Background:
Semaphorins are a large family of conserved secreted and membrane associated proteins which possess a semaphorin (Sema) domain and a PSI domain (found in plexins,semaphorins and integrins) in the N-terminal extracellular portion. Based on sequence and structural similarities,semaphorins are put into eight classes: invertebrates contain classes 1 and 2,viruses have class V,and vertebrates contain classes 3-7. Semaphorins serve as axon guidance ligands via multimeric receptor complexes,some (if not all) containing plexin proteins. Multiple transcript variants encoding different isoforms have been found for this gene.