Defining the spatiotemporal expression pattern of Rap1 in the chicken embryonic spinal cord.

The developmental mechanisms by which neurons are generated and migrate to their final locations within the developing spinal cord are not fully understood. Expression of Rap1, a small GTPase, has been previously implicated in cellular differentiation and migration across multiple tissues in various model organisms. Therefore, we investigated Rap1 expression in the embryonic chicken spinal cord at times when progenitor cells within the ventricular zone give rise to differentiated neurons that migrate towards the lateral surface of the spinal cord. Our results indicate that Rap1 is broadly expressed within the developing spinal cord across the dorsal-ventral axis during neurogenesis, including expression within neuronal progenitors in the ventricular zone and laterally within migrating neurons. We also observed Rap1 expression in spinal commissural axons and within the floor plate, where commissural axons cross the midline. In addition to the spinal cord, we observed expression of Rap1 within the developing dorsal root ganglia and ventral motor axons. Our expression analysis suggests that Rap1 may play a role in determination of progenitor cellular identity, production and migration of neurons, and commissural axons within the spinal cord.