R-2HG Exhibits Anti-tumor Activity by Targeting FTO/m6A/MYC/CEBPA Signaling.

R-2-hydroxyglutarate (R-2HG), produced at high levels by mutant isocitrate dehydrogenase 1/2 (IDH1/2) enzymes, was reported as an oncometabolite. We show here that R-2HG also exerts a broad anti-leukemic activity in vitro and in vivo by inhibiting leukemia cell proliferation/viability and by promoting cell-cycle arrest and apoptosis. Mechanistically, R-2HG inhibits fat mass and obesity-associated protein (FTO) activity, thereby increasing global N6-methyladenosine (m6A) RNA modification in R-2HG-sensitive leukemia cells, which in turn decreases the stability of MYC/CEBPA transcripts, leading to the suppression of relevant pathways. Ectopically expressed mutant IDH1 and S-2HG recapitulate the effects of R-2HG. High levels of FTO sensitize leukemic cells to R-2HG, whereas hyperactivation of MYC signaling confers resistance that can be reversed by the inhibition of MYC signaling. R-2HG also displays anti-tumor activity in glioma. Collectively, while R-2HG accumulated in IDH1/2 mutant cancers contributes to cancer initiation, our work demonstrates anti-tumor effects of 2HG in inhibiting proliferation/survival of FTO-high cancer cells via targeting FTO/m6A/MYC/CEBPA signaling.

A lncRNA from the FTO locus acts as a suppressor of the m6A writer complex and p53 tumor suppression signaling.

N6-methyladenosine (m6A) of mRNAs modulated by the METTL3-METTL14-WTAP-RBM15 methyltransferase complex and m6A demethylases such as FTO play important roles in regulating mRNA stability, splicing, and translation. Here, we demonstrate that FTO-IT1 long noncoding RNA (lncRNA) was upregulated and positively correlated with poor survival of patients with wild-type p53-expressing prostate cancer (PCa). m6A RIP-seq analysis revealed that FTO-IT1 knockout increased mRNA m6A methylation of a subset of p53 transcriptional target genes (e.g., FAS, TP53INP1, and SESN2) and induced PCa cell cycle arrest and apoptosis. We further showed that FTO-IT1 directly binds RBM15 and inhibits RBM15 binding, m6A methylation, and stability of p53 target mRNAs. Therapeutic depletion of FTO-IT1 restored mRNA m6A level and expression of p53 target genes and inhibited PCa growth in mice. Our study identifies FTO-IT1 lncRNA as a bona fide suppressor of the m6A methyltransferase complex and p53 tumor suppression signaling and nominates FTO-IT1 as a potential therapeutic target of cancer.

R-2-hydroxyglutarate attenuates aerobic glycolysis in leukemia by targeting the FTO/m6A/PFKP/LDHB axis.

R-2-hydroxyglutarate (R-2HG), a metabolite produced by mutant isocitrate dehydrogenases (IDHs), was recently reported to exhibit anti-tumor activity. However, its effect on cancer metabolism remains largely elusive. Here we show that R-2HG effectively attenuates aerobic glycolysis, a hallmark of cancer metabolism, in (R-2HG-sensitive) leukemia cells. Mechanistically, R-2HG abrogates fat-mass- and obesity-associated protein (FTO)/N6-methyladenosine (m6A)/YTH N6-methyladenosine RNA binding protein 2 (YTHDF2)-mediated post-transcriptional upregulation of phosphofructokinase platelet (PFKP) and lactate dehydrogenase B (LDHB) (two critical glycolytic genes) expression and thereby suppresses aerobic glycolysis. Knockdown of FTO, PFKP, or LDHB recapitulates R-2HG-induced glycolytic inhibition in (R-2HG-sensitive) leukemia cells, but not in normal CD34+ hematopoietic stem/progenitor cells, and inhibits leukemogenesis in vivo; conversely, their overexpression reverses R-2HG-induced effects. R-2HG also suppresses glycolysis and downregulates FTO/PFKP/LDHB expression in human primary IDH-wild-type acute myeloid leukemia (AML) cells, demonstrating the clinical relevance. Collectively, our study reveals previously unrecognized effects of R-2HG and RNA modification on aerobic glycolysis in leukemia, highlighting the therapeutic potential of targeting cancer epitranscriptomics and metabolism.

Where, When, and How: Context-Dependent Functions of RNA Methylation Writers, Readers, and Erasers.

Cellular RNAs are naturally decorated with a variety of chemical modifications. The structural diversity of the modified nucleosides provides regulatory potential to sort groups of RNAs for organized metabolism and functions, thus affecting gene expression. Recent years have witnessed a burst of interest in and understanding of RNA modification biology, thanks to the emerging transcriptome-wide sequencing methods for mapping modified sites, highly sensitive mass spectrometry for precise modification detection and quantification, and extensive characterization of the modification "effectors," including enzymes ("writers" and "erasers") that alter the modification level and binding proteins ("readers") that recognize the chemical marks. However, challenges remain due to the vast heterogeneity in expression abundance of different RNA species, further complicated by divergent cell-type-specific and tissue-specific expression and localization of the effectors as well as modifications. In this review, we highlight recent progress in understanding the function of N6-methyladenosine (m6A), the most abundant internal mark on eukaryotic mRNA, in light of the specific biological contexts of m6A effectors. We emphasize the importance of context for RNA modification regulation and function.

Endoribonucleolytic Cleavage of m6A-Containing RNAs by RNase P/MRP Complex.

N6-methyladenosine (m6A) is the most abundant internal modification in RNAs and plays regulatory roles in a variety of biological and physiological processes. Despite its important roles, the molecular mechanism underlying m6A-mediated gene regulation is poorly understood. Here, we show that m6A-containing RNAs are subject to endoribonucleolytic cleavage via YTHDF2 (m6A reader protein), HRSP12 (adaptor protein), and RNase P/MRP (endoribonucleases). We demonstrate that HRSP12 functions as an adaptor to bridge YTHDF2 and RNase P/MRP, eliciting rapid degradation of YTHDF2-bound RNAs. Transcriptome-wide analyses show that m6A RNAs that are preferentially targeted for endoribonucleolytic cleavage have an HRSP12-binding site and a RNase P/MRP-directed cleavage site upstream and downstream of the YTHDF2-binding site, respectively. We also find that a subset of m6A-containing circular RNAs associates with YTHDF2 in an HRSP12-dependent manner and is selectively downregulated by RNase P/MRP. Thus, our data expand the known functions of RNase P/MRP to endoribonucleolytic cleavage of m6A RNAs.

Differential m6A, m6Am, and m1A Demethylation Mediated by FTO in the Cell Nucleus and Cytoplasm.

FTO, the first RNA demethylase discovered, mediates the demethylation of internal N6-methyladenosine (m6A) and N6, 2-O-dimethyladenosine (m6Am) at the +1 position from the 5' cap in mRNA. Here we demonstrate that the cellular distribution of FTO is distinct among different cell lines, affecting the access of FTO to different RNA substrates. We find that FTO binds multiple RNA species, including mRNA, snRNA, and tRNA, and can demethylate internal m6A and cap m6Am in mRNA, internal m6A in U6 RNA, internal and cap m6Am in snRNAs, and N1-methyladenosine (m1A) in tRNA. FTO-mediated demethylation has a greater effect on the transcript levels of mRNAs possessing internal m6A than the ones with cap m6Am in the tested cells. We also show that FTO can directly repress translation by catalyzing m1A tRNA demethylation. Collectively, FTO-mediated RNA demethylation occurs to m6A and m6Am in mRNA and snRNA as well as m1A in tRNA.

N6-Methyladenosine Guides mRNA Alternative Translation during Integrated Stress Response.

The integrated stress response (ISR) facilitates cellular adaptation to stress conditions via the common target eIF2α. During ISR, the selective translation of stress-related mRNAs often relies on alternative mechanisms, such as leaky scanning or reinitiation, but the underlying mechanism remains incompletely understood. Here we report that, in response to amino acid starvation, the reinitiation of ATF4 is not only governed by the eIF2α signaling pathway, but is also subjected to regulation by mRNA methylation in the form of N6-methyladenosine (m6A). While depleting m6A demethylases represses ATF4 reinitiation, knocking down m6A methyltransferases promotes ATF4 translation. We demonstrate that m6A in the 5' UTR controls ribosome scanning and subsequent start codon selection. Global profiling of initiating ribosomes reveals widespread alternative translation events influenced by dynamic mRNA methylation. Consistently, Fto transgenic mice manifest enhanced ATF4 expression, highlighting the critical role of m6A in translational regulation of ISR at cellular and organismal levels.

Epitranscriptic regulation of HRAS by N6-methyladenosine drives tumor progression.

Overexpression of Ras, in addition to the oncogenic mutations, occurs in various human cancers. However, the mechanisms for epitranscriptic regulation of RAS in tumorigenesis remain unclear. Here, we report that the widespread N6-methyladenosine (m6A) modification of HRAS, but not KRAS and NRAS, is higher in cancer tissues compared with the adjacent tissues, which results in the increased expression of H-Ras protein, thus promoting cancer cell proliferation and metastasis. Mechanistically, three m6A modification sites of HRAS 3' UTR, which is regulated by FTO and bound by YTHDF1, but not YTHDF2 nor YTHDF3, promote its protein expression by the enhanced translational elongation. In addition, targeting HRAS m6A modification decreases cancer proliferation and metastasis. Clinically, up-regulated H-Ras expression correlates with down-regulated FTO and up-regulated YTHDF1 expression in various cancers. Collectively, our study reveals a linking between specific m6A modification sites of HRAS and tumor progression, which provides a new strategy to target oncogenic Ras signaling.

Highly pathogenic PRRSV upregulates IL-13 production through nonstructural protein 9-mediated inhibition of N6-methyladenosine demethylase FTO.

Porcine reproductive and respiratory syndrome virus (PRRSV), a highly infectious virus, causes severe losses in the swine industry by regulating the inflammatory response, inducing tissue damage, suppressing the innate immune response, and promoting persistent infection in hosts. Interleukin-13 (IL-13) is a cytokine that plays a critical role in regulating immune responses and inflammation, particularly in immune-related disorders, certain types of cancer, and numerous bacterial and viral infections; however, the underlying mechanisms of IL-13 regulation during PRRSV infection are not well understood. In this study, we demonstrated that PRRSV infection elevates IL-13 levels in porcine alveolar macrophages. PRRSV enhances m6A-methylated RNA levels while reducing the expression of fat mass and obesity associated protein (FTO, an m6A demethylase), thereby augmenting IL-13 production. PRRSV nonstructural protein 9 (nsp9) was a key factor for this modulation. Furthermore, we found that the residues Asp567, Tyr586, Leu593, and Asp595 were essential for nsp9 to induce IL-13 production via attenuation of FTO expression. These insights delineate PRRSV nsp9's role in FTO-mediated IL-13 release, advancing our understanding of PRRSV's impact on host immune and inflammatory responses.

Targeted inhibition of m6A demethylase FTO by FB23 attenuates allergic inflammation in the airway epithelium.

Epithelial cells play a crucial role in asthma, contributing to chronic inflammation and airway hyperresponsiveness. m6A modification, which involves key proteins such as the demethylase fat mass and obesity-associated protein (FTO), is crucial in the regulation of various diseases, including asthma. However, the role of FTO in epithelial cells and the development of asthma remains unclear. In this study, we investigated the demethylase activity of FTO using a small-molecule inhibitor FB23 in epithelial cells and allergic inflammation in vivo and in vitro. We examined the FTO-regulated transcriptome-wide m6A profiling by methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA-seq under FB23 treatment and allergic inflammation conditions. Immunofluorescence staining was performed to assess the tissue-specific expression of FTO in asthmatic bronchial mucosa. We demonstrated that FB23 alleviated allergic inflammation in IL-4/IL-13-treated epithelial cells and house dust mite (HDM)-induced allergic airway inflammation mouse model. The demethylase activity of FTO contributed to the regulation of TNF-α signaling via NF-κB and epithelial-mesenchymal transition-related pathways under allergic inflammation conditions in epithelial cells. FTO was expressed in epithelial, submucosal gland, and smooth muscle cells in human bronchial mucosa. In conclusion, FB23-induced inhibition of FTO alleviates allergic inflammation in epithelial cells and HDM-induced mice, potentially through diverse cellular processes and epithelial-mesenchymal transition signaling pathways, suggesting that FTO is a potential therapeutic target in asthma management.

FTO-mediated m6A modification of serum amyloid A2 mRNA promotes podocyte injury and inflammation by activating the NF-κB signaling pathway.

Diabetic kidney disease (DKD) is one of the severe complications of diabetes mellitus, yet there is no effective treatment. Exploring the development of DKD is essential to treatment. Podocyte injury and inflammation are closely related to the development of DKD. However, the mechanism of podocyte injury and progression in DKD remains largely unclear. Here, we observed that FTO expression was significantly upregulated in high glucose-induced podocytes and that overexpression of FTO promoted podocyte injury and inflammation. By performing RNA-seq and MeRIP-seq with control podocytes and high glucose-induced podocytes with or without FTO knockdown, we revealed that serum amyloid A2 (SAA2) is a target of FTO-mediated m6A modification. Knockdown of FTO markedly increased SAA2 mRNA m6A modification and decreased SAA2 mRNA expression. Mechanistically, we demonstrated that SAA2 might participate in podocyte injury and inflammation through activation of the NF-κB signaling pathway. Furthermore, by generating podocyte-specific adeno-associated virus 9 (AAV9) to knockdown SAA2 in mice, we discovered that the depletion of SAA2 significantly restored podocyte injury and inflammation. Together, our results suggested that upregulation of SAA2 promoted podocyte injury through m6A-dependent regulation, thus suggesting that SAA2 may be a therapeutic target for diabetic kidney disease.

FTO negatively regulates the cytotoxic activity of natural killer cells.

N6 -Methyladenosine (m6 A) is the most abundant epitranscriptomic mark and plays a fundamental role in almost every aspect of mRNA metabolism. Although m6 A writers and readers have been widely studied, the roles of m6 A erasers are not well-understood. Here, we investigate the role of FTO, one of the m6 A erasers, in natural killer (NK) cell immunity. We observe that FTO-deficient NK cells are hyperactivated. Fto knockout (Fto-/- ) mouse NK cells prevent melanoma metastasis in vivo, and FTO-deficient human NK cells enhance the antitumor response against leukemia in vitro. We find that FTO negatively regulates IL-2/15-driven JAK/STAT signaling by increasing the mRNA stability of suppressor of cytokine signaling protein (SOCS) family genes. Our results suggest that FTO is an essential modulator of NK cell immunity, providing a new immunotherapeutic strategy for allogeneic NK cell therapies.

GnRH-driven FTO-mediated RNA m6A modification promotes gonadotropin synthesis and secretion.

BACKGROUND: Gonadotropin precisely controls mammalian reproductive activities. Systematic analysis of the mechanisms by which epigenetic modifications regulate the synthesis and secretion of gonadotropin can be useful for more precise regulation of the animal reproductive process. Previous studies have identified many differential m6A modifications in the GnRH-treated adenohypophysis. However, the molecular mechanism by which m6A modification regulates gonadotropin synthesis and secretion remains unclear. RESULTS: Herein, it was found that GnRH can promote gonadotropin synthesis and secretion by promoting the expression of FTO. Highly expressed FTO binds to Foxp2 mRNA in the nucleus, exerting a demethylation function and reducing m6A modification. After Foxp2 mRNA exits the nucleus, the lack of m6A modification prevents YTHDF3 from binding to it, resulting in increased stability and upregulation of Foxp2 mRNA expression, which activates the cAMP/PKA signaling pathway to promote gonadotropin synthesis and secretion. CONCLUSIONS: Overall, the study reveals the molecular mechanism of GnRH regulating the gonadotropin synthesis and secretion through FTO-mediated m6A modification. The results of this study allow systematic interpretation of the regulatory mechanism of gonadotropin synthesis and secretion in the pituitary at the epigenetic level and provide a theoretical basis for the application of reproductive hormones in the regulation of animal artificial reproduction.

The molecular regulated mechanism of METTL3 and FTO in lipid metabolism of Hu sheep.

BACKGROUND: Balanced lipid metabolism can improve the growth performance and meat quality of livestock. The m6A methylation-related genes METTL3 and FTO play important roles in animal lipid metabolism; however, the mechanism through which they regulate lipid metabolism in sheep is unclear. RESULTS: We established lipid deposition models of hepatocytes and preadipocytes in Hu sheep. In the hepatocyte lipid deposition model, the genes expression levels of FABP4, Accα, ATGL and METTL3, METTL14, and FTO-were significantly up-regulated after lipid deposition (P < 0.05). Transcriptomic and metabolomic analyses showed that lipid deposition had a significant effect on MAPK, steroid biosynthesis, and glycerophospholipid metabolism pathway in hepatocytes. The m6A methylation level decreased but the difference was not significant after METTL3 interference, and the expression levels of FABP4 and ATGL increased significantly (P < 0.05); the m6A methylation level significantly increased following METTL3 overexpression, and LPL and ATGL expression levels significantly decreased (P < 0.05), indicating that overexpression of METTL3 inhibited the expression of lipid deposition-related genes in a m6A-dependent manner. The m6A methylation level was significantly increased, ATGL expression was significantly decreased (P < 0.05), and LPL, FABP4, and Accα expression was not significantly changed following FTO interference (P > 0.05); the m6A methylation level was significantly decreased after FTO overexpression, and LPL, FABP4, and ATGL expression was significantly increased (P < 0.05), indicating that FTO overexpression increased the expression of lipid deposition-related genes in a m6A-dependent manner. Transcriptomic and metabolomic analyses showed that m6A methylation modification mainly regulated lipid metabolism through triglyceride metabolism, adipocytokine signaling, MAPK signaling, and fat digestion and absorption in hepatocytes. In the lipid deposition model of preadipocytes, the regulation of gene expression is the same as that in hepatocytes. CONCLUSIONS: METTL3 significantly inhibited the expression of lipid deposition-related genes, whereas FTO overexpression promoted lipid deposition. Our study provides a theoretical basis and reference for accurately regulating animal lipid deposition by mastering METTL3 and FTO genes to promote high-quality animal husbandry.

FTO Deficiency Alleviates LPS-induced Acute Lung Injury by TXNIP/NLRP3-mediated Alveolar Epithelial Cell Pyroptosis.

N6-methyladenosine (m6A) plays a role in various diseases, but it has rarely been reported in acute lung injury (ALI). The FTO (fat mass and obesity-associated) protein can regulate mRNA metabolism by removing m6A residues. The aim of this study was to examine the role and mechanism of the m6A demethylase FTO in LPS-induced ALI. Lung epithelial FTO-knockout mice and FTO-knockdown/overexpression human alveolar epithelial (A549) cell lines were constructed to evaluate the effects of FTO on ALI. Bioinformatics analysis and a series of in vivo and in vitro assays were used to examine the mechanism of FTO regulation. Rescue assays were conducted to examine whether the impact of FTO on ALI depended on the TXNIP/NLRP3 pathway. In LPS-induced ALI, RNA m6A modification amounts were upregulated, and FTO expression was downregulated. In vivo, lung epithelial FTO knockout alleviated alveolar structure disorder, tissue edema, and pulmonary inflammation and improved the survival of ALI mice. In vitro, FTO knockdown reduced A549 cell damage and death induced by LPS, whereas FTO overexpression exacerbated cell damage and death. Mechanistically, bioinformatics analysis revealed that TXNIP was a downstream target of FTO. FTO deficiency mitigated pyroptosis in LPS-induced ALI via the TXNIP/NLRP3 pathway. Rescue assays confirmed that the impact of FTO on the TXNIP/NLRP3 pathway was significantly reversed by the TXNIP inhibitor SRI-37330. Deficiency of FTO alleviates LPS-induced ALI via TXNIP/NLRP3 pathway-mediated alveolar epithelial cell pyroptosis, which might be a novel therapeutic strategy for combating ALI.

Fat mass and obesity-associated factor (FTO)-mediated N6-methyladenosine regulates spermatogenesis in an age-dependent manner.

N6-methyladenosine (m6A) is the most prevalent reversible RNA modification in the mammalian transcriptome. It has recently been demonstrated that m6A is crucial for male germline development. Fat mass and obesity-associated factor (FTO), a known m6A demethylase, is widely expressed in human and mouse tissues and is involved in manifold biological processes and human diseases. However, the function of FTO in spermatogenesis and male fertility remains poorly understood. Here, we generated an Fto knockout mouse model using CRISPR/Cas9-mediated genome editing techniques to address this knowledge gap. Remarkably, we found that loss of Fto in mice caused spermatogenesis defects in an age-dependent manner, resulting from the attenuated proliferation ability of undifferentiated spermatogonia and increased male germ cell apoptosis. Further research showed that FTO plays a vital role in the modulation of spermatogenesis and Leydig cell maturation by regulating the translation of the androgen receptor in an m6A-dependent manner. In addition, we identified two functional mutations of FTO in male infertility patients, resulting in truncated FTO protein and increased m6A modification in vitro. Our results highlight the crucial effects of FTO on spermatogonia and Leydig cells for the long-term maintenance of spermatogenesis and expand our understanding of the function of m6A in male fertility.

N6-methyladenosine demethyltransferase FTO alleviates sepsis by upregulating BNIP3 to induce mitophagy.

N6-methyladenosine (m6A) is known to be crucial in various biological processes, but its role in sepsis-induced circulatory and cardiac dysfunction is not well understood. Specifically, mitophagy, a specialized form of autophagy, is excessively activated during lipopolysaccharide (LPS)-induced myocardial injury. This study aimed to investigate the impact of LPS-induced endotoxemia on m6A-RNA methylation and its role in regulating mitophagy in sepsis-induced myocardial dysfunction. Our research demonstrated that FTO (fat mass and obesity-associated protein), an m6A demethylase, significantly affects abnormal m6A modification in the myocardium and cardiomyocytes following LPS treatment. In mice, cardiac dysfunction and cardiomyocyte apoptosis worsened after adeno-associated virus serotype 9 (AAV9)-mediated FTO knockdown. Further analyses to uncover the cellular mechanisms improving cardiac function showed that FTO reduced mitochondrial reactive oxygen species, restored both basal and maximal respiration, and preserved mitochondrial membrane potential. We revealed that FTO plays a critical role in activating mitophagy by targeting BNIP3. Additionally, the cardioprotective effects of AAV-FTO were significantly compromised by mdivi-1, a mitophagy inhibitor. Mechanistically, FTO interacted with BNIP3 transcripts and regulated their expression in an m6A-dependent manner. Following FTO silencing, BNIP3 transcripts with elevated m6A modification levels in their coding regions were bound by YTHDF2 (YT521-B homology m6A RNA-binding protein 2), leading to mRNA destabilization and decreased BNIP3 protein levels. These findings highlight the importance of FTO-dependent cardiac m6A methylation in regulating mitophagy and enhance our understanding of this critical interplay, which is essential for developing therapeutic strategies to protect cardiac mitochondrial function, alleviate cardiac dysfunction, and improve survival during sepsis.

FTO blocks RNA translational activity via the loss of N6-methyladenosine methylation at 5' UTR regulated by RBM5 in cisplatin-resistant NSCLC.

N6-methyladenosine (m6A) methylation has been widely regarded in numerous biological functions including CR. Nonetheless, the molecular process of m6A methylation behind CR in non-small cell lung cancer (NSCLC) has no apparent significance. We identified in this study that the expression of FTO alpha-ketoglutarate dependent dioxygenase (FTO) was downregulated in CR NSCLC tissues and cells in vivo and in vitro. Additionally, RIP-seq indicated that loss of FTO contributed to the elevated m6A methylation at 5'-untranslated region of RNAs which were closely connected with tumor resistance and malignancy, and FTO exerted to exclude the recruitment of eIF3A to these target genes in CR NSCLC. Moreover, FTO-enriched transcripts displayed a reduced translational capability in CR NSCLC compared to the regular NSCLC cells. Finally, we also identified RNA binding motif protein 5 (RBM5) that could specially interact with FTO in regular NSCLC compared to CR NSCLC. Deficiency of RBM5 resulted in the abnormal recognition of transcripts by FTO, and led to the translation silencing of genes associated with CR such as ATP7A, ERCC1, CD99, CDKN3, XRCC5, and NOL3. Taken together, our data characterized FTO as a novel translation regulator and revealed the molecular mechanism on gene translation through the synergistic effects with RBM5 and m6A methylation in CR NSCLC cells.

N6-Methyladenosine-Modified KREMEN2 Promotes Tumorigenesis and Malignant Progression of High-Grade Serous Ovarian Cancer.

High-grade serous ovarian cancer (HGSOC) remains the most lethal female cancer by far. Herein, clinical HGSOC samples had higher N6-methyladenosine (m6A) modification than normal ovarian tissue, and its dysregulation had been reported to drive aberrant transcription and translation programs. However, Kringle-containing transmembrane protein 2 (KREMEN2) and its m6A modification have not been fully elucidated in HGSOC. In this study, the data from the high-throughput messenger RNA (mRNA) sequencing of clinical samples were processed using the weighted correlation network analysis and functional enrichment analysis. Results revealed that KREMEN2 was a driver gene in the tumorigenesis of HGSOC and a potential target of m6A demethylase fat-mass and obesity-associated protein (FTO). KREMEN2 and FTO levels were upregulated and downregulated, respectively, and correlation analysis showed a significant negative correlation in HGSOC samples. Importantly, upregulated KREMEN2 was remarkably associated with lymph node metastasis, distant metastasis, peritoneal metastasis, and high International Federation of Gynecology and Obstetrics stage (Ⅲ/Ⅳ), independent of the age of patients. KREMEN2 promoted the growth of HGSOC in vitro and in vivo, which was dependent on FTO. The methylated RNA immunoprecipitation qPCR and RNA immunoprecipitation assays were performed to verify the m6A level and sites of KREMEN2. FTO overexpression significantly decreased m6A modification in the 3' and 5' untranslated regions of KREMEN2 mRNA and downregulated its expression. In addition, we found that FTO-mediated m6A modification of KREMEN2 mRNA was recognized and stabilized by the m6A reader IGF2BP1 rather than by IGF2BP2 or IGF2BP3. This study highlights the m6A modification of KREMEN2 and extends the importance of RNA epigenetics in HGSOC.

The role of N6-methyladenosine RNA methylation in the crosstalk of circadian clock and neuroinflammation in rodent suprachiasmatic nuclei.

N6-methyladenosine (m6A) is the most abundant epitranscriptomic mark that regulates the fate of RNA molecules. Recent studies have revealed a bidirectional interaction between m6A modification and the circadian clock. However, the precise temporal dynamics of m6A global enrichment in the central circadian pacemaker have not been fully elucidated. Our study investigates the relationship between FTO demethylase and molecular clocks in primary cells of the suprachiasmatic nucleus (SCN). In addition, we examined the effects of lipopolysaccharide (LPS) on Fto expression and the role of FTO in LPS-induced reactive oxygen species (ROS) production in primary SCN cell culture. We observed circadian rhythmicity in the global m6A levels, which mirrored the rhythmic expression of the Fto demethylase. Silencing FTO using siRNA reduced the mesor of Per2 rhythmicity in SCN primary cells and extended the period of the PER2 rhythm in SCN primary cell cultures from PER2::LUC mice. When examining the immune response, we discovered that exposure to LPS upregulated global m6A levels while downregulating Fto expression in SCN primary cell cultures. Interestingly, we found a loss of circadian rhythmicity in Fto expression following LPS treatment, indicating that the decrease of FTO levels may contribute to m6A upregulation without directly regulating its circadian rhythm. To explore potential protective mechanisms against neurotoxic inflammation, we examined ROS production following LPS treatment in SCN primary cell cultures pretreated with FTO siRNA. We observed a time-dependent pattern of ROS induction, with significant peak at 32 h but not at 20 h after synchronization. Silencing the FTO demethylase abolished ROS induction following LPS exposure, supporting the hypothesis that FTO downregulation serves as a protective mechanism during LPS-induced neuroinflammation in SCN primary cell cultures.