Developmental expression of sema3G, a novel zebrafish semaphorin

The semaphorins are a large, evolutionarily conserved family of signaling molecules with broad functions during development. The class 3 semaphorins are a subclass of secreted semaphorins found in vertebrates. There have been six class 3 semaphorins identified to date (sema3A to sema3F) and some have been shown to function in axon guidance and cardiovascular development. However, the functions of many class 3 semaphorins and their potential interactions in vivo are still not well understood. As a step toward understanding the actions of all class 3 semaphorins in vivo, we have cloned and analyzed the developmental expression pattern of a novel zebrafish class 3 semaphorin, sema3G. sema3G is expressed in a dynamic pattern throughout the first 3 days of development. It is expressed in the adaxial cells of the somite during somitogenesis. In the brain, sema3G is expressed in cell clusters in the midbrain and diencephalon, and is expressed in the telencephalon in close proximity to the olfactory epithelium. sema3G also is expressed in the pharyngeal arches, the pectoral fin bud, and the developing pronephros. These results provide a basis for studying how expression of multiple semaphorins could be essential for aspects of early development.