Axons of retinal ganglion neurons traverse molecularly distinct territories and choice points on their way to the optic tectum. The navigational behavior of their growth cones is governed by extracellular guidance factors that elicit chemotropic responses through local protein synthesis and degradation. Cyclic nucleotide signaling modulates these processes to allow response switching. Little is known about the orchestration of molecular mechanisms in axonal navigation, mainly due to a lack of intracellular real-time assays. In isolated neurons and the Xenopus brain, we wish to study how guidance cues are interpreted and integrated by the growth cone to produce the desired behavior. For this, we will apply a novel optical sensor paradigm that can offer a detailed quantitative view of the molecular navigation reactions in the growing tip, while minimizing possible deleterious effects of the introduction of sensor constructs. These approaches will be used to generate uniquely high-content information on the key reactions of local protein translation, folding, and proteasomal degradation. These powerful tools and highly interdisciplinary approaches will allow the dynamic dissection in vitro and in vivo of molecular events elicited by extracellular signals, and the molecular functional definition of their interplay at key choice points in the visual pathway where axons change their behavior in response to changes in guidance cues.