The Role of cxc Ligand 12a, (cxcl12a) in Projection of Axons from the Habenula in Zebrafish

The habenula is a brain region in the posterior diencephalon that affects emotional behaviors such as addiction, depression, anxiety, sleep, punishment, and rewards. Previous work in zebrafish has shown that chemokine signaling is critical for the correct orientation of habenular axons in their initial outgrowth. The chemokine receptor, Cxcr4b, is found in axons of newly forming habenular neurons, and the chemokine ligand cxcl12a is found in the region of the developing habenula. The focus of this research is to examine the role of cxcl12a in directing axon outgrowth from the habenula. To explore the role of cxcl12a, we use a method to artificially induce overexpression of cxcl12a in fish carrying a genetically encoded fluorescent marker of the habenular and its axons. Our data suggest that overexpression of cxcl12a in zebrafish embryos at 31 hours post fertilization (hpf) does not disrupt axon projection from the habenula. We are currently inducing overexpression at 32 hpf and are planning to test additional time points to determine if cxcl12a is required but insufficient for abnormal chemokine signaling in the habenula.