RAG1 and colitis: Consistent with normal levels of Foxp3 in the recovered Tregs, Hif1a-knockout re-established the ability of Dtx1−/− tTregs to repress CD4+CD25− T cell-induced colitis in Rag1−/− mice as determined by colitis score readout (Fig. 6f), body weight loss and intestinal morphology (Supplementary Fig. 12).