Meeting Abstract
Cephalopods have a highly-acute, image-forming camera-type eye and a large, complex nervous system. Essential to building this nervous system is the process of axon pathfinding, where neurons extend axons toward their target cells, form synapses and build a precise network. While axon guidance molecules and mechanisms of axon pathfinding have been studied in vertebrates and Drosophila, very little is known about this process in cephalopods. Many proteins have been previously shown to play a role in axon pathfinding in vertebrates and Drosophila and include members of highly conserved families of axon guidance molecules: Semaphorins, Netrin, DCC, Slit, ROBO, Eph, and Ephrin. These proteins are the attractive and repulsive cues that guide axons as they grow toward their target cells and often work in pairs. As a model to study axon guidance in the squid, we focus on a step during visual system development when photoreceptors in the cephalopod eye extend their axons to synapse on the outer nuclear layer of the optic lobe, where visual processing occurs. Our goal is to better understand which guidance cues may be important during this process. We have used the squid Doryteuthis pealeii as an embryological model to characterize the spatiotemporal expression of 12 candidate genes during visual system development. The expression patterns of these genes give insight into their function during cephalopod neurodevelopment and the process of photoreceptor axon growth and synapse formation in the optic lobe. This work is the first investigation of the role of canonical axon guidance molecules during nervous system development of any cephalopod.
