Mettl3-mediated m6 A modification of Lrp2 facilitates neurogenesis through Ythdc2 and elicits antidepressant-like effects

The complex roles of m 6 A modifications in neural stem cell proliferation, differentiation, and self-renewal and implications for memory and neurodegenerative diseases

N6-methyladenosine (m 6 A), the most prevalent and conserved RNA modification in eukaryotic cells, profoundly influences virtually all aspects of mRNA metabolism. mRNA plays crucial roles in neural stem cell genesis and neural regeneration, where it is highly concentrated and actively involved in these processes. Changes in m 6 A modification levels and the expression levels of related enzymatic proteins can lead to neurological dysfunction and contribute to the development of neurological diseases. Furthermore, the proliferation and differentiation of neural stem cells, as well as nerve regeneration, are intimately linked to memory function and neurodegenerative diseases. This paper presents a comprehensive review of the roles of m 6 A in neural stem cell proliferation, differentiation, and self-renewal, as well as its implications in memory and neurodegenerative diseases. m 6 A has demonstrated divergent effects on the proliferation and differentiation of neural stem cells. These observed contradictions may arise from the time-specific nature of m 6 A and its differential impact on neural stem cells across various stages of development. Similarly, the diverse effects of m 6 A on distinct types of memory could be attributed to the involvement of specific brain regions in memory formation and recall. Inconsistencies in m 6 A levels across different models of neurodegenerative disease, particularly Alzheimer's disease and Parkinson's disease, suggest that these disparities are linked to variations in the affected brain regions. Notably, the opposing changes in m 6 A levels observed in Parkinson's disease models exposed to manganese compared to normal Parkinson's disease models further underscore the complexity of m 6 A's role in neurodegenerative processes. The roles of m 6 A in neural stem cell proliferation, differentiation, and self-renewal, and its implications in memory and neurodegenerative diseases, appear contradictory. These inconsistencies may be attributed to the time-specific nature of m 6 A and its varying effects on distinct brain regions and in different environments.

Peli1, regulated by m6A modification, suppresses NLRP3 inflammasome activation in atherosclerosis by inhibiting YB-1

The activation of pyrin domain-containing-3 (NLRP3) inflammasome in macrophages is a risk factor accelerating the progression of atherosclerosis (AS). Here, the function of pellino 1 (Peli1) in regulating the activation of NLRP3 inflammasome during the development of AS was investigated. Our results showed that Y-box binding protein 1 (YB-1) knockdown could inhibit the progression of AS in vivo, and YB-1 silencing repressed oxidized low-density lipoprotein (ox-LDL)-mediated lipid accumulation and inflammation in macrophages by inactivating NLRP3 inflammasome. E3 ubiquitination ligase Peli1 mediated ubiquitination-dependent degradation of YB-1 during AS progression. Moreover, it was found that YTH domain-containing 2 (YTHDC2) recognized methyltransferase-like 3 (METTL3)-mediated Peli1 N6-methyladenosine (m6A) modification and mediated Peli1 mRNA degradation. Rescue studies revealed that YB-1 upregulation abrogated the repressive effect of Peli1 upregulation on AS progression both in vitro and in vivo. Taken together, Peli1, regulated by m6A modification, inhibited YB-1-mediated activation of NLRP3 inflammasome in macrophages by promoting YB-1 ubiquitination to suppress the progression of AS.

Emerging importance of m6A modification in liver cancer and its potential therapeutic role

Liver cancer refers to malignant tumors that form in the liver and is usually divided into several types, the most common of which is hepatocellular carcinoma (HCC), which originates in liver cells. Other rare types of liver cancer include intrahepatic cholangiocarcinoma (iCCA). m6A modification is a chemical modification of RNA that usually manifests as the addition of a methyl group to adenine in the RNA molecule to form N6-methyladenosine. This modification exerts a critical role in various biological processes by regulating the metabolism of RNA, affecting gene expression. Recent studies have shown that m6A modification is closely related to the occurrence and development of liver cancer, and m6A regulators can further participate in the pathogenesis of liver cancer by regulating the expression of key genes and the function of specific cells. In this review, we provided an overview of the latest advances in m6A modification in liver cancer research and explored in detail the specific functions of different m6A regulators. Meanwhile, we deeply analyzed the mechanisms and roles of m6A modification in liver cancer, aiming to provide novel insights and references for the search for potential therapeutic targets. Finally, we discussed the prospects and challenges of targeting m6A regulators in liver cancer therapy.

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.

Ultrafine Particulate Matter Exacerbates the Risk of Delayed Neural Differentiation: Modulation Role of METTL3-Mediated m6A Modification

Air pollution, especially from ultrafine particles (PM0.1, ≤0.1 μm), is increasingly recognized for its detrimental effects on health. The influence of PM0.1 on neurodevelopmental disorders and its underlying mechanisms remain incompletely understood but are of significant concern. Through an investigation using mouse embryonic stem cells (mESCs), our study has uncovered disruptions in cell cycle dynamics, reduced neural precursor formation, and impaired neurogenesis during mESC neural differentiation as a result of PM0.1-induced neurodevelopmental toxicity. By employing N6-methyladenosine (m6A) methylated RNA immunoprecipitation sequencing and bioinformatics, we identified Zic1 as a key target of PM0.1-induced developmental disturbances. Our mechanistic findings indicate that PM0.1 enhances m6A methylation of Zic1 by upregulating Mettl3, leading to decreased mRNA stability and expression of this gene. Furthermore, the efficacy of the METTL3 inhibitor in alleviating nerve differentiation impairments emphasizes the significance of this pathway. In addition, source analysis, molecular docking, and toxicity analyses show that PAHs with higher ring structures in PM0.1 from combustion sources competitively bind to METTL3, potentially exacerbating neurodevelopmental toxicity. This study not only underscores the severe impact of PM0.1 on neurodevelopment but also reveals the pivotal role of m6A modification in mediating these effects, providing valuable insights and potential therapeutic targets for mitigating PM0.1-related health risks.

Comprehensive Analysis and Experimental Validation of the Parkinson's Disease Lysosomal Gene ACP2 and Pan-cancer

The pivotal role of lysosomal function in preserving neuronal homeostasis is recognized, with its dysfunction being implicated in neurodegenerative processes, notably in Parkinson's disease (PD). Yet, the molecular underpinnings of lysosome-related genes (LRGs) in the context of PD remain partially elucidated. We collected RNA-seq data from the brain substantia nigra of 30 PD patients and 20 normal subjects from the GEO database. We obtained molecular classification clusters from the screened lysosomal expression patterns. The lysosome-related diagnostic model of Parkinson's disease was constructed by XGBoost and Random Forest. And we validated the expression patterns of signature LRGs in the diagnostic model by constructing a PD rat model. Finally, the linkage between PD and cancer through signature genes was explored. The expression patterns of the 33 LRGs screened can be divided into two groups of PD samples, enabling exploration of the variance in biological processes and immune elements. Cluster A had a higher disease severity. Subsequently, critical genes were sieved through the application of machine learning methodologies culminating in the identification of two intersecting feature genes (ACP2 and LRP2). A PD risk prediction model was constructed grounded on these signature genes. The model's validity was assessed through nomogram evaluation, which demonstrated robust confidence validity. Then we analyzed the correlation analysis, immune in-filtration, biological function, and rat expression validation of the two genes with common pathogenic genes in Parkinson's disease, indicating that these two genes play an important role in the pathogenesis of PD. We then selected ACP2, which had a significant immune infiltration correlation, as the entry gene for the pan-cancer analysis. The pan-cancer analysis revealed that ACP2 has profound associations with prognostic indicators, immune infiltration, and tumor-related regulatory processes across various neoplasms, suggesting its potential as a therapeutic target in a range of human diseases, including PD and cancers. Our study comprehensively analyzed the molecular grouping of LRGs expression patterns in Parkinson's disease, and the disease progression was more severe in cluster A. And the PD diagnosis model related to LRGs is constructed. Finally, ACP2 is a potential target for the relationship between Parkinson's disease and tumor.

RNA methylation in neurodevelopment and related diseases

Biological development and genetic information transfer are governed by genetic, epigenetic, transcriptional, and posttranscriptional mechanisms. RNA methylation, the attachment of methyl (-CH 3) groups to RNA molecules, is a posttranscriptional modification that has gained increasing attention in recent years because of its role in RNA epitranscriptomics. RNA modifications (RMs) influence various aspects of RNA metabolism and are involved in the regulation of diverse biological processes and diseases. Neural cell types emerge at specific stages of brain development, and recent studies have revealed that neurodevelopment, aging, and disease are tightly linked to transcriptome dysregulation. In this review, we discuss the roles of N6-methyladenine (m6A) and 5-methylcytidine (m5C) RNA modifications in neurodevelopment, physiological functions, and related diseases.

Single-cell discovery of m6A RNA modifications in the hippocampus

N 6-Methyladenosine (m6A) is a prevalent and highly regulated RNA modification essential for RNA metabolism and normal brain function. It is particularly important in the hippocampus, where m6A is implicated in neurogenesis and learning. Although extensively studied, its presence in specific cell types remains poorly understood. We investigated m6A in the hippocampus at a single-cell resolution, revealing a comprehensive landscape of m6A modifications within individual cells. Through our analysis, we uncovered transcripts exhibiting a dense m6A profile, notably linked to neurological disorders such as Alzheimer's disease. Our findings suggest a pivotal role of m6A-containing transcripts, particularly in the context of CAMK2A neurons. Overall, this work provides new insights into the molecular mechanisms underlying hippocampal physiology and lays the foundation for future studies investigating the dynamic nature of m6A RNA methylation in the healthy and diseased brain.

m1A demethylase Alkbh3 regulates neurogenesis through m1A demethylation of Mmp15 mRNA

BACKGROUND

N1-Methyladenosine (m1A) is an abundant modification of transcripts regulating mRNA structure and translation efficiency. However, the characteristics and biological functions of mRNA m1A modification in adult hippocampal neurogenesis remain enigmatic.

RESULTS

We found that m1A demethylase Alkbh3 was dramatically enriched in neurons and neuronal genesis. Functionally, depletion of Alkbh3 in neural stem cells (NSCs) significantly decreased m1A modification, neuronal differentiation and proliferation coupling with increasing gliogenesis, whereas overexpressing Alkbh3 facilitated neuronal differentiation and proliferation. Mechanistically, the m1A demethylation of Mmp15 mRNA by Alkbh3 improved its RNA stability and translational efficacy, which promoted neurogenesis. Therapeutically, the silencing of Alkbh3 reduced hippocampal neurogenesis and impaired spatial memory in the adult mice.

CONCLUSIONS

We reveal a novel function of m1A demethylation on Mmp15 mRNA in Alkbh3-mediated neurogenesis, which shed light on advancing Alkbh3 regulation of neurogenesis as a novel neurotherapeutic strategy.

SENP1 facilitates OM-MSC differentiation through activating OPTN-mediated mitophagy to mitigate the neurologic impairment following ICH

Previous studies have indicated the neuroprotective effect of olfactory mucosa mesenchymal stem cells (OM-MSCs) on brain injury. Intracerebral hemorrhage (ICH) models were established in rats by injecting autologous blood. SENP1 expression was enhanced in neurons but decreased in astrocytes compared to that in OM-MSCs. Overexpression of SENP1 promoted the proliferation and neuronal differentiation, while inhibiting the astrocytic differentiation of OM-MSCs. Conversely, its knockdown had the opposite effect. Moreover, OM-MSCs reduced neurological dysfunction in rats after ICH, and the neuroprotective effect of OM-MSCs could be further enhanced by SENP1 overexpression. In addition, SENP1 promoted mitophagy, which might be related to SENP1-mediated OPTN deSUMOylation. Furthermore, SENP1 promoted neuronal differentiation of OM-MSCs through mitophagy mediated by OPTN. Similar to SENP1, OPTN transfection further enhanced the remission effect of OM-MSC on ICH rats. SENP1 promoted neuronal differentiation of OM-MSCs through OPTN-mediated mitophagy to improve neurological deficits in ICH rats.

The biological function of the N6-Methyladenosine reader YTHDC2 and its role in diseases

N6-methyladenosine (m6A) stands as the most prevalent modified form of RNA in eukaryotes, pivotal in various biological processes such as regulating RNA stability, translation, and transcription. All members within the YT521-B homology (YTH) gene family are categorized as m6A reading proteins, capable of identifying and binding m6A modifications on RNA, thereby regulating RNA metabolism and functioning across diverse physiological processes. YTH domain-containing 2 (YTHDC2), identified as the latest member of the YTH family, has only recently started to emerge for its biological function. Numerous studies have underscored the significance of YTHDC2 in human physiology, highlighting its involvement in both tumor progression and non-tumor diseases. Consequently, this review aims to further elucidate the pathological mechanisms of YTHDC2 by summarizing its functions and roles in tumors and other diseases, with a particular focus on its downstream molecular targets and signaling pathways.

Endometriotic mesenchymal stem cells promote the fibrosis process of endometriosis through paracrine TGF-β1 mediated RASAL1 inhibition

BACKGROUND

Endometrial-derived stem cells are key players in endometriosis (EMs) pathogenesis, while the mechanism involved is still unclear. Herein, the role and regulatory mechanism of endometriotic mesenchymal stem cells (ecto-MSCs) in regulating fibrosis during EMs progression were investigated.

METHODS

The mRNA and protein expressions were assessed using qRT-PCR, western blot, and immunofluorescence. Flow cytometry was adopted to analyze the markers of MSCs. Transwell assay was adopted to examine endometriotic stromal cells (ESCs) migration and invasion. The interactions between DNMT3A and RASAL1 were analyzed by ChIP assay. In addition, MSP was employed to detect RASAL1 promoter methylation level.

RESULTS

Ecto-MSCs promoted ESCs migration, invasion, and fibrosis process by TGF-β1 paracrine. It was subsequently revealed that TGF-β1 upregulated DNMT3A in ESCs in a SMAD3-dependent manner. As expected, DNMT3A knockdown abolished ecto-MSCs' facilitation on ESCs migration, invasion, and fibrosis process. DNMT3A, as a methyltransferase, reduced RASAL1 expression in TGF-β1-treated ESCs by increasing RASAL1 promoter methylation level. RASAL1, as an antifibrotic protein, was lowly expressed in TGF-β1-treated ESCs, and its overexpression ameliorated TGF-β1-induced increase in ESCs migration, invasion, and fibrosis process.

CONCLUSION

TGF-β1 secreted by ecto-MSCs facilitated fibrogenesis in EMs through SMAD3/DNMT3A-mediated RASAL1 inhibition.

Epigenetic regulation in major depression and other stress-related disorders: molecular mechanisms, clinical relevance and therapeutic potential

Major depressive disorder (MDD) is a chronic, generally episodic and debilitating disease that affects an estimated 300 million people worldwide, but its pathogenesis is poorly understood. The heritability estimate of MDD is 30-40%, suggesting that genetics alone do not account for most of the risk of major depression. Another factor known to associate with MDD involves environmental stressors such as childhood adversity and recent life stress. Recent studies have emerged to show that the biological impact of environmental factors in MDD and other stress-related disorders is mediated by a variety of epigenetic modifications. These epigenetic modification alterations contribute to abnormal neuroendocrine responses, neuroplasticity impairment, neurotransmission and neuroglia dysfunction, which are involved in the pathophysiology of MDD. Furthermore, epigenetic marks have been associated with the diagnosis and treatment of MDD. The evaluation of epigenetic modifications holds promise for further understanding of the heterogeneous etiology and complex phenotypes of MDD, and may identify new therapeutic targets. Here, we review preclinical and clinical epigenetic findings, including DNA methylation, histone modification, noncoding RNA, RNA modification, and chromatin remodeling factor in MDD. In addition, we elaborate on the contribution of these epigenetic mechanisms to the pathological trait variability in depression and discuss how such mechanisms can be exploited for therapeutic purposes.

METTL3 Affects Spinal Cord Neuronal Apoptosis by Regulating Bcl-2 m6A Modifications After Spinal Cord Injury

OBJECTIVE

Spinal cord injury (SCI) is a severe type of neurological trauma. N6-methyladenosine (m6A) modification is one of the most common internal modifications of RNA. The role of METTL3, the predominant methylation enzyme of m6A modification, in SCI remains unclear. This study aimed to investigate the role of methyltransferase METTL3 in SCI.

METHODS

After establishing the oxygen-glucose deprivation (OGD) model of PC12 cells and rat spinal cord hemisection model, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. The m6A modification was identified on B-cell lymphoma 2 (Bcl-2) messenger RNA (mRNA) by bioinformatics analysis, and m6A-RNA immunoprecipitation and RNA immunoprecipitation. In addition, METTL3 was blocked by the specific inhibitor STM2457 and gene knockdown, and then apoptosis levels were measured.

RESULTS

In different models, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. After inducing OGD, inhibition of METTL3 activity or expression increased the mRNA and protein levels of Bcl-2, inhibited neuronal apoptosis, and improved neuronal viability in the spinal cord.

CONCLUSION

Inhibition of METTL3 activity or expression can inhibit the apoptosis of spinal cord neurons after SCI through the m6A/Bcl-2 signaling pathway.

The Regulatory Network of METTL3 in the Nervous System: Diagnostic Biomarkers and Therapeutic Targets

Methyltransferase-like 3 (METTL3) is a typical component of N6-methyladenosine writers that exhibits methyltransferase activity and deposits methyl groups on RNA. Currently, accumulating studies have demonstrated the involvement of METTL3 in the regulation of neuro-physiological and pathological events. However, no reviews have comprehensively summarized and analyzed the roles and mechanisms of METTL3 in these events. Herein, we are focused on reviewing the roles of METTL3 in regulating normal neurophysiological (Neurogenesis, Synaptic Plasticity and Glial Plasticity, Neurodevelopment, Learning and Memory,) and neuropathological (Autism Spectrum Disorder, Major Depressive Disorder, Neurodegenerative disorders, Brain Tumors, Brain Injuries, and Other Brain Disorders) events. Our review found that although the down-regulated levels of METTL3 function through different roles and mechanisms in the nervous system, it primarily inactivates neuro-physiological events and triggers or worsens neuropathological events. In addition, our review suggests that METTL3 could be used as a diagnostic biomarker and therapeutic target in the nervous system. Collectively, our review has provided an up-to-date research outline of METTL3 in the nervous system. In addition, the regulatory network for METTL3 in the nervous system has been mapped, which could provide directions for future research, biomarkers for clinical diagnosis, and targets for disease treatment. Furthermore, this review has provided a comprehensive view, which could improve our understanding of METTL3 functions in the nervous system.

Pexidartinib (PLX3397) through restoring hippocampal synaptic plasticity ameliorates social isolation-induced mood disorders

Social behavior is essential for the well-being and survival of individuals. However, social isolation is a serious public health issue, especially during the COVID-19 pandemic, affecting a significant number of people worldwide, and can lead to serious psychological crises. Microglia, innate immune cells in the brain, are strongly implicated in the development of psychiatry. Although many microglial inhibitors have been used to treat depression, there is no literature report on pexidartinib (PLX3397) and social isolation. Herein, we adopted PLX3397 to investigate the role of microglia in the modulation of social isolation. Our results found that social isolation during adolescence caused depressive-like, but not anxiety-like behavior in mice in adulthood, with enhanced expression of the microglial marker Iba1 in the hippocampus. In addition, treatment with PLX3397 reduced the expression of the microglial marker Iba1, decreased the mRNA expression of IL-1β, increased the mRNA expression of Arg1, elevated the protein levels of DCX and GluR1 and restored the dendritic spine branches and density, ultimately mitigating depressive-like behavior in mice. These findings suggest that inhibition of microglia in the hippocampus could ameliorate mood disorders in mice, providing a new perspective for the treatment of psychiatric disorders such as depression.