Asthma is a chronic respiratory disease characterized by airway inflammation and remodeling. Epithelial-mesenchymal transition (EMT) of bronchial epithelial cells is considered to be a crucial player in asthma. Methyltransferase-like 14 (METTL14), an RNA methyltransferase, is implicated in multiple pathological processes, including EMT, cell proliferation and migration. However, the role of METTL14 in asthma remains uncertain. This research aimed to explore the biological functions of METTL14 in asthma and its underlying upstream mechanisms. METTL14 expression was down-regulated in asthmatic from three GEO datasets (GSE104468, GSE165934, and GSE74986). Consistent with this trend, METTL14 was decreased in the lung tissues of OVA-induced asthmatic mice and transforming growth factor-β1 (TGF-β1)-stimulated human bronchial epithelial cells (Beas-2B) in this study. Overexpression of METTL14 caused reduction in mesenchymal markers (FN1, N-cad, Col-1 and α-SMA) in TGF-β1-treated cells, but caused increase in epithelial markers (E-cad), thus inhibiting EMT. Also, METTL14 suppressed the proliferation and migration ability of TGF-β1-treated Beas-2B cells. Two transcription factors, ETS1 and RBPJ, could both bind to the promoter region of METTL14 and drive its expression. Elevating METTL14 expression could reversed EMT, cell proliferation and migration promoted by ETS1 or RBPJ deficiency. These results indicate that the ETS1/METTL14 and RBPJ/METTL14 transcription axes exhibit anti-EMT, anti-proliferation and anti-migration functions in TGF-β1-induced bronchial epithelial cells, implying that METTL14 may be considered an alternative candidate target for the treatment of asthma.

UNASSIGNED: N6-methyladenosine (m6A) of RNA is involved in the progression of non-small cell lung cancer (NSCLC).
UNASSIGNED: This study investigated the role of METTL14 in NSCLC and the mechanism.
UNASSIGNED: Expression levels were assessed by quantitative real-time PCR and ELISA assays. Cells viability was assessed by cell counting kit-8. M6A methylation was analysed by methylated RNA immunoprecipitation (MeRIP), RIP, luciferase assay, and mRNA stability assay.
UNASSIGNED: The results showed that METTL14 was highly expressed in NSCLC tissues and cell lines. Knockdown of METTL14 inhibited the cell viability while induced ferroptosis of NSCLC cells. Mechanistically, METTL14 interacts with GPX4, mediates m6A modification of GPX4, enhances its mRNA stability, and upregulates its expression. In addition, IGF2BP1 recognises the m6A-methylated GPX4 and mediates the elevated mRNA stability. Moreover, GPX4 reversed the effects of METTL14 depletion.
UNASSIGNED: The METTL14/GPX4 axis promotes NSCLC progression by inhibiting cell ferroptosis through the recognition of m6A modification mediated by IGF2BP1.

METTL3 and METTL14 are traditionally posited to assemble the m6A methyltransferase complex in a stoichiometric 1:1 ratio, modulating mRNA fate via m6A modifications. Nevertheless, recent investigations reveal inconsistent expression levels and prognostic significance of METTL3 and METTL14 across various tumor types, challenging their consistent functional engagement in neoplastic contexts. A pan-cancer analysis leveraging The Cancer Genome Atlas (TCGA) data has identified pronounced disparities in the expression patterns, functional roles, and correlations with tumor burden between METTL3 and METTL14, particularly in esophageal squamous cell carcinoma (ESCC). Knockdown experiments of METTL3 in EC109 cells markedly suppress cell proliferation both in vitro and in vivo, whereas METTL14 knockdown shows a comparatively muted effect on proliferation and does not significantly alter METTL3 protein levels. mRNA sequencing indicates that METTL3 singularly governs the expression of 1615 genes, with only 776 genes co-regulated with METTL14. Additionally, immunofluorescence co-localization studies suggest discrepancies in cellular localization between METTL3 and METTL14. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses demonstrate that METTL3 uniquely associates with the Nop56p-linked pre-rRNA complex and mRNA splicing machinery, independent of METTL14. Preliminary bioinformatics and multi-omics investigations reveal that METTL3\'s autonomous role in modulating tumor cell proliferation and its involvement in mRNA splicing are potentially pivotal molecular mechanisms. Our study lays both experimental and theoretical groundwork for a deeper understanding of the m6A methyltransferase complex and the development of targeted tumor therapies focusing on METTL3.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor of the nasopharyngeal mucosa with a high incidence rate all over the world. Methyltransferase-like 14 (METTL14) is a major RNA N6-adenosine methyltransferase implicated in tumor progression by regulating RNA function. This study is designed to explore the biological function and mechanism of METTL14 in NPC.
METHODS: METTL14 and Amine oxidase copper containing 1 (AOC1) expression were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The protein levels of METTL14, AOC1, Cyclin D1, B-cell lymphoma-2 (Bcl-2), and N-cadherin were measured using western blot. Cell proliferation, cycle progression, apoptosis, migration, and invasion were assessed using 5-ethynyl-2\'-deoxyuridine (EdU), Colony formation, flow cytometry, wound scratch, and transwell assays. The interaction between METTL14 and AOC1 was verified using RNA immunoprecipitation (RIP), methylated RNA immunoprecipitation (MeRIP), and dual-luciferase reporter assays. The biological role of METTL14 on NPC tumor growth was examined by the xenograft tumor model in vivo.
RESULTS: METTL14 and AOC1 were highly expressed in NPC tissues and cells. Moreover, METTL14 knockdown might block NPC cell proliferation, migration, invasion, and induce cell apoptosis in vitro. In mechanism, METTL14 might enhance the stability of AOC1 mRNA via m6A methylation. METTL14 silencing might repress NPC tumor growth in vivo.
CONCLUSIONS: METTL14 might boosted the development of NPC cells partly by regulating the stability of AOC1 mRNA, which provided a promising therapeutic target for NPC treatment.

Prolyl 4-hydroxylase beta subunit (P4HB) plays a vital role in bone formation. This study intends to clarify the role of P4HB in the therapeutic effect of Icariin (ICA) on osteoporosis. Herein, in vivo and in vitro models were constructed by performing ovariectomy (OVX) in rats and inducing osteogenic differentiation in bone marrow stem cells (BMSCs), respectively. Hematoxylin and eosin staining and micro-computed tomography analysis were performed to evaluate osteoporosis in OVX rats. Alizarin Red staining, alkaline phosphatase staining, and the ALP activity test were employed to assess osteogenesis. m6A dot blotting and methylated RNA immunoprecipitation were used to determine m6A modification. We found that P4HB was downregulated in bone tissues of patients with osteoporosis and OVX rats. P4HB facilitated osteogenic differentiation of BMSCs. What\'s more, ICA upregulated P4HB expression, promoted osteogenic differentiation of BMSCs, and alleviated osteoporosis in OVX rats, which were reversed by knocking down P4HB. ICA enhanced the stability and m6A modification of P4HB. METTL14 mediated m6A modification of P4HB mRNA. In addition, METTL14 knockdown overturned the promotive effects of ICA on P4HB m6A level and BMSC osteogenic differentiation. To sum up, ICA elevated the METTL14-mediated m6A modification of P4HB to facilitate BMSC osteogenic differentiation.

OBJECTIVE: Osteoporosis is linked to impaired function of osteoblasts, and decreased expression of METTL14 may result in abnormal differentiation of these bone-forming cells. However, the specific impact of METTL14 on osteoblast differentiation and its underlying mechanisms are not yet fully understood.
RESULTS: This study discovered a positive correlation between METTL14 expression and bone formation in specimens from osteoporosis patients and ovariectomized (OVX) mice. Additionally, METTL14 targeting of SLC25A3 contributed to the restoration of mitochondrial ROS levels and mitochondrial membrane potential in osteoblasts and promoted osteoblast differentiation. Moreover, in vivo experiments showed that METTL14 enhanced bone formation, and therapeutic introduction of METTL14 countered the decrease in bone formation in OVX mice.
CONCLUSIONS: Overall, these findings emphasize the crucial role of the METTL14/SLC25A3 signaling axis in osteoblast activity, suggesting that this axis could be a potential target for improving osteoporosis.

Multiple epigenetic regulatory mechanisms exert critical roles in tumor development, and understanding the interactions and impact of diverse epigenetic modifications on gene expression in cancer is crucial for the development of precision medicine. We found that methyltransferase-like 14 (METTL14) was significantly downregulated in non-small-cell lung cancer (NSCLC) tissues. Functional experiments demonstrated that overexpression of METTL14 inhibited the proliferation and migration of NSCLC cells both in vivo and in vitro, and the colorimetric m6A quantification assay also showed that knockdown of METTL14 notably reduced global m6A modification levels in NSCLC cells. By using the methylated-RNA immunoprecipitation-qPCR and dual-luciferase reporter assays, we verified that long noncoding RNA LINC02747 was a target of METTL14 and was regulated by METTL14-mediated m6A modification, and silencing LINC02747 inhibited the malignant progression of NSCLC by modulating the PI3K/Akt and CDK4/Cyclin D1 signaling pathway. Further studies revealed that overexpression of METTL14 promoted m6A methylation and accelerated the decay of LINC02747 mRNA via increased recognition of the \"GAACU\" binding site by YTHDC2. Additionally, histone demethylase lysine-specific histone demethylase 5B (KDM5B) mediated the demethylation of histone H3 lysine 4 tri-methylation (H3K4me3) in the METTL14 promoter region and repressed its transcription. In summary, KDM5B downregulated METTL14 expression at the transcriptional level in a H3K4me3-dependent manner, while METTL14 modulated LINC02747 expression via m6A modification. Our results demonstrate a synergy of multiple mechanisms in regulating the malignant phenotype of NSCLC, revealing the complex regulation involved in the occurrence and development of cancer.

N6-methyladenosine (m6A) methylation mediates cancer development by regulating cell proliferation and metastasis. This study aimed to identify whether methyltransferase 14 (METTL14) affects gastric cancer (GC) cellular functions and its underlying mechanism. METTL14 and TATA-box binding protein associated factor 10 (TAF10) levels were examined using quantitative real-time PCR, immunohistochemical assay, and Western blot. Biological functions were assessed using cell counting kit-8, colony formation, and transwell assays. The interaction between METTL14 and TAF10 was analyzed using RNA immunoprecipitation, methylated RNA immunoprecipitation, and luciferase reporter assay. A xenograft tumor mouse model was established to assess the role of METTL14 in vivo. The results suggested that METTL14 was low expressed and TAF10 was highly expressed in GC tissues and cells. METTL14 overexpression inhibited GC cell viability, colony, migration, and invasion. TAF10 was predicted and confirmed to be negatively related to METTL14. METTL14 promoted m6A methylation of TAF10 and inhibited TAF10 stability. Moreover, TAF10 counteracted the cellular behaviors regulated by METTL14. Overexpression of METTL14 inhibited tumor growth and histopathology. In conclusion, METTL14 inhibits GC progression by attenuating GC cell proliferation, migration, and invasion. Mechanistically, METTL14 promoted m6A methylation of TAF10, suppressed the stability of TAF10, and thus downregulated the TAF10 levels, These results provide a new insight into GC therapy.

Ulcerative colitis (UC) is a chronic and relapsing inflammatory bowel disease (IBD) characterized by colorectal inflammation. The N6-methyladenosine (m6A) modification of RNA regulates gene expression through the modulation of RNA metabolism, thus influencing various physiological and pathological processes. The aim of this study was to investigate the biological function of m6A methyltransferase METTL14 in colorectal epithelial cell inflammation. Bioinformatics analysis indicated that METTL14 expression was decreased in UC and was associated with disease severity and immune infiltration. We also noted a downregulation of METTL14 expression and a decrease in the total m6A RNA levels in TNF-α-stimulated Caco-2 cells. Moreover, METTL14 knockdown promoted inflammation and inhibited autophagy in TNF-α-stimulated Caco-2 cells, as indicated by the upregulation of NF-κB signaling and pro-inflammatory cytokine expression as well as LC3B protein downregulation. Treatment with the autophagy activator Torin-1 ameliorated the pro-inflammatory effects of METTL14 silencing. Furthermore, METTL14 knockdown significantly reduced the expression of ATG5. ATG5 overexpression could nullify the pro-inflammatory effect of METTL14 knockdown in TNF-α-stimulated Caco-2 cells. Mechanistically, METTL14 knockdown promoted ATG5 mRNA degradation, and luciferase analysis identified ATG5 as a target of m6A modification by METTL14. Taken together, silencing METTL14 promoted inflammation in Caco-2 cells via the downregulation of ATG5. Our findings revealed the importance of the m6A modification in colonic inflammation and autophagy, indicating that targeting METTL14 might be a potential therapeutic strategy for anti-inflammatory treatment in UC.

Epilepsy is a common neurological disorder which can cause significant morbidity and mortality. N6-methyladenosine (m6A), the most common chemical epigenetic modification among mRNA post-transcriptional modifications, implicated in various physiological and pathological processes, but its role in epilepsy is still unknown. Here, we provide strong evidences in support of an association of m6A and its regulatory proteins with epilepsy. Our results indicated that the level of m6A was declined significantly in the dentate gyrus (DG) of hippocampus of pentylenetetrazol (PTZ)-induced seizure mice. Both the seizure-like behaviors and the excessive activation of DG area neuron were significantly mitigated after the administration of m6A agonist betaine. Mechanically, we found that both the m6A methyltransferase METTL14 and recognition protein YTHDC1 were decreased by PTZ stimulation, which might contribute to the reduced m6A level. Additionally, DG-specific over-expression of METTL14 or YTHDC1 by lentivirus injection could significantly ameliorate seizure-like behaviors and prevent the excessive activation of neuron in epilepsy mice induced by PTZ injection, which might be due to the normalized m6A level. Together, this study identified that METTL14/YTHDC1-mediated m6A modification could participate in seizure-like behaviors, which might provide m6A regulation as a potential and novel therapeutic strategy for epilepsy.