Receptor tyrosine kinases (RTKs) are a class of cell membrane proteins, which have a high affinity for specific growth factors, hormones, and cytokines. Binding of the receptor to the specific ligand results in the activation of secondary messengers, thus, leading to a signal transduction cascade within the cell. Most RTKs function as key regulators of normal cellular processes. ROR2 (Receptor Tyrosine Kinase-Like Orphan Receptor 2) belongs to the RTK family. Like other RTKs, the ROR2 protein also consists of an extracellular region, a transmembrane section, and an intracellular structure. The extracellular region consists of an immunoglobulin-like (Ig) domain, a frizzled-like cysteine rich domain (CRD), and a kringle domain (KD), and these motifs are expected to be involved in protein-protein interactions. The intracellular region, on the other hand, contains the tyrosine kinase (TK) domain. However, it is an orphan receptor, implying that the ligand specific to it, if existent, is not known at present. Although the exact biochemical and molecular function of the ROR2 protein is not known, it is assumed that the receptor and its signaling events are involved in the early formation of chondrocytes, and that it may be required for the development of cartilages and growth plates.
The function of ROR2 is supported by its role in diseases of the skeletal system. Mutations in ROR2 are responsible for brachydactyly type B (BDB) and autosomal recessive Robinow syndrome.