Tong et al. reported that the conditional knockout of Mettl3 in regulatory T-cells (Foxp3-Cre, Mettl3fl/fl) results in severe autoimmune disease, accompanied by the increased percentage of IL-17 and Ifn-γ producing CD4+ cells, indicating a defect in Treg suppressive function. The gene discussed is CD4; the disease is autoimmune disease.