Circadian circuits control plasticity of group 3 innate lymphoid cells by sustaining epigenetic configuration of RORγt.

The gut experiences daily fluctuations in microbes and nutrients aligned with circadian rhythms that regulate nutrient absorption and immune function. Group 3 innate lymphoid cells (ILC3s) support gut homeostasis through interleukin-22 (IL-22) but can convert into interferon-γ-producing ILC1s. How circadian proteins control this plasticity remains unclear. Here we showed that the circadian proteins REV-ERBα and REV-ERBβ maintain ILC3 identity. Their combined deletion promoted ILC3-to-ILC1 conversion, reduced energy metabolism and IL-22 production, increased interferon-γ production, and heightened susceptibility to Citrobacter rodentium infection. Single-cell multiomics and gene editing revealed that REV-ERBα/REV-ERBβ deficiency upregulated the transcription factor NFIL3, which repressed the expression of RORγt via a -2-kb cis-regulatory element in the Rorc gene, shifting cells toward a T-bet-driven state. Chromatin and metabolic analyses indicated that REV-ERBα/REV-ERBβ loss reprogrammed regulatory and metabolic circuits. Thus, REV-ERBα/REV-ERBβ safeguard gut integrity by regulating clock genes that control RORγt expression and preserve ILC3 identity and resistance to intestinal inflammation.