Ryk together with the Ror2 were found to regulate the Wnt5a (Wnt/PCP) signaling via interacting with Vangl2.12,35 These findings were supported in Ryk-deficient mice that showed typical PCP defects similar to Wnt5a- and Ror2-null mice.35, -37 Therefore, mutations in human RYK might cause RS and brachydactyly and provide new insight into the etiology of these diseases. Here, RYK is linked to X-linked retinoschisis.