Aberrant Information Transfer Interferes with Functional Axon Regeneration

Functional axon regeneration requires regenerating neurons to restore appropriate synaptic connectivity and circuit function. To model this process, we developed a single-neuron assay in C. elegans that links axon regeneration and synapse reformation with recovery of relevant behavior. After axon injury to the DA9 neuron, regeneration restores synapses to their pre-injury location. Surprisingly, presynapses also accumulate in the dendrite. Both axonal and dendritic synapses are functional. Dendritic synapses result in information misrouting that suppresses behavioral recovery. Formation of dendritic synapses is specifically dependent on dynein-mediated transport and jnk-1. However, even when information transfer is corrected, axonal synapses fail to adequately transmit information. Our study reveals unexpected plasticity during functional regeneration. Regeneration of the axon is not sufficient for the reformation of correct neuronal circuits after injury. Rather, synapse reformation and function are also key variables, and manipulation of circuit reformation improves behavioral recovery.