Visualizing Circuits in the Visual System

Formation of neural circuits requires that axons recognize appropriate cells, and even appropriate parts of cells, upon which to synapse. In the retina, amacrine and bipolar cells form synapses on retinal ganglion cells (RGCs) in the inner plexiform layer (IPL). The visual features to which different RGC subtypes respond depend on what input they receive, prime determinants of which are the IPL sublaminae in which their dendrites make synapses. We have therefore sought molecules that mark RGC subtyoes and mediate lamina-specific connectivity.  Candidates include members of the immunoglobulin superfamily, such as Sidekicks, Dscams and JAMs, and members of the cadherin superfamily, such as Class II and protocadherins.  I will discuss our progress toward identifying and testing such candidates. I will also discuss methods for tracing connections of retinal neurons in wild-type and mutant mice, so that we can assess the consequences of perturbing target recognition systems.