Neural network in planarian revealed by an antibody against planarian synaptotagmin homologue.

In order to investigate the neural connection of planarian, it is imperative to produce an antibody that specifically stains axons. To identify axon-specific genes, we constructed a cDNA library from a single eye by using a single cell PCR method, in which visual neurons are major components, and sequenced one thousand independent clones. We succeeded in the identification of a planarian homologue of synaptotagmin, Djsyt, whose specific expression in neurons was confirmed by in situ hybridization. The antibody against DjSYT specifically stained axons although its mRNA is distributed in the cell bodies. By using anti-DjSYT, we succeeded in the visualization of neural connections in planarians by whole mount staining. The anti-DjSYT antibody will become a powerful tool to analyze the molecular mechanisms underlying neural network formation in planarian.