IDENTIFICATION OF A NOVEL TRANSMEMBRANE SEMAPHORIN EXPRESSED ON LYMPHOCYTES

Semaphorin (also known as collapsin) members are thought to be involve d in axon guidance during neural network formation, Here, we report th e isolation of a novel member, mouse semaphorin G (M-sema G), which en codes a semaphorin domain followed by a single putative immunoglobulin -like domain, a transmembrane domain, and a cytoplasmic domain, M-sema G; is most closely related to M-sema F, which we previously reported, and semB and semC, These four members appear to constitute a transmem brane type subfamily in mouse semaphorins, In contrast to the predomin ant expression of M-sema G mRNAs in the nervous tissues, M-sema G mRNA s are strongly expressed in lymphoid tissues, especially in the thymus , as well as in the nervous tissues, The mRNAs are also detected in va rious cell lines from hematopoietic cells, By generating specific anti bodies, we confirmed the strong expression of M-Sema G proteins on the surface of lymphocytes, These results provide the first evidence that semaphorin is expressed on lymphocytes and suggest that semaphorins m ay play an important role in the immune system, as well as in the nerv ous system.