RORgamma (Retinoid-related orphan receptor gamma) belongs to the nuclear hormone receptor family, NR1 subfamily. It contains one nuclear receptor DNA-binding domain. RORgamma has two isoforms: gamma1 and gamma2 (also referred to as RORgammat). RORgammat differs from the RORgamma1 isoform in that it lacks the amino terminus of RORgamma1. RORgamma1 contains 516 amino acids, and RORgammat contains 495 amino acids. RORgamma1 has a molecular weight of approximately 58 kD. RORgamma1 is highly expressed in thymus, kidney, liver, muscle, and brown fat but not in white fat tissue. RORgammat is specifically expressed in only two cell populations, DP thymocytes and lymphoid tissue inducers (LTi). RORgamma plays a critical role in controlling apoptosis during thymopoiesis and T cell homeostasis. RORgamma is said to regulate the TCRalpha repertoire by virtue of its positive regulatory role on Bcl-x expression. RORgamma is essential for lymph node and Peyer's patch development.