CLARK, Stephanie; GRUNOW, Eric; SIMANTON, Wendy; BROWNE, William; HASLEY, Andrew; HILL, Brandon; DUMAN-SCHEEL, Molly*; Albion College, Michigan; Albion College, Michigan; Albion College, Michigan; University of Hawaii, Honolulu; Albion College, Michigan; Albion College, Michigan; Albion College, Michigan: Divergent Axon Growth Patterns among Arthropods coincide with Changes in Netrin Expression
In recent years, the discovery of numerous axon guidance molecules has allowed us to make great strides in understanding how axons find their targets. Many of these molecules, including Netrins, are conserved among divergent organisms. Such discoveries, while fascinating, have failed to explain how different neural network patterns have arisen in divergent organisms. For example, despite the presence of homologous neuroblasts and neurons in crustaceans and insects, we have observed differences in ventral nerve cord formation in various arthropods. In insects and in some crustaceans, such as the malacostracan Parhyale hawaiiensis, commissural axon tracts are established prior to the longitudinals. However, in several branchiopod crustaceans, such as the brine shrimp Artemia franciscana, we have noted that the longitudinal axon tracts are established prior to commissural axon growth. This observation led us to postulate that changes in the expression of axon guidance molecules may be responsible for such differences. In order to investigate this idea, we cloned the Artemia franciscana netrin (afnet) gene. An antibody to the afNet protein was generated and used to elucidate a novel pattern of Netrin expression in Artemia. This antibody was also found to cross-react to Netrin proteins in other insect and crustacean species, a discovery that has allowed us to efficiently study Netrin expression patterns across arthropods. Our findings indicate that the changes in Netrin expression patterns observed in Artemia are conserved among branchiopods. Such changes have likely contributed to the divergent mechanism of nerve cord formation observed in branchiopod crustaceans.
