RAR-related orphan receptor

The RAR-related orphan receptors (RORs) are members of the nuclear receptor family of intracellular transcription factors. There are three forms of ROR, ROR-α, -β, and -γ and each is encoded by a separate gene (,, and respectively). The RORs are somewhat unusual in that they appear to bind as monomers to hormone response elements as opposed to the majority of other nuclear receptors which bind as dimers.

Melatonin is reported to be the endogenous ligand for ROR-α In contrast, all-trans retinoic acid binds with high affinity to ROR-β but not ROR-α or -γ.

The three forms of RORs fulfill a number of critical roles including:
 * ROR-α - development of the cerebellum, maintenance of bone, lymph node development, immune response
 * ROR-β
 * ROR-γ - immune response