Figure 1.

A phylogenetic tree of semaphorin sequences, showing groupings of related semaphorin genes and their organization into different classes. D, Drosophila; M, mouse; V, viral; Z, sequence identified only in zebrafish and not in mammals. A Sema5D has also been described, but our analysis indicates that it is a splice variant of Sema5B. Protein sequences were aligned using ClustalW in Vector NTI software and the tree was generated using the neighbor-joining method, ignoring positions with gaps.