METTL3-Mediated N6-Methyladenosine Methylation Modifies Foxp3 mRNA Levels and Affects the Treg Cells Proportion in Peripheral Blood of Patients with Asthma.

To investigate the regulatory effect and mechanism of methyltransferase-like protein 3 (METTL3)-mediated N6-methyladenosine methylation (m6A) on forkhead box protein 3 (Foxp3) levels and the proportion of regulatory T (Treg) cells in the peripheral blood of patients with asthma. Flow cytometry and ELISA were used to detect the differences in the proportions of Treg cells and serum interleukins (ILs) 4 and 7, respectively, in the peripheral blood between healthy individuals and patients with different asthma conditions. Reverse transcription-quantitative PCR (RT-qPCR) and Western blotting were used to detect the mRNA and protein expression levels, respectively, of METTL3 and Foxp3 in CD4+ T cells in the peripheral blood samples of different groups. M6A blot and m6A coimmunoprecipitation-PCR were used to detect the global and Foxp3 mRNA m6A levels, respectively, in the peripheral blood CD4+ T cells. CD4+ T cells collected from the peripheral blood of patients with asthma were subjected to in vitro transfection to knockdown the METTL3 levels and observe changes in the Foxp3 mRNA, protein, m6A levels, and RNA stability. Flow cytometry and ELISA were used to detect the changes in the Treg cell proportion and IL-4 and IL-17 levels in the cell culture supernatant. Compared with the healthy individuals, the ratio of Treg cells to peripheral blood CD4+ T cells was significantly decreased and the Foxp3 mRNA and protein expression was downregulated in patients with asthma with disease progression. The Foxp3 mRNA and protein expression levels were positively correlated with the Treg cell proportion and negatively correlated with IL-17 expression. The global and Foxp3 mRNA m6A levels were increased in the peripheral blood CD4+ T cells of patients with asthma. METTL3 expression was significantly higher in the peripheral blood CD4+ T cells of patients with asthma compared with healthy individuals. After METTL3 knockdown, the Foxp3 mRNA m6A level was reduced, and the stability of Foxp3 mRNA and protein expression was increased. YTHDF2 could bind to the m6A site in 3'UTR of Foxp3 mRNA. Knockdown of YTHDF2 regulated the level and stability of Foxp3 mRNA. METTL3 knockdown reduced the ratio of Treg cells to CD4+ T cells and the IL-4 and IL-17 secretion levels from CD4+ T cells in the peripheral blood of patients with asthma. High METTL3 expression in the peripheral blood CD4+ T cells of patients with asthma increased the m6A level and reduced the stability of Foxp3 mRNA in a YTHDF2-dependent way, thereby reducing the expression of Foxp3 and the proportion of Treg cells.

Fan L ，Wu J ，Wang H ，Chen Q ，He X ，Wang Q ，Yang Z ... -  《-》

METTL3-regulated m6A modification impairs the decidualization of endometrial stromal cells by regulating YTHDF2-mediated degradation of FOXO1 mRNA in endometriosis-related infertility.

Endometriosis-related infertility is a common worldwide reproductive health concern. Despite ongoing research, the causes of infertility remain unclear. Evidence suggests that epigenetic regulation is crucial in reproduction. However, the role of N6-methyladenosine (m6A) modification of RNA in endometriosis-related infertility requires further investigation. We examined the expression of m6A and methyltransferase-like 3 (METTL3) in endometrial samples taken from normal fertile women in the proliferative phase (the NP group) or the mid-secretory phase (the NS group) or from women with endometriosis-related infertility at the mid-secretory phase (the ES group). We treated primary endometrial stromal cells (ESCs) with medroxyprogesterone acetate and 8-Bromo-cyclic adenosine monophosphate for in vitro decidualization and detected the expression of m6A, METTL3, and decidual markers. We analyzed the expression of m6A, METTL3, and forkhead box O1 (FOXO1) in ESCs from normal fertile women (the ND group) or women with endometriosis-related infertility (the ED group). We also assessed the expression of m6A, METTL3, and decidual markers, as well as the embryo adhesion rate, upon METTL3 overexpression or knockdown. Additionally, we investigated the role of METTL3 in embryo implantation in vivo by applying mice with endometriosis. Furthermore, we performed RNA stability assays, RNA immunoprecipitation (RIP), and methylated RIP assays to explore the mechanisms underlying the regulation of FOXO1 by METTL3-mediated m6A. The expression of m6A and METTL3 was reduced only in the NS group; the NP and ES groups demonstrated increased m6A and METTL3 levels. m6A and METTL3 levels decreased in ESCs with prolonged decidual treatment. Compared to the ND group, m6A and METTL3 levels in the ED group increased after decidual treatment, whereas the expression of FOXO1 decreased. METTL3 overexpression suppressed the expression of decidual markers and embryo implantation in vitro; METTL3 knockdown exhibited the opposite effect. Inhibition of METTL3 promoted embryo implantation in vivo. Furthermore, we observed that METTL3-mediated m6A regulated the degradation of FOXO1 mRNA through YTHDF2, a m6A binding protein. METTL3-regulated m6A promotes YTHDF2-mediated decay of FOXO1 mRNA, thereby affecting cellular decidualization and embryo implantation. These findings provide novel insights into the development of therapies for women with endometriosis-related infertility.

Li X ，Jin J ，Long X ，Weng R ，Xiong W ，Liang J ，Liu J ，Sun J ，Cai X ，Zhang L ，Liu Y ... -  《Reproductive Biology and Endocrinology》

m(6)A methyltransferase METTL3 programs CD4(+) T-cell activation and effector T-cell differentiation in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disorder in which excessive CD4+ T-cell activation and imbalanced effector T-cell differentiation play critical roles. Recent studies have implied a potential association between posttranscriptional N6-methyladenosine (m6A) modification and CD4+ T-cell-mediated humoral immunity. However, how this biological process contributes to lupus is not well understood. In this work, we investigated the role of the m6A methyltransferase like 3 (METTL3) in CD4+ T-cell activation, differentiation, and SLE pathogenesis both in vitro and in vivo. The expression of METTL3 was knocked down and METTL3 enzyme activity was inhibited using siRNA and catalytic inhibitor, respectively. In vivo evaluation of METTL3 inhibition on CD4+ T-cell activation, effector T-cell differentiation, and SLE pathogenesis was achieved using a sheep red blood cell (SRBC)-immunized mouse model and a chronic graft versus host disease (cGVHD) mouse model. RNA-seq was performed to identify pathways and gene signatures targeted by METTL3. m6A RNA-immunoprecipitation qPCR was applied to confirm the m6A modification of METTL3 targets. METTL3 was defective in the CD4+ T cells of SLE patients. METTL3 expression varied following CD4+ T-cell activation and effector T-cell differentiation in vitro. Pharmacological inhibition of METTL3 promoted the activation of CD4+ T cells and influenced the differentiation of effector T cells, predominantly Treg cells, in vivo. Moreover, METTL3 inhibition increased antibody production and aggravated the lupus-like phenotype in cGVHD mice. Further investigation revealed that catalytic inhibition of METTL3 reduced Foxp3 expression by enhancing Foxp3 mRNA decay in a m6A-dependent manner, hence suppressing Treg cell differentiation. In summary, our findings demonstrated that METTL3 was required for stabilizing Foxp3 mRNA via m6A modification to maintain the Treg differentiation program. METTL3 inhibition contributed to the pathogenesis of SLE by participating in the activation of CD4+ T cells and imbalance of effector T-cell differentiation, which could serve as a potential target for therapeutic intervention in SLE.

Lu S ，Wei X ，Zhu H ，Hu Z ，Zheng M ，Wu J ，Zhao C ，Yang S ，Feng D ，Jia S ，Zhao H ，Zhao M ... -  《-》

The m6A Methyltransferase METTL3-Mediated N6-Methyladenosine Modification of DEK mRNA to Promote Gastric Cancer Cell Growth and Metastasis.

Zhang HM ，Qi FF ，Wang J ，Duan YY ，Zhao LL ，Wang YD ，Zhang TC ，Liao XH ... -  《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

METTL3 mediates SOX5 m6A methylation in bronchial epithelial cells to attenuate Th2 cell differentiation in T2 asthma.

Asthma, a chronic inflammatory disease in which type 2 T helper cells (Th2) play a causative role in the development of T2 asthma. N6-methyladenosine (m6A) modification, an mRNA modification, and methyltransferase-like 3 (METTL3) is involved in the development of T2 asthma by inhibiting Th2 cell differentiation. Sex determining region Y-box protein 5 (SOX5) is involved in regulating T cell differentiation, but its role in T2 asthma was unclear. The objective of this study was to explore the role of METTL3 and SOX5 in T2 asthma and whether there is an interaction between the two. Adults diagnosed with T2 asthma (n = 14) underwent clinical information collection and pulmonary function tests. In vivo and in vitro T2 asthma models were established using female C57BL/6 mice and human bronchial epithelial cells (HBE). The expressions of METTL3 and SOX5 were detected by Western blot and qRT-PCR and Western blot. Th2 cell differentiation was determined by flow cytometry and IL-4 level was detected by ELISA. m6A methylation level was determined by m6A quantitative assay. The relationship between METTL3 expression and clinical parameters was determined by Spearman rank correlation analysis. The function of METTL3 and SOX5 genes in asthma was investigated in vitro and in vivo. The RNA immunoprecipitation assay detected the specific interaction between METTL3 and SOX5. Patients with T2 asthma displayed lower METTL3 levels compared to healthy controls. Within this group, a negative correlation was observed between METTL3 and Th2 cells, while a positive correlation was noted between METTL3 and clinical parameters as well as Th1 cells. In both in vitro and in vivo models representing T2 asthma, METTL3 levels decreased significantly, while SOX5 levels showed the opposite trend. Overexpression of METTL3 gene in HBE cells significantly inhibited Th2 cell differentiation and increased m6A methylation activity. From a mechanism perspective, low METTL3 negatively regulates SOX5 expression through m6A modification dependence, while high SOX5 expression is positively associated with T2 asthma severity. Cell transfection experiments confirmed that METTL3 regulates Th2 cell differentiation and IL-4 release through SOX5. Overall, our results indicate that METTL3 alleviates Th2 cell differentiation in T2 asthma by modulating the m6A methylation activity of SOX5 in bronchial epithelial cells. This mechanism could potentially serve as a target for the prevention and management of T2 asthma.

Chen Z ，Shang Y ，Zhang X ，Duan W ，Li J ，Zhu L ，Ma L ，Xiang X ，Jia J ，Ji X ，Gong S ... -  《Heliyon》