumors and the procedures to conduct PDX studies in SCID mice. We also provide our detailed step-by-step protocol on in vivo imaging system (IVIS) of the PDX tumors as a noninvasive method to trace the cells and tumor volume.

Advances of Genome Editing with CRISPR/Cas9 in Neurodegeneration: The Right Path towards Therapy

The rate of neurodegenerative disorders (NDDs) is rising rapidly as the world's population ages. Conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), and dementia are becoming more prevalent and are now the fourth leading cause of death, following heart disease, cancer, and stroke. Although modern diagnostic techniques for detecting NDDs are varied, scientists are continuously seeking new and improved methods to enable early and precise detection. In addition to that, the present treatment options are limited to symptomatic therapy, which is effective in reducing the progression of neurodegeneration but lacks the ability to target the root cause-progressive loss of neuronal functioning. As a result, medical researchers continue to explore new treatments for these conditions. Here, we present a comprehensive summary of the key features of NDDs and an overview of the underlying mechanisms of neuroimmune dysfunction. Additionally, we dive into the cutting-edge treatment options that gene therapy provides in the quest to treat these disorders.

Sbp2l contributes to oligodendrocyte maturation through translational control in Tcf7l2 signaling

Oligodendrocytes (OLs) are the myelin-forming cells in the CNS that support neurons through the insulating sheath of axons. This unique feature and developmental processes are achieved by extrinsic and intrinsic gene expression programs, where RNA-binding proteins can contribute to dynamic and fine-tuned post-transcriptional regulation. Here, we identified SECIS-binding protein 2-like (Sbp2l), which is specifically expressed in OLs by integrated transcriptomics. Histological analysis revealed that Sbp2l is a molecular marker of OL maturation. Sbp2l knockdown (KD) led to suppression of matured OL markers, but not a typical selenoprotein, Gpx4. Transcriptome analysis demonstrated that Sbp2l KD decreased cholesterol-biosynthesis-related genes regulated by Tcf7l2 transcription factor. Indeed, we confirmed the downregulation of Tcf7l2 protein without changing its mRNA in Sbp2l KD OPCs. Furthermore, Sbp2l KO mice showed the decrease of Tcf7l2 protein and deficiency of OL maturation. These results suggest that Sbp2l contributes to OL maturation by translational control of Tcf7l2.

Musashi-1 regulates cell cycle and confers resistance to cisplatin treatment in Group 3/4 medulloblastomas cells

Groups (Grp) 3 and 4 are aggressive molecular subgroups of medulloblastoma (MB), with high rates of leptomeningeal dissemination. To date, there is still a paucity of biomarkers for these subtypes of MBs. In this study, we investigated the clinical significance and biological functions of Musashi-1 (MSI1) in Grp3 and Grp4-MBs. First, we assessed the expression profile of MSI1 in 59 primary MB samples (15-WNT, 18-SHH, 9-Grp3, and 17-Grp4 subgroups) by qRT-PCR. MSI1 mRNA expression levels were also validated in an additional public dataset of MBs (GSE85217). The ROC curve was used to validate the diagnostic standards of MSI1 expression. Next, the potential correlated cell-cycle genes were measured by RNA-Seq. Cell cycle, cell viability, and apoptosis were evaluated in a Grp3/Grp4 MB cell line after knockdown of MSI1 and cisplatin treatment. We identified an overexpression of MSI1 with a high accuracy to discriminate Grp3/Grp4-MBs from non-Grp3/Grp4-MBs. We identified that MSI1 knockdown not only triggered transcriptional changes in the cell-cycle pathway, but also affected G2/M phase in vitro, supporting the role of knockdown of MSI1 in cell-cycle arrest. Finally, MSI1 knockdown decreased cell viability and sensitized D283-Med cells to cisplatin treatment by enhancing cell apoptosis. Based on these findings, we suggest that MSI1 modulates cell-cycle progression and may play a role as biomarker for Grp3/Grp4-MBs. In addition, MSI1 knockdown combined with cisplatin may offer a potential strategy to be further explored in Grp3/Grp4-MBs.

Short C-terminal Musashi-1 proteins regulate pluripotency states in embryonic stem cells

The RNA-binding protein Musashi-1 (MSI1) regulates the proliferation and differentiation of adult stem cells. However, its role in embryonic stem cells (ESCs) and early embryonic development remains poorly understood. Here, we report the presence of short C-terminal MSI1 (MSI1-C) proteins in early mouse embryos and mouse ESCs, but not in human ESCs, under conventional culture conditions. In mouse embryos and mESCs, deletion of MSI1-C together with full-length MSI1 causes early embryonic developmental arrest and pluripotency dissolution. MSI1-C is induced upon naive induction and facilitates hESC naive pluripotency acquisition, elevating the pluripotency of primed hESCs toward a formative-like state. MSI1-C proteins are nuclear localized and bind to RNAs involved in DNA-damage repair (including MLH1, BRCA1, and MSH2), conferring on hESCs better survival in human-mouse interspecies cell competition and prolonged ability to form blastoids. This study identifies MSI1-C as an essential regulator in ESC pluripotency states and early embryonic development.

Perturbations in neural stem cell function during a neurotropic viral infection in juvenile mice

Viral infections of the central nervous system (CNS) often cause worse neurological outcomes in younger hosts. Throughout childhood, the brain undergoes extensive development and refinement to produce functional neural networks. Network function is maintained partly with the help of neural stem cells (NSCs) that replace neuronal and glia subtypes in the two neurogenic niches of the brain (the hippocampus and subventricular zone). Accumulating evidence suggests that viruses disrupt NSC function in adulthood and infancy, but the in vivo impact of childhood infections on acute and long-term NSC function is unknown. Using a juvenile mouse model of measles virus (MeV) infection, where only mature neurons in the brain are infected, we defined the effects of the antiviral immune response on NSCs from juvenile to adult stages of life. We found that (a) virus persists in the brains of survivors despite an anti-viral immune response; (b) NSC numbers decrease dramatically during early infection, but ultimately stabilize in adult survivors; (c) infection is associated with mild apoptosis throughout the juvenile brain, but NSC proliferation is unchanged; (d) the loss of NSC numbers is dependent upon the stage of NSC differentiation; and (e) immature neurons increase early during infection, concurrent with depletion of NSC pools. Collectively, we show that NSCs are exquisitely sensitive to the inflammatory microenvironment created during neuron-restricted MeV infection in juveniles, responding with an early loss of NSCs but increased neurogenesis. These studies provide insight into potential cellular mechanisms associated with long-term neurological deficits in survivors of childhood CNS infections.

The Musashi RNA-binding proteins in female cancers: insights on molecular mechanisms and therapeutic relevance

RNA-binding proteins have increasingly been identified as important regulators of gene expression given their ability to bind distinct RNA sequences and regulate their fate. Mounting evidence suggests that RNA-binding proteins are involved in the onset and progression of multiple malignancies, prompting increasing interest in their potential for therapeutic intervention.The Musashi RNA binding proteins Musashi-1 and Musashi-2 were initially identified as developmental factors of the nervous system but have more recently been found to be ubiquitously expressed in physiological tissues and may be involved in pathological cell behavior. Both proteins are increasingly investigated in cancers given dysregulation in multiple tumor entities, including in female malignancies. Recent data suggest that the Musashi proteins serve as cancer stem cell markers as they contribute to cancer cell proliferation and therapy resistance, prompting efforts to identify mechanisms to target them. However, as the picture remains incomplete, continuous efforts to elucidate their role in different signaling pathways remain ongoing.In this review, we focus on the roles of Musashi proteins in tumors of the female - breast, endometrial, ovarian and cervical cancer - as we aim to summarize current knowledge and discuss future perspectives.

Neurogenic Stem Cell Niche in the Auditory Thalamus: In Vitro Evidence of Neural Stem Cells in the Rat Medial Geniculate Body

The medial geniculate body (MGB) is a nucleus of the diencephalon representing a relevant segment of the auditory pathway and is part of the metathalamus. It receives afferent information via the inferior brachium of the inferior colliculus and transmits efferent fibers via acoustic radiations to the auditory cortex. Neural stem cells (NSCs) have been detected in certain areas along the auditory pathway. They are of great importance as the induction of an adult stem cell niche might open a regenerative approach to a causal treatment of hearing disorders. Up to now, the existence of NSCs in the MGB has not been determined. Therefore, this study investigated whether the MGB has a neural stem cell potential. For this purpose, cells were extracted from the MGB of PND 8 Sprague-Dawley rats and cultured in a free-floating cell culture assay, which showed mitotic activity and positive staining for stem cell and progenitor markers. In differentiation assays, the markers β-III-tubulin, GFAP, and MBP demonstrated the capacity of single cells to differentiate into neuronal and glial cells. In conclusion, cells from the MGB exhibited the cardinal features of NSCs: self-renewal, the formation of progenitor cells, and differentiation into all neuronal lineage cells. These findings may contribute to a better understanding of the development of the auditory pathway.

Effect of 3D Spheroid Culturing on NF-κB Signaling Pathway and Neurogenic Potential in Human Amniotic Fluid Stem Cells

Human amniotic fluid stem cells (hAFSCs) are known for their advantageous properties when compared to somatic stem cells from other sources. Recently hAFSCs have gained attention for their neurogenic potential and secretory profile. However, hAFSCs in three-dimensional (3D) cultures remain poorly investigated. Therefore, we aimed to evaluate cellular properties, neural differentiation, and gene and protein expression in 3D spheroid cultures of hAFSCs in comparison to traditional two-dimensional (2D) monolayer cultures. For this purpose, hAFSCs were obtained from amniotic fluid of healthy pregnancies and cultivated in vitro, either in 2D, or 3D under untreated or neuro-differentiated conditions. We observed upregulated expression of pluripotency genes OCT4, NANOG, and MSI1 as well as augmentation in gene expression of NF-κB-TNFα pathway genes (NFKB2, RELA and TNFR2), associated miRNAs (miR103a-5p, miR199a-3p and miR223-3p), and NF-κB p65 protein levels in untreated hAFSC 3D cultures. Additionally, MS analysis of the 3D hAFSCs secretome revealed protein upregulation of IGFs signaling the cascade and downregulation of extracellular matrix proteins, whereas neural differentiation of hAFSC spheroids increased the expression of SOX2, miR223-3p, and MSI1. Summarizing, our study provides novel insights into how 3D culture affects neurogenic potential and signaling pathways of hAFSCs, especially NF-κB, although further studies are needed to elucidate the benefits of 3D cultures more thoroughly.

MiMIC analysis reveals an isoform specific role for Drosophila Musashi in follicle stem cell maintenance and escort cell function

The Drosophila ovary is regenerated from germline and somatic stem cell populations that have provided fundamental conceptual understanding on how adult stem cells are regulated within their niches. Recent ovarian transcriptomic studies have failed to identify mRNAs that are specific to follicle stem cells (FSCs), suggesting that their fate may be regulated post-transcriptionally. We have identified that the RNA-binding protein, Musashi (Msi) is required for maintaining the stem cell state of FSCs. Loss of msi function results in stem cell loss, due to a change in differentiation state, indicated by upregulation of Lamin C in the stem cell population. In msi mutant ovaries, Lamin C upregulation was also observed in posterior escort cells that interact with newly formed germ cell cysts. Mutant somatic cells within this region were dysfunctional, as evidenced by the presence of germline cyst collisions, fused egg chambers and an increase in germ cell cyst apoptosis. The msi locus produces two classes of mRNAs (long and short). We show that FSC maintenance and escort cell function specifically requires the long transcripts, thus providing the first evidence of isoform-specific regulation in a population of Drosophila epithelial cells. We further demonstrate that although male germline stem cells have previously been shown to require Msi function to prevent differentiation this is not the case for female germline stem cells, indicating that these similar stem cell types have different requirements for Msi, in addition to the differential use of Msi isoforms between soma and germline. In summary, we show that different isoforms of the Msi RNA-binding protein are expressed in specific cell populations of the ovarian stem cell niche where Msi regulates stem cell differentiation, niche cell function and subsequent germ cell survival and differentiation.

RNA splicing regulators play critical roles in neurogenesis

Alternative RNA splicing increases transcript diversity in different cell types and under varying conditions. It is executed with the help of RNA splicing regulators (RSRs), which are operationally defined as RNA-binding proteins (RBPs) that regulate alternative splicing, but not directly catalyzing the chemical reactions of splicing. By systematically searching for RBPs and manually identifying those that regulate splicing, we curated 305 RSRs in the human genome. Surprisingly, most of the RSRs are involved in neurogenesis. Among these RSRs, we focus on nine families (PTBP, NOVA, RBFOX, ELAVL, CELF, DBHS, MSI, PCBP, and MBNL) that play essential roles in the neurogenic pathway. A better understanding of their functions will provide novel insights into the role of splicing in brain development, health, and disease. This comprehensive review serves as a stepping-stone to explore the diverse and complex set of RSRs as fundamental regulators of neural development. This article is categorized under: RNA-Based Catalysis > RNA Catalysis in Splicing and Translation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Processing > Splicing Regulation/Alternative Splicing.

Neurogenesis during Brittle Star Arm Regeneration Is Characterised by a Conserved Set of Key Developmental Genes

Simple Summary

Injuries to the central nervous system most often lead to irreversible damage in humans. Brittle stars are marine animals related to sea stars and sea urchins, and are one of our closest evolutionary relatives among invertebrates. Extraordinarily, they can perfectly regenerate their nerves even after completely severing the nerve cord after arm amputation. Understanding what genes and cellular mechanisms are used for this natural repair process in the brittle star might lead to new insights to guide strategies for therapeutics to improve outcomes for central nervous system injuries in humans.

Abstract

Neural regeneration is very limited in humans but extremely efficient in echinoderms. The brittle star Amphiura filiformis can regenerate both components of its central nervous system as well as the peripheral system, and understanding the molecular mechanisms underlying this ability is key for evolutionary comparisons not only within the echinoderm group, but also wider within deuterostomes. Here we characterise the neural regeneration of this brittle star using a combination of immunohistochemistry, in situ hybridization and Nanostring nCounter to determine the spatial and temporal expression of evolutionary conserved neural genes. We find that key genes crucial for the embryonic development of the nervous system in sea urchins and other animals are also expressed in the regenerating nervous system of the adult brittle star in a hierarchic and spatio-temporally restricted manner.

Optimal therapeutic conditions for the neural stem cell-based management of ischemic stroke: a systematic review and network meta-analysis based on animal studies

BACKGROUND

In order to promote the clinical translation of preclinical findings, it is imperative to identify the most optimal therapeutic conditions and adopt them for further animal and human studies. This study aimed to fully explore the optimal conditions for neural stem cell (NSC)-based ischemic stroke treatment based on animal studies.

METHODS

The PubMed, Ovid-Embase, and Web of Science databases were searched in December 2021. The screening of search results, extraction of relevant data, and evaluation of study quality were performed independently by two reviewers.

RESULTS

In total, 52 studies were included for data analysis. Traditional meta-analysis showed that NSCs significantly reduced the modified neurological severity score (mNSS) and volume of cerebral infarct in animal models of ischemic stroke. Network meta-analysis showed that allogeneic embryonic tissue was the best source of NSCs. Further, intracerebral transplantation was the most optimal route of NSC transplantation, and the acute phase was the most suitable stage for intervention. The optimal number of NSCs for transplantation was 1-5×10⁵ in mouse models and 1×10⁶ or 1.8×10⁶ in rat models.

CONCLUSIONS

We systematically explored the therapeutic strategy of NSCs in ischemic stroke, but additional research is required to develop optimal therapeutic strategies based on NSCs. Moreover, it is necessary to further improve and standardize the design, implementation, measuring standards, and reporting of animal-based studies to promote the development of better animal experiments and clinical research.

Emerging Roles of RNA-Binding Proteins in Neurodevelopment

Diverse cell types in the central nervous system (CNS) are generated by a relatively small pool of neural stem cells during early development. Spatial and temporal regulation of stem cell behavior relies on precise coordination of gene expression. Well-studied mechanisms include hormone signaling, transcription factor activity, and chromatin remodeling processes. Much less is known about downstream RNA-dependent mechanisms including posttranscriptional regulation, nuclear export, alternative splicing, and transcript stability. These important functions are carried out by RNA-binding proteins (RBPs). Recent work has begun to explore how RBPs contribute to stem cell function and homeostasis, including their role in metabolism, transport, epigenetic regulation, and turnover of target transcripts. Additional layers of complexity are provided by the different target recognition mechanisms of each RBP as well as the posttranslational modifications of the RBPs themselves that alter function. Altogether, these functions allow RBPs to influence various aspects of RNA metabolism to regulate numerous cellular processes. Here we compile advances in RNA biology that have added to our still limited understanding of the role of RBPs in neurodevelopment.

Differences in stem cell marker and osteopontin expression in primary and recurrent glioblastoma

Background

Despite of a multimodal approach, recurrences can hardly be prevented in glioblastoma. This may be in part due to so called glioma stem cells. However, there is no established marker to identify these stem cells.

Methods

Paired samples from glioma patients were analyzed by immunohistochemistry for expression of the following stem cell markers: CD133, Musashi, Nanog, Nestin, octamer-binding transcription factor 4 (Oct4), and sex determining region Y-box 2 (Sox2). In addition, the expression of osteopontin (OPN) was investigated. The relative number of positively stained cells was determined. By means of Kaplan–Meier analysis, a possible association with overall survival by marker expression was investigated.

Results

Sixty tissue samples from 30 patients (17 male, 13 female) were available for analysis. For Nestin, Musashi and OPN a significant increase was seen. There was also an increase (not significant) for CD133 and Oct4. Patients with mutated Isocitrate Dehydrogenase-1/2 (IDH-1/2) status had a reduced expression for CD133 and Nestin in their recurrent tumors. Significant correlations were seen for CD133 and Nanog between OPN in the primary and recurrent tumor and between CD133 and Nestin in recurrent tumors. By confocal imaging we could demonstrate a co-expression of CD133 and Nestin within recurrent glioma cells. Patients with high CD133 expression had a worse prognosis (22.6 vs 41.1 months, p = 0.013). A similar trend was seen for elevated Nestin levels (24.9 vs 41.1 months, p = 0.08).

Conclusions

Most of the evaluated markers showed an increased expression in their recurrent tumor. CD133 and Nestin were associated with survival and are candidate markers for further clinical investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02510-4.

The Fine Art of Writing a Message: RNA Metabolism in the Shaping and Remodeling of the Nervous System

Neuronal morphogenesis, integration into circuits, and remodeling of synaptic connections occur in temporally and spatially defined steps. Accordingly, the expression of proteins and specific protein isoforms that contribute to these processes must be controlled quantitatively in time and space. A wide variety of post-transcriptional regulatory mechanisms, which act on pre-mRNA and mRNA molecules contribute to this control. They are thereby critically involved in physiological and pathophysiological nervous system development, function, and maintenance. Here, we review recent findings on how mRNA metabolism contributes to neuronal development, from neural stem cell maintenance to synapse specification, with a particular focus on axon growth, guidance, branching, and synapse formation. We emphasize the role of RNA-binding proteins, and highlight their emerging roles in the poorly understood molecular processes of RNA editing, alternative polyadenylation, and temporal control of splicing, while also discussing alternative splicing, RNA localization, and local translation. We illustrate with the example of the evolutionary conserved Musashi protein family how individual RNA-binding proteins are, on the one hand, acting in different processes of RNA metabolism, and, on the other hand, impacting multiple steps in neuronal development and circuit formation. Finally, we provide links to diseases that have been associated with the malfunction of RNA-binding proteins and disrupted post-transcriptional regulation.

TNF-α up-regulates Nanog by activating NF-κB pathway to induce primary rat spinal cord astrocytes dedifferentiation

AIMS

Astrocytes re-acquire stem cell potential upon inflammation, thereby becoming a promising source of cells for regenerative medicine. Nanog is an essential transcription factor to maintain the characteristics of stem cells. We aimed to investigate the role of Nanog in astrocyte dedifferentiation.

MAIN METHODS

TNF-α was used to induce the dedifferentiation of primary rat spinal cord astrocytes. The expression of immature markers CD44 and Musashi-1 was detected by qRT-PCR and immunofluorescence. The Nanog gene is knocked down by small interference RNA. Nanog expression was measured by qRT-PCR and western blotting. BAY 11-7082 was used to suppress NF-κB signals in astrocytes. NF-κB signaling was evaluated by Western blotting.

KEY FINDINGS

Our results showed that TNF-α promoted the re-expression of CD44 and Musashi-1 in astrocytes. Dedifferentiated astrocytes could be induced to differentiate into oligodendrocyte lineage cells indicating that the astrocytes had pluripotency. In addition, TNF-α treatment activated NF-κB signaling pathway and up-regulated Nanog. Knockdown of Nanog reversed the increase of CD44 and Musashi-1 induced by TNF-α without affecting the activation of NF-κB signaling. Importantly, blocking NF-κB signaling by BAY 11-7082 inhibited the expression of immature markers suggesting that TNF-α induces dedifferentiation of astrocytes through the NF-κB signaling pathway. BAY 11-7082 could also inhibit the expression of Nanog, which indicated that Nanog was regulated by NF-κB signaling pathway.

SIGNIFICANCE

These findings indicate that activation of the NF-κB signaling pathway through TNF-α leads to astrocytes dedifferentiation via Nanog. These results expand our understanding of the mechanism of astrocytes dedifferentiation.

Long-term selective stimulation of transplanted neural stem/progenitor cells for spinal cord injury improves locomotor function

In cell transplantation therapy for spinal cord injury (SCI), grafted human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs) mainly differentiate into neurons, forming synapses in a process similar to neurodevelopment. In the developing nervous system, the activity of immature neurons has an important role in constructing and maintaining new synapses. Thus, we investigate how enhancing the activity of transplanted hiPSC-NS/PCs affects both the transplanted cells themselves and the host tissue. We find that chemogenetic stimulation of hiPSC-derived neural cells enhances cell activity and neuron-to-neuron interactions in vitro. In a rodent model of SCI, consecutive and selective chemogenetic stimulation of transplanted hiPSC-NS/PCs also enhances the expression of synapse-related genes and proteins in surrounding host tissues and prevents atrophy of the injured spinal cord, thereby improving locomotor function. These findings provide a strategy for enhancing activity within the graft to improve the efficacy of cell transplantation therapy for SCI.

Developing a mechanically matched decellularized spinal cord scaffold for the in situ matrix-based neural repair of spinal cord injury

Tissue engineering is a promising strategy to repair spinal cord injury (SCI). However, a bioscaffold with mechanical properties that match those of the pathological spinal cord tissue and a pro-regenerative matrix that allows robust neurogenesis for overcoming post-SCI scar formation has yet to be developed. Here, we report that a mechanically enhanced decellularized spinal cord (DSC) scaffold with a thin poly (lactic-co-glycolic acid) (PLGA) outer shell may fulfill the requirements for effective in situ neuroengineering after SCI. Using chemical extraction and electrospinning methods, we successfully constructed PLGA thin shell-ensheathed DSC scaffolds (PLGA-DSC scaffolds) in a way that removed major inhibitory components while preserving the permissive matrix. The DSCs exhibited good cytocompatibility with neural stem cells (NSCs) and significantly enhanced their differentiation toward neurons in vitro. Due to the mechanical reinforcement, the implanted PLGA-DSC scaffolds showed markedly increased resilience to infiltration by myofibroblasts and the deposition of dense collagen matrix, thereby creating a neurogenic niche favorable for the targeted migration, residence and neuronal differentiation of endogenous NSCs after SCI. Furthermore, PLGA-DSC presented a mild immunogenic property but prominent ability to polarize macrophages from the M1 phenotype to the M2 phenotype, leading to significant tissue regeneration and functional restoration after SCI. Taken together, the results demonstrate that the mechanically matched PLGA-DSC scaffolds show promise for effective tissue repair after SCI.

Reviving through human hippocampal newborn neurons

Recent contradictory data has renewed discussion regarding the existence of adult hippocampal neurogenesis (AHN) in humans, i.e., the continued production of new neurons in the brain after birth. The present review revisits the debate of AHN in humans from a historical point of view in the face of contradictory evidence, analyzing the methods employed to investigate this phenomenon. Thus, to date, of the 57 studies performed in humans that we reviewed, 84% (48) concluded in favor of the presence of newborn neurons in the human adult hippocampus. Besides quality of the tissue (such as postmortem intervals below 26hours as well as tissue conservation and fixation), considerations for assessing and quantify AHN in the human brain require the use of stereology and toxicological analyses of clinical data of the patient.

Leukemia Inhibitory Factor Is Required for Subventricular Zone Astrocyte Progenitor Proliferation and for Prokineticin-2 Production after a Closed Head Injury in Mice

Astrogliosis is one of the hallmarks of brain injury, and after a mild injury activated astrocytes subserve neuroprotective and pro-regenerative functions. We previously found that the astroglial response to closed head injury (CHI) was blunted in mice that were haplodeficient in leukemia inhibitory factor (LIF); therefore, the goal of these studies was to determine if the delayed astrogliosis was due to decreased recruitment of subventricular zone (SVZ) progenitors. CHI's were performed on post-natal day 20 on LIF heterozygous (Het) and wild-type (WT) mice. At 48 h post-CHI, astrocyte progenitor proliferation within the SVZ increased ∼250% in WT mice but was reduced by ∼200% in LIF Het mice compared with sham controls. Using neurospheres to model the SVZ, LIF increased the percentage of proliferating astrocyte progenitors by 2-fold compared with controls but had no effect on neural stem cell proliferation. To rule out the involvement of other cytokines, 105 cytokines were analyzed using a multi-plex array and with targeted validation on injured LIF Het versus WT neocortex. Of the cytokines analyzed, only prokineticin-2 (ProK2) required LIF signaling. Correspondingly, LIF-treated neurospheres expressed higher levels of ProK2, the ProK1 and ProK2 receptors (ProKR1 and ProKR2). Using in situ hybridization, ProK2 messenger RNA (mRNA) was most abundant in neocortical neurons and highly expressed within the SVZ. However, in contrast to LIF, ProK2 decreased astrocyte progenitor proliferation 2-fold. Altogether, these data demonstrate that LIF is necessary for astrocyte progenitor proliferation after injury and reveal a new role for LIF as an essential regulator of the neurotrophic factor ProK2.

Imbalance of Excitatory/Inhibitory Neuron Differentiation in Neurodevelopmental Disorders with an NR2F1 Point Mutation

Recent studies have revealed an essential role for embryonic cortical development in the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder (ASD). However, the genetic basis and underlying mechanisms remain unclear. Here, we generate mutant human embryonic stem cell lines (Mut hESCs) carrying an NR2F1-R112K mutation that has been identified in a patient with ASD features and investigate their neurodevelopmental alterations. Mut hESCs overproduce ventral telencephalic neuron progenitors (ventral NPCs) and underproduce dorsal NPCs, causing the imbalance of excitatory/inhibitory neurons. These alterations can be mainly attributed to the aberrantly activated Hedgehog signaling pathway. Moreover, the corresponding Nr2f1 point-mutant mice display a similar excitatory/inhibitory neuron imbalance and abnormal behaviors. Antagonizing the increased inhibitory synaptic transmission partially alleviates their behavioral deficits. Together, our results suggest that the NR2F1-dependent imbalance of excitatory/inhibitory neuron differentiation caused by the activated Hedgehog pathway is one precursor of neurodevelopmental disorders and may enlighten the therapeutic approaches.

Musashi-1-A Stemness RBP for Cancer Therapy?

The RNA-binding protein Musashi-1 (MSI1) promotes stemness during development and cancer. By controlling target mRNA turnover and translation, MSI1 is implicated in the regulation of cancer hallmarks such as cell cycle or Notch signaling. Thereby, the protein enhanced cancer growth and therapy resistance to standard regimes. Due to its specific expression pattern and diverse functions, MSI1 represents an interesting target for cancer therapy in the future. In this review we summarize previous findings on MSI1's implications in developmental processes of other organisms. We revisit MSI1's expression in a set of solid cancers, describe mechanistic details and implications in MSI1 associated cancer hallmark pathways and highlight current research in drug development identifying the first MSI1-directed inhibitors with anti-tumor activity.

Potential Role of Musashi-2 RNA-Binding Protein in Cancer EMT

Local invasion and distant metastasis are the key hallmarks in the aggressive progression of malignant tumors, including the ability of cancer cells to detach from the extracellular matrix overcome apoptosis, and disseminate into distant sites. It is generally believed that this malignant behavior is stimulated by epithelial-mesenchymal transition (EMT). Musashi (MSI) RNA-binding proteins, belonging to the evolutionarily conserved RNA-binding proteins (RBP) family, were originally discovered to regulate asymmetric cell division during embryonic development. Recently, Musashi-2 (MSI2), as a key member of MSI family, has been prevalently reported to be tightly associated with the advanced clinical stage of several cancers. Multiple oncogenic signaling pathways mediated by MSI2 play vital roles in EMT. Here, we systematically reviewed the detailed role and signal networks of MSI2 in regulating cancer development, especially in EMT signal transduction, involving EGF, TGF-β, Notch, and Wnt pathways.

Neuregulin-1 converts reactive astrocytes toward oligodendrocyte lineage cells via upregulating the PI3K-AKT-mTOR pathway to repair spinal cord injury

Axonal demyelination is a consistent pathological characteristic of Spinal cord injury (SCI). Promoting differentiation of oligodendrocytes is of importance for remyelination. Conversion of reactive astrocytes with stem cell potential to oligodendrocytes is proposed as an innovative strategy for SCI repair. Neuregulin-1 (Nrg1) plays an essential role in the differentiation of oligodendrocytes. Therefore, it's a potential treatment for demyelination in SCI that using Nrg1 to drive reactive astrocytes toward oligodendrocyte lineage cells. In this study, tumor necrosis factor-α (TNF-α) was used to induce dedifferentiation of primary rat spinal cord astrocytes into reactive astrocytes and Nrg1 was used to induce astrocytes in vitro and in vivo. The results showed that astrocytes treated with TNF-α expressed immaturity markers CD44 and Musashi1 at mRNA and protein levels, indicating that TNF-α induced the stem cell state of astrocytes. Nrg1 induced reactive astrocytes to express oligodendrocyte markers PDGFR-α and O4 at mRNA and protein levels, indicating that Nrg1 directly converts reactive astrocytes toward oligodendrocyte lineage cells. Moreover, upregulation of PI3K-AKT-mTOR signaling activation in response to Nrg1 was observed. In rats with SCI, intrathecal treatment with Nrg1 converted reactive astrocytes to oligodendrocyte lineage cells, inhibited astrogliosis, promoted remyelination, protected axons and eventually improved BBB score. All the biological effects of Nrg1 were significantly reversed by the co-administration of Nrg1 and ErbB inhibitor, suggesting that Nrg1 functioned through the receptor ErbB. Our findings indicate that Nrg1 is sufficient to trans-differentiate reactive astrocytes to oligodendrocytes via the PI3K-AKT-mTOR signaling pathway and repair SCI. Delivery of Nrg1 for the remyelination processes could be a promising strategy for spinal cord repair.

Evaluation of the Neurogenic Potential in the Rat Inferior Colliculus from Early Postnatal Days Until Adulthood

Neural stem cells (NSCs) have been recently identified in the inferior colliculus (IC). These cells are of particular interest, as no casual therapeutic options for impaired neural structures exist. This research project aims to evaluate the neurogenic potential in the rat IC from early postnatal days until adulthood. The IC of rats from postnatal day 6 up to 48 was examined by neurosphere assays and histological sections. In free-floating IC cell cultures, neurospheres formed from animals from early postnatal to adulthood. The amount of generated neurospheres decreased in older ages and increased with the number of cell line passages. Cells in the neurospheres and the histological sections stained positively with NSC markers (Doublecortin, Sox-2, Musashi-1, Nestin, and Atoh1). Dissociated single cells from the neurospheres differentiated and were stained positively for the neural lineage markers β-III-tubulin, glial fibrillary acidic protein, and myelin basic protein. In addition, NSC markers (Doublecortin, Sox-2, CDK5R1, and Ascl-1) were investigated by qRT-PCR. In conclusion, a neurogenic potential in the rat IC was detected and evaluated from early postnatal days until adulthood. The identification of NSCs in the rat IC and their age-specific characteristics contribute to a better understanding of the development and the plasticity of the auditory pathway and might be activated for therapeutic use.

Potential roles of stem cell marker genes in axon regeneration

Axon regeneration is orchestrated by many genes that are differentially expressed in response to injury. Through a comparative analysis of gene expression profiling, injury-responsive genes that are potential targets for understanding the mechanisms underlying regeneration have been revealed. As the efficiency of axon regeneration in both the peripheral and central nervous systems can be manipulated, we suggest that identifying regeneration-associated genes is a promising approach for developing therapeutic applications in vivo. Here, we review the possible roles of stem cell marker- or stemness-related genes in axon regeneration to gain a better understanding of the regeneration mechanism and to identify targets that can enhance regenerative capacity.

Lithium increases mitochondrial respiration in iPSC-derived neural precursor cells from lithium responders

Lithium (Li), valproate (VPA) and lamotrigine (LTG) are commonly used to treat bipolar disorder (BD). While their clinical efficacy is well established, the mechanisms of action at the molecular level are still incompletely understood. Here we investigated the molecular effects of Li, LTG and VPA treatment in induced pluripotent stem cell (iPSC)-derived neural precursor cells (NPCs) generated from 3 healthy controls (CTRL), 3 affective disorder Li responsive patients (Li-R) and 3 Li non-treated patients (Li-N) after 6 h and 1 week of exposure. Differential expression (DE) analysis after 6 h of treatment revealed a transcriptional signature that was associated with all three drugs and most significantly enriched for ribosome and oxidative phosphorylation (OXPHOS) pathways. In addition to the shared DE genes, we found that Li exposure was associated with 554 genes uniquely regulated in Li-R NPCs and enriched for spliceosome, OXPHOS and thermogenesis pathways. In-depth analysis of the treatment-associated transcripts uncovered a significant decrease in intron retention rate, suggesting that the beneficial influence of these drugs might partly be related to splicing. We examined the mitochondrial respiratory function of the NPCs by exploring the drugs' effects on oxygen consumption rate (OCR) and glycolytic rate (ECAR). Li improved OCR levels only in Li-R NPCs by enhancing maximal respiration and reserve capacity, while VPA enhanced maximal respiration and reserve capacity in Li-N NPCs. Overall, our findings further support the involvement of mitochondrial functions in the molecular mechanisms of mood stabilizers and suggest novel mechanisms related to the spliceosome, which warrant further investigation.

Is There Such a Thing as a Genuine Cancer Stem Cell Marker? Perspectives from the Gut, the Brain and the Dental Pulp

The conversion of healthy stem cells into cancer stem cells (CSCs) is believed to underlie tumor relapse after surgical removal and fuel tumor growth and invasiveness. CSCs often arise from the malignant transformation of resident multipotent stem cells, which are present in most human tissues. Some organs, such as the gut and the brain, can give rise to very aggressive types of cancers, contrary to the dental pulp, which is a tissue with a very remarkable resistance to oncogenesis. In this review, we focus on the similarities and differences between gut, brain and dental pulp stem cells and their related CSCs, placing a particular emphasis on both their shared and distinctive cell markers, including the expression of pluripotency core factors. We discuss some of their similarities and differences with regard to oncogenic signaling, telomerase activity and their intrinsic propensity to degenerate to CSCs. We also explore the characteristics of the events and mutations leading to malignant transformation in each case. Importantly, healthy dental pulp stem cells (DPSCs) share a great deal of features with many of the so far reported CSC phenotypes found in malignant neoplasms. However, there exist literally no reports about the contribution of DPSCs to malignant tumors. This raises the question about the particularities of the dental pulp and what specific barriers to malignancy might be present in the case of this tissue. These notable differences warrant further research to decipher the singular properties of DPSCs that make them resistant to transformation, and to unravel new therapeutic targets to treat deadly tumors.

Musashi expression in intestinal stem cells attenuates radiation-induced decline in intestinal permeability and survival in Drosophila

Exposure to genotoxic stress by environmental agents or treatments, such as radiation therapy, can diminish healthspan and accelerate aging. We have developed a Drosophila melanogaster model to study the molecular effects of radiation-induced damage and repair. Utilizing a quantitative intestinal permeability assay, we performed an unbiased GWAS screen (using 156 strains from the Drosophila Genetic Reference Panel) to search for natural genetic variants that regulate radiation-induced gut permeability in adult D. melanogaster. From this screen, we identified an RNA binding protein, Musashi (msi), as one of the possible genes associated with changes in intestinal permeability upon radiation. The overexpression of msi promoted intestinal stem cell proliferation, which increased survival after irradiation and rescued radiation-induced intestinal permeability. In summary, we have established D. melanogaster as an expedient model system to study the effects of radiation-induced damage to the intestine in adults and have identified msi as a potential therapeutic target.

The Dynamic Proteome of Oligodendrocyte Lineage Differentiation Features Planar Cell Polarity and Macroautophagy Pathways

BACKGROUND

Generation of oligodendrocytes is a sophisticated multistep process, the mechanistic underpinnings of which are not fully understood and demand further investigation. To systematically profile proteome dynamics during human embryonic stem cell differentiation into oligodendrocytes, we applied in-depth quantitative proteomics at different developmental stages and monitored changes in protein abundance using a multiplexed tandem mass tag-based proteomics approach.

FINDINGS

Our proteome data provided a comprehensive protein expression profile that highlighted specific expression clusters based on the protein abundances over the course of human oligodendrocyte lineage differentiation. We identified the eminence of the planar cell polarity signalling and autophagy (particularly macroautophagy) in the progression of oligodendrocyte lineage differentiation-the cooperation of which is assisted by 106 and 77 proteins, respectively, that showed significant expression changes in this differentiation process. Furthermore, differentially expressed protein analysis of the proteome profile of oligodendrocyte lineage cells revealed 378 proteins that were specifically upregulated only in 1 differentiation stage. In addition, comparative pairwise analysis of differentiation stages demonstrated that abundances of 352 proteins differentially changed between consecutive differentiation time points.

CONCLUSIONS

Our study provides a comprehensive systematic proteomics profile of oligodendrocyte lineage cells that can serve as a resource for identifying novel biomarkers from these cells and for indicating numerous proteins that may contribute to regulating the development of myelinating oligodendrocytes and other cells of oligodendrocyte lineage. We showed the importance of planar cell polarity signalling in oligodendrocyte lineage differentiation and revealed the autophagy-related proteins that participate in oligodendrocyte lineage differentiation.

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 Stemness Gene Mex3A Is a Key Regulator of Neuroblast Proliferation During Neurogenesis

Mex3A is an RNA binding protein that can also act as an E3 ubiquitin ligase to control gene expression at the post-transcriptional level. In intestinal adult stem cells, MEX3A is required for cell self-renewal and when overexpressed, MEX3A can contribute to support the proliferation of different cancer cell types. In a completely different context, we found mex3A among the genes expressed in neurogenic niches of the embryonic and adult fish brain and, notably, its expression was downregulated during brain aging. The role of mex3A during embryonic and adult neurogenesis in tetrapods is still unknown. Here, we showed that mex3A is expressed in the proliferative region of the developing brain in both Xenopus and mouse embryos. Using gain and loss of gene function approaches, we showed that, in Xenopus embryos, mex3A is required for neuroblast proliferation and its depletion reduced the neuroblast pool, leading to microcephaly. The tissue-specific overexpression of mex3A in the developing neural plate enhanced the expression of sox2 and msi-1 keeping neuroblasts into a proliferative state. It is now clear that the stemness property of mex3A, already demonstrated in adult intestinal stem cells and cancer cells, is a key feature of mex3a also in developing brain, opening new lines of investigation to better understand its role during brain aging and brain cancer development.

High glucose alters the DNA methylation pattern of neurodevelopment associated genes in human neural progenitor cells in vitro

Maternal diabetes alters the global epigenetic mechanisms and expression of genes involved in neural tube development in mouse embryos. Since DNA methylation is a critical epigenetic mechanism that regulates gene functions, gene-specific DNA methylation alterations were estimated in human neural progenitor cells (hNPCs) exposed to high glucose (HG) in the present study. The DNA methylation pattern of genes involved in several signalling pathways including axon guidance (SLIT1-ROBO2 pathway), and Hippo pathway (YAP and TAZ) was altered in hNPCs exposed to HG. The expression levels of SLIT1-ROBO2 pathways genes (including its effectors, SRGAP1 and CDC42) which mediates diverse cellular processes such as proliferation, neurogenesis and axon guidance, and Hippo pathway genes (YAP and TAZ) which regulates proliferation, stemness, differentiation and organ size were downregulated in hNPCs exposed to HG. A recent report suggests a possible cross-talk between SLIT1-ROBO2 and TAZ via CDC42, a mediator of actin dynamics. Consistent with this, SLIT1 knockdown downregulated the expression of its effectors and TAZ in hNPCs, suggesting that HG perturbs the cross-talk between SLIT1-ROBO2 and TAZ in hNPCs. Overall, this study demonstrates that HG epigenetically alters the SLIT1-ROBO2 and Hippo signalling pathways in hNPCs, forming the basis for neurodevelopmental disorders in offspring of diabetic pregnancy.

Identification and Validation of an Aspergillus nidulans Secondary Metabolite Derivative as an Inhibitor of the Musashi-RNA Interaction

RNA-binding protein Musashi-1 (MSI1) is a key regulator of several stem cell populations. MSI1 is involved in tumor proliferation and maintenance, and it regulates target mRNAs at the translational level. The known mRNA targets of MSI1 include Numb, APC, and P21^WAF-1, key regulators of Notch/Wnt signaling and cell cycle progression, respectively. In this study, we aim to identify small molecule inhibitors of MSI1-mRNA interactions, which could block the growth of cancer cells with high levels of MSI1. Using a fluorescence polarization (FP) assay, we screened small molecules from several chemical libraries for those that disrupt the binding of MSI1 to its consensus RNA. One cluster of hit compounds is the derivatives of secondary metabolites from Aspergillus nidulans. One of the top hits, Aza-9, from this cluster was further validated by surface plasmon resonance and nuclear magnetic resonance spectroscopy, which demonstrated that Aza-9 binds directly to MSI1, and the binding is at the RNA binding pocket. We also show that Aza-9 binds to Musashi-2 (MSI2) as well. To test whether Aza-9 has anti-cancer potential, we used liposomes to facilitate Aza-9 cellular uptake. Aza-9-liposome inhibits proliferation, induces apoptosis and autophagy, and down-regulates Notch and Wnt signaling in colon cancer cell lines. In conclusion, we identified a series of potential lead compounds for inhibiting MSI1/2 function, while establishing a framework for identifying small molecule inhibitors of RNA binding proteins using FP-based screening methodology.

Inhibition of Sonic Hedgehog Signaling Suppresses Glioma Stem-Like Cells Likely Through Inducing Autophagic Cell Death

Glioblastoma (GBM) often recurs after radio- and chemotherapies leading to poor prognosis. Glioma stem-like cells (GSCs) contribute to drug resistance and recurrence. Thus, understanding cellular mechanism underlying the growth of GSCs is critical for the treatment of GBM. Here GSCs were isolated from human U87 GBM cells with magnetic-activated cell sorting (MACS) using CD133 as a marker. The CD133⁺ cells highly expressed sonic hedgehog (Shh) and were capable of forming tumor spheroids in vitro and tumor in vivo. Athymic mice received intracranial injection of luciferase transduced parental and CD133⁺ GBM cells was utilized as orthotopic GBM model. Inhibited Shh by LDE225 delayed GBM growth in vivo, and downregulated Ptch1 and Gli1. CD133⁺ cell proliferation was more sensitive to inhibition by LDE225 than that of CD133⁻ cells. Treatment with LDE225 significantly reduced CD133⁺-derived tumor spheroid formation. Large membranous vacuoles appeared in the LDE225-treated cells concomitant with the conversion of LC3-I to LC3-II. In addition, LDE225-induced cell death was mitigated in the presence of autophagy inhibitor 3-methyladenine (3-MA). Tumor growth was much slower in Shh shRNA-knockdown mice than in control RNA-transfected mice. Conversely, tumor growth was faster in Shh overexpressed mice. Furthermore, combination of LDE225 and rapamycin treatment resulted in additive effect on LC3-I to LC3-II conversion and reduction in cell viability. However, LDE225 did not affect the phosphorylated level of mTOR. Similarly, amiodarone, an mTOR-independent autophagy enhancer, reduced CD133⁺ cell viability and tumor spheroid formation in vitro and exhibited anti-tumor activity in vivo. These results suggest that Shh inhibitor induces autophagy of CD133⁺ cells likely through mTOR independent pathway. Targeting Shh signal pathway may overcome chemoresistance and provide a therapeutic strategy for patients with malignant gliomas.

Intracellular functions of RNA-binding protein, Musashi1, in stem and cancer cells

RNA-binding protein, musashi1 (MSI1), is a main protein in asymmetric cell division of the sensory organ precursor cells, whereas its expression is reported to be upregulated in cancers. This protein is a critical element in proliferation of stem and cancer stem cells, which acts through Wnt and Notch signaling pathways. Moreover, MSI1 modulates malignancy and chemoresistance of lung cancer cells via activating the Akt signaling. Due to the main role of MSI1 in metastasis and cancer development, MSI1 would be an appropriate candidate for cancer therapy. Downregulation of MSI1 inhibits proliferation of cancer stem cells and reduces the growth of solid tumors in several cancers. On the other hand, MSI1 expression is regulated by microRNAs in such a way that several different tumor suppressor miRNAs negatively regulate oncogenic MSI1 and inhibit migration and tumor metastasis. The aim of this review is summarizing the role of MSI1 in stem cell proliferation and cancer promotion.

Musashi1 enhances chemotherapy resistance of pediatric glioblastoma cells in vitro

BACKGROUND

Glioblastoma (GBM) is the most aggressive form of glioma in adults and children and is associated with very poor prognosis. Pediatric tumors are biologically distinct from adult GBM and differ in response to current GBM treatment protocols. Regarding pediatric GBM, new drug combinations and the molecular background of chemotherapy effects need to be investigated, in order to increase patient survival outcome.

METHODS

The expression of the RNA-binding protein Musashi1 (MSI1) in pediatric glioma samples of different WHO tumor grades was investigated on the protein (immunohistochemistry) and on the RNA level (publicly accessible RNA sequencing dataset). The impact of the chemotherapeutic temozolomide (TMZ) in combination with valproic acid (VPA) was tested in two pediatric glioblastoma-derived cell lines. The supportive effect of MSI1 expression against this treatment was investigated via transient knockdown and protein overexpression.

RESULTS

MSI1 expression correlates with pediatric high-grade glioma (HGG). The combination of TMZ with VPA significantly increases the impact of drug treatment on cell viability in vitro. MSI1 was found to promote drug resistance to the combined treatment with TMZ and VPA.

CONCLUSION

MSI1 expression is a potential marker for pediatric HGG and increases chemoresistance. Inhibition of MSI1 might lead to an improved patient outcome and therapy response.

Medulloblastoma cancer stem cells: molecular signatures and therapeutic targets

Medulloblastoma (MB) is the most common malignant primary intracranial neoplasm diagnosed in childhood. Although numerous efforts have been made during the past few years to exploit novel targeted therapies for this aggressive neoplasm, there still exist substantial hitches hindering successful management of MB. Lately, progress in cancer biology has shown evidence that a subpopulation of cells within the tumour, namely cancer stem cells (CSCs), are thought to be responsible for the resistance to most chemotherapeutic agents and radiation therapy, accounting for cancer recurrence. Hence, it is crucial to identify the molecular signatures and genetic aberrations that characterise those CSCs and develop therapies that specifically target them. In this review, we aim to give an overview of the main genetic and molecular cues that depict MB-CSCs and provide a synopsis of the novel therapeutic approaches that specifically target this population of cells to attain enhanced antitumorous effects and therefore overcome resistance to therapy.

Interaction between SDF1 and CXCR4 Promotes Photoreceptor Differentiation via Upregulation of NFκB Pathway Signaling Activity in Pax6 Gene-Transfected Photoreceptor Precursors

BACKGROUND

CCL2 (also known as monocyte chemoattractant protein 1) and CX3CR1 (also known as Fractalkine receptor)-deficient mice have damaged photoreceptors.

OBJECTIVES

We examined the interaction of SDF1 and CXCR4 on the differentiation of retinal progenitors into rhodopsin-positive photoreceptors.

METHODS

Cloned retinal progenitors were obtained by Pax6 gene transfection of mouse iPS cells followed by serial dilution. Clones were selected by expression of nestin, Musashi1, Six3, and Chx10 mRNA. Cell surface protein expression was analyzed by flow cytometry. The levels of mRNA and intracellular protein were examined by real-time PCR and immunochemistry, respectively. Transient transfection experiments of retinal progenitors were conducted using a human rhodopsin promoter luciferase plasmid.

RESULTS

We selected 10 clones that expressed Six3, Chx10, Crx, Rx1, Nrl, CD73, and rhodopsin mRNA, which, except for rhodopsin, are photoreceptor precursor markers. Clones expressed both CD73 and CXCR4 on the cell surface and differentiated into rhodopsin-positive photoreceptors, which was reinforced by the addition of exogenous SDF1. A CXCR4 inhibitor AMD3100 blocked SDF1-mediated differentiation of progenitors into photoreceptors. SDF1 enhanced human rhodopsin promoter transcription activity, possibly via the NFκB pathway. Addition of SDF1 to the cell culture induced nuclear translocation of NFκB on retinal progenitor cell clones. Neonatal and newborn mouse retinas expressed SDF1 and CXCR4. Cells in the outer nuclear layer where photoreceptors are located expressed CXCR4 at P14 and P56. Cells in the inner nuclear layer expressed SDF1.

CONCLUSIONS

These findings suggest that retinal progenitor cell differentiation was at least partly regulated by SDF1 and CXCR4 via upregulation of NFκB activity.

Systems Biology-Based Analysis Indicates Global Transcriptional Impairment in Lead-Treated Human Neural Progenitor Cells

Lead poisoning effects are wide and include nervous system impairment, peculiarly during development, leading to neural damage. Lead interaction with calcium and zinc-containing metalloproteins broadly affects cellular metabolism since these proteins are related to intracellular ion balance, activation of signaling transduction cascades, and gene expression regulation. In spite of lead being recognized as a neurotoxin, there are gaps in knowledge about the global effect of lead in modulating the transcription of entire cellular systems in neural cells. In order to investigate the effects of lead poisoning in a systemic perspective, we applied the transcriptogram methodology in an RNA-seq dataset of human embryonic-derived neural progenitor cells (ES-NP cells) treated with 30 µM lead acetate for 26 days. We observed early downregulation of several cellular systems involved with cell differentiation, such as cytoskeleton organization, RNA, and protein biosynthesis. The downregulated cellular systems presented big and tightly connected networks. For long treatment times (12 to 26 days), it was possible to observe a massive impairment in cell transcription profile. Taking the enriched terms together, we observed interference in all layers of gene expression regulation, from chromatin remodeling to vesicle transport. Considering that ES-NP cells are progenitor cells that can originate other neural cell types, our results suggest that lead-induced gene expression disturbance might impair cells’ ability to differentiate, therefore influencing ES-NP cells’ fate.

Overlapping migratory mechanisms between neural progenitor cells and brain tumor stem cells

Neural stem cells present in the subventricular zone (SVZ), the largest neurogenic niche of the mammalian brain, are able to self-renew as well as generate neural progenitor cells (NPCs). NPCs are highly migratory and traverse the rostral migratory stream (RMS) to the olfactory bulb, where they terminally differentiate into mature interneurons. NPCs from the SVZ are some of the few cells in the CNS that migrate long distances during adulthood. The migratory process of NPCs is highly regulated by intracellular pathway activation and signaling from the surrounding microenvironment. It involves modulation of cell volume, cytoskeletal rearrangement, and isolation from compact extracellular matrix. In malignant brain tumors including high-grade gliomas, there are cells called brain tumor stem cells (BTSCs) with similar stem cell characteristics to NPCs but with uncontrolled cell proliferation and contribute to tumor initiation capacity, tumor progression, invasion, and tumor maintenance. These BTSCs are resistant to chemotherapy and radiotherapy, and their presence is believed to lead to tumor recurrence at distal sites from the original tumor location, principally due to their high migratory capacity. BTSCs are able to invade the brain parenchyma by utilizing many of the migratory mechanisms used by NPCs. However, they have an increased ability to infiltrate the tight brain parenchyma and utilize brain structures such as myelin tracts and blood vessels as migratory paths. In this article, we summarize recent findings on the mechanisms of cellular migration that overlap between NPCs and BTSCs. A better understanding of the intersection between NPCs and BTSCs will to provide a better comprehension of the BTSCs' invasive capacity and the molecular mechanisms that govern their migration and eventually lead to the development of new therapies to improve the prognosis of patients with malignant gliomas.

Musashi 1-positive cells derived from mouse embryonic stem cells treated with LY294002 are prone to differentiate into intestinal epithelial-like tissues

The majority of Musashi 1 (Msi1)‑positive cells derived from mouse embryonic stem cells (mESCs) are prone to differentiate into neural epithelial‑like cells, and only a small proportion of Msi1‑positive cells differentiate into intestinal epithelial‑like cells. Whether inhibiting the phosphatidylinositol 3‑kinase (PI3K) signaling of mESCs can promote the differentiation of Msi1‑positive cells into intestinal epithelial‑like cells remains to be fully elucidated. In the present study, to inhibit PI3K signaling, mESCs were treated with LY294002. A pMsi1‑green fluorescence protein reporter plasmid was used to sort the Msi1‑positive cells from mESCs treated and untreated with LY294002 (5 µmol/l). The Msi1‑positive cells were hypodermically engrafted into the backs of non‑obese diabetic/severe combined immunodeficient mice. The presence of neural and intestinal epithelial‑like cells in the grafts was detected by reverse transcription‑quantitative polymerase chain reaction analysis and immunohistochemistry. Compared with the Msi1‑positive cells derived from mESCs without LY294002 treatment, Msi1‑positive cells derived from mESCs treated with LY294002 expressed higher levels of leucine‑rich repeat‑containing G‑protein coupled receptor, a marker of intestinal epithelial stem cells, and lower levels of Nestin, a marker of neural epithelial stem cells. The grafts from Msi1‑positive cells treated with LY294002 contained more intestinal epithelial‑like tissues and fewer neural epithelial‑like tissues, compared with those from untreated Msi1‑positive cells. LY294002 had the ability to promote the differentiation of mESCs into intestinal epithelial‑like tissues. The Msi1‑positive cells selected from the cell population derived from mESCs treated with LY294002 exhibited more characteristics of intestinal epithelial stem cells than those from the untreated group.