Abstract: Disclosed herein are methods of purifying growth cones from specific projections in the brain comprising a combination of in vivo labeling, subcellular fractionation, and fluorescent small particle sorting. The methods disclosed herein enable the quantitative profiling of the proteomes and transcriptomes of growth cones and their parent cell bodies from callosal projection neurons. Also disclosed herein are specific RNA and protein networks involved in callosal circuit formation and core growth cone proteomic machinery. The inventions disclosed herein are adaptable to any projection in the brain, providing insight into the molecular networks that control the wiring of specific neural circuits in vivo.