ROR2

The second member of the ROR family, ROR2, is a Wnt5a receptor with an immunoglobulin-like domain, a frizzled cysteine-rich domain, and a catalytically competent kinase domain followed by serine/threonine-rich and proline-rich tails. Much of its Wnt5a signaling proceeds through kinase-independent, planar cell polarity-type mechanisms. ROR2 is essential for skeletal development: heterozygous dominant mutations cause brachydactyly type B, while biallelic loss-of-function produces Robinow syndrome with limb, vertebral, and facial anomalies. In adults ROR2 is expressed in kidney, lung, and heart, and its reactivation in melanoma, osteosarcoma, and other tumors promotes Wnt5a-driven invasion and metastasis, distinguishing it from the more lymphoid-restricted oncofetal ROR1.