Correct wiring of motor and sensory circuits during development is a prerequisite to enable an organism to respond to and interact with its environment. During development, outgrowing axons are guided by attractive and repulsive guidance cues. Class 3 semaphorins and their receptors, the Neuropilins, are involved in several crucial steps during the formation of the sensory-motor system, including timing of axonal growth, axon fasciculation, and specific targeting events.

It is, however, unclear which role the Neuropilins play in the inter-axonal communication between sensory and motor projections and what the consequences of this embryonic mis-wiring are for the postnatal development.

Using a conditional approach in mouse to ablate Neuropilin-1 tissue-specifically in either motor or sensory axons we revealed an unexpected dependency of motor axon development on sensory fibers.