RORγt serine 182 tightly regulates T cell heterogeneity to maintain mucosal homeostasis and restrict tissue inflammation

Intestine homeostasis is maintained by the delicate balance of Th17 effector cells and Treg cells. Dysregulation of these cell populations contributes to inflammation, tissue damage, and chronic conditions. ROR{gamma}t is essential for the differentiation of Th17 and a subset of Treg (ROR{gamma}t+ Treg) cells involved in intestinal inflammation. ROR{gamma}t belongs to the nuclear receptor family of transcription factors with hinge regions that are highly flexible for co-activator/co-repressor interactions. Serine 182 at the hinge region of ROR{gamma}t is phosphorylated. This study aims to uncover how S182 on ROR{gamma}t contributes to mucosal homeostasis and diseases. We used CRISRP technology to generate a phosphor-null knock-in mutant mouse line (ROR{gamma}tS182A) to assess its role in intestine physiology. scRNA-seq was performed on WT and ROR{gamma}tS182A cohoused littermates to evaluate colonic T cell heterogeneity under steady state and colitis settings. Single-cell transcriptomics revealed that ROR{gamma}tS182 maintains colonic T cell heterogeneity under steady state, without interfering T cell development and differentiation. In inflamed tissues, ROR{gamma}tS182 simultaneously restricts IL-1{beta}-mediated Th17 activities and promotes anti-inflammatory cytokine IL-10 production in LT-like Treg cells. Phospho-null ROR{gamma}tS182A knock-in mice challenged with DSS induced colitis and EAE experienced delayed recovery and exacerbated pathology. The double switch role of ROR{gamma}tS182 is critical in resolving T cell-mediated inflammation and provides a potential therapeutic target to combat autoimmune diseases.