UC San Diego

The targeting and refinement of retinal projections to their primary targets in the brain has served as a model system to study the formation of sensory maps. Prior to the development of vision, immature retinas spontaneously generate correlated activity, called retinal waves, that has been demonstrated to play a critical role in map formation. However, these previous studies were based on anatomical techniques that labeled large clusters of retinal ganglion cell (RGC) axons. To gain further insights into the mechanisms that govern map formation, it is critical to visualize the normal development of individual retinal ganglion cell axons. Here, single-cell in vivo electroporation was used to transfect individual RGCs with DNA encoding the fluorescent protein GFP. In initial studies, I used this technique to determine the projection of individual RGCs in the dorsal lateral geniculate nucleus (dLGN) of the thalamus. In wildtype mice, single RGC axons branch several arbors at multiple points into the dLGN and these individual axonal branches increase in length and complexity over the first two postnatal weeks. In transgenic mice that lack normal retinal waves, single RGC termination zones were qualitatively larger and more diffuse than in wild-type mice. These findings suggest that correlated retinal activity is required for normal refinement of single retinogeniculate projections into compact termination zones that underlie organization of visual maps