SMAD7 and rheumatoid arthritis: Among top 20 genes up-regulated in double E2-deficient Treg cells (group 4) (Fig. S3A), Smad7 is the only one known to be involved in regulation of Treg cells, whose up-regulation by the EZH2-FOXP3-RUNX1 axis inhibited Treg cell differentiation in rheumatoid arthritis [41].