Identification of Natural RORγ Ligands that Regulate the Development of Lymphoid Cells

Mice deficient in the nuclear hormone receptor ROR gamma t have defective development of thymocytes, lymphoid organs, Th17 cells, and type 3 innate lymphoid cells. ROR gamma t binds to oxysterols derived from cholesterol catabolism, but it is not clear whether these are its natural ligands. Here, we show that sterol lipids are necessary and sufficient to drive ROR gamma t-dependent transcription. We combined overexpression, RNAi, and genetic deletion of metabolic enzymes to study ROR gamma-dependent transcription. Our results are consistent with the ROR gamma t ligand(s) being a cholesterol biosynthetic intermediate (CBI) downstream of lanosterol and upstream of zymosterol. Analysis of lipids bound to ROR gamma identified molecules with molecular weights consistent with CBIs. Furthermore, CBIs stabilized the ROR gamma ligand-binding domain and induced coactivator recruitment. Genetic deletion of metabolic enzymes upstream of the ROR gamma t-ligand(s) affected the development of lymph nodes and Th17 cells. Our data suggest that CBIs play a role in lymphocyte development potentially through regulation of ROR gamma t.