CRASP: CFP reconstitution across synaptic partners.

Mapping the pattern of connectivity between neurons is widely regarded to be critical for understanding the nervous system. GRASP (GFP reconstitution across synaptic partners) has been used as a promising method for mapping neuronal connectivity, but is currently available in the green color only, limiting its potential applications. Here we demonstrate CRASP (CFP reconstitution across synaptic partners), a cyan-colored version of GRASP. We validated the system in HEK 293T cells, and generated transgenic Drosophila lines to show that the system could reliably detect neuronal contacts in the brain. Furthermore, we showed that the CRASP signal could be selectively amplified using standard immunohistochemistry methods. The CRASP system adds to the toolkit available to researchers for mapping neuronal connectivity, and substantially expands the potential application of GRASP-like strategies.