The histone demethylase KDM5A is required for the repression of astrocytogenesis and regulated by the translational machinery in neural progenitor cells

Epigenetic regulation by KDM5A mediates the effects of prenatal PM2.5 exposure on hippocampal development and synaptic integrity through the Shh signaling pathway

Prenatal environmental exposure could be an essential health risk factor associated with neurodevelopmental disorders in offspring. However, the exact mechanisms underlying the impact of prenatal PM2.5 exposure on offspring cognition remain unclear. In our recent study using a PM2.5 exposed pregnant mouse model, we observed significant synaptic dysfunction in the hippocampi of the offspring. Concurrently, the epigenetic regulator of KDM5A and the Shh signaling pathway exhibited decreased activities. Significantly, changes in hippocampal KDM5A and Shh levels directly correlated with PM2.5 exposure intensity. Subsequent experiments revealed a marked reduction in the expression of Shh signaling and related synaptic proteins when KDM5A was silenced in cells. Notably, the effects of KDM5A deficiency were reversed significantly with the supplementation of a Shh activator. Furthermore, our findings indicate that Shh activation significantly attenuates PM2.5-induced synaptic impairments in hippocampal neurons. We further demonstrated that EGR1, a transcriptional inhibitor, plays a direct role in KDM5A's regulation of the Shh pathway under conditions of PM2.5 exposure. Our results suggest that the KDM5A's inhibitory regulation on the Shh pathway through the EGR1 gene is a crucial epigenetic mechanism underlying the synaptic dysfunction in hippocampal neurons caused by maternal PM2.5 exposure. This emphasizes the role of epigenetic regulations in neurodevelopmental disorders caused by environmental factors.

Histone Lysine Demethylase KDM5 Inhibitor CPI-455 Induces Astrocytogenesis in Neural Stem Cells

Lysine-specific histone demethylase 5A (KDM5A) is known to facilitate proliferation in cancer cells and maintain stemness to repress the astrocytic differentiation of neural stem cells (NSCs). In the study presented here, we investigated the effect of a KDM5 inhibitor, CPI-455, on NSC fate control. CPI-455 induced astrocytogenesis in NSCs during differentiation. Kdm5a, but not Kdm5c, knockdown induced glial fibrillary acidic protein (Gfap) transcription. CPI-455 induced signal transducer and activator of transcription 3, increased bone morphogenetic protein 2 expression, and enhanced mothers against decapentaplegic homolog 1/5/9 phosphorylation. The treatment of CPI-455 enhanced the methylation of histone H3 lysine 4 in the Gfap promoter when compared to that of the dimethyl sulfoxide control. In addition, CPI-455 treatment significantly reduced the recruitment of KDM5A to the Gfap promoter. Our data suggest that the KDM5 inhibitor CPI-455 effectively controls NSC cell fate via KDM5A inhibition and induces astrocytogenesis.

Emerging Functional Connections Between Metabolism and Epigenetic Remodeling in Neural Differentiation

Stem cells possess extraordinary capacities for self-renewal and differentiation, making them highly valuable in regenerative medicine. Among these, neural stem cells (NSCs) play a fundamental role in neural development and repair processes. NSC characteristics and fate are intricately regulated by the microenvironment and intracellular signaling. Interestingly, metabolism plays a pivotal role in orchestrating the epigenome dynamics during neural differentiation, facilitating the transition from undifferentiated NSC to specialized neuronal and glial cell types. This intricate interplay between metabolism and the epigenome is essential for precisely regulating gene expression patterns and ensuring proper neural development. This review highlights the mechanisms behind metabolic regulation of NSC fate and their connections with epigenetic regulation to shape transcriptional programs of stemness and neural differentiation. A comprehensive understanding of these molecular gears appears fundamental for translational applications in regenerative medicine and personalized therapies for neurological conditions.

Bortezomib Is Toxic but Induces Neurogenesis and Inhibits TUBB3 Degradation in Rat Neural Stem Cells

Bortezomib (BTZ) is a proteasome inhibitor used to treat multiple myeloma (MM). However, the induction of peripheral neuropathy is one of the major concerns in using BTZ to treat MM. In the current study, we have explored the effects of BTZ (0.01-5 nM) on rat neural stem cells (NSCs). BTZ (5 nM) induced cell death; however, the percentage of neurons was increased in the presence of mitogens. BTZ reduced the B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X protein ratio in proliferating NSCs and differentiated cells. Inhibition of βIII-tubulin (TUBB3) degradation was observed, but not inhibition of glial fibrillary acidic protein degradation, and a potential PEST sequence was solely found in TUBB3. In the presence of growth factors, BTZ increased cAMP response element-binding protein (CREB) phosphorylation, brain-derived neurotrophic factor (Bdnf) transcription, BDNF expression, and Tubb3 transcription in NSCs. However, in the neuroblastoma cell line, SH-SY5Y, BTZ (1-20 nM) only increased cell death without increasing CREB phosphorylation, Bdnf transcription, or TUBB3 induction. These results suggest that although BTZ induces cell death, it activates neurogenic signals and induces neurogenesis in NSCs.

Domain architecture and protein-protein interactions regulate KDM5A recruitment to the chromatin

Tri-methylation of Histone 3 lysine 4 (H3K4) is an important epigenetic modification whose deposition and removal can affect the chromatin at structural and functional levels. KDM5A is one of the four known H3K4-specific demethylases. It is a part of the KDM5 family, which is characterized by a catalytic Jumonji domain capable of removing H3K4 di- and tri-methylation marks. KDM5A has been found to be involved in multiple cellular processes such as differentiation, metabolism, cell cycle, and transcription. Its link to various diseases, including cancer, makes KDM5A an important target for drug development. However, despite several studies outlining its significance in various pathways, our lack of understanding of its recruitment and function at the target sites on the chromatin presents a challenge in creating effective and targeted treatments. Therefore, it is essential to understand the recruitment mechanism of KDM5A to chromatin, and its activity therein, to comprehend how various roles of KDM5A are regulated. In this review, we discuss how KDM5A functions in a context-dependent manner on the chromatin, either directly through its structural domain, or through various interacting partners, to bring about a diverse range of functions.

Context-dependent regulation of Notch signaling in glial development and tumorigenesis

In the mammalian brain, Notch signaling maintains the cortical stem cell pool and regulates the glial cell fate choice and differentiation. However, the function of Notch in regulating glial development and its involvement in tumorigenesis have not been well understood. Here, we show that Notch inactivation by genetic deletion of Rbpj in stem cells decreases astrocytes but increases oligodendrocytes with altered internal states. Inhibiting Notch in glial progenitors does not affect cell generation but instead accelerates the growth of Notch-deprived oligodendrocyte progenitor cells (OPCs) and OPC-related glioma. We also identified a cross-talk between oligodendrocytes and astrocytes, with premyelinating oligodendrocytes secreting BMP4, which is repressed by Notch, to up-regulate GFAP expression in adjacent astrocytes. Moreover, Notch inactivation in stem cells causes a glioma subtype shift from astroglia-associated to OPC-correlated patterns and vice versa. Our study reveals Notch's context-dependent function, promoting astrocytes and astroglia-associated glioma in stem cells and repressing OPCs and related glioma in glial progenitors.

Histone demethylases in neurodevelopment and neurodegenerative diseases

Neurodevelopment can be precisely regulated by epigenetic mechanisms, including DNA methylations, noncoding RNAs, and histone modifications. Histone methylation was a reversible modification, catalyzed by histone methyltransferases and demethylases. So far, dozens of histone lysine demethylases (KDMs) have been discovered, and they (members from KDM1 to KDM7 family) are important for neurodevelopment by regulating cellular processes, such as chromatin structure and gene transcription. The role of KDM5C and KDM7B in neural development is particularly important, and mutations in both genes are frequently found in human X-linked mental retardation (XLMR). Functional disorders of specific KDMs, such as KDM1A can lead to the development of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Several KDMs can serve as potential therapeutic targets in the treatment of neurodegenerative diseases. At present, the function of KDMs in neurodegenerative diseases is not fully understood, so more comprehensive and profound studies are needed. Here, the role and mechanism of histone demethylases were summarized in neurodevelopment, and the potential of them was introduced in the treatment of neurodegenerative diseases.

Drawing a line between histone demethylase KDM5A and KDM5B: their roles in development and tumorigenesis

Distinct epigenetic modifiers ensure coordinated control over genes that govern a myriad of cellular processes. Growing evidence shows that dynamic regulation of histone methylation is critical for almost all stages of development. Notably, the KDM5 subfamily of histone lysine-specific demethylases plays essential roles in the proper development and differentiation of tissues, and aberrant regulation of KDM5 proteins during development can lead to chronic developmental defects and even cancer. In this review, we adopt a unique perspective regarding the context-dependent roles of KDM5A and KDM5B in development and tumorigenesis. It is well known that these two proteins show a high degree of sequence homology, with overlapping functions. However, we provide deeper insights into their substrate specificity and distinctive function in gene regulation that at times divert from each other. We also highlight both the possibility of targeting KDM5A and KDM5B to improve cancer treatment and the limitations that must be overcome to increase the efficacy of current drugs.

Inhibition of KDM5A attenuates cisplatin-induced hearing loss via regulation of the MAPK/AKT pathway

The study aimed to investigate the potential role of lysine-specific demethylase 5A (KDM5A) in cisplatin-induced ototoxicity. The effect of the KDM5A inhibitor CPI-455 was assessed by apoptosis assay, immunofluorescence, flow cytometry, seahorse respirometry assay, and auditory brainstem response test. RNA sequencing, qRT-PCR, and CUT&Tag assays were used to explore the mechanism underlying CPI-455-induced protection. Our results demonstrated that the expression of KDM5A was increased in cisplatin-injured cochlear hair cells compared with controls. CPI-455 treatment markedly declined KDM5A and elevated H3K4 trimethylation levels in cisplatin-injured cochlear hair cells. Moreover, CPI-455 effectively prevented the death of hair cells and spiral ganglion neurons and increased the number of ribbon synapses in a cisplatin-induced ototoxicity mouse model both in vitro and in vivo. In HEI-OC1 cells, KDM5A knockdown reduced reactive oxygen species accumulation and improved mitochondrial membrane potential and oxidative phosphorylation under cisplatin-induced stress. Mechanistically, through transcriptomics and epigenomics analyses, a set of apoptosis-related genes, including Sos1, Sos2, and Map3k3, were regulated by CPI-455. Altogether, our findings indicate that inhibition of KDM5A may represent an effective epigenetic therapeutic target for preventing cisplatin-induced hearing loss.

Pharmacological inhibition of KDM5A for cancer treatment

Lysine-specific demethylase 5A (KDM5A, also named RBP2 or JARID1A) is a demethylase that can remove methyl groups from histones H3K4me1/2/3. It is aberrantly expressed in many cancers, where it impedes differentiation and contributes to cancer cell proliferation, cell metastasis and invasiveness, drug resistance, and is associated with poor prognosis. Pharmacological inhibition of KDM5A has been reported to significantly attenuate tumor progression in vitro and in vivo in a range of solid tumors and acute myeloid leukemia. This review will present the structural aspects of KDM5A, its role in carcinogenesis, a comparison of currently available approaches for screening KDM5A inhibitors, a classification of KDM5A inhibitors, and its potential as a drug target in cancer therapy.

Different Flavors of Astrocytes: Revising the Origins of Astrocyte Diversity and Epigenetic Signatures to Understand Heterogeneity after Injury

Astrocytes are a specific type of neuroglial cells that confer metabolic and structural support to neurons. Astrocytes populate all regions of the nervous system and adopt a variety of phenotypes depending on their location and their respective functions, which are also pleiotropic in nature. For example, astrocytes adapt to pathological conditions with a specific cellular response known as reactive astrogliosis, which includes extensive phenotypic and transcriptional changes. Reactive astrocytes may lose some of their homeostatic functions and gain protective or detrimental properties with great impact on damage propagation. Different astrocyte subpopulations seemingly coexist in reactive astrogliosis, however, the source of such heterogeneity is not completely understood. Altered cellular signaling in pathological compared to healthy conditions might be one source fueling astrocyte heterogeneity. Moreover, diversity might also be encoded cell-autonomously, for example as a result of astrocyte subtype specification during development. We hypothesize and propose here that elucidating the epigenetic signature underlying the phenotype of each astrocyte subtype is of high relevance to understand another regulative layer of astrocyte heterogeneity, in general as well as after injury or as a result of other pathological conditions. High resolution methods should allow enlightening diverse cell states and subtypes of astrocyte, their adaptation to pathological conditions and ultimately allow controlling and manipulating astrocyte functions in disease states. Here, we review novel literature reporting on astrocyte diversity from a developmental perspective and we focus on epigenetic signatures that might account for cell type specification.

A KDM5-Prospero transcriptional axis functions during early neurodevelopment to regulate mushroom body formation

Mutations in the lysine demethylase 5 (KDM5) family of transcriptional regulators are associated with intellectual disability, yet little is known regarding their spatiotemporal requirements or neurodevelopmental contributions. Utilizing the mushroom body (MB), a major learning and memory center within the Drosophila brain, we demonstrate that KDM5 is required within ganglion mother cells and immature neurons for proper axogenesis. Moreover, the mechanism by which KDM5 functions in this context is independent of its canonical histone demethylase activity. Using in vivo transcriptional and binding analyses, we identify a network of genes directly regulated by KDM5 that are critical modulators of neurodevelopment. We find that KDM5 directly regulates the expression of prospero, a transcription factor that we demonstrate is essential for MB morphogenesis. Prospero functions downstream of KDM5 and binds to approximately half of KDM5-regulated genes. Together, our data provide evidence for a KDM5-Prospero transcriptional axis that is essential for proper MB development.

The emerging role of KDM5A in human cancer

Histone methylation is a key posttranslational modification of chromatin, and its dysregulation affects a wide array of nuclear activities including the maintenance of genome integrity, transcriptional regulation, and epigenetic inheritance. Variations in the pattern of histone methylation influence both physiological and pathological events. Lysine-specific demethylase 5A (KDM5A, also known as JARID1A or RBP2) is a KDM5 Jumonji histone demethylase subfamily member that erases di- and tri-methyl groups from lysine 4 of histone H3. Emerging studies indicate that KDM5A is responsible for driving multiple human diseases, particularly cancers. In this review, we summarize the roles of KDM5A in human cancers, survey the field of KDM5A inhibitors including their anticancer activity and modes of action, and the current challenges and potential opportunities of this field.

The KDM5 Inhibitor KDM5-C70 Induces Astrocyte Differentiation in Rat Neural Stem Cells

Members of the lysine-specific histone demethylase 5 (KDM5/JARID1) family are known to play important roles in stem cell fate determination. Here, using the KDM5 inhibitor C70 (KDM5-C70), we demonstrated that the histone demethylase activity of the KDM5 enzyme is essential for the repression of astrocytic differentiation of neural stem cells (NSCs). KDM5-C70 treatment activated the glial fibrillary acidic protein (Gfap) gene by increasing the trimethylation of histone H3 lysine 4 in the promoter regions and subsequently induced astrocytogenesis in NSCs. In addition, treatment of NSCs with KDM5-C70 activated Janus kinase-signal transducer and activator of transcription (JAK-STAT3) signaling and increased the mRNA expression of transforming growth factor-beta 1 (Tgf-β1). Our data provide evidence that KDM5 is a promising target for NSC fate modulation and suggest that epigenetic regulation is important for NSC fate determination.

Regulation of GFAP Expression

Expression of the GFAP gene has attracted considerable attention because its onset is a marker for astrocyte development, its upregulation is a marker for reactive gliosis, and its predominance in astrocytes provides a tool for their genetic manipulation. The literature on GFAP regulation is voluminous, as almost any perturbation of development or homeostasis in the CNS will lead to changes in its expression. In this review, we limit our discussion to mechanisms proposed to regulate GFAP synthesis through a direct interaction with its gene or mRNA. Strengths and weaknesses of the supportive experimental findings are described, and suggestions made for additional studies. This review covers 15 transcription factors, DNA and histone methylation, and microRNAs. The complexity involved in regulating the expression of this intermediate filament protein suggests that GFAP function may vary among both astrocyte subtypes and other GFAP-expressing cells, as well as during development and in response to perturbations.

2-Oxoglutarate-dependent dioxygenases in cancer

2-Oxoglutarate-dependent dioxygenases (2OGDDs) are a superfamily of enzymes that play diverse roles in many biological processes, including regulation of hypoxia-inducible factor-mediated adaptation to hypoxia, extracellular matrix formation, epigenetic regulation of gene transcription and the reprogramming of cellular metabolism. 2OGDDs all require oxygen, reduced iron and 2-oxoglutarate (also known as α-ketoglutarate) to function, although their affinities for each of these co-substrates, and hence their sensitivity to depletion of specific co-substrates, varies widely. Numerous 2OGDDs are recurrently dysregulated in cancer. Moreover, cancer-specific metabolic changes, such as those that occur subsequent to mutations in the genes encoding succinate dehydrogenase, fumarate hydratase or isocitrate dehydrogenase, can dysregulate specific 2OGDDs. This latter observation suggests that the role of 2OGDDs in cancer extends beyond cancers that harbour mutations in the genes encoding members of the 2OGDD superfamily. Herein, we review the regulation of 2OGDDs in normal cells and how that regulation is corrupted in cancer.

Proteasome Inhibitor MG132 is Toxic and Inhibits the Proliferation of Rat Neural Stem Cells but Increases BDNF Expression to Protect Neurons

Regulation of protein expression is essential for maintaining normal cell function. Proteasomes play important roles in protein degradation and dysregulation of proteasomes is implicated in neurodegenerative disorders. In this study, using a proteasome inhibitor MG132, we showed that proteasome inhibition reduces neural stem cell (NSC) proliferation and is toxic to NSCs. Interestingly, MG132 treatment increased the percentage of neurons in both proliferation and differentiation culture conditions of NSCs. Proteasome inhibition reduced B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X protein ratio. In addition, MG132 treatment induced cAMP response element-binding protein phosphorylation and increased the expression of brain-derived neurotrophic factor transcripts and proteins. These data suggest that proteasome function is important for NSC survival and differentiation. Moreover, although MG132 is toxic to NSCs, it may increase neurogenesis. Therefore, by modifying MG132 chemical structure and developing none toxic proteasome inhibitors, neurogenic chemicals can be developed to control NSC cell fate.

Molecular mechanisms of KDM5A in cellular functions: Facets during development and disease

Gene expression is influenced at many layers by a fine-tuned crosstalk between multiple extrinsic signalling pathways and intrinsic regulatory molecules that respond to environmental stimuli. Epigenetic modifiers like DNA methyltransferases, histone modifying enzymes and chromatin remodellers are reported to act as triggering factors in many scenarios by exhibiting their control over most of the cellular processes. These epigenetic players can either directly regulate gene expression or interact with some effector molecules that harmonize the expression of downstream genes. One such epigenetic regulator which exhibits multifaceted regulation over gene expression is KDM5A. It is classically a transcriptional repressor acting as H3K4me3 demethylase, but also is reported to act as an activator in many contexts either by loss of activity due to inhibition manifested by other interacting proteins or by downregulating the negative players of a given physiological process thereby escalating the framework. Through this review, we draw attention to the remarkable modes of functioning laid by KDM5A on transcriptional and translational processes, affecting gene expression during differentiation and development and finally summing up on role in disease causation (Fig. 1). We also shed light on different orthologs of KDM5A and their organism specific roles, along with comparison of the sequence similarity to extrapolate some unanswered questions about this protein.

Early But Not Delayed Optogenetic RAF Activation Promotes Astrocytogenesis in Mouse Neural Progenitors

The RAS/RAF/MEK/ERK pathway promotes gliogenesis but the kinetic role of RAF1, a key RAF kinase, in the induction of astrocytogenesis remains to be elucidated. To address this challenge, we determine the temporal functional outcome of RAF1 during mouse neural progenitor cell differentiation using an optogenetic RAF1 system (OptoRAF1). OptoRAF1 allows for reversible activation of the RAF/MEK/ERK pathway via plasma membrane recruitment of RAF1 based on blue light-sensitive protein dimerizer CRY2/CIB1. We found that early light-induced OptoRAF1 activation in neural progenitor cells promotes cell proliferation and increased expression of glial markers and glia-enriched genes. However, delayed OptoRAF1 activation in differentiated neural progenitor had little effect on glia marker expression, suggesting that RAF1 is required to promote astrocytogenesis only within a short time window. In addition, activation of OptoRAF1 did not have a significant effect on neurogenesis, but was able to promote neuronal neurite growth.

Ribosome and Translational Control in Stem Cells

Embryonic stem cells (ESCs) and adult stem cells (ASCs) possess the remarkable capacity to self-renew while remaining poised to differentiate into multiple progenies in the context of a rapidly developing embryo or in steady-state tissues, respectively. This ability is controlled by complex genetic programs, which are dynamically orchestrated at different steps of gene expression, including chromatin remodeling, mRNA transcription, processing, and stability. In addition to maintaining stem cell homeostasis, these molecular processes need to be rapidly rewired to coordinate complex physiological modifications required to redirect cell fate in response to environmental clues, such as differentiation signals or tissue injuries. Although chromatin remodeling and mRNA expression have been extensively studied in stem cells, accumulating evidence suggests that stem cell transcriptomes and proteomes are poorly correlated and that stem cell properties require finely tuned protein synthesis. In addition, many studies have shown that the biogenesis of the translation machinery, the ribosome, is decisive for sustaining ESC and ASC properties. Therefore, these observations emphasize the importance of translational control in stem cell homeostasis and fate decisions. In this review, we will provide the most recent literature describing how ribosome biogenesis and translational control regulate stem cell functions and are crucial for accommodating proteome remodeling in response to changes in stem cell fate.

Functional Group-Dependent Induction of Astrocytogenesis and Neurogenesis by Flavone Derivatives

Neural stem cells (NSCs) differentiate into multiple cell types, including neurons, astrocytes, and oligodendrocytes, and provide an excellent platform to screen drugs against neurodegenerative diseases. Flavonoids exert a wide range of biological functions on several cell types and affect the fate of NSCs. In the present study, we investigated whether the structure-activity relationships of flavone derivatives influence NSC differentiation. As previously reported, we observed that PD98059 (2′-amino-3′-methoxy-flavone), compound 2 (3′-methoxy-flavone) induced astrocytogenesis. In the present study, we showed that compound 3 (2′-hydroxy-3′-methoxy-flavone), containing a 3′-methoxy group, and a non-bulky group at C2′ and C4′, induced astrocytogenesis through JAK-STAT3 signaling pathway. However, compound 1 and 7–12 without the methoxy group did not show such effects. Interestingly, the compounds 4 (2′,3′-dimethoxyflavone), 5 (2′-N-phenylacetamido-3′-methoxy-flavone), and 6 (3′,4′-dimethoxyflavone) containing 3′-methoxy could not promote astrocytic differentiation, suggesting that both the methoxy groups at C3′ and non-bulky group at C2′ and C4′ are required for the induction of astrocytogenesis. Notably, compound 6 promoted neuronal differentiation, whereas its 4′-demethoxylated analog, compound 2, repressed neurogenesis, suggesting an essential role of the methoxy group at C4′ in neurogenesis. These findings revealed that subtle structural changes of flavone derivatives have pronounced effects on NSC differentiation and can guide to design and develop novel flavone chemicals targeting NSCs fate regulation.

Cell Fate Control by Translation: mRNA Translation Initiation as a Therapeutic Target for Cancer Development and Stem Cell Fate Control

Translation of mRNA is an important process that controls cell behavior and gene regulation because proteins are the functional molecules that determine cell types and function. Cancer develops as a result of genetic mutations, which lead to the production of abnormal proteins and the dysregulation of translation, which in turn, leads to aberrant protein synthesis. In addition, the machinery that is involved in protein synthesis plays critical roles in stem cell fate determination. In the current review, recent advances in the understanding of translational control, especially translational initiation in cancer development and stem cell fate control, are described. Therapeutic targets of mRNA translation such as eIF4E, 4EBP, and eIF2, for cancer treatment or stem cell fate regulation are reviewed. Upstream signaling pathways that regulate and affect translation initiation were introduced. It is important to regulate the expression of protein for normal cell behavior and development. mRNA translation initiation is a key step to regulate protein synthesis, therefore, identifying and targeting molecules that are critical for protein synthesis is necessary and beneficial to develop cancer therapeutics and stem cells fate regulation.

Neurochemical regulation of the expression and function of glial fibrillary acidic protein in astrocytes

Glial fibrillary acidic protein (GFAP), a type III intermediate filament, is a marker of mature astrocytes. The expression of GFAP gene is regulated by many transcription factors (TFs), mainly Janus kinase-2/signal transducer and activator of transcription 3 cascade and nuclear factor κ-light-chain-enhancer of activated B cell signaling. GFAP expression is also modulated by protein kinase and other signaling molecules that are elicited by neuronal activity and hormones. Abnormal expression of GFAP proteins occurs in neuroinflammation, neurodegeneration, brain edema-eliciting diseases, traumatic brain injury, psychiatric disorders and others. GFAP, mainly in α-isoform, is the major component of cytoskeleton and the scaffold of astrocytes, which is essential for the maintenance of astrocytic structure and shape. GFAP also has highly morphological plasticity because of its quick changes in assembling and polymerizing states in response to environmental challenges. This plasticity and its corresponding cellular morphological changes endow astrocytes the functions of physical barrier between adjacent neurons and stabilizer of extracellular environment. Moreover, GFAP colocalizes and even molecularly associates with many functional molecules. This feature allows GFAP to function as a platform for direct interactions between different molecules. Last, GFAP involves transportation and localization of other functional proteins and thus serves as a protein transport guide in astrocytes. This guiding role of GFAP involves an elastic retraction and extension cytoskeletal network that couples with GFAP reassembling, transporting, and membrane protein recycling machinery. This paper reviews our current understanding of the expression and functions of GFAP as well as their regulation.

Differential effects of MEK inhibitors on rat neural stem cell differentiation: Repressive roles of MEK2 in neurogenesis and induction of astrocytogenesis by PD98059

Neural stem cells (NSCs) proliferate and differentiate into neurons and glia depending on the culture environment. However, the underlying mechanisms determining the fate of NSCs are not fully understood. Growth factors facilitate NSC proliferation through mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) and MAPK activation, and NSCs differentiate into neurons, astrocytes, or oligodendrocytes when mitogens are withdrawn from the culture media. Here, we aimed to identify the effects and roles of MEK signaling on the determination of NSC fate. MEK inhibitors, U0126, SL327, and PD98059, had differential effects on NSC differentiation. U0126 and SL327, which are known to inhibit MEK1 and MEK2, induced neuronal differentiation, whereas PD98059, which is reported to preferentially inhibit MEK1 at higher concentrations, increased astrocytogenesis. Knockdown of MEK2 using small interfering RNA increased neurogenesis and over-expression of wild type (WT) MEK2 inhibited neurogenesis, suggesting a repressive role of MEK2 in neuronal differentiation. The chemical structure of PD98059 appears to be important for induction of astrocytogenesis because not only PD98059 (2'-amino-3'-methoxyflavone) but also its chemical structural mimetic, 3'-methoxyflavone, enhanced astrocytogenesis. Therefore, in our study, we suggest that MEK inhibitors have distinct functions in determining NSC fate. Inhibition of MEK2 is important for induction of neurogenesis in NSCs. U0126 and SL327 increase neurogenesis through MEK2 inhibition, whereas PD98059 induced astrocytogenesis in NSCs, which is mediated by the chemical structure, particularly the 3'-methoxy group rather than its renowned MEK1 inhibition.

Characterization and classification of rat neural stem cells and differentiated cells by comparative metabolic and lipidomic profiling

It is necessary to characterize and classify neural stem cells (NSCs) and differentiated cells (DCs) for potential use of NSC to treat neurodegenerative diseases. We therefore performed an analysis of NSCs and DCs using gas chromatography mass spectrometry (GC-MS) and direct infusion mass spectrometry (DI-MS) with elaborate multivariate statistical analysis for the characterization and classification of rat NSCs and DCs. GC-MS and DI-MS detected a total of 92 metabolites and lipids in NSCs and DCs, and the levels of 72 of them differed significantly between NSCs and DCs. The optimal model for partial least squares (PLS) discriminant analysis was constructed by applying 3 and 2 PLS components with a unit-variance scaling method for classifying NSCs and DCs based on the data obtained in the GC-MS and DI-MS analyses, respectively. The obtained results from PCA and PLS-DA suggest that creatinine, lactic acid, lysine, glutamine, glycine, pyroglutamic acid, PG 18:1/20:2, PS 18:0/20:2, PI 18:0/20:3, PC 16:0/20:4, PI 16:0/20:4, and PI 18:1/20:4 were the main contributors that provided distinct characteristics of NSCs and DCs. The results of this study suggest objective and complementary criteria for the characterization and classification of NSCs and DCs for potential clinical applications. Graphical abstract.

Histone demethylase KDM5A is transactivated by the transcription factor C/EBPβ and promotes preadipocyte differentiation by inhibiting Wnt/β-catenin signaling

β-Catenin signaling is triggered by WNT proteins and is an important pathway that negatively regulates adipogenesis. However, the mechanisms controlling the expression of WNT proteins during adipogenesis remain incompletely understood. Lysine demethylase 5A (KDM5A) is a histone demethylase that removes trimethyl (me3) marks from lysine 4 of histone 3 (H3K4) and serves as a general transcriptional corepressor. Here, using the murine 3T3-L1 preadipocyte differentiation model and an array of biochemical approaches, including ChIP, immunoprecipitation, RT-qPCR, and immunoblotting assays, we show that Kdm5a is a target gene of CCAAT/enhancer-binding protein β (C/EBPβ), an important early transcription factor required for adipogenesis. We found that C/EBPβ binds to the Kdm5a gene promoter and transactivates its expression. We also found that siRNA-mediated KDM5A down-regulation inhibits 3T3-L1 preadipocyte differentiation. The KDM5A knockdown significantly up-regulates the negative regulator of adipogenesis Wnt6, having increased levels of the H3K4me3 mark on its promoter. We further observed that WNT6 knockdown significantly rescues adipogenesis inhibited by the KDM5A knockdown. Moreover, we noted that C/EBPβ negatively regulates Wnt6 expression by binding to the Wnt6 gene promoter and repressing Wnt6 transcription. Further experiments indicated that KDM5A interacts with C/EBPβ and that their interaction cooperatively inhibits Wnt6 transcription. Of note, C/EBPβ knockdown impaired the recruitment of KDM5A to the Wnt6 promoter, which had higher H3K4me3 levels. Our results suggest a mechanism involving C/EBPβ and KDM5A activities that down-regulates the Wnt/β-catenin pathway during 3T3-L1 preadipocyte differentiation.

Regulation of Neural Stem Cell Fate by Natural Products

Neural stem cells (NSCs) can proliferate and differentiate into multiple cell types that constitute the nervous system. NSCs can be derived from developing fetuses, embryonic stem cells, or induced pluripotent stem cells. NSCs provide a good platform to screen drugs for neurodegenerative diseases and also have potential applications in regenerative medicine. Natural products have long been used as compounds to develop new drugs. In this review, natural products that control NSC fate and induce their differentiation into neurons or glia are discussed. These phytochemicals enable promising advances to be made in the treatment of neurodegenerative diseases.

Transcriptional and epigenetic mechanisms underlying astrocyte identity

Astrocytes play a significant role in coordinating neural development and provide critical support for the function of the CNS. They possess important adaptation capacities that range from their transition towards reactive astrocytes to their ability to undergo reprogramming, thereby revealing their potential to retain latent features of neural progenitor cells. We propose that the mechanisms underlying reactive astrogliosis or astrocyte reprogramming provide an opportunity for initiating neuronal regeneration, a process that is notably reduced in the mammalian nervous system throughout evolution. Conversely, this plasticity may also affect normal astrocytic functions resulting in pathologies ranging from neurodevelopmental disorders to neurodegenerative diseases and brain tumors. We postulate that epigenetic mechanisms linking extrinsic cues and intrinsic transcriptional programs are key factors to maintain astrocyte identity and function, and critically, to control the balance of regenerative and degenerative activity. Here, we will review the main evidences supporting this concept. We propose that unravelling the epigenetic and transcriptional mechanisms underlying the acquisition of astrocyte identity and plasticity, as well as understanding how these processes are modulated by the local microenvironment under specific threatening or pathological conditions, may pave the way to new therapeutic avenues for several neurological disorders including neurodegenerative diseases and brain tumors of astrocytic lineage.

Increased Expression of Lysine-Specific Demethylase 5B (KDM5B) Promotes Tumor Cell Growth in Hep3B Cells and is an Independent Prognostic Factor in Patients with Hepatocellular Carcinoma

BACKGROUND Lysine-specific demethylase 5B (KDM5B) is overexpressed in several types of cancer. However, the clinical significance of KDM5B expression in hepatocellular carcinoma (HCC) remains unclear. The aims of the present study were to examine the functional effects of KDM5B in the Hep3B cell line, the expression levels of KDM5B in human HCC tissues, and the association between KDM5B expression and clinical outcome in patients with HCC. MATERIAL AND METHODS Immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR) were used to examine the expression levels of KDM5B in HCC tissues and adjacent normal liver tissues. In the HCC cell line, Hep3B, the effects of KDM5B on cell proliferation and migration, and KDM5B small interfering RNA (siRNA) were used to study KDM5B knockdown. Univariate and multivariate analysis assessed the prognostic role of KDM5B in HCC patients. Kaplan-Meier analysis and the log-rank test evaluated clinical outcomes. RESULTS In the HCC cell line, Hep3B, KDM5B expression promoted promote tumor cell proliferation and colony formation. Increased expression of KDM5B in HCC tissues, compared with adjacent normal liver tissues, and was associated with larger tumor size, advanced TNM stage, and reduced overall survival in patients with HCC. Multivariate analysis identified KDM5B expression as an independent prognostic factor. CONCLUSIONS Increased expression of KDM5B was significantly correlated with poorer prognosis in patients with patients with HCC, indicating the possible potential of KDM5B as a novel clinical biomarker and therapeutic target.

Neural Stem Cell Differentiation Using Microfluidic Device-Generated Growth Factor Gradient

Neural stem cells (NSCs) have the ability to self-renew and differentiate into multiple nervous system cell types. During embryonic development, the concentrations of soluble biological molecules have a critical role in controlling cell proliferation, migration, differentiation and apoptosis. In an effort to find optimal culture conditions for the generation of desired cell types in vitro, we used a microfluidic chip-generated growth factor gradient system. In the current study, NSCs in the microfluidic device remained healthy during the entire period of cell culture, and proliferated and differentiated in response to the concentration gradient of growth factors (epithermal growth factor and basic fibroblast growth factor). We also showed that overexpression of ASCL1 in NSCs increased neuronal differentiation depending on the concentration gradient of growth factors generated in the microfluidic gradient chip. The microfluidic system allowed us to study concentration-dependent effects of growth factors within a single device, while a traditional system requires multiple independent cultures using fixed growth factor concentrations. Our study suggests that the microfluidic gradient-generating chip is a powerful tool for determining the optimal culture conditions.