Genetics and Epigenetics in Adult Neurogenesis

Personalized Stem Cell-Based Regeneration in Spinal Cord Injury Care

Spinal cord injury (SCI) remains a major clinical challenge, with limited therapeutic options for restoring lost neurological function. While efforts to mitigate secondary damage have improved early-phase management, achieving sustained neurorepair and functional recovery remains elusive. Advances in stem cell engineering and regenerative medicine have opened new avenues for targeted interventions, particularly through the transplantation of neural stem/progenitor cells (NSPCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs). However, patient-specific factors such as cellular senescence, genetic and epigenetic variability, injury microenvironment, and comorbidities influence the efficacy of stem cell therapies by affecting graft survival and differentiation. Overcoming these challenges necessitates cutting-edge technologies, including single-cell transcriptomics, CRISPR-mediated hypoimmunogenic engineering, and biomaterial-based delivery platforms, which enable personalized and precision-driven SCI repair. Leveraging these advancements may help stem cell therapies overcome translational barriers and establish clinically viable regenerative solutions. This review explores the intersection of patient-specific variability, bioengineering innovations, and transcriptomic-guided precision medicine to define the next frontier in SCI therapy.

Sustaining Brain Youth by Neural Stem Cells: Physiological and Therapeutic Perspectives

In the last two decades, stem cells (SCs) have attracted considerable interest for their research value and therapeutic potential in many fields, namely in neuroscience. On the other hand, the discovery of adult neurogenesis, the process by which new neurons are generated in the adult brain, challenged the traditional view that the brain is a static structure after development. The recent findings showing that adult neurogenesis has a significant role in brain plasticity, learning and memory, and emotional behavior, together with the fact that it is strongly dependent on several external and internal factors, have sparked more interest in this area. The mechanisms of adult neural stem cell (NSC) regulation, the physiological role of NSC-mediated neuroplasticity throughout life, and the most recent NSC-based therapeutic applications will be concisely reviewed. Noteworthy, due to their multipotency, self-renewal potential, and ability to secrete growth and immunomodulatory factors, NSCs have been mainly suggested for (1) transplantation, (2) neurotoxicology tests, and (3) drug screening approaches. The clinical trials of NSC-based therapy for different neurologic conditions are, nonetheless, mostly in the early phases and have not yet demonstrated conclusive efficacy or safety. Here, we provide an outlook of the major challenges and limitations, as well as some promising directions that could help to move toward stem cell widespread use in the treatment and prevention of several neurological disorders.

Integrating epigenetic modification and stem cell therapy strategies: A novel approach for advancing Alzheimer's disease treatment - A literature review

Alzheimer's disease (AD) is the most frequent form of dementia and represents an increasing global burden, particularly in countries like Indonesia, where the population has begun to age significantly. Current medications, including cholinesterase inhibitors and NMDA receptor antagonists, have modest effects on clinical symptoms in the early to middle stages, but there is no curative treatment available so far despite progress. Activating or repressing epigenetic modifications, including DNA methylation, histone modification and microRNA regulation, appears to play an important role in AD development. These alterations further enact transcriptional changes relevant to the signature AD pathologies of amyloid-β deposition, tau protein malfunctioning, neuroinflammation, and neuronal death. Here, we discuss the feasibility of targeting these epigenetic alterations as a new treatment strategy due to the reversibility of epigenetics and their ability to correct faulty gene expression. We also review the combined promise of stem cell therapies and epigenetic modulation in neurodegeneration, inflammation and cognitive decline. This combined approach may provide a multifaceted strategy to slow disease progression, replace lost neurons, and restore neural function. Despite challenges, including ethical, financial, and methodological barriers, ongoing research in epigenetic modulation and stem cell therapy holds promise for pioneering therapies in AD.

Using Small Molecules to Reprogram RPE Cells in Regenerative Medicine for Degenerative Eye Disease

The main purpose of regenerative medicine for degenerative eye diseases is to create cells to replace lost or damaged ones. Due to their anatomical, genetic, and epigenetic features, characteristics of origin, evolutionary inheritance, capacity for dedifferentiation, proliferation, and plasticity, mammalian and human RPE cells are of great interest as endogenous sources of new photoreceptors and other neurons for the degrading retina. Promising methods for the reprogramming of RPE cells into retinal cells include genetic methods and chemical methods under the influence of certain low-molecular-weight compounds, so-called small molecules. Depending on the goal, which can be the preservation or the replacement of lost RPE cells and cellular structures, various small molecules are used to influence certain biological processes at different levels of cellular regulation. This review discusses the potential of the chemical reprogramming of RPE cells in comparison with other somatic cells and induced pluripotent stem cells (iPSCs) into neural cells of the brain and retina. Possible mechanisms of the chemically induced reprogramming of somatic cells under the influence of small molecules are explored and compared. This review also considers other possibilities in using them in the treatment of retinal degenerative diseases based on the protection, preservation, and support of survived RPE and retinal cells.

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.

Fucosyltransferase 8 regulates adult neurogenesis and cognition of mice by modulating the Itga6-PI3K/Akt signaling pathway

Fucosyltransferase 8 (Fut8) and core fucosylation play critical roles in regulating various biological processes, including immune response, signal transduction, proteasomal degradation, and energy metabolism. However, the function and underlying mechanism of Fut8 and core fucosylation in regulating adult neurogenesis remains unknown. We have shown that Fut8 and core fucosylation display dynamic features during the differentiation of adult neural stem/progenitor cells (aNSPCs) and postnatal brain development. Fut8 depletion reduces the proliferation of aNSPCs and inhibits neuronal differentiation of aNSPCs in vitro and in vivo, respectively. Additionally, Fut8 deficiency impairs learning and memory in mice. Mechanistically, Fut8 directly interacts with integrin α6 (Itga6), an upstream regulator of the PI3k-Akt signaling pathway, and catalyzes core fucosylation of Itga6. Deletion of Fut8 enhances the ubiquitination of Itga6 by promoting the binding of ubiquitin ligase Trim21 to Itga6. Low levels of Itga6 inhibit the activity of the PI3K/Akt signaling pathway. Moreover, the Akt agonist SC79 can rescue neurogenic and behavioral deficits caused by Fut8 deficiency. In summary, our study uncovers an essential function of Fut8 and core fucosylation in regulating adult neurogenesis and sheds light on the underlying mechanisms.

An Overview of the Epigenetic Modifications in the Brain under Normal and Pathological Conditions

Epigenetic changes are changes in gene expression that do not involve alterations to the DNA sequence. These changes lead to establishing a so-called epigenetic code that dictates which and when genes are activated, thus orchestrating gene regulation and playing a central role in development, health, and disease. The brain, being mostly formed by cells that do not undergo a renewal process throughout life, is highly prone to the risk of alterations leading to neuronal death and neurodegenerative disorders, mainly at a late age. Here, we review the main epigenetic modifications that have been described in the brain, with particular attention on those related to the onset of developmental anomalies or neurodegenerative conditions and/or occurring in old age. DNA methylation and several types of histone modifications (acetylation, methylation, phosphorylation, ubiquitination, sumoylation, lactylation, and crotonylation) are major players in these processes. They are directly or indirectly involved in the onset of neurodegeneration in Alzheimer's or Parkinson's disease. Therefore, this review briefly describes the roles of these epigenetic changes in the mechanisms of brain development, maturation, and aging and some of the most important factors dynamically regulating or contributing to these changes, such as oxidative stress, inflammation, and mitochondrial dysfunction.

Epigenetic regulation in adult neural stem cells

Neural stem cells (NSCs) exhibit self-renewing and multipotential properties. Adult NSCs are located in two neurogenic regions of adult brain: the ventricular-subventricular zone (V-SVZ) of the lateral ventricle and the subgranular zone of the dentate gyrus in the hippocampus. Maintenance and differentiation of adult NSCs are regulated by both intrinsic and extrinsic signals that may be integrated through expression of some key factors in the adult NSCs. A number of transcription factors have been shown to play essential roles in transcriptional regulation of NSC cell fate transitions in the adult brain. Epigenetic regulators have also emerged as key players in regulation of NSCs, neural progenitor cells and their differentiated progeny via epigenetic modifications including DNA methylation, histone modifications, chromatin remodeling and RNA-mediated transcriptional regulation. This minireview is primarily focused on epigenetic regulations of adult NSCs during adult neurogenesis, in conjunction with transcriptional regulation in these processes.

Does DNA methylation in the fetal brain leave an epigenetic memory in the blood?

Epigenetic memory is an emerging concept that refers to the process in which epigenetic changes occurring early-in life can lead to long-term programs of gene regulation in time and space. By leveraging neural network regression modeling of DNA methylation data in pigs, we show that specific methylations in the adult blood can reliably predict methylation changes that occurred in the fetal brain. Genes associated with these methylations represented known markers of specific cell types of blood including bone marrow hematopoietic progenitor cells, and ependymal and oligodendrocyte cells of brain. This suggested that methylation changes that occurred in the developing brain were maintained as an epigenetic memory in the blood through the adult life.

Adult neurogenesis research in China

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Polycomb repressive complex 2 regulates basal cell fate during adult olfactory neurogenesis

Adult neurogenesis occurs in the mammalian olfactory epithelium to maintain populations of neurons that are vulnerable to injury yet essential for olfaction. Multipotent olfactory basal stem cells are activated by damage, although mechanisms regulating lineage decisions are not understood. Using mouse lesion models, we focused on defining the role of Polycomb repressive complexes (PRCs) in olfactory neurogenesis. PRC2 has a well-established role in developing tissues, orchestrating transcriptional programs via chromatin modification. PRC2 proteins are expressed in olfactory globose basal cells (GBCs) and nascent neurons. Conditional PRC2 loss perturbs lesion-induced neuron production, accompanied by altered histone modifications and misexpression of lineage-specific transcription factors in GBCs. De-repression of Sox9 in PRC2-mutant GBCs is accompanied by increased Bowman's gland production, defining an unrecognized role for PRC2 in regulating gland versus neuron cell fate. Our findings support a model for PRC2-dependent mechanisms promoting sensory neuronal differentiation in an adult neurogenic niche.

Mechanisms underlying the effect of voluntary running on adult hippocampal neurogenesis

Adult hippocampal neurogenesis is important for preserving learning and memory-related cognitive functions. Physical exercise, especially voluntary running, is one of the strongest stimuli to promote neurogenesis and has beneficial effects on cognitive functions. Voluntary running promotes exit of neural stem cells (NSCs) from the quiescent stage, proliferation of NSCs and progenitors, survival of newborn cells, morphological development of immature neuron, and integration of new neurons into the hippocampal circuitry. However, the detailed mechanisms driving these changes remain unclear. In this review, we will summarize current knowledge with respect to molecular mechanisms underlying voluntary running-induced neurogenesis, highlighting recent genome-wide gene expression analyses. In addition, we will discuss new approaches and future directions for dissecting the complex cellular mechanisms driving change in adult-born new neurons in response to physical exercise.

Conserved and Distinct Functions of the Autism-Related Chromatin Remodeler CHD8 in Embryonic and Adult Forebrain Neurogenesis

The chromatin remodeler CHD8 represents a high-confidence risk factor in autism, a multistage progressive neurologic disorder, however the underlying stage-specific functions remain elusive. In this study, by analyzing Chd8 conditional knock-out mice (male and female), we find that CHD8 controls cortical neural stem/progenitor cell (NSC) proliferation and survival in a stage-dependent manner. Strikingly, inducible genetic deletion reveals that CHD8 is required for the production and fitness of transit-amplifying intermediate progenitors (IPCs) essential for upper-layer neuron expansion in the embryonic cortex. p53 loss of function partially rescues apoptosis and neurogenesis defects in the Chd8-deficient brain. Further, transcriptomic and epigenomic profiling indicates that CHD8 regulates the chromatin accessibility landscape to activate neurogenesis-promoting factors including TBR2, a key regulator of IPC neurogenesis, while repressing DNA damage- and p53-induced apoptotic programs. In the adult brain, CHD8 depletion impairs forebrain neurogenesis by impeding IPC differentiation from NSCs in both subventricular and subgranular zones; however, unlike in embryos, it does not affect NSC proliferation and survival. Treatment with an antidepressant approved by the Federal Drug Administration (FDA), fluoxetine, partially restores adult hippocampal neurogenesis in Chd8-ablated mice. Together, our multistage functional studies identify temporally specific roles for CHD8 in developmental and adult neurogenesis, pointing to a potential strategy to enhance neurogenesis in the CHD8-deficient brain.SIGNIFICANCE STATEMENT The role of the high-confidence autism gene CHD8 in neurogenesis remains incompletely understood. Here, we identify a stage-specific function of CHD8 in development of NSCs in developing and adult brains by conserved, yet spatiotemporally distinct, mechanisms. In embryonic cortex, CHD8 is critical for the proliferation, survival, and differentiation of both NSC and IPCs during cortical neurogenesis. In adult brain, CHD8 is required for IPC generation but not the proliferation and survival of adult NSCs. Treatment with FDA-approved antidepressant fluoxetine partially rescues the adult neurogenesis defects in CHD8 mutants. Thus, our findings help resolve CHD8 functions throughout life during embryonic and adult neurogenesis and point to a potential avenue to promote neurogenesis in CHD8 deficiency.

m6A Modification Involves in Enriched Environment-Induced Neurogenesis and Cognition Enhancement

Although previous studies have shown that an enriched environment (EE) promotes neurogenesis and alters DNA and histone modifications, it remains largely unknown whether an EE affects epitranscriptome in the context of neuronal development. Here, we showed that EE exposure enhanced the pool of adult neural stem/progenitor cells (aNSPCs) and promoted neuronal differentiation of aNSPCs. EE exposure also improved cognitive capabilities and altered the expression of genes relating to neuronal development, neurogenesis, and memory. N6-Methyladenosine (m6A) immunoprecipitation combined with deep sequencing (MeRIP-seq) data analysis revealed that EE exposure increased the global level of m6A and led to differential m6A mRNA modification. Differential m6A modification-associated genes are involved in neuronal development, neurogenesis, and so on. Notably, EE exposure decreased the protein level of m6A eraser Fto, but did not affect the protein level of m6A writers METTL3 and METTL14. Taken together, our results suggest that enriched environment exposure induces differential m6A mRNA modification and adds a novel layer to the interaction between the environment and epigenetics in the context of postnatal neuronal development.

NAD+ Modulates the Proliferation and Differentiation of Adult Neural Stem/Progenitor Cells via Akt Signaling Pathway

Nicotinamide adenine dinucleotide hydrate (NAD+) acts as the essential component of the tricarboxylic citric acid (TCA) cycle and has important functions in diverse biological processes. However, the roles of NAD+ in regulating adult neural stem/progenitor cells (aNSPCs) remain largely unknown. Here, we show that NAD+ exposure leads to the reduced proliferation and neuronal differentiation of aNSPCs and induces the apoptosis of aNSPCs. In addition, NAD+ exposure inhibits the morphological development of neurons. Mechanistically, RNA sequencing revealed that the transcriptome of aNSPCs is altered by NAD+ exposure. NAD+ exposure significantly decreases the expression of multiple genes related to ATP metabolism and the PI3k-Akt signaling pathway. Collectively, our findings provide some insights into the roles and mechanisms in which NAD+ regulates aNSPCs and neuronal development.

The transcriptional corepressor CTBP-1 acts with the SOX family transcription factor EGL-13 to maintain AIA interneuron cell identity in Caenorhabditis elegans

Cell identity is characterized by a distinct combination of gene expression, cell morphology, and cellular function established as progenitor cells divide and differentiate. Following establishment, cell identities can be unstable and require active and continuous maintenance throughout the remaining life of a cell. Mechanisms underlying the maintenance of cell identities are incompletely understood. Here, we show that the gene ctbp-1, which encodes the transcriptional corepressor C-terminal binding protein-1 (CTBP-1), is essential for the maintenance of the identities of the two AIA interneurons in the nematode Caenorhabditis elegans. ctbp-1 is not required for the establishment of the AIA cell fate but rather functions cell-autonomously and can act in later larval stage and adult worms to maintain proper AIA gene expression, morphology and function. From a screen for suppressors of the ctbp-1 mutant phenotype, we identified the gene egl-13, which encodes a SOX family transcription factor. We found that egl-13 regulates AIA function and aspects of AIA gene expression, but not AIA morphology. We conclude that the CTBP-1 protein maintains AIA cell identity in part by utilizing EGL-13 to repress transcriptional activity in the AIAs. More generally, we propose that transcriptional corepressors like CTBP-1 might be critical factors in the maintenance of cell identities, harnessing the DNA-binding specificity of transcription factors like EGL-13 to selectively regulate gene expression in a cell-specific manner.

H3K9 Methyltransferases Suv39h1 and Suv39h2 Control the Differentiation of Neural Progenitor Cells in the Adult Hippocampus

In the dentate gyrus of the adult hippocampus new neurons are generated from neural precursor cells through different stages including proliferation and differentiation of neural progenitor cells and maturation of newborn neurons. These stages are controlled by the expression of specific transcription factors and epigenetic mechanisms, which together orchestrate the progression of the neurogenic process. However, little is known about the involvement of histone posttranslational modifications, a crucial epigenetic mechanism in embryonic neurogenesis that regulates fate commitment and neuronal differentiation. During embryonic development, the repressive modification trimethylation of histone H3 on lysine 9 (H3K9me3) contributes to the cellular identity of different cell-types. However, the role of this modification and its H3K9 methyltransferases has not been elucidated in adult hippocampal neurogenesis. We determined that during the stages of neurogenesis in the adult mouse dentate gyrus and in cultured adult hippocampal progenitors (AHPs), there was a dynamic change in the expression and distribution of H3K9me3, being enriched at early stages of the neurogenic process. A similar pattern was observed in the hippocampus for the dimethylation of histone H3 on lysine 9 (H3K9me2), another repressive modification. Among H3K9 methyltransferases, the enzymes Suv39h1 and Suv39h2 exhibited high levels of expression at early stages of neurogenesis and their expression decreased upon differentiation. Pharmacological inhibition of these enzymes by chaetocin in AHPs reduced H3K9me3 and concomitantly decreased neuronal differentiation while increasing proliferation. Moreover, Suv39h1 and Suv39h2 knockdown in newborn cells of the adult mouse dentate gyrus by retrovirus-mediated RNA interference impaired neuronal differentiation of progenitor cells. Our results indicate that H3K9me3 and H3K9 methyltransferases Suv39h1 and Suv39h2 are critically involved in the regulation of adult hippocampal neurogenesis by controlling the differentiation of neural progenitor cells.

Artificial Light at Night, Higher Brain Functions and Associated Neuronal Changes: An Avian Perspective

In recent times, there has been an unprecedented increase in usage of electrical lightning. This has led to increase in artificial light at night (ALAN), and it has been suggested as a source of environmental pollution. ALAN exposure has been reported to be associated with disruption of daily rhythms and serious health consequences, such as immune, metabolic, and cognitive dysfunctions in both birds and mammals. Given the worldwide pervasiveness of ALAN, this research topic is also important from an ecological perspective. In birds, daily timings and appropriate temporal niches are important for fitness and survival. Daily rhythms in a wide array of functions are regulated by the circadian clock(s) and endogenous oscillators present in the body. There is accumulating evidence that exposure to ALAN disrupts clock-regulated daily rhythms and suppresses melatonin and sleep in birds. Circadian clock, melatonin, and sleep regulate avian cognitive performance. However, there is limited research on this topic, and most of the insights on the adverse effects of ALAN on cognitive functions are from behavioural studies. Nevertheless, these results raise an intriguing question about the molecular underpinning of the ALAN-induced negative consequences on brain functions. Further research should be focused on the molecular links between ALAN and cognitive performance, including the role of melatonin, which could shed light on the mechanism by which ALAN exposures lead to negative consequences.

Altered White Matter and microRNA Expression in a Murine Model Related to Williams Syndrome Suggests That miR-34b/c Affects Brain Development via Ptpru and Dcx Modulation

Williams syndrome (WS) is a multisystem neurodevelopmental disorder caused by a de novo hemizygous deletion of ~26 genes from chromosome 7q11.23, among them the general transcription factor II-I (GTF2I). By studying a novel murine model for the hypersociability phenotype associated with WS, we previously revealed surprising aberrations in myelination and cell differentiation properties in the cortices of mutant mice compared to controls. These mutant mice had selective deletion of Gtf2i in the excitatory neurons of the forebrain. Here, we applied diffusion magnetic resonance imaging and fiber tracking, which showed a reduction in the number of streamlines in limbic outputs such as the fimbria/fornix fibers and the stria terminalis, as well as the corpus callosum of these mutant mice compared to controls. Furthermore, we utilized next-generation sequencing (NGS) analysis of cortical small RNAs' expression (RNA-Seq) levels to identify altered expression of microRNAs (miRNAs), including two from the miR-34 cluster, known to be involved in prominent processes in the developing nervous system. Luciferase reporter assay confirmed the direct binding of miR-34c-5p to the 3'UTR of PTPRU-a gene involved in neural development that was elevated in the cortices of mutant mice relative to controls. Moreover, we found an age-dependent variation in the expression levels of doublecortin (Dcx)-a verified miR-34 target. Thus, we demonstrate the substantial effect a single gene deletion can exert on miRNA regulation and brain structure, and advance our understanding and, hopefully, treatment of WS.

Luteolin Modulates Neural Stem Cells Fate Determination: In vitro Study on Human Neural Stem Cells, and in vivo Study on LPS-Induced Depression Mice Model

Luteolin is a natural flavone with neurotrophic effects observed on different neuronal cell lines. In the present study, we aimed to assess the effect of luteolin on hNSCs fate determination and the LPS-induced neuroinflammation in a mouse model of depression with astrocytogenesis defect. hNSCs were cultured in basal cell culture medium (control) or medium supplemented with luteolin or AICAR, a known inducer of astrogenesis. A whole-genome transcriptomic analysis showed that luteolin upregulated the expressions of genes related to neurotrophin, dopaminergic, hippo, and Wnt signaling pathways, and downregulated the genes involved in p53, TNF, FOXO, and Notch signaling pathways. We also found that astrocyte-specific gene GFAP, as well as other genes of the key signaling pathways involved in astrogenesis such as Wnt, BMP, and JAK-STAT pathways were upregulated in luteolin-treated hNSCs. On the other hand, neurogenesis and oligodendrogenesis-related genes, TUBB3, NEUROD 1 and 6, and MBP, were downregulated in luteolin-treated hNSCs. Furthermore, immunostaining showed that percentages of GFAP+ cells were significantly higher in luteolin- and AICAR-treated hNSCs compared to control hNSCs. Additionally, RT-qPCR results showed that luteolin upregulated the expressions of GFAP, BMP2, and STAT3, whereas the expression of TUBB3 remained unchanged. Next, we evaluated the effects of luteolin in LPS-induced mice model of depression that represents defects in astrocytogenesis. We found that oral administration of luteolin (10 mg/Kg) for eight consecutive days could decrease the immobility time on tail suspension test, a mouse behavioral test measuring depression-like behavior, and attenuate LPS-induced inflammatory responses by significantly decreasing IL-6 production in mice brain-derived astrocytes and serum, and TNFα and corticosterone levels in serum. Luteolin treatment also significantly increased mature BDNF, dopamine, and noradrenaline levels in the hypothalamus of LPS-induced depression mice. Though the behavioral effects of luteolin did not reach statistical significance, global gene expression analyses of mice hippocampus and brain-derived NSCs highlighted the modulatory effects of luteolin on different signaling pathways involved in the pathophysiology of depression. Altogether, our findings suggest an astrocytogenic potential of luteolin and its possible therapeutic benefits in neuroinflammatory and neurodegenerative diseases. However, further studies are required to identify the specific mechanism of action of luteolin.

Fto-modulated lipid niche regulates adult neurogenesis through modulating adenosine metabolism

Adult neurogenesis is regulated by diverse factors including the local environment, i.e. the neurogenic niche. However, whether the lipid in the brain regulates adult neurogenesis and related mechanisms remains largely unknown. In the present study, we found that lipid accumulates in the brain during postnatal neuronal development. Conditional knockout of Fto (cKO) in lipid not only reduced the level of lipid in the brain but also impaired the learning and memory of mice. In addition, Fto deficiency in lipid did not affect the proliferation of adult neural stem cells (aNSCs), but it did inhibit adult neurogenesis by inducing cell apoptosis. Mechanistically, specific deleting Fto in lipid altered gene expression and increased adenosine secretion of adipocytes. The treatment of adenosine promoted the apoptosis of newborn neurons. As a whole, these results reveal the important function of the lipid niche and its associated mechanism in regulating adult neurogenesis.

Heavy metals and adult neurogenesis

With extensive use in industrial and agriculture applications, overexposure to heavy metals has become a global public health concern. The nervous system is vulnerable to many heavy metals, including cadmium, lead, and mercury. However, the knowledge about the underlying mechanisms of these metals' neurotoxicity is still very limited. Adult neurogenesis is a process of generating functional neurons from adult neural progenitor/stem cells (aNPCs), which plays an important role in cognitive function and olfaction. The studies of adult neurogenesis provide new insights into mechanisms of heavy metal neurotoxicity. This review summarizes the current research about the effects of heavy metals on adult neurogenesis and discusses their importance in understanding the mechanisms of heavy metals neurotoxicity, as well as challenges and future directions.

Formation and integration of new neurons in the adult hippocampus

Neural stem cells (NSCs) generate new neurons throughout life in the mammalian brain. Adult-born neurons shape brain function, and endogenous NSCs could potentially be harnessed for brain repair. In this Review, focused on hippocampal neurogenesis in rodents, we highlight recent advances in the field based on novel technologies (including single-cell RNA sequencing, intravital imaging and functional observation of newborn cells in behaving mice) and characterize the distinct developmental steps from stem cell activation to the integration of newborn neurons into pre-existing circuits. Further, we review current knowledge of how levels of neurogenesis are regulated, discuss findings regarding survival and maturation of adult-born cells and describe how newborn neurons affect brain function. The evidence arguing for (and against) lifelong neurogenesis in the human hippocampus is briefly summarized. Finally, we provide an outlook of what is needed to improve our understanding of the mechanisms and functional consequences of adult neurogenesis and how the field may move towards more translational relevance in the context of acute and chronic neural injury and stem cell-based brain repair.

Proteins in DNA methylation and their role in neural stem cell proliferation and differentiation

BACKGROUND

Epigenetic modifications, namely non-coding RNAs, DNA methylation, and histone modifications such as methylation, phosphorylation, acetylation, ubiquitylation, and sumoylation play a significant role in brain development. DNA methyltransferases, methyl-CpG binding proteins, and ten-eleven translocation proteins facilitate the maintenance, interpretation, and removal of DNA methylation, respectively. Different forms of methylation, including 5-methylcytosine, 5-hydroxymethylcytosine, and other oxidized forms, have been detected by recently developed sequencing technologies. Emerging evidence suggests that the diversity of DNA methylation patterns in the brain plays a key role in fine-tuning and coordinating gene expression in the development, plasticity, and disorders of the mammalian central nervous system. Neural stem cells (NSCs), originating from the neuroepithelium, generate neurons and glial cells in the central nervous system and contribute to brain plasticity in the adult mammalian brain.

MAIN BODY

Here, we summarized recent research in proteins responsible for the establishment, maintenance, interpretation, and removal of DNA methylation and those involved in the regulation of the proliferation and differentiation of NSCs. In addition, we discussed the interactions of chemicals with epigenetic pathways to regulate NSCs as well as the connections between proteins involved in DNA methylation and human diseases.

CONCLUSION

Understanding the interplay between DNA methylation and NSCs in a broad biological context can facilitate the related studies and reduce potential misunderstanding.

Ogt controls neural stem/progenitor cell pool and adult neurogenesis through modulating Notch signaling

Ogt catalyzed O-linked N-acetylglucosamine (O-GlcNAcylation, O-GlcNAc) plays an important function in diverse biological processes and diseases. However, the roles of Ogt in regulating neurogenesis remain largely unknown. Here, we show that Ogt deficiency or depletion in adult neural stem/progenitor cells (aNSPCs) leads to the diminishment of the aNSPC pool and aberrant neurogenesis and consequently impairs cognitive function in adult mice. RNA sequencing reveals that Ogt deficiency alters the transcription of genes relating to cell cycle, neurogenesis, and neuronal development. Mechanistic studies show that Ogt directly interacts with Notch1 and catalyzes the O-GlcNAc modification of Notch TM/ICD fragment. Decreased O-GlcNAc modification of TM/ICD increases the binding of E3 ubiquitin ligase Itch to TM/ICD and promotes its degradation. Itch knockdown rescues neurogenic defects induced by Ogt deficiency in vitro and in vivo. Our findings reveal the essential roles and mechanisms of Ogt and O-GlcNAc modification in regulating mammalian neurogenesis and cognition.

AlCl3 exposure regulates neuronal development by modulating DNA modification

BACKGROUND

As the third most abundant element, aluminum is widespread in the environment. Previous studies have shown that aluminum has a neurotoxic effect and its exposure can impair neuronal development and cognitive function.

AIM

To study the effects of aluminum on epigenetic modification in neural stem cells and neurons.

METHODS

Neural stem cells were isolated from the forebrain of adult mice. Neurons were isolated from the hippocampi tissues of embryonic day 16-18 mice. AlCl₃ at 100 and 200 μmol/L was applied to stem cells and neurons.

RESULTS

Aluminum altered the differentiation of adult neural stem cells and caused apoptosis of newborn neurons while having no significant effects on the proliferation of neural stem cells. Aluminum application also significantly inhibited the dendritic development of hippocampal neurons. Mechanistically, aluminum exposure significantly affected the levels of DNA 5-hydroxy-methylcytosine, 5-methylcytosine, and N⁶-methyladenine in stem cells and neurons.

CONCLUSION

Our findings indicate that aluminum may regulate neuronal development by modulating DNA modifications.

Communication, Cross Talk, and Signal Integration in the Adult Hippocampal Neurogenic Niche

Radial glia-like neural stem cells (RGLs) in the dentate gyrus subregion of the hippocampus give rise to dentate granule cells (DGCs) and astrocytes throughout life, a process referred to as adult hippocampal neurogenesis. Adult hippocampal neurogenesis is sensitive to experiences, suggesting that it may represent an adaptive mechanism by which hippocampal circuitry is modified in response to environmental demands. Experiential information is conveyed to RGLs, progenitors, and adult-born DGCs via the neurogenic niche that is composed of diverse cell types, extracellular matrix, and afferents. Understanding how the niche performs its functions may guide strategies to maintain its health span and provide a permissive milieu for neurogenesis. Here, we first discuss representative contributions of niche cell types to regulation of neural stem cell (NSC) homeostasis and maturation of adult-born DGCs. We then consider mechanisms by which the activity of multiple niche cell types may be coordinated to communicate signals to NSCs. Finally, we speculate how NSCs integrate niche-derived signals to govern their regulation.

Chemical Genetics Screen Identifies Epigenetic Mechanisms Involved in Dopaminergic and Noradrenergic Neurogenesis in Zebrafish

The cell type diversity and complexity of the nervous system is generated by a network of signaling events, transcription factors, and epigenetic regulators. Signaling and transcriptional control have been easily amenable to forward genetic screens in model organisms like zebrafish. In contrast, epigenetic mechanisms have been somewhat elusive in genetic screens, likely caused by broad action in multiple developmental pathways that masks specific phenotypes, but also by genetic redundancies of epigenetic factors. Here, we performed a screen using small molecule inhibitors of epigenetic mechanisms to reveal contributions to specific aspects of neurogenesis in zebrafish. We chose development of dopaminergic and noradrenergic neurons from neural progenitors as target of epigenetic regulation. We performed the screen in two phases: First, we tested a small molecule inhibitor library that targets a broad range of epigenetic protein classes and mechanisms, using expression of the dopaminergic and noradrenergic marker tyrosine hydroxylase as readout. We identified 10 compounds, including HDAC, Bromodomain and HAT inhibitors, which interfered with dopaminergic and noradrenergic development in larval zebrafish. In the second screening phase, we aimed to identify neurogenesis stages affected by these 10 inhibitors. We analyzed treated embryos for effects on neural stem cells, growth progression of the retina, and apoptosis in neural tissues. In addition, we analyzed effects on islet1 expressing neuronal populations to determine potential selectivity of compounds for transmitter phenotypes. In summary, our targeted screen of epigenetic inhibitors identified specific compounds, which reveal chromatin regulator classes that contribute to dopaminergic and noradrenergic neurogenesis in vivo.

Adenosine kinase inhibition promotes proliferation of neural stem cells after traumatic brain injury

Traumatic brain injury (TBI) is a major public health concern and remains a leading cause of disability and socio-economic burden. To date, there is no proven therapy that promotes brain repair following an injury to the brain. In this study, we explored the role of an isoform of adenosine kinase expressed in the cell nucleus (ADK-L) as a potential regulator of neural stem cell proliferation in the brain. The rationale for this hypothesis is based on coordinated expression changes of ADK-L during foetal and postnatal murine and human brain development indicating a role in the regulation of cell proliferation and plasticity in the brain. We first tested whether the genetic disruption of ADK-L would increase neural stem cell proliferation after TBI. Three days after TBI, modelled by a controlled cortical impact, transgenic mice, which lack ADK-L (ADK^Δneuron) in the dentate gyrus (DG) showed a significant increase in neural stem cell proliferation as evidenced by significant increases in doublecortin and Ki67-positive cells, whereas animals with transgenic overexpression of ADK-L in dorsal forebrain neurons (ADK-L^tg) showed an opposite effect of attenuated neural stem cell proliferation. Next, we translated those findings into a pharmacological approach to augment neural stem cell proliferation in the injured brain. Wild-type C57BL/6 mice were treated with the small molecule adenosine kinase inhibitor 5-iodotubercidin for 3 days after the induction of TBI. We demonstrate significantly enhanced neural stem cell proliferation in the DG of 5-iodotubercidin-treated mice compared to vehicle-treated injured animals. To rule out the possibility that blockade of ADK-L has any effects in non-injured animals, we quantified baseline neural stem cell proliferation in ADK^Δneuron mice, which was not altered, whereas baseline neural stem cell proliferation in ADK-L^tg mice was enhanced. Together these findings demonstrate a novel function of ADK-L involved in the regulation of neural stem cell proliferation after TBI.

Reprogramming of DNA methylation at NEUROD2-bound sequences during cortical neuron differentiation

The characteristics of DNA methylation changes that occur during neurogenesis in vivo remain unknown. We used whole-genome bisulfite sequencing to quantitate DNA cytosine modifications in differentiating neurons and their progenitors isolated from mouse brain at the peak of embryonic neurogenesis. Localized DNA hypomethylation was much more common than hypermethylation and often occurred at putative enhancers within genes that were upregulated in neurons and encoded proteins crucial for neuronal differentiation. The hypomethylated regions strongly overlapped with mapped binding sites of the key neuronal transcription factor NEUROD2. The 5-methylcytosine oxidase ten-eleven translocation 2 (TET2) interacted with NEUROD2, and its reaction product 5-hydroxymethylcytosine accumulated at the demethylated regions. NEUROD2-targeted differentially methylated regions retained higher methylation levels in Neurod2 knockout mice, and inducible expression of NEUROD2 caused TET2-associated demethylation at its in vivo binding sites. The data suggest that the reorganization of DNA methylation in developing neurons involves NEUROD2 and TET2-mediated DNA demethylation.

Neurons-derived extracellular vesicles promote neural differentiation of ADSCs: a model to prevent peripheral nerve degeneration

Potential mechanisms involved in neural differentiation of adipocyte derived stem cells (ADSCs) are still unclear. In the present study, extracellular vesicles (EVs) were tested as a potential mechanism involved in the neuronal differentiation of stem cells. In order to address this, ADSCs and neurons (BRC) were established in primary culture and co-culture at three timepoints. Furthermore, we evaluated protein and transcript levels of differentiated ADSCs from the same timepoints, to confirm phenotype change to neuronal linage. Importantly, neuron-derived EVs cargo and EVs originated from co-culture were analyzed and tested in terms of function, such as gene expression and microRNA levels related to the adult neurogenesis process. Ideal neuron-like cells were identified and, therefore, we speculated the in vivo function of these cells in acute sciatic nerve injury. Overall, our data demonstrated that ADSCs in indirect contact with neurons differentiated into neuron-like cells. Neuron-derived EVs appear to play an important role in this process carrying SNAP25, miR-132 and miR-9. Additionally, in vivo neuron-like cells helped in microenvironment modulation probably preventing peripheral nerve injury degeneration. Consequently, our findings provide new insight of future methods of ADSC induction into neuronal linage to be applied in peripheral nerve (PN) injury.

m6A Regulates Neurogenesis and Neuronal Development by Modulating Histone Methyltransferase Ezh2

N⁶-methyladenosine (m⁶A), catalyzed by the methyltransferase complex consisting of Mettl3 and Mettl14, is the most abundant RNA modification in mRNAs and participates in diverse biological processes. However, the roles and precise mechanisms of m⁶A modification in regulating neuronal development and adult neurogenesis remain unclear. Here, we examined the function of Mettl3, the key component of the complex, in neuronal development and adult neurogenesis of mice. We found that the depletion of Mettl3 significantly reduced m⁶A levels in adult neural stem cells (aNSCs) and inhibited the proliferation of aNSCs. Mettl3 depletion not only inhibited neuronal development and skewed the differentiation of aNSCs more toward glial lineage, but also affected the morphological maturation of newborn neurons in the adult brain. m⁶A immunoprecipitation combined with deep sequencing (MeRIP-seq) revealed that m⁶A was predominantly enriched in transcripts related to neurogenesis and neuronal development. Mechanistically, m⁶A was present on the transcripts of histone methyltransferase Ezh2, and its reduction upon Mettl3 knockdown decreased both Ezh2 protein expression and consequent H3K27me3 levels. The defects of neurogenesis and neuronal development induced by Mettl3 depletion could be rescued by Ezh2 overexpression. Collectively, our results uncover a crosstalk between RNA and histone modifications and indicate that Mettl3-mediated m⁶A modification plays an important role in regulating neurogenesis and neuronal development through modulating Ezh2.

Neurogenesis in the adult hippocampus: history, regulation, and prospective roles

BACKGROUND

The hippocampus is one of the sites in the mammalian brain that is capable of continuously generating controversy. Adult neurogenesis is a remarkable process, and yet an intensely debatable topic in contemporary neuroscience due to its distinctiveness and conceivable impact on neural activity. The belief that neurogenesis continues through adulthood has provoked remarkable efforts to describe how newborn neurons differentiate and incorporate into the adult brain. It has also encouraged studies that investigate the consequences of inadequate neurogenesis in neuropsychiatric and neurodegenerative diseases and explore the potential role of neural progenitor cells in brain repair. The adult nervous system is not static; it is subjected to morphological and physiological alterations at various levels. This plastic mechanism guarantees that the behavioral regulation of the adult nervous system is adaptable in response to varying environmental stimuli. Three regions of the adult brain, the olfactory bulb, the hypothalamus, and the hippocampal dentate gyrus, contain new-born neurons that exhibit an essential role in the natural functional circuitry of the adult brain. Purpose/Aim: This article explores current advancements in adult hippocampal neurogenesis by presenting its history and evolution and studying its association with neural plasticity. The article also discusses the prospective roles of adult hippocampal neurogenesis and describes the intracellular, extracellular, pathological, and environmental factors involved in its regulation. Abbreviations AHN Adult hippocampal neurogenesis AKT Protein kinase B BMP Bone Morphogenic Protein BrdU Bromodeoxyuridine CNS Central nervous system DG Dentate gyrus DISC1 Disrupted-in-schizophrenia 1 FGF-2 Fibroblast Growth Factor 2 GABA Gamma-aminobutyric acid Mbd1 Methyl-CpG-binding domain protein 1 Mecp2 Methyl-CpG-binding protein 2 mTOR Mammalian target of rapamycin NSCs Neural stem cells OB Olfactory bulb; P21: cyclin-dependent kinase inhibitor 1 RBPj Recombination Signal Binding protein for Immunoglobulin Kappa J Region RMS Rostral migratory Stream SGZ Subgranular zone Shh Sonic hedgehog SOX2 SRY (sex determining region Y)-box 2 SVZ Subventricular zone Wnt3 Wingless-type mouse mammary tumor virus.

Molecular Mechanisms of Transdifferentiation of Adipose-Derived Stem Cells into Neural Cells: Current Status and Perspectives

Neurological diseases can severely compromise both physical and psychological health. Recently, adult mesenchymal stem cell- (MSC-) based cell transplantation has become a potential therapeutic strategy. However, most studies related to the transdifferentiation of MSCs into neural cells have had disappointing outcomes. Better understanding of the mechanisms underlying MSC transdifferentiation is necessary to make adult stem cells more applicable to treating neurological diseases. Several studies have focused on adipose-derived stromal/stem cell (ADSC) transdifferentiation. The purpose of this review is to outline the molecular characterization of ADSCs, to describe the methods for inducing ADSC transdifferentiation, and to examine factors influencing transdifferentiation, including transcription factors, epigenetics, and signaling pathways. Exploring and understanding the mechanisms are a precondition for developing and applying novel cell therapies.

The Epigenetic Factor Landscape of Developing Neocortex Is Regulated by Transcription Factors Pax6→ Tbr2→ Tbr1

Epigenetic factors (EFs) regulate multiple aspects of cerebral cortex development, including proliferation, differentiation, laminar fate, and regional identity. The same neurodevelopmental processes are also regulated by transcription factors (TFs), notably the Pax6→ Tbr2→ Tbr1 cascade expressed sequentially in radial glial progenitors (RGPs), intermediate progenitors, and postmitotic projection neurons, respectively. Here, we studied the EF landscape and its regulation in embryonic mouse neocortex. Microarray and in situ hybridization assays revealed that many EF genes are expressed in specific cortical cell types, such as intermediate progenitors, or in rostrocaudal gradients. Furthermore, many EF genes are directly bound and transcriptionally regulated by Pax6, Tbr2, or Tbr1, as determined by chromatin immunoprecipitation-sequencing and gene expression analysis of TF mutant cortices. Our analysis demonstrated that Pax6, Tbr2, and Tbr1 form a direct feedforward genetic cascade, with direct feedback repression. Results also revealed that each TF regulates multiple EF genes that control DNA methylation, histone marks, chromatin remodeling, and non-coding RNA. For example, Tbr1 activates Rybp and Auts2 to promote the formation of non-canonical Polycomb repressive complex 1 (PRC1). Also, Pax6, Tbr2, and Tbr1 collectively drive massive changes in the subunit isoform composition of BAF chromatin remodeling complexes during differentiation: for example, a novel switch from Bcl7c (Baf40c) to Bcl7a (Baf40a), the latter directly activated by Tbr2. Of 11 subunits predominantly in neuronal BAF, 7 were transcriptionally activated by Pax6, Tbr2, or Tbr1. Using EFs, Pax6→ Tbr2→ Tbr1 effect persistent changes of gene expression in cell lineages, to propagate features such as regional and laminar identity from progenitors to neurons.

Regulation of Adult Neurogenesis by the Fragile X Family of RNA Binding Proteins

The fragile X mental retardation protein (FMRP) has an important role in neural development. Functional loss of FMRP in humans leads to fragile X syndrome, and it is the most common monogenetic contributor to intellectual disability and autism. FMRP is part of a larger family of RNA-binding proteins known as FXRs, which also includes fragile X related protein 1 (FXR1P) and fragile X related protein 2 (FXR2P). Despite the similarities of the family members, the functions of FXR1P and FXR2P in human diseases remain unclear. Although most studies focus on FMRP's role in mature neurons, all three FXRs regulate adult neurogenesis. Extensive studies have demonstrated important roles of adult neurogenesis in neuroplasticity, learning, and cognition. Impaired adult neurogenesis is implicated in neuropsychiatric disorders, neurodegenerative diseases, and neurodevelopmental disorders. Interventions aimed at regulating adult neurogenesis are thus being evaluated as potential therapeutic strategies. Here, we review and discuss the functions of FXRs in adult neurogenesis and their known similarities and differences. Understanding the overlapping regulatory functions of FXRs in adult neurogenesis can give us insights into the adult brain and fragile X syndrome.

METTL3-mediated m6A modification is required for cerebellar development

N⁶-methyladenosine (m⁶A) RNA methylation is the most abundant modification on mRNAs and plays important roles in various biological processes. The formation of m⁶A is catalyzed by a methyltransferase complex including methyltransferase-like 3 (METTL3) as a key factor. However, the in vivo functions of METTL3 and m⁶A modification in mammalian development remain unclear. Here, we show that specific inactivation of Mettl3 in mouse nervous system causes severe developmental defects in the brain. Mettl3 conditional knockout (cKO) mice manifest cerebellar hypoplasia caused by drastically enhanced apoptosis of newborn cerebellar granule cells (CGCs) in the external granular layer (EGL). METTL3 depletion–induced loss of m⁶A modification causes extended RNA half-lives and aberrant splicing events, consequently leading to dysregulation of transcriptome-wide gene expression and premature CGC death. Our findings reveal a critical role of METTL3-mediated m⁶A in regulating the development of mammalian cerebellum.

N⁶-methyladenosine (m⁶A) is an abundant modification in mRNA molecules and regulates mRNA metabolism and various biological processes, such as cell fate control, early embryonic development, sex determination, and diseases like diabetes and obesity. Adenosine methylation is regulated by a large methyltransferase complex and by demethylases, as well as by other binding proteins. METTL3 is one of the core subunits of the methyltransferase complex catalyzing m⁶A formation. However, the role of METTL3-mediated m⁶A in mammalian brain development remains unclear mainly because of the lack of specific spatiotemporal knockout animal models, as conventional METTL3 knockout in mice leads to early embryonic death. In this study, we specifically inactivated METTL3 in the developing mouse brain. We detected a drastic depletion of m⁶A accompanied by severe developmental defects in the cerebellum of these mice. Further analysis established that METTL3-mediated m⁶A participates in cerebellar development by controlling mRNA stability of genes related to cerebellar development and apoptosis and by regulating alternative splicing of pre-mRNAs of synapse-associated genes.

On the Run for Hippocampal Plasticity

Accumulating research in rodents and humans indicates that exercise benefits brain function and may prevent or delay onset of neurodegenerative conditions. In particular, exercise modifies the structure and function of the hippocampus, a brain area important for learning and memory. This review addresses the central and peripheral mechanisms underlying the beneficial effects of exercise on the hippocampus. We focus on running-induced changes in adult hippocampal neurogenesis, neural circuitry, neurotrophins, synaptic plasticity, neurotransmitters, and vasculature. The role of peripheral factors in hippocampal plasticity is also highlighted. We discuss recent evidence that systemic factors released from peripheral organs such as muscle (myokines), liver (hepatokines), and adipose tissue (adipokines) during exercise contribute to hippocampal neurotrophin and neurogenesis levels, and memory function. A comprehensive understanding of the body-brain axis is needed to elucidate how exercise improves hippocampal plasticity and cognition.

Dexras1 is a homeostatic regulator of exercise-dependent proliferation and cell survival in the hippocampal neurogenic niche

Adult hippocampal neurogenesis is highly responsive to exercise, which promotes the proliferation of neural progenitor cells and the integration of newborn granule neurons in the dentate gyrus. Here we show that genetic ablation of the small GTPase, Dexras1, suppresses exercise-induced proliferation of neural progenitors, alters survival of mitotic and post-mitotic cells in a stage-specific manner, and increases the number of mature newborn granule neurons. Dexras1 is required for exercise-triggered recruitment of quiescent neural progenitors into the cell cycle. Pharmacological inhibition of NMDA receptors enhances SGZ cell proliferation in wild-type but not dexras1-deficient mice, suggesting that NMDA receptor-mediated signaling is dependent on Dexras1. At the molecular level, the absence of Dexras1 abolishes exercise-dependent activation of ERK/MAPK and CREB, and inhibits the upregulation of NMDA receptor subunit NR2A, bdnf, trkB and vegf-a expression in the dentate gyrus. Our study reveals Dexras1 as an important stage-specific regulator of exercise-induced neurogenesis in the adult hippocampus by enhancing pro-mitogenic signaling to neural progenitor cells and modulating cell survival.

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

Histone demethylases are known to play important roles in the determination of the fate of stem cells and in cancer progression. In this study, we show that the lysine 4 of histone H3 (H3K4), lysine-specific demethylase 5A (KDM5A) is essential for the repression of astrocyte differentiation in neural progenitor cells (NPCs), and its expression is regulated by translational machinery. Knockdown of KDM5A in NPCs increased astrocytogenesis, and conversely, KDM5A overexpression reduced the transcriptional activity of the Gfap promoter. Induction of astrocytogenesis by ciliary neurotrophic factor (CNTF) or small interfering RNA-induced knockdown of KDM5A decreased KDM5A recruitment to the Gfap promoter and increased H3K4 methylation. The transcript level of Kdm5a was high, whereas KDM5A protein level was low in CNTF induced astrocytes. During astroglial differentiation, translational activity indicated by the phosphorylation of eukaryotic translation initiation factor (eIF)4E was decreased. Treatment of NPCs with the cercosporamide, a MAPK-interacting kinases inhibitor, reduced eIF4E phosphorylation and KDM5A protein expression, increased GFAP levels, and enhanced astrocytogenesis. These data suggest that KDM5A is a key regulator that maintains NPCs in an undifferentiated state by repressing astrocytogenesis and that its expression is translationally controlled during astrocyte differentiation. Thus, KDM5A is a promising target for the modulation of NPC fate.-Kong, S.-Y., Kim, W., Lee, H.-R., Kim, H.-J. The histone demethylase KDM5A is required for the repression of astrocytogenesis and regulated by the translational machinery in neural progenitor cells.

miRNA-Mediated Regulation of Adult Hippocampal Neurogenesis; Implications for Epilepsy

Hippocampal neural stem/progenitor cells (NSPCs) proliferate and differentiate to generate new neurons across the life span of most mammals, including humans. This process takes place within a characteristic local microenvironment where NSPCs interact with a variety of other cell types and encounter systemic regulatory factors. Within this microenvironment, cell intrinsic gene expression programs are modulated by cell extrinsic signals through complex interactions, in many cases involving short non-coding RNA molecules, such as miRNAs. Here we review the regulation of gene expression in NSPCs by miRNAs and its possible implications for epilepsy, which has been linked to alterations in adult hippocampal neurogenesis.

Fat mass and obesity-associated (FTO) protein regulates adult neurogenesis

Fat mass and obesity-associated gene (FTO) is a member of the Fe (II)- and oxoglutarate-dependent AlkB dioxygenase family and is linked to both obesity and intellectual disability. The role of FTO in neurodevelopment and neurogenesis, however, remains largely unknown. Here we show that FTO is expressed in adult neural stem cells and neurons and displays dynamic expression during postnatal neurodevelopment. The loss of FTO leads to decreased brain size and body weight. We find that FTO deficiency could reduce the proliferation and neuronal differentiation of adult neural stem cells in vivo, which leads to impaired learning and memory. Given the role of FTO as a demethylase of N6-methyladenosine (m6A), we went on to perform genome-wide m6A profiling and observed dynamic m6A modification during postnatal neurodevelopment. The loss of FTO led to the altered expression of several key components of the brain derived neurotrophic factor pathway that were marked by m6A. These results together suggest FTO plays important roles in neurogenesis, as well as in learning and memory.

DNA methylation: an epigenetic mark of cellular memory

DNA methylation is a stable epigenetic mark that can be inherited through multiple cell divisions. During development and cell differentiation, DNA methylation is dynamic, but some DNA methylation patterns may be retained as a form of epigenetic memory. DNA methylation profiles can be useful for the lineage classification and quality control of stem cells such as embryonic stem cells, induced pluripotent cells and mesenchymal stem cells. During cancer initiation and progression, genome-wide and gene-specific DNA methylation changes occur as a consequence of mutated or deregulated chromatin regulators. Early aberrant DNA methylation states occurring during transformation appear to be retained during tumor evolution. Similarly, DNA methylation differences among different regions of a tumor reflect the history of cancer cells and their response to the tumor microenvironment. Therefore, DNA methylation can be a useful molecular marker for cancer diagnosis and drug treatment.

Transplantation of mesenchymal stem cells reverses behavioural deficits and impaired neurogenesis caused by prenatal exposure to valproic acid

Neurodevelopmental impairment can affect lifelong brain functions such as cognitive and social behaviour, and may contribute to aging-related changes of these functions. In the present study, we hypothesized that bone marrow-derived mesenchymal stem cells (MSC) administration may repair neurodevelopmental behavioural deficits by modulating adult hippocampal neurogenesis. Indeed, postnatal intracerebral transplantation of MSC has restored cognitive and social behaviour in mice prenatally exposed to valproic acid (VPA). MSC transplantation also restored post-developmental hippocampal neurogenesis, which was impaired in VPA-exposed mice displaying delayed differentiation and maturation of newly formed neurons in the granular cell layer of the dentate gyrus. Importantly, a statistically significant correlation was found between neuronal differentiation scores and behavioural scores, suggesting a mechanistic relation between the two. We thus conclude that post-developmental MSC administration can overcome prenatal neurodevelopmental deficits and restore cognitive and social behaviours via modulation of hippocampal adult neurogenesis.

Age-related epigenetic regulation in the brain and its role in neuronal diseases

Accumulating evidence indicates many brain functions are mediated by epigenetic regulation of neural genes, and their dysregulations result in neuronal disorders. Experiences such as learning and recall, as well as physical exercise, induce neuronal activation through epigenetic modifications and by changing the noncoding RNA profiles. Animal models, brain samples from patients, and the development of diverse analytical methods have broadened our understanding of epigenetic regulation in the brain. Diverse and specific epigenetic changes are suggested to correlate with neuronal development, learning and memory, aging and age-related neuronal diseases. Although the results show some discrepancies, a careful comparison of the data (including methods, regions and conditions examined) would clarify the problems confronted in understanding epigenetic regulation in the brain.