Unified Nomenclature for the Semaphorins/Collapsins

designation of eight subclasses into which all known Semaphorins/Collapsins semaphorins can be assigned. These subclasses are defined in Figure 1. We note that other proteins, including plexins and The semaphorins are a large family of secreted and certain receptor tyrosine kinases, have recently been membrane-associated proteins, many of which appear shown to contain semaphorin domains. These domains to affect axon steering, fasciculation, branching, and are, however, quite distantly related to the sema do-synapse formation through their action as inhibitors or mains of semaphorins, and phylogenetic tree analysis chemorepellents. Recent studies indicate that sema-shows these other proteins to be well separated evolu-phorins may also influence axon guidance decisions by tionarily from the semaphorins. Therefore, it seems best functioning as attractants. Though semaphorin function for these proteins to retain their original nomenclature. was initially addressed with respect to neuronal guidance, Numbering it is becoming clear that semaphorins play important Semaphorins will be assigned to individual subclasses roles in the immune system and may affect organogene-based on the overall structural and phylogenetic charac-sis, vascularization and angiogenesis, and the progres-teristics defined above. Subclasses will be designated sion of certain cancers. To date, the semaphorin family by an Arabic numeral (with the exception of the viral includes at least 19 different members in warm-and subclass), and within each subclass semaphorins will cold-blooded vertebrates and at least 3 different mem-be assigned a letter. The order of letter assignation will bers in invertebrates. be based on the date of availability in a public database Over the past seven years since the identification of such as GenBank or the EMBL sequence database of an the first semaphorin, new members of this gene family essentially full-length sequence (complete semaphorin have been characterized by many laboratories at an ever domain and C terminus). If this is not available, the date increasing rate. This has resulted in the use of many differ-of publication in a peer-reviewed journal will be used. ent names and classification systems, making it very Therefore, the actual name of any semaphorin is " sema-difficult to follow the literature and also to name newly phorin subclass n member X. " Abbreviations for verte-characterized semaphorins. In order to address this brate semaphorins will contain either all capital letters problem, several researchers whose laboratories work on semaphorin function met at the " Axon Guidance and Neural Plasticity " meeting held at Cold Spring Harbor, New York, in September, 1998. At …