Mettl14-mediated m6A modification enhances the function of Foxp3+ regulatory T cells and promotes allograft acceptance

Abstract

N6-methyladenosine (m6A), the most prevalent form of internal mRNA modification, is extensively involved in Treg cells differentiation and function. However, the involvement of m6A in functional Treg cells for transplantation tolerance remains to be elucidated. By using an experimental transplantation mouse model, we found that m6A levels in Treg cells were altered during the induction of transplant tolerance by performing a dot blotting assay. Subsequently, we used the heterogenic Treg-specific Mettl14 knockout mice (Foxp3-Mettl14f/+ cKO) to reduce METTL14 expression and performed islets allograft transplantation. Our result revealed that reduced expression of METTL14 prevented Treg cells expansion and promoted the infiltration of CD4+ and CD8+ T cells around the allograft, which led to rapid allograft rejection in Foxp3-Mettl14f/+ cKO mice. The expression of regulatory cytokines including IL-10 and TGF-β was significantly decreased in Foxp3-Mettl14f/+ cKO mice, and the suppressive function of Treg cells was also abrogated. In addition, an analysis of RNA-seq data revealed that the SOCS family (SOCS1, SOCS2 and SOCS3) is the subsequent signaling pathway affected by the METTL14 mediated m6A modification in Treg cells to modulate the suppressive function after transplantation. Taken together, our study showed for the first time that the METTL14-mediated m6A modification is essential for the suppressive function of Treg cells in transplantation and may serve as a regulatory element of Treg cell-based therapy in transplant medicine.

m6A methylation modification and immune cell infiltration: implications for targeting the catalytic subunit m6A-METTL complex in gastrointestinal cancer immunotherapy

“…This resulted in the inhibition of the JAK-STAT signaling pathway, causing Treg to lose its ability to suppress effector T cells and naive T cells (70). Similar findings were observed in METTL14, where the knockdown of METTL14 inhibited Treg cell growth while promoting the infiltration of CD4 + and CD8 + cells (71). Additionally, METTL3-mediated modification of circQSOX1 leads to the sponging of miR-326 and miR-330-5p, thus promoting PGAM1 expression.…”

Tregs in transplantation tolerance: role and therapeutic potential

“…There are diverse factors that can impact the suppressive ability of Tregs in a transplantation context, one of which is posttranscriptional modifications that affect Treg differentiation, function, and stability. For instance, N6-methyladenosine mRNA modification was involved in Treg differentiation and function, and was regulated by "reader" and "writer" proteins including methyltransferase like 14 (METTL14), Wilms tumor 1-associating protein (WTAP), and methyltransferase like 3, all of which were necessary for Treg function (119)(120)(121)(122). The ability of these proteins to modulate Treg functional ability is important in tolerance.…”

“…The ability of these proteins to modulate Treg functional ability is important in tolerance. Mice with METTL14-deficient Tregs rapidly rejected allografts and had lower levels of IL-10 and TGFβ ( 121 ). Similarly, expression of WTAP in peripheral blood samples from tolerant kidney allograft recipients was correlated with a higher Treg percentage in the peripheral blood and WTAP overexpression in naïve CD4 + T cells resulted in Foxo1 upregulation, promoting Treg differentiation and suppressive ability as well as improving allograft survival in mice ( 122 ).…”