[P249]: Class III semaphorin signaling is required for differential target recognition by the left and right habenular nuclei of the zebrafish brain

all, pioneer axon guidance effects of SLT-1 acting through the SAX-3/Robo receptor, but does not appear to be involved in SLT1-independent signaling by SAX-3/Robo. The more restricted set of axons affected by eva-1 and slt-1 mutations compared to sax-3 mutations and the more limited expression of EVA-1 compared to SAX-3, suggests that in neurons expressing EVA-1 and SAX-3 (e.g., AVM) EVA-1 causes SAX-3 to respond to SLT-1 as a guidance cue. Consistent with this, genetic mosaic analysis and rescue of AVM guidance defects by cell-specific expression indicate that EVA-1, like SAX-3, acts in AVM to perform its guidance functions.