The Plexin gene family is comprised of at least 9 members in 4 subfamilies. Plexins are widely expressed in neurons but have been also detected in epithelial cells1. Plexins closely interact with a large family of proteins called Semaphorins which control a variety of processes in the CNS including cell migration and axonal growth.Plexins and Semaphorins share a common feature of a conserved 500 amino acid “sema” domain2. The ectodomain of PLXNA2 is an N-terminal seven bladed β-propeller sema domain followed by a cysteine rich PSI (plexin-semaphorin-integrin) domain. PLXNA2 has four N-terminal domains and unlike semaphorins the sema domain of unliganded PLXNA2 does not homodimerize readily.
