Ezh2 regulates adult hippocampal neurogenesis and memory. J Neurosci. 2014;34:5184-5199. [PMID: 24719098 DOI: 10.1523/jneurosci.4129-13.2014]

Antisense-mediated exon skipping targeting EZH2 suppresses tumor growth in a xenograft mouse model of hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2) catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3), which promotes heterochromatin formation and gene silencing. Expression of EZH2 is frequently elevated in various malignancies, including hepatocellular carcinoma (HCC). Silencing of EZH2 has been pursued as a promising strategy to halt cancer progression. Here, we identified antisense oligonucleotides (ASOs) that efficiently silence EZH2 through promoting skipping of its exon 14, an exon encoding part of the essential CXC domain, increasing production of an internally shortened isoform that exerts dominant negative effect on the full-length EZH2. A lead ASO, hybridizing to an exonic splicing enhancer element bound by SRSF3, robustly promoted exon 14 skipping not only in cultured human HCC cell lines but also in mouse peripheral tissues after systemic administration, leading to dramatic reduction of EZH2 and H3K27me3 levels. The lead ASO potently inhibited HCC cell proliferation through multiple mechanisms including enhanced apoptosis, cell-cycle arrest, and reversed epithelial-mesenchymal transition, which is likely attributable to the suppression of diverse cancer-related pathways. In an orthotopic xenograft HCC mouse model, ASO treatment repressed tumor growth, improved tissue phenotype, and extended the median survival. Our data highlight therapeutic potential of the lead exon-skipping ASO in treating HCC.

Neotenic expansion of adult-born dentate granule cells reconfigures GABAergic inhibition to enhance social memory consolidation

Adult-born dentate granule cells (abDGCs) contribute to hippocampal dentate gyrus (DG)-CA3/CA2 circuit functions in memory encoding, retrieval and consolidation. Heightened synaptic and structural plasticity of immature abDGCs is thought to govern their distinct contributions to circuit and network mechanisms of hippocampal-dependent memory operations. Protracted maturation or neoteny of abDGCs in higher mammals is hypothesized to offset decline in adult hippocampal neurogenesis by expanding the capacity for circuit and network plasticity underlying different memory operations. Here, we provide evidence for this hypothesis by genetically modelling the effective impact of neoteny of abDGCs on circuitry, network properties and social cognition in mice. We show that selective synchronous expansion of a single cohort of 4 weeks old immature, but not 8 weeks old mature abDGCs, increases functional recruitment of fast spiking parvalbumin expressing inhibitory interneurons (PV INs) in CA3/CA2, number of PV IN-CA3/CA2 synapses, and GABAergic inhibition of CA3/CA2. This transient increase in feed-forward inhibition in DG-CA2 decreased social memory interference and enhanced social memory consolidation. In vivo local field potential recordings revealed that the expansion of a single cohort of 4-week-old abDGCs increased baseline power, amplitude, and duration, as well as sensitivity to social investigation-dependent rate changes of sharp-wave ripples (SWRs) in CA1 and CA2, a neural substrate for memory consolidation. Inhibitory neuron-targeted chemogenetic manipulations implicate CA3/CA2 INs, including PV INs, as necessary and sufficient for social memory consolidation following neotenic expansion of the abDGC population and in wild-type mice, respectively. These studies suggest that neoteny of abDGCs may represent an evolutionary adaptation to support cognition by reconfiguring PV IN-CA3/CA2 circuitry and emergent network properties underlying memory consolidation.

Neotenic expansion of adult-born dentate granule cells reconfigures GABAergic inhibition to enhance social memory consolidation

Adult-born dentate granule cells (abDGCs) contribute to hippocampal dentate gyrus (DG)-CA3/CA2 circuit functions in memory encoding, retrieval and consolidation. Heightened synaptic and structural plasticity of immature abDGCs is thought to govern their distinct contributions to circuit and network mechanisms of hippocampal-dependent memory operations. Protracted maturation or neoteny of abDGCs in higher mammals is hypothesized to offset decline in adult hippocampal neurogenesis by expanding the capacity for circuit and network plasticity underlying different memory operations. Here, we provide evidence for this hypothesis by genetically modelling the effective impact of neoteny of abDGCs on circuitry, network properties and social cognition in mice. We show that selective synchronous expansion of a single cohort of 4 weeks old immature, but not 8 weeks old mature abDGCs, increases functional recruitment of fast spiking parvalbumin expressing inhibitory interneurons (PV INs) in CA3/CA2, number of PV IN-CA3/CA2 synapses, and GABAergic inhibition of CA3/CA2. This transient increase in feed-forward inhibition in DG-CA2 decreased social memory interference and enhanced social memory consolidation. In vivo local field potential recordings revealed that the expansion of a single cohort of 4-week-old abDGCs increased baseline power, amplitude, and duration, as well as sensitivity to social investigation-dependent rate changes of sharp-wave ripples (SWRs) in CA1 and CA2, a neural substrate for memory consolidation. Inhibitory neuron-targeted chemogenetic manipulations implicate CA3/CA2 INs, including PV INs, as necessary and sufficient for social memory consolidation following neotenic expansion of the abDGC population and in wild-type mice, respectively. These studies suggest that neoteny of abDGCs may represent an evolutionary adaptation to support cognition by reconfiguring PV IN-CA3/CA2 circuitry and emergent network properties underlying memory consolidation.

Neural stem cell heterogeneity in adult hippocampus

Adult neurogenesis is a unique cellular process of the ongoing generation of new neurons throughout life, which primarily occurs in the subgranular zone (SGZ) of the dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricle. In the adult DG, newly generated granule cells from neural stem cells (NSCs) integrate into existing neural circuits, significantly contributing to cognitive functions, particularly learning and memory. Recently, more and more studies have shown that rather than being a homogeneous population of identical cells, adult NSCs are composed of multiple subpopulations that differ in their morphology and function. In this study, we provide an overview of the origin, regional characteristics, prototypical morphology, and molecular factors that contribute to NSC heterogeneity. In particular, we discuss the molecular mechanisms underlying the balance between activation and quiescence of NSCs. In summary, this review highlights that deciphering NSC heterogeneity in the adult brain is a challenging but critical step in advancing our understanding of tissue-specific stem cells and the process of neurogenesis in the adult brain.

Epigenetic targeting of PGBD5-dependent DNA damage in SMARCB1-deficient sarcomas

Despite the potential of targeted epigenetic therapies, most cancers do not respond to current epigenetic drugs. The Polycomb repressive complex EZH2 inhibitor tazemetostat was recently approved for the treatment of SMARCB1-deficient epithelioid sarcomas, based on the functional antagonism between PRC2 and loss of SMARCB1. Through the analysis of tazemetostat-treated patient tumors, we recently defined key principles of their response and resistance to EZH2 epigenetic therapy. Here, using transcriptomic inference from SMARCB1-deficient tumor cells, we nominate the DNA damage repair kinase ATR as a target for rational combination EZH2 epigenetic therapy. We show that EZH2 inhibition promotes DNA damage in epithelioid and rhabdoid tumor cells, at least in part via its induction of the transposase-derived PGBD5. We leverage this collateral synthetic lethal dependency to target PGBD5-dependent DNA damage by inhibition of ATR but not CHK1 using elimusertib. Consequently, combined EZH2 and ATR inhibition improves therapeutic responses in diverse patient-derived epithelioid and rhabdoid tumors in vivo. This advances a combination epigenetic therapy based on EZH2-PGBD5 synthetic lethal dependency suitable for immediate translation to clinical trials for patients.

Maternal obesity alters histone modifications mediated by the interaction between EZH2 and AMPK, impairing neural differentiation in the developing embryonic brain cortex

Neurodevelopmental disorders have complex origins that manifest early during embryonic growth and are associated with intricate gene regulation dynamics. A perturbed metabolic environment such as hyperglycemia or dyslipidemia, particularly due to maternal obesity, poses a threat to the optimal development of the embryonic central nervous system. Accumulating evidence suggests that these metabolic irregularities during pregnancy may alter neurogenesis pathways, thereby predisposing the developing fetus to neurodevelopmental disorders. One primary mechanism through which such disruptions may occur involves changes in histone modifications resulting from fluctuations in the expression of histone-modifying enzymes or the availability of their substrates. Herein, we have used a rat model of maternal obesity induced by a high-fat diet before and during gestation to investigate the cellular and molecular repercussions of maternal obesity on embryonic cortical neurogenesis. Maternal obesity impairs neurogenesis by reducing cell proliferation, increasing neuronal marker expression, and shifting development toward astrogliogenesis. Differentially expressed genes revealed disruptions in key developmental signaling pathways and reduced AKT phosphorylation, particularly at E14.5. These changes were associated with epigenetic alterations, mainly the differential expression and phosphorylation of EZH2 and subsequent changes in global histone modifications. Chromatin immunoprecipitation sequencing revealed reduced H3K27me3 at genes upregulated due to maternal obesity, which could have resulted from reduced expression and increased phosphorylation of EZH2 at Thr311. Interestingly, EZH2 also showed increased O-GlcNAcylation in high-fat diet embryos along with increased association with AMPK-Thr172 in accordance with previous studies showing that Ampk catalyzes EZH2-Thr311p. These results suggest that an epigenetic gene regulatory mechanism mediated by Ampk and Ezh2 interactions resulted in reduced H3K27me3 and derepression of key developmental genes, which could have led to cell fate changes observed in the developing embryo brain cortex due to maternal obesity.

A core scientific problem in the treatment of central nervous system diseases: newborn neurons

It has long been asserted that failure to recover from central nervous system diseases is due to the system's intricate structure and the regenerative incapacity of adult neurons. Yet over recent decades, numerous studies have established that endogenous neurogenesis occurs in the adult central nervous system, including humans'. This has challenged the long-held scientific consensus that the number of adult neurons remains constant, and that new central nervous system neurons cannot be created or renewed. Herein, we present a comprehensive overview of the alterations and regulatory mechanisms of endogenous neurogenesis following central nervous system injury, and describe novel treatment strategies that target endogenous neurogenesis and newborn neurons in the treatment of central nervous system injury. Central nervous system injury frequently results in alterations of endogenous neurogenesis, encompassing the activation, proliferation, ectopic migration, differentiation, and functional integration of endogenous neural stem cells. Because of the unfavorable local microenvironment, most activated neural stem cells differentiate into glial cells rather than neurons. Consequently, the injury-induced endogenous neurogenesis response is inadequate for repairing impaired neural function. Scientists have attempted to enhance endogenous neurogenesis using various strategies, including using neurotrophic factors, bioactive materials, and cell reprogramming techniques. Used alone or in combination, these therapeutic strategies can promote targeted migration of neural stem cells to an injured area, ensure their survival and differentiation into mature functional neurons, and facilitate their integration into the neural circuit. Thus can integration replenish lost neurons after central nervous system injury, by improving the local microenvironment. By regulating each phase of endogenous neurogenesis, endogenous neural stem cells can be harnessed to promote effective regeneration of newborn neurons. This offers a novel approach for treating central nervous system injury.

Adeno-associated Virus-mediated Ezh2 Knockdown Reduced the Increment of Newborn Neurons Induced by Forebrain Ischemia in Gerbil Dentate Gyrus

It is established that neurogenesis of dentate gyrus is increased after ischemic insult, although the regulatory mechanisms have not yet been elucidated. In this study, we focused on Ezh2 which suppresses gene expression through catalyzing trimethylation of lysine 27 of histone 3. Male gerbils were injected with adeno-associated virus (AAV) carrying shRNA targeting to Ezh2 into right dentate gyrus 2 weeks prior to forebrain ischemia. One week after ischemia, animals were injected with thymidine analogue to label proliferating cells. Three weeks after ischemia, animals were killed for histological analysis. AAV-mediated knockdown of Ezh2 significantly decreased the ischemia-induced increment of proliferating cells, and the proliferated cells after ischemia showed significantly longer migration from subgranular zone (SGZ), compared to the control group. Furthermore, the number of neural stem cells in SGZ significantly decreased after ischemia with Ezh2 knockdown group. Of note, Ezh2 knockdown did not affect the number of proliferating cells or the migration from SGZ in the non-ischemic condition. Our data showed that, specifically after ischemia, Ezh2 knockdown shifted the balance between self-renewal and differentiation toward differentiation in adult dentate gyrus.

Functional role of lncRNA MEG3 on pyroptosis through interacting with EZH2 and YTHDC1 in postoperative cognitive dysfunction

BACKGROUND

The molecular biology mechanisms underlying postoperative cognitive dysfunction (POCD) remain unclear, resulting in a lack of specific therapeutic targets and limited clinical treatment options. The NLRP3 pyroptotic pathway, induced by neuroinflammation, is known to promote the development of POCD. Research has shown that lncRNA MEG3 exacerbates cell pyroptosis in various neurological injuries, though the precise mechanism remains to be investigated.

METHODS

In vitro and in vivo models of POCD were established through treatment with sevoflurane. Gene and protein expression were investigated using qRT-PCR, Western blot analysis, ELISA, and histological staining. Additionally, cell viability and injury were assessed through CCK-8 and LDH assays. Hippocampal-dependent memory and cognitive abilities were evaluated using the Morris Water Maze (MWM) test. Furthermore, the interactions between MEG3 and EZH2/YTHDC1 were validated through RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP).

RESULTS

Our findings reveal that sevoflurane significantly reduced MEG3 and pyroptosis-related proteins in mice. The overexpression of MEG3 protected mice against sevoflurane-induced cognitive dysfunction and reversed sevoflurane-induced pyroptosis in hippocampal neurons. MEG3 induced the downregulation of NLRP3 expression and reduced mRNA stability through its interaction with EZH2/YTHDC1.

CONCLUSION

In conclusion, our study elucidates that MEG3 inhibits the NLRP3 inflammasome and hippocampal neuron pyroptosis through the recruitment of EZH2/YTHDC1. These findings shed light on the underlying mechanism of MEG3 in the regulation of POCD and suggest that MEG3 could serve as a potential therapeutic target for the treatment of POCD.

The role of EZH2 and its regulatory lncRNAs as a serum-based biomarker in Alzheimer's disease

BACKGROUND

Long noncoding RNAs (lncRNAs) have become a hot topic in the human nervous system. Moreover, circulating lncRNAs have been suggested as possible biomarkers for central nervous system processes and neurodegenerative diseases. The present research aimed to highlight the role of plasma lncRNAs TUG1, FEZF1-AS1, and EZH2 gene as diagnostic biomarkers in Alzheimer's disease (AD).

METHODS

Plasma samples for the study were provided by 100 AD patients and 100 matched controls. Real-time quantitative reverse transcriptase PCR was used to determine the plasma level of the aforementioned lncRNAs. Furthermore, the plasma level of EZH2 protein in the participants' blood was determined using the ELISA technique.

RESULTS

In contrast to controls, down-regulation of the EZH2 gene and protein was reported in the plasma of patients with AD. Additionally, plasma samples from AD patients showed up-and-down-regulation of the lncRNAs TUG1 and FEZF1-AS1, respectively.

CONCLUSION

Our new findings suggest that the EZH2 gene, plasma lncRNA TUG1, and FEZF1-AS1 may contribute, as valuable biomarkers, to AD diagnosis.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

Escape from X-chromosome inactivation and sex differences in Alzheimer's disease

Sex differences exist in the onset and progression of Alzheimer's disease. Globally, women have a higher prevalence, while men with Alzheimer's disease experience earlier mortality and more pronounced cognitive decline than women. The cause of sex differences in Alzheimer's disease remains unclear. Accumulating evidence suggests the potential role of X-linked genetic factors in the sex difference of Alzheimer's disease (AD). During embryogenesis, a remarkable process known as X-chromosome inactivation (XCI) occurs in females, leading to one of the X chromosomes undergoing transcriptional inactivation, which balances the effects of two X chromosomes in females. Nevertheless, certain genes exceptionally escape from XCI, which provides a basis for dual expression dosage of specific genes in females. Based on recent research findings, we explore key escape genes and their potential therapeutic use associated with Alzheimer's disease. Also, we discuss their possible role in driving the sex differences in Alzheimer's disease. This will provide new perspectives for precision medicine and gender-specific treatment of AD.

Ethanol changes Nestin-promoter induced neural stem cells to disturb newborn dendritic spine remodeling in the hippocampus of mice

Adolescent binge drinking leads to long-lasting disorders of the adult central nervous system, particularly aberrant hippocampal neurogenesis. In this study, we applied in vivo fluorescent tracing using NestinCreERT2::Rosa26-tdTomato mice and analyzed the endogenous neurogenesis lineage progression of neural stem cells (NSCs) and dendritic spine formation of newborn neurons in the subgranular zone of the dentate gyrus. We found abnormal orientation of tamoxifen-induced tdTomato+ (tdTom+) NSCs in adult mice 2 months after treatment with EtOH (5.0 g/kg, i.p.) for 7 consecutive days. EtOH markedly inhibited tdTom+ NSCs activation and hippocampal neurogenesis in mouse dentate gyrus from adolescence to adulthood. EtOH (100 mM) also significantly inhibited the proliferation to 39.2% and differentiation of primary NSCs in vitro. Adult mice exposed to EtOH also exhibited marked inhibitions in dendritic spine growth and newborn neuron maturation in the dentate gyrus, which was partially reversed by voluntary running or inhibition of the mammalian target of rapamycin-enhancer of zeste homolog 2 pathway. In vivo tracing revealed that EtOH induced abnormal orientation of tdTom+ NSCs and spatial misposition defects of newborn neurons, thus causing the disturbance of hippocampal neurogenesis and dendritic spine remodeling in mice.

Targeting ageing with rapamycin and its derivatives in humans: a systematic review

Rapamycin and its derivatives (rapalogs) are inhibitors of mTOR, a major regulator of the ageing process. We aimed to summarise the effects of rapamycin and its derivatives on the severity of ageing-related physiological changes and disease in adults. A search across five databases yielded 18 400 unique articles, resulting in 19 included studies. Rapamycin and its derivatives improved physiological parameters associated with ageing in the immune, cardiovascular, and integumentary systems of healthy individuals or individuals with ageing-related diseases. Overall, no significant effects on the endocrine, muscular, or neurological systems were found. The effects of rapamycin or its derivatives on the respiratory, digestive, renal, and reproductive systems were not assessed. No serious adverse events attributed to rapamycin and its derivatives were reported in healthy individuals; however, there were increased numbers of infections and increases in total cholesterol, LDL cholesterol, and triglycerides in individuals with ageing-related diseases. Future studies should assess the remaining unexamined systems and test the effects of long-term exposure to rapamycin and its derivatives.

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.

KDM2B regulates hippocampal morphogenesis by transcriptionally silencing Wnt signaling in neural progenitors

The hippocampus plays major roles in learning and memory, and its formation requires precise coordination of patterning, cell proliferation, differentiation, and migration. Here we removed the chromatin-association capability of KDM2B in the progenitors of developing dorsal telencephalon (Kdm2b∆CxxC) to discover that Kdm2b∆CxxC hippocampus, particularly the dentate gyrus, became drastically smaller with disorganized cellular components and structure. Kdm2b∆CxxC mice display prominent defects in spatial memory, motor learning and fear conditioning, resembling patients with KDM2B mutations. The migration and differentiation of neural progenitor cells is greatly impeded in the developing Kdm2b∆CxxC hippocampus. Mechanism studies reveal that Wnt signaling genes in developing Kdm2b∆CxxC hippocampi are de-repressed due to reduced enrichment of repressive histone marks by polycomb repressive complexes. Activating the Wnt signaling disturbs hippocampal neurogenesis, recapitulating the effect of KDM2B loss. Together, we unveil a previously unappreciated gene repressive program mediated by KDM2B that controls progressive fate specifications and cell migration, hence morphogenesis of the hippocampus.

Neuronal Histone Methyltransferase EZH2 Regulates Neuronal Morphogenesis, Synaptic Plasticity, and Cognitive Behavior in Mice

The histone methyltransferase enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2)-mediated trimethylation of histone H3 lysine 27 (H3K27me3) regulates neural stem cell proliferation and fate specificity through silencing different gene sets in the central nervous system. Here, we explored the function of EZH2 in early post-mitotic neurons by generating a neuron-specific Ezh2 conditional knockout mouse line. The results showed that a lack of neuronal EZH2 led to delayed neuronal migration, more complex dendritic arborization, and increased dendritic spine density. Transcriptome analysis revealed that neuronal EZH2-regulated genes are related to neuronal morphogenesis. In particular, the gene encoding p21-activated kinase 3 (Pak3) was identified as a target gene suppressed by EZH2 and H3K27me3, and expression of the dominant negative Pak3 reversed Ezh2 knockout-induced higher dendritic spine density. Finally, the lack of neuronal EZH2 resulted in impaired memory behaviors in adult mice. Our results demonstrated that neuronal EZH2 acts to control multiple steps of neuronal morphogenesis during development, and has long-lasting effects on cognitive function in adult mice.

Role of NAD+ and FAD in Ischemic Stroke Pathophysiology: An Epigenetic Nexus and Expanding Therapeutic Repertoire

The redox coenzymes viz., oxidized β-nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD) by way of generation of optimal reducing power and cellular energy currency (ATP), control a staggering array of metabolic reactions. The prominent cellular contenders for NAD+ utilization, inter alia, are sirtuins (SIRTs) and poly(ADP-ribose) polymerase (PARP-1), which have been significantly implicated in ischemic stroke (IS) pathogenesis. NAD+ and FAD are also two crucial epigenetic enzyme-required metabolites mediating histone deacetylation and poly(ADP-ribosyl)ation through SIRTs and PARP-1 respectively, and demethylation through FAD-mediated lysine specific demethylase activity. These enzymes and post-translational modifications impinge on the components of neurovascular unit, primarily neurons, and elicit diverse functional upshots in an ischemic brain. These could be circumstantially linked with attendant cognitive deficits and behavioral outcomes in post-stroke epoch. Parsing out the contribution of NAD+/FAD-synthesizing and utilizing enzymes towards epigenetic remodeling in IS setting, together with their cognitive and behavioral associations, combined with possible therapeutic implications will form the crux of this review.

Histone bivalency regulates the timing of cerebellar granule cell development

Developing neurons undergo a progression of morphological and gene expression changes as they transition from neuronal progenitors to mature neurons. Here we used RNA-seq and H3K4me3 and H3K27me3 ChIP-seq to analyze how chromatin modifications control gene expression in a specific type of CNS neuron: the mouse cerebellar granule cell (GC). We found that in proliferating GC progenitors (GCPs), H3K4me3/H3K27me3 bivalency is common at neuronal genes and undergoes dynamic changes that correlate with gene expression during migration and circuit formation. Expressing a fluorescent sensor for bivalent domains revealed subnuclear bivalent foci in proliferating GCPs. Inhibiting H3K27 methyltransferases EZH1 and EZH2 in vitro and in organotypic cerebellar slices dramatically altered the expression of bivalent genes, induced the down-regulation of migration-related genes and up-regulation of synaptic genes, inhibited glial-guided migration, and accelerated terminal differentiation. Thus, histone bivalency is required to regulate the timing of the progression from progenitor cells to mature neurons.

Competition on presynaptic resources enhances the discrimination of interfering memories

Evidence suggests that hippocampal adult neurogenesis is critical for discriminating considerably interfering memories. During adult neurogenesis, synaptic competition modifies the weights of synaptic connections nonlocally across neurons, thus providing a different form of unsupervised learning from Hebb's local plasticity rule. However, how synaptic competition achieves separating similar memories largely remains unknown. Here, we aim to link synaptic competition with such pattern separation. In synaptic competition, adult-born neurons are integrated into the existing neuronal pool by competing with mature neurons for synaptic connections from the entorhinal cortex. We show that synaptic competition and neuronal maturation play distinct roles in separating interfering memory patterns. Furthermore, we demonstrate that a feedforward neural network trained by a competition-based learning rule can outperform a multilayer perceptron trained by the backpropagation algorithm when only a small number of samples are available. Our results unveil the functional implications and potential applications of synaptic competition in neural computation.

The roles of EZH2 in cancer and its inhibitors

The enhancer of zeste homolog 2 (EZH2) is encoded by the Enhancer of zeste 2 polycomb repressive complex 2 subunit gene. EZH2 is involved in the cell cycle, DNA damage repair, cell differentiation, autophagy, apoptosis, and immunological modulation. The main function of EZH2 is to catalyze the methylation of H3 histone of H3K27Me3, which inhibits the transcription of target genes, such as tumor suppressor genes. EZH2 also forms complexes with transcriptions factors or directly binds to the promoters of target genes, leading to regulate gene transcriptions. EZH2 has been as a prominent target for cancer therapy and a growing number of potential targeting medicines have been developed. This review summarized the mechanisms that EZH2 regulates gene transcription and the interactions between EZH2 and important intracellular signaling molecules (Wnt, Notch, MEK, Akt) and as well the clinical applications of EZH2-targeted drugs.

Sevoflurane Preconditioning Alleviates Posttraumatic Stress Disorder-Induced Apoptosis in the Hippocampus via the EZH2-Regulated Akt/mTOR Axis and Improves Synaptic Plasticity

Posttraumatic stress disorder (PTSD) is a persistent and severe psychological and mental disorder resulting from experiences of serious trauma or stress and is suffered by many individuals. Previous studies have shown that pretreatment with sevoflurane is efficient in reducing the incidence of PTSD. However, we require a more comprehensive understanding of the specific mechanisms by which sevoflurane works. Enhancer of zeste homolog 2 (EZH2) has been reported to be regulated by sevoflurane, and to improve patient cognition. In this study, we aimed to explore the mechanisms of sevoflurane and the role of EZH2 in PTSD cases. We explored the effects of sevoflurane and EPZ-6438 (inhibitor of EZH2) on rat behavior, followed by an investigation of EZH2 mRNA and protein expression. The effects of sevoflurane and EZH2 on neuronal survival were assessed by western blotting and TUNEL staining, while western blotting was used to examine the expression of PSD95 and the AKT/mTOR proteins. Sevoflurane preconditioning restored EZH2 expression and significantly inhibited apoptosis by regulating phosphorylation of the AKT/mTOR pathway. Synaptic plasticity was also significantly improved. These results suggest that pretreatment with sevoflurane could play an important role in PTSD prevention by regulating EZH2 expression.

Histone bivalency regulates the timing of cerebellar granule cell development

Developing neurons undergo a progression of morphological and gene expression changes as they transition from neuronal progenitors to mature, multipolar neurons. Here we use RNA-seq and H3K4me3 and H3K27me3 ChIP-seq to analyze how chromatin modifications control gene expression in a specific type of CNS neuron, the mouse cerebellar granule cell (GC). We find that in proliferating GC progenitors (GCPs), H3K4me3/H3K27me3 bivalency is common at neuronal genes and undergoes dynamic changes that correlate with gene expression during migration and circuit formation. Expressing a fluorescent sensor for bivalent H3K4me3 and H3K27me3 domains revealed subnuclear bivalent foci in proliferating GCPs. Inhibiting H3K27 methyltransferases EZH1 and EZH2 in vitro and in organotypic cerebellar slices dramatically altered the expression of bivalent genes and induced the downregulation of migration-related genes and upregulation of synaptic genes, inhibited glial-guided migration, and accelerated terminal differentiation. Thus, histone bivalency is required to regulate the timing of the progression from progenitor cells to mature neurons.

Small molecule modulators of chromatin remodeling: from neurodevelopment to neurodegeneration

The dynamic changes in chromatin conformation alter the organization and structure of the genome and further regulate gene transcription. Basically, the chromatin structure is controlled by reversible, enzyme-catalyzed covalent modifications to chromatin components and by noncovalent ATP-dependent modifications via chromatin remodeling complexes, including switch/sucrose nonfermentable (SWI/SNF), inositol-requiring 80 (INO80), imitation switch (ISWI) and chromodomain-helicase DNA-binding protein (CHD) complexes. Recent studies have shown that chromatin remodeling is essential in different stages of postnatal and adult neurogenesis. Chromatin deregulation, which leads to defects in epigenetic gene regulation and further pathological gene expression programs, often causes a wide range of pathologies. This review first gives an overview of the regulatory mechanisms of chromatin remodeling. We then focus mainly on discussing the physiological functions of chromatin remodeling, particularly histone and DNA modifications and the four classes of ATP-dependent chromatin-remodeling enzymes, in the central and peripheral nervous systems under healthy and pathological conditions, that is, in neurodegenerative disorders. Finally, we provide an update on the development of potent and selective small molecule modulators targeting various chromatin-modifying proteins commonly associated with neurodegenerative diseases and their potential clinical applications.

KDM6B cooperates with Tau and regulates synaptic plasticity and cognition via inducing VGLUT1/2

The excitatory neurotransmitter glutamate shapes learning and memory, but the underlying epigenetic mechanism of glutamate regulation in neuron remains poorly understood. Here, we showed that lysine demethylase KDM6B was expressed in excitatory neurons and declined in hippocampus with age. Conditional knockout of KDM6B in excitatory neurons reduced spine density, synaptic vesicle number and synaptic activity, and impaired learning and memory without obvious effect on brain morphology in mice. Mechanistically, KDM6B upregulated vesicular glutamate transporter 1 and 2 (VGLUT1/2) in neurons through demethylating H3K27me3 at their promoters. Tau interacted and recruited KDM6B to the promoters of Slc17a7 and Slc17a6, leading to a decrease in local H3K27me3 levels and induction of VGLUT1/2 expression in neurons, which could be prevented by loss of Tau. Ectopic expression of KDM6B, VGLUT1, or VGLUT2 restored spine density and synaptic activity in KDM6B-deficient cortical neurons. Collectively, these findings unravel a fundamental mechanism underlying epigenetic regulation of synaptic plasticity and cognition.

Role of EZH2 in adipogenesis and obesity: Current state of the art and implications - A review

Obesity is characterized by excessive accumulation of adiposity and has been implicated in a strong predisposition to metabolic disorders and cancer, constituting one of the major public health issues worldwide. The formation of new mature adipocytes through differentiation of progenitor or precursor cells during adipogenesis can lead to the expansion of adipose tissue. Recent studies have revealed that the intrinsic risk of obesity arises not only through genetic variants but also through epigenetic predisposition. Enhancer of zeste homolog 2 (EZH2) is an enzymatic catalytic component of polycomb repressive complex 2 that acts as an epigenetic modulator in the regulation of gene expression. EZH2 can modulate the expression of its target genes by the trimethylation of Lys-27 in histone 3 or methylation of non-histone proteins. Emerging evidence has shown the important role played by EZH2 in adipogenesis and obesity. This review provides the latest knowledge about the involvement of EZH2 in the process of adipogenesis and obesity involving adipocyte differentiation, extract key concepts, and highlight open questions toward a better understanding of EZH2 function and the molecular mechanisms underlying obesity.

Neuromodulating roles of estrogen and phytoestrogens in cognitive therapeutics through epigenetic modifications during aging

Estrogen (E2) plays important role in regulating hippocampal learning and memory. The decline of E2 after menopause affects learning and memory and increases the risk of neurodegenerative diseases like Alzheimer's disease (AD). Additionally, from the estrogen receptor (ER) mediated gene regulation; E2 also regulates gene expression at the transcriptional and posttranscriptional levels through epigenetic modifications. E2 recruits a number of proteins called co-regulators at the promoter region of genes. These co-regulators act as chromatin modifiers, alter DNA and histone modifications and regulate gene expression. Several studies show that E2 regulates learning and memory by altering chromatin at the promoters of memory-linked genes. Due to structural similarities with E2 and low side effects, phytoestrogens are now used as neuroprotective agents to recover learning and memory in animal models as well as human subjects during aging and different neurological disorders. Growing evidence suggests that apart from anti-oxidative and anti-inflammatory properties, phytoestrogens also act as epigenetic modifiers and regulate gene expression through epigenetic modifications. The epigenetic modifying properties of phytoestrogens are mostly studied in cancer cells but very little is known regarding the regulation of synaptic plasticity genes, learning and memory, and neurological disorders. In this article, we discuss the epigenetic modifying properties of E2 and the roles of phytoestrogens as epigenetic modifiers in the brain to recover and maintain cognitive functions.

The role of histone modifications: from neurodevelopment to neurodiseases

Epigenetic regulatory mechanisms, including DNA methylation, histone modification, chromatin remodeling, and microRNA expression, play critical roles in cell differentiation and organ development through spatial and temporal gene regulation. Neurogenesis is a sophisticated and complex process by which neural stem cells differentiate into specialized brain cell types at specific times and regions of the brain. A growing body of evidence suggests that epigenetic mechanisms, such as histone modifications, allow the fine-tuning and coordination of spatiotemporal gene expressions during neurogenesis. Aberrant histone modifications contribute to the development of neurodegenerative and neuropsychiatric diseases. Herein, recent progress in understanding histone modifications in regulating embryonic and adult neurogenesis is comprehensively reviewed. The histone modifications implicated in neurodegenerative and neuropsychiatric diseases are also covered, and future directions in this area are provided.

EZH2-Mediated H3K27me3 Targets Transcriptional Circuits of Neuronal Differentiation

The Polycomb Repressive Complex 2 (PRC2) plays important roles in the epigenetic regulation of cellular development and differentiation through H3K27me3-dependent transcriptional repression. Aberrant PRC2 activity has been associated with cancer and neurodevelopmental disorders, particularly with respect to the malfunction of sits catalytic subunit EZH2. Here, we investigated the role of the EZH2-mediated H3K27me3 apposition in neuronal differentiation. We made use of a transgenic mouse model harboring Ezh2 conditional KO alleles to derive embryonic stem cells and differentiate them into glutamatergic neurons. Time course transcriptomics and epigenomic analyses of H3K27me3 in absence of EZH2 revealed a significant dysregulation of molecular networks affecting the glutamatergic differentiation trajectory that resulted in: (i) the deregulation of transcriptional circuitries related to neuronal differentiation and synaptic plasticity, in particular LTD, as a direct effect of EZH2 loss and (ii) the appearance of a GABAergic gene expression signature during glutamatergic neuron differentiation. These results expand the knowledge about the molecular pathways targeted by Polycomb during glutamatergic neuron differentiation.

Brain Regeneration Resembles Brain Cancer at Its Early Wound Healing Stage and Diverges From Cancer Later at Its Proliferation and Differentiation Stages

Gliomas are the most frequent type of brain cancers and characterized by continuous proliferation, inflammation, angiogenesis, invasion and dedifferentiation, which are also among the initiator and sustaining factors of brain regeneration during restoration of tissue integrity and function. Thus, brain regeneration and brain cancer should share more molecular mechanisms at early stages of regeneration where cell proliferation dominates. However, the mechanisms could diverge later when the regenerative response terminates, while cancer cells sustain proliferation. To test this hypothesis, we exploited the adult zebrafish that, in contrast to the mammals, can efficiently regenerate the brain in response to injury. By comparing transcriptome profiles of the regenerating zebrafish telencephalon at its three different stages, i.e., 1 day post-lesion (dpl)-early wound healing stage, 3 dpl-early proliferative stage and 14 dpl-differentiation stage, to those of two brain cancers, i.e., low-grade glioma (LGG) and glioblastoma (GBM), we reveal the common and distinct molecular mechanisms of brain regeneration and brain cancer. While the transcriptomes of 1 dpl and 3 dpl harbor unique gene modules and gene expression profiles that are more divergent from the control, the transcriptome of 14 dpl converges to that of the control. Next, by functional analysis of the transcriptomes of brain regeneration stages to LGG and GBM, we reveal the common and distinct molecular pathways in regeneration and cancer. 1 dpl and LGG and GBM resemble with regard to signaling pathways related to metabolism and neurogenesis, while 3 dpl and LGG and GBM share pathways that control cell proliferation and differentiation. On the other hand, 14 dpl and LGG and GBM converge with respect to developmental and morphogenetic processes. Finally, our global comparison of gene expression profiles of three brain regeneration stages, LGG and GBM exhibit that 1 dpl is the most similar stage to LGG and GBM while 14 dpl is the most distant stage to both brain cancers. Therefore, early convergence and later divergence of brain regeneration and brain cancer constitutes a key starting point in comparative understanding of cellular and molecular events between the two phenomena and development of relevant targeted therapies for brain cancers.

Epigenetic regulation in the neurogenic niche of the adult dentate gyrus

The adult dentate gyrus (DG) of the hippocampal formation is a specialized region of the brain that creates new adult-born neurons from a pool of resident adult neural stem and progenitor cells (aNSPCs) throughout life. These aNSPCs undergo epigenetic and epitranscriptomic regulation, including 3D genome interactions, histone modifications, DNA modifications, noncoding RNA mechanisms, and RNA modifications, to precisely control the neurogenic process. Furthermore, the specialized neurogenic niche also uses epigenetic mechanisms in mature neurons and glial cells to communicate signals to direct the behavior of the aNSPCs. Here, we review recent advances of epigenetic regulation in aNSPCs and their surrounding niche cells within the adult DG.

Mini review: The relationship between energy status and adult hippocampal neurogenesis

The ability to generate new hippocampal neurons throughout adulthood and successfully integrate them into existing neural networks is critical to cognitive function, while disordered regulation of this process results in neurodegenerative or psychiatric disease. Consequently, identifying the molecular mechanisms promoting homeostatic hippocampal neurogenesis in adults is essential to understanding the etiologies of these disorders and developing therapeutic interventions. For example, recent evidence identifies a strong association between metabolic function and adult hippocampal neurogenesis. Hippocampal neural stem cell (NSC) fate dynamically fluctuates with changes in substrate availability and energy status (AMP/ATP and NAD⁺/NADH ratios). Furthermore, many metabolic hormones, such as insulin, insulin-like growth factors, and leptin exhibit dual functions also modulating hippocampal neurogenesis and neuron survivability. These diverse metabolic inputs to NSC's from various tissues seemingly suggest the existence of a system in which energy status can finely modulate hippocampal neurogenesis. Supporting this hypothesis, interventions promoting energy balance, such as caloric restriction, intermittent fasting, and exercise, have shown encouraging potential enhancing hippocampal neurogenesis and cognitive function. Overall, there is a clear relationship between whole body energy status, adult hippocampal neurogenesis, and neuron survival; however, the molecular mechanisms underlying this phenomenon are multifaceted. Thus, the aim of this review is to analyze the literature investigating energy status-mediated regulation of adult neurogenesis in the hippocampus, highlight the neurocircuitry and intracellular signaling involved, and propose impactful future directions in the field.

Epigenetic Mechanisms in Memory and Cognitive Decline Associated with Aging and Alzheimer's Disease

Epigenetic mechanisms, which include DNA methylation, a variety of post-translational modifications of histone proteins (acetylation, phosphorylation, methylation, ubiquitination, sumoylation, serotonylation, dopaminylation), chromatin remodeling enzymes, and long non-coding RNAs, are robust regulators of activity-dependent changes in gene transcription. In the brain, many of these epigenetic modifications have been widely implicated in synaptic plasticity and memory formation. Dysregulation of epigenetic mechanisms has been reported in the aged brain and is associated with or contributes to memory decline across the lifespan. Furthermore, alterations in the epigenome have been reported in neurodegenerative disorders, including Alzheimer’s disease. Here, we review the diverse types of epigenetic modifications and their role in activity- and learning-dependent synaptic plasticity. We then discuss how these mechanisms become dysregulated across the lifespan and contribute to memory loss with age and in Alzheimer’s disease. Collectively, the evidence reviewed here strongly supports a role for diverse epigenetic mechanisms in memory formation, aging, and neurodegeneration in the brain.

Optimal culture conditions for neurosphere formation and neuronal differentiation from human dental pulp stem cells

Objectives

Human dental pulp stem cells (DPSCs) have been used to regenerate damaged nervous tissues. However, the methods of committing DPSCs into neural stem/progenitor cells (NSPCs) or neurospheres are highly diverse, resulting in many neuronal differentiation outcomes. This study aims to validate an optimal protocol for inducing DPSCs into neurospheres and neurons.

Methodology

After isolation and characterization of mesenchymal stem cell identity, DPSCs were cultured in a NSPC induction medium and culture vessels. The durations of the culture, dissociation methods, and passage numbers of DPSCs were varied.

Results

Neurosphere formation requires a special surface that inhibits cell attachment. Five-days was the most appropriate duration for generating proliferative neurospheres and they strongly expressed Nestin, an NSPC marker. Neurosphere reformation after being dissociated by the Accutase enzyme was significantly higher than other methods. Passage number of DPSCs did not affect neurosphere formation, but did influence neuronal differentiation. We found that the cells expressing a neuronal marker, β-tubulin III, and exhibiting neuronal morphology were significantly higher in the early passage of the DPSCs.

Conclusion

These results suggest a guideline to obtain a high efficiency of neurospheres and neuronal differentiation from DPSCs for further study and neurodegeneration therapeutics.

The phenomenal epigenome in neurodevelopmental disorders

Disruption of chromatin structure due to epimutations is a leading genetic etiology of neurodevelopmental disorders, collectively known as chromatinopathies. We show that there is an increasing level of convergence from the high diversity of genes that are affected by mutations to the molecular networks and pathways involving the respective proteins, the disrupted cellular and subcellular processes, and their consequence for higher order cellular network function. This convergence is ultimately reflected by specific phenotypic features shared across the various chromatinopathies. Based on these observations, we propose that the commonly disrupted molecular and cellular anomalies might provide a rational target for the development of symptomatic interventions for defined groups of genetically distinct neurodevelopmental disorders.

Transcriptomic Analysis of HCN-2 Cells Suggests Connection among Oxidative Stress, Senescence, and Neuron Death after SARS-CoV-2 Infection

According to the neurological symptoms of SARS-CoV-2 infection, it is known that the nervous system is influenced by the virus. We used pediatric human cerebral cortical cell line HCN-2 as a neuronal model of SARS-CoV-2 infection, and, through transcriptomic analysis, our aim was to evaluate the effect of SARS-CoV-2 in this type of cells. Transcriptome analyses revealed impairment in TXN gene, resulting in deregulation of its antioxidant functions, as well as a decrease in the DNA-repairing mechanism, as indicated by the decrease in KAT5. Western blot analyses of SOD1 and iNOS confirmed the impairment of reduction mechanisms and an increase in oxidative stress. Upregulation of CDKN2A and a decrease in CDK4 and CDK6 point to the blocking of the cell cycle that, according to the deregulation of repairing mechanism, has apoptosis as the outcome. A high level of proapoptotic gene PMAIP1 is indeed coherent with neuronal death, as also supported by increased levels of caspase 3. The upregulation of cell-cycle-blocking genes and apoptosis suggests a sufferance state of neurons after SARS-CoV-2 infection, followed by their inevitable death, which can explain the neurological symptoms reported. Further analyses are required to deeply explain the mechanisms and find potential treatments to protect neurons from oxidative stress and prevent their death.

Epigenetic plasticity and redox regulation of neural stem cell state and fate

The neural stem cells (NSCs) are essential for normal brain development and homeostasis. The cell state (i.e. quiescent versus activated) and fate (i.e. the cell lineage of choice upon differentiation) of NSCs are tightly controlled by various redox and epigenetic regulatory mechanisms. There is an increasing appreciation that redox and epigenetic regulations are intimately linked, but how this redox-epigenetics crosstalk affects NSC activity remains poorly understood. Another unresolved topic is whether the NSCs actually contribute to brain ageing and neurodegenerative diseases. In this review, we aim to 1) distill concepts that underlie redox and epigenetic regulation of NSC state and fate; 2) provide examples of the redox-epigenetics crosstalk in NSC biology; and 3) highlight potential redox- and epigenetic-based therapeutic opportunities to rescue NSC dysfunctions in ageing and neurodegenerative diseases.

The m6A-epitranscriptome in brain plasticity, learning and memory

Activity-dependent gene expression and protein translation underlie the ability of neurons to dynamically adjust their synaptic strength in response to sensory experience and during learning. The emerging field of epitranscriptomics (RNA modifications) has rapidly shifted our views on the mechanisms that regulate gene expression. Among hundreds of biochemical modifications on RNA, N⁶-methyladenosine (m⁶A) is the most abundant reversible mRNA modification in the brain. Its dynamic nature and ability to regulate all aspects of mRNA processing have positioned m⁶A as an important and versatile regulator of nervous system functions, including neuronal plasticity, learning and memory. In this review, we summarise recent experimental evidence that supports the role of m⁶A signalling in learning and memory, as well as providing an overview of the underlying molecular mechanisms in neurons. We also discuss the consequences of perturbed m⁶A signalling and/or its regulatory networks which are increasingly being linked to various cognitive disorders in humans.

The role and mechanisms of polycomb repressive complex 2 on the regulation of osteogenic and neurogenic differentiation of stem cells

The stem cells differentiate into osteoblasts or neurocytes is the key process for treatment of bone- or neural tissue-related diseases which is caused by ageing, fracture, injury, inflammation, etc Polycomb group complexes (PcGs), especially the polycomb repressive complex 2 (PRC2), act as pivotal epigenetic regulators by modifying key developmental regulatory genes during stem cells differentiation. In this review, we summarize the core subunits, the variants and the potential functions of PRC2. We also highlight the underlying mechanisms of PRC2 associated with the osteogenic and neurogenic differentiation of stem cells, including its interaction with non-coding RNAs, histone acetyltransferases, histone demethylase, DNA methyltransferase and polycomb repressive complex 1. This review provided a substantial information of epigenetic regulation mediated by PRC2 which leads to the osteogenic and neurogenic differentiation of stem cells.

Age-related changes in polycomb gene regulation disrupt lineage fidelity in intestinal stem cells

Tissue homeostasis requires long-term lineage fidelity of somatic stem cells. Whether and how age-related changes in somatic stem cells impact the faithful execution of lineage decisions remains largely unknown. Here, we address this question using genome-wide chromatin accessibility and transcriptome analysis as well as single-cell RNA-seq to explore stem-cell-intrinsic changes in the aging Drosophila intestine. These studies indicate that in stem cells of old flies, promoters of Polycomb (Pc) target genes become differentially accessible, resulting in the increased expression of enteroendocrine (EE) cell specification genes. Consistently, we find age-related changes in the composition of the EE progenitor cell population in aging intestines, as well as a significant increase in the proportion of EE-specified intestinal stem cells (ISCs) and progenitors in aging flies. We further confirm that Pc-mediated chromatin regulation is a critical determinant of EE cell specification in the Drosophila intestine. Pc is required to maintain expression of stem cell genes while ensuring repression of differentiation and specification genes. Our results identify Pc group proteins as central regulators of lineage identity in the intestinal epithelium and highlight the impact of age-related decline in chromatin regulation on tissue homeostasis.

Impact of neonatal anoxia and hypothermic treatment on development and memory of rats

Therapeutic hypothermia (TH) is well established as a standard treatment for term and near-term infants. However, therapeutic effects of hypothermia following neonatal anoxia in very premature babies remains inconclusive. The present rodent model of preterm neonatal anoxia has been shown to alter developmental milestones and hippocampal neurogenesis, and to disrupt spatial learning and memory in adulthood. These effects seem to be reduced by post-insult hypothermia. Epigenetic-related mechanisms have been postulated as valuable tools for developing new therapies. Dentate gyrus neurogenesis is regulated by epigenetic factors. This study evaluated whether TH effects in a rodent model of preterm oxygen deprivation are based on epigenetic alterations. The effects of TH on both developmental features (somatic growth, maturation of physical characteristics and early neurological reflexes) and performance of behavioral tasks at adulthood (spatial reference and working memory, and fear conditioning) were investigated in association with the possible involvement of the epigenetic operator Enhancer of zeste homolog 2 (Ezh2), possibly related to long-lasting effects on hippocampal neurogenesis. Results showed that TH reduced both anoxia-induced hippocampal neurodegeneration and anoxia-induced impairments on risk assessment behavior, acquisition of spatial memory, and extinction of auditory and contextual fear conditioning. In contrast, TH did not prevent developmental alterations caused by neonatal anoxia and did not restore hippocampal neurogenesis or cause changes in EZH2 levels. In conclusion, despite the beneficial effects of TH in hippocampal neurodegeneration and in reversing disruption of performance of behavioral tasks following oxygen deprivation in prematurity, these effects seem not related to developmental alterations and hippocampal neurogenesis and, apparently, is not caused by Ezh2-mediated epigenetic alteration.

Modeling heritability of temperamental differences, stress reactivity, and risk for anxiety and depression: Relevance to research domain criteria (RDoC)

Animal models provide important tools to study biological and environmental factors that shape brain function and behavior. These models can be effectively leveraged by drawing on concepts from the National Institute of Mental Health Research Domain Criteria (RDoC) Initiative, which aims to delineate molecular pathways and neural circuits that underpin behavioral anomalies that transcend psychiatric conditions. To study factors that contribute to individual differences in emotionality and stress reactivity, our laboratory utilized Sprague-Dawley rats that were selectively bred for differences in novelty exploration. Selective breeding for low versus high locomotor response to novelty produced rat lines that differ in behavioral domains relevant to anxiety and depression, particularly the RDoC Negative Valence domains, including acute threat, potential threat, and loss. Bred Low Novelty Responder (LR) rats, relative to their High Responder (HR) counterparts, display high levels of behavioral inhibition, conditioned and unconditioned fear, avoidance, passive stress coping, anhedonia, and psychomotor retardation. The HR/LR traits are heritable, emerge in the first weeks of life, and appear to be driven by alterations in the developing amygdala and hippocampus. Epigenomic and transcriptomic profiling in the developing and adult HR/LR brain suggest that DNA methylation and microRNAs, as well as differences in monoaminergic transmission (dopamine and serotonin in particular), contribute to their distinct behavioral phenotypes. This work exemplifies ways that animal models such as the HR/LR rats can be effectively used to study neural and molecular factors driving emotional behavior, which may pave the way toward improved understanding the neurobiological mechanisms involved in emotional disorders.

Neuronal Bmi-1 is critical for melatonin induced ubiquitination and proteasomal degradation of α-synuclein in experimental Parkinson's disease models

Epigenetic polycomb repressor complex-1 subunit BMI-1 plays a pivotal role in the process of gene repression to maintain the self-renewal and differentiation state of neurogenic tissues. Accumulating reports links lower expression of BMI-1 fails to regulate the repression of anti-oxidant response genes disrupt mitochondrial homeostasis underlying neurodegeneration. Interestingly, this negative relation between BMI-1 function and neurodegeneration is distinct but has not been generalized as a potential biomarker particularly in Parkinson's disease (PD). Hyperphosphorylated BMI-1 undergoes canonical polycomb E3 ligase function loss, thereby leads to reduce monoubiquitylation of histone 2A at lysine 119 (H2AK119ub) corroborates cellular accumulation of α-synuclein protein phosphorylated at serine 129 (pα-SYN (S129). In general, neuroprotectant suppressing pα-SYN (S129) level turns ineffective upon depletion of neuronal BMI-1. However, it has been observed that our neuroprotectant exposure suppresses the cellular pα-SYN (S129) and restore the the BMI-1 expression level in neuronal tissues. The pharmacological inhibition and activation of proteasomal machinery promote the cellular accumulation and degradation of neuronal pα-SYN (S129), respectively. Furthermore, our investigation reveals that accumulated pα-SYN (S129) are priorly complexed with BMI-1 undergoes ubiquitin-dependent proteasomal degradation and established as key pathway for therpeutic effect in PD. These findings linked the unestablished non-canonical role of BMI-1 in the clearance of pathological α-SYN and suspected to be a novel therapeutic target in PD.

Histone Variants and Histone Modifications in Neurogenesis

During embryonic brain development, neurogenesis requires the orchestration of gene expression to regulate neural stem cell (NSC) fate specification. Epigenetic regulation with specific emphasis on the modes of histone variants and histone post-translational modifications are involved in interactive gene regulation of central nervous system (CNS) development. Here, we provide a broad overview of the regulatory system of histone variants and histone modifications that have been linked to neurogenesis and diseases. We also review the crosstalk between different histone modifications and discuss how the 3D genome affects cell fate dynamics during brain development. Understanding the mechanisms of epigenetic regulation in neurogenesis has shifted the paradigm from single gene regulation to synergistic interactions to ensure healthy embryonic neurogenesis.

The Schizophrenia Susceptibility Gene OPCML Regulates Spine Maturation and Cognitive Behaviors through Eph-Cofilin Signaling

Previous genetic and biological evidence converge on the involvement of synaptic dysfunction in schizophrenia, and OPCML, encoding a synaptic membrane protein, is reported to be genetically associated with schizophrenia. However, its role in the pathophysiology of schizophrenia remains largely unknown. Here, we found that Opcml is strongly expressed in the mouse hippocampus; ablation of Opcml leads to reduced phosphorylated cofilin and dysregulated F-actin dynamics, which disturbs the spine maturation. Furthermore, Opcml interacts with EphB2 to control the stability of spines by regulating the ephrin-EphB2-cofilin signaling pathway. Opcml-deficient mice display impaired cognitive behaviors and abnormal sensorimotor gating, which are similar to features in neuropsychiatric disorders such as schizophrenia. Notably, the administration of aripiprazole partially restores the abnormal behaviors in Opcml^-/- mice by increasing the phosphorylated cofilin level and facilitating spine maturation. We demonstrated a critical role of the schizophrenia-susceptible gene OPCML in spine maturation and cognitive behaviors via regulating the ephrin-EphB2-cofilin signaling pathway, providing further insights into the characteristics of schizophrenia.

Epigenetic Mechanisms Underlying Adult Post Stroke Neurogenesis

Stroke remains the leading cause of adult disability. Post-stroke neurogenesis contributes to functional recovery. As an intrinsic neurorestorative process, it is important to elucidate the molecular mechanism underlying stroke-induced neurogenesis and to develop therapies designed specifically to augment neurogenesis. Epigenetic mechanisms include DNA methylation, histone modification and its mediation by microRNAs and long-non-coding RNAs. In this review, we highlight how epigenetic factors including DNA methylation, histone modification, microRNAs and long-non-coding RNAs mediate stroke-induced neurogenesis including neural stem cell self-renewal and cell fate determination. We also summarize therapies targeting these mechanisms in the treatment of stroke.

The eroding chromatin landscape of aging stem cells

Adult stem cells undergo both replicative and chronological aging in their niches, with catastrophic declines in regenerative potential with age. Due to repeated environmental insults during aging, the chromatin landscape of stem cells erodes, with changes in both DNA and histone modifications, accumulation of damage, and altered transcriptional response. A body of work has shown that altered chromatin is a driver of cell fate changes and a regulator of self-renewal in stem cells and therefore a prime target for juvenescence therapeutics. This review focuses on chromatin changes in stem cell aging and provides a composite view of both common and unique epigenetic themes apparent from the studies of multiple stem cell types.

Mediator Med23 Regulates Adult Hippocampal Neurogenesis

Mammalian Mediator (Med) is a key regulator of gene expression by linking transcription factors to RNA polymerase II (Pol II) transcription machineries. The Mediator subunit 23 (Med23) is a member of the conserved Med protein complex and plays essential roles in diverse biological processes including adipogenesis, carcinogenesis, osteoblast differentiation, and T-cell activation. However, its potential functions in the nervous system remain unknown. We report here that Med23 is required for adult hippocampal neurogenesis in mouse. Deletion of Med23 in adult hippocampal neural stem cells (NSCs) was achieved in Nestin-Cre^ER:Med23^flox/flox mice by oral administration of tamoxifen. We found an increased number of proliferating NSCs shown by pulse BrdU-labeling and immunostaining of MCM2 and Ki67, which is possibly due to a reduction in cell cycle length, with unchanged GFAP⁺/Sox2⁺ NSCs and Tbr2⁺ progenitors. On the other hand, neuroblasts and immature neurons indicated by NeuroD and DCX were decreased in number in the dentate gyrus (DG) of Med23-deficient mice. In addition, these mice also displayed defective dendritic morphogenesis, as well as a deficiency in spatial and contextual fear memory. Gene ontology (GO) analysis of hippocampal NSCs revealed an enrichment in genes involved in cell proliferation, Pol II-associated transcription, Notch signaling pathway and apoptosis. These results demonstrate that Med23 plays roles in regulating adult brain neurogenesis and functions.

Clinical Implications of Epigenetic Dysregulation in Perinatal Hypoxic-Ischemic Brain Damage

Placental and fetal hypoxia caused by perinatal hypoxic-ischemic events are major causes of stillbirth, neonatal morbidity, and long-term neurological sequelae among surviving neonates. Brain hypoxia and associated pathological processes such as excitotoxicity, apoptosis, necrosis, and inflammation, are associated with lasting disruptions in epigenetic control of gene expression contributing to neurological dysfunction. Recent studies have pointed to DNA (de)methylation, histone modifications, and non-coding RNAs as crucial components of hypoxic-ischemic encephalopathy (HIE). The understanding of epigenetic dysregulation in HIE is essential in the development of new clinical interventions for perinatal HIE. Here, we summarize our current understanding of epigenetic mechanisms underlying the molecular pathology of HI brain damage and its clinical implications in terms of new diagnostic, prognostic, and therapeutic tools.