Decreased expression of Chrna4 by METTL3-mediated m6A modification participates in BPA-induced spatial memory deficit

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.

m6A methylation: a new frontier in epilepsy research and therapeutics

Epilepsy is a highly complex and global neurological disorder, for which available treatments only inadequately control the disease in many patients. Recent advances in molecular research have identified N6-methyladenosine (m6A) RNA modifications as key regulators of neuronal processes that underpin the pathophysiology of epilepsy. This review critically discusses the emerging significance of m6A modifications in epilepsy, focusing on dynamic regulations of m6A "writers," "erasers," and "readers" for modulating gene expression, neuronal excitability, and synaptic plasticity in epilepsy. Dysregulation of m6A machinery promotes epilepsy by exacerbating oxidative stress, mitochondrial dysfunction, and neuronal damage. We also discuss the prognostic significance of m6A alterations as a potential biomarker in epilepsy diagnosis and disease progression, along with advanced therapeutic strategies against m6A, including small molecules, RNA editing technologies, and precision medicine. This review highlights the transformational significance of m6A modulation in epilepsy therapy and opens new avenues for personalized therapeutic strategies that may revolutionize the field of drug-resistant epilepsy and improve the prognosis for patients. See also the graphical abstract(Fig. 1).

Pathological α-synuclein dysregulates epitranscriptomic writer METTL3 to drive neuroinflammation in microglia

Recent reports suggest dysregulation of the N6-methyladenosine (m6A) RNA modification may contribute to the pathology of neurodegenerative diseases. Herein, we show the m6A methyltransferase complex including METTL3-the catalytic component of the nuclear-localized complex-is robustly upregulated in human microglia and astrocytes exposed to αSynf and Mn. Subcellular localization studies reveal METTL3 was predominantly cytoplasmic following Mn insult but remained nuclear following αSynf stimulation in activated microglia. Functional analysis revealed METTL3 and downstream m6A readers, including YTHDF2 and IGF2BP1-3, may regulate the proinflammatory secretome of activated microglia. Notably, methyltransferase activity and m6A abundance were significantly increased following Mn and αSynf treatment. METTL3 in Mn and αSynfin vivo models of neuroinflammation, along with human postmortem tissues from Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB) patients, was significantly upregulated. This was further confirmed by single-cell RNA sequencing (scRNA-seq) analysis. Overall, we demonstrate the m6A writer METTL3 may function as a major regulator of chronic neuroinflammation in synucleinopathies.

Bisphenol B restrains rat leydig cell function via H3K27me3/H3K9me3 histone modifications

As an alternative compound of bisphenol A (BPA), bisphenol B (BPB) was widely used in plastic materials. The potential actions of BPB on the function of Leydig cells through the regulation of H3K27me3 and H3K9me3 remains unclear. Our goal was to assess how BPB influences Leydig cell function via histone modifications mediated by H3K27me3 and H3K9me3. Male 56-day-old Sprague-Dawley rats were given with 0, 50, 100, and 200 mg/kg/day of BPB by the oral administration for 14 days to study the impact of BPB on the function of Leydig cells in rats. The findings indicated that BPB significantly reduced the serum testosterone levels at the dose of 100 mg/kg and 200 mg/kg and follicle-stimulating hormone levels at the doses of 50, 100, and 200 mg/kg, while increasing estradiol levels at the dose of 200 mg/kg. BPB did not alter the numbers of CYP11A1+ Leydig cells and SOX9+ Sertoli cells, but it downregulated the expression of key genes in testosterone synthesis pathway (Lhcgr, Scarb1, Star, Cyp11a1, Cyp17a1, Hsd11b1, Hsd17b3, and Insl3) and their corresponding protein levels. Notably, BPB significantly boosted the expressions of histone methylation markers like EEF1A1, SUZ12, EED, EZH2, H3K27me3, and H3K9me3 in vivo. H3K27me3 and H3K9me3 levels were enhanced at the proximal promoters of Lhcgr, Cyp11a1, and Star through ChIP and PCR analyses. Furthermore, adult Leydig cells were extracted and cultured with BPB (0, 10, 50, 100, and 200 μM) alone or in combination with H3K27me3 antagonist GSK-J4. The results demonstrated that BPB significantly decreased testosterone output, which was counteracted by GSK-J4 to reverse BPB-mediated testosterone suppression. Additionally, BPB significantly elevated the levels of EEF1A1, EEF1A2, EED, H3K27me3, and H3K9me3 in vitro. BPB could potentially hinder the growth and function of Leydig cells by modulating H3K27me3 and H3K9me3. The findings of the study indicate the involvement of histone methylation (H3K27me3) in BPB-induced steroidogenic dysfunction, emphasizing the correlation between histone modifications and male reproductive toxicity.

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.

METTL Family in Healthy and Disease

Transcription, RNA splicing, RNA translation, and post-translational protein modification are fundamental processes of gene expression. Epigenetic modifications, such as DNA methylation, RNA modifications, and protein modifications, play a crucial role in regulating gene expression. The methyltransferase-like protein (METTL) family, a constituent of the 7-β-strand (7BS) methyltransferase subfamily, is broadly distributed across the cell nucleus, cytoplasm, and mitochondria. Members of the METTL family, through their S-adenosyl methionine (SAM) binding domain, can transfer methyl groups to DNA, RNA, or proteins, thereby impacting processes such as DNA replication, transcription, and mRNA translation, to participate in the maintenance of normal function or promote disease development. This review primarily examines the involvement of the METTL family in normal cell differentiation, the maintenance of mitochondrial function, and its association with tumor formation, the nervous system, and cardiovascular diseases. Notably, the METTL family is intricately linked to cellular translation, particularly in its regulation of translation factors. Members represent important molecules in disease development processes and are associated with patient immunity and tolerance to radiotherapy and chemotherapy. Moreover, future research directions could include the development of drugs or antibodies targeting its structural domains, and utilizing nanomaterials to carry miRNA corresponding to METTL family mRNA. Additionally, the precise mechanisms underlying the interactions between the METTL family and cellular translation factors remain to be clarified.

Health risks of Bisphenol-A exposure: From Wnt signaling perspective

Human beings are routinely exposed to chronic and low dose of Bisphenols (BPs) due to their widely pervasiveness in the environment. BPs hold similar chemical structures to 17β-estradiol (E2) and thyroid hormone, thus posing threats to human health by rendering the endocrine system dysfunctional. Among BPs, Bisphenol-A (BPA) is the best-known and extensively studied endocrine disrupting compound (EDC). BPA possesses multisystem toxicity, including reproductive toxicity, neurotoxicity, hepatoxicity and nephrotoxicity. Particularly, the central nervous system (CNS), especially the developing one, is vulnerable to BPA exposure. This review describes our current knowledge of BPA toxicity and the related molecular mechanisms, with an emphasis on the role of Wnt signaling in the related processes. We also discuss the role of oxidative stress, endocrine signaling and epigenetics in the regulation of Wnt signaling by BPA exposure. In summary, dysfunction of Wnt signaling plays a key role in BPA toxicity and thus can be a potential target to alleviate EDCs induced damage to organisms.